method of preparing a chromium-based catalyst for polymerizing an olefin to a polyolefin

专利摘要:
A method that includes contacting a chromium-based catalyst with a reducing agent in a solvent to reduce an oxidation state of at least a few chromiums in the chromium-based catalyst to obtain a reduced chromium-based catalyst, drying the catalyst at chromium-based reduced to a temperature, and adjust the temperature to affect the flow rate response of the reduced chromium-based catalyst.
公开号:BR112017003639B1
申请号:R112017003639-8
申请日:2015-09-01
公开日:2021-01-19
发明作者:Kevin J. Cann；Mark G. Goode；Kevin R. Gross；John H. Moorhouse
申请人:Univation Technologies, Llc；
IPC主号:

专利说明:

Field of the Invention
[0001] The present invention relates generally to the production of polyolefins with chromium-based catalysts and, more particularly, to the preparation and reduction of chromium-based catalysts for the polymerization of olefins in a polyolefin in a polymerization reactor. Description of the Related Art
[0002] Polyolefins have been widely used in a wide variety of applications, including food packaging, textiles, and resin materials for various molded articles. Different properties of the polymer may be desired, depending on the intended use of the polymer. For example, polyolefins with relatively low molecular weights and narrow molecular weight distributions are suitable for articles molded by an injection molding process. On the other hand, polyolefins with relatively high molecular weights and wide molecular weight distributions are suitable for articles molded by blow molding or inflation molding. For example, in many applications, medium to high molecular weight polyethylenes are desirable. These polyethylenes have sufficient strength for applications that require this strength (for example, piping applications) and, at the same time, have good processing characteristics. Similarly, polyolefins with a particular flow index or within a particular flow index range are suitable for various applications.
[0003] Ethylene polymers with wide molecular weight distributions can be obtained by using a chromium-based catalyst obtained by calcining a chromium compound transported in an inorganic oxide vehicle in a non-reducing atmosphere to activate it in such a way. so that, for example, at least a portion of the transported chromium atoms are converted to hexavalent chromium atoms (Cr + 6). This type of catalyst is generally referred to in the art as the Phillips catalyst. The chromium compound is impregnated on silica, dried to a free flowing solid and heated in the presence of oxygen to about 400 ° C to 860 ° C, converting most or all of the chromium from the +3 to + oxidation state 6.
[0004] Another chromium-based catalyst used for high density polyethylene applications consists of silyl chromate (for example, bis-triphenylsilyl chromate) chemidicated on dehydrated silica and subsequently reduced with diethyl aluminum ethoxide (DEAlE). The resulting polyethylenes produced by each of these catalysts are different with regard to some important properties. Chromium oxide catalysts on silica have good productivity (g PE / g catalyst), also measured by activity (g PE / g catalyst-h), but they often produce polyethylene with narrower molecular weight distributions than desired for applications such as blow molding to a large extent, film and pressure tubing. Silyl chromate-based catalysts produce polyethylenes with desirable molecular weight characteristics (wider molecular weight distribution with a high molecular weight thickness on the molecular weight distribution curve), but often they may not have as much productivity or activity high as chromium oxide catalysts on silica.
[0005] Monoi et al., In Japanese Patent Application 2002020412, describe the use of solid components (A) containing Cr + 6 supported with inorganic oxide prepared by activation under non-reducing conditions, then adding alkoxides containing functional groups of dialkylaluminium (B ) containing an Al-OCX functional group where X is an oxygen or nitrogen atom and trialkylaluminium (C) to polymerize ethylene. The resulting ethylene polymers are said to have good resistance to cracking by environmental stress and good resistance to creep by blow molding.
[0006] Monoi et al., In US Patent 6,326,443, disclose the preparation of a polyethylene polymerization catalyst using a chromium compound, adding an organic aluminum compound more quickly than specified by a given mathematical formula and drying the resulting product at a temperature not exceeding 60 ° C, more quickly than specified by another mathematical formula. Both formulas are expressed as batch size functions. Monoi teaches that by minimizing the addition time of the organic aluminum compound and the drying time, a catalyst with high activity and a good hydrogen response is obtained.
[0007] Monoi et al., In US Patent 6,646,069, describe a method of polymerizing ethylene in hydrogen copresence using a chromium-based catalyst carried by trialkylaluminum compound, in which the chromium-based catalyst is obtained by activation of a carrier chromium compound on an inorganic oxide support by calcination, reducing the atmosphere to convert chromium atoms in the +6 state, treating the resulting substance with a trialkylaluminum compound in an inert hydrocarbon solvent and then removing the solvent.
[0008] Hasebe et al., In Japanese Patent Publication 2001-294612, describe catalysts containing chromium compounds supported by inorganic oxide calcined at 300 ° C - 1100 ° C in a non-reducing atmosphere, R3-nAlLn (R = C1- C8 alkyl; L = C1-C8 alkoxy or phenoxy and 0 <n <1), and Lewis-based organic compounds. Catalysts are said to produce polyolefins with high molecular weight and narrow molecular weight distribution.
[0009] Da et al, in Chinese Patent 1,214,344, teaches a supported chromium-based catalyst for the polymerization in gas phase of ethylene prepared by impregnating an inorganic oxide support having a hydroxyl group on the surface with an aqueous solution of inorganic chromium compound. The particles formed are dried in air and activated in an atmosphere containing oxygen. The activated intermediate catalyst is reduced with an organic aluminum compound.
[0010] Durand et al., In US Patent 5,075,395, teaches a process for eliminating the induction period in ethylene polymerization. The polymerization is carried out with a filler powder, in the presence of a catalyst that comprises a chromium oxide compound associated with a granular support and activated by heat treatment, this catalyst being used in the form of a prepolymer. The Durand process is characterized by the fact that the filler powder used is previously subjected to a contact treatment of the filler powder with an organoaluminium compound, in such a way that the polymerization begins immediately after the contact of the ethylene with the powder. charge in the presence of the prepolymer.
[0011] The chromium-based catalysts described above can be used to produce selected polymer grades. Very often, polymerization reactors are needed to produce a wide variety of products, having flow rates that can vary from 0.1 dg / min to about 100 dg / min, for example. The flow index response of a chromium-based catalyst refers to the range of the polymer flow index produced by the catalyst under a given set of polymerization conditions. summary
[0012] One embodiment relates to a method of preparing a chromium-based catalyst for the polymerization of an olefin into a polyolefin, the method including: contacting a chromium-based catalyst with a reducing agent in a solvent for decreasing an oxidation state of at least some chromium in the chromium-based catalyst to give a reduced chromium-based catalyst; drying the reduced chromium-based catalyst at an outlet temperature of the drying line; and adjusting the drying line outlet temperature to change the flow rate response of the reduced chromium-based catalyst.
[0013] Another modality concerns a method of preparing a chromium-based catalyst for the production of polyolefin, the method including: contacting a chromium-based catalyst with a reducing agent in the presence of a solvent in a container mixing to produce a reduced chromium-based catalyst; evaporating the solvent at a drying temperature to dry the reduced chromium-based catalyst; and specifying the drying temperature to give a desired flow index response of the reduced chromium-based catalyst.
[0014] Yet another embodiment refers to a method that includes the preparation of a chromium oxide catalyst for the polymerization of an olefin in a polyolefin, the preparation involving: mixing the chromium oxide catalyst with a reducing agent in a solvent to give a reduced chromium oxide catalyst; removing the solvent from the reduced chromium oxide catalyst to a specified temperature setpoint; and adjusting the specified temperature setpoint to give a desired flow index response of the reduced chromium oxide catalyst. The method includes collecting the reduced chromium oxide catalyst for distribution to a polyolefin polymerization reactor. Brief description of the drawings
[0015] FIG. 1 is a block flow diagram of a reduction system for a chrome based catalyst according to the modalities of the present techniques.
[0016] FIG. 2 is a simplified process flow diagram of the reduction system of FIG. 1, according to the modalities of the present techniques.
[0017] FIG. 3A is a diagrammatic representation of a duct extension for a mixing vessel of a chromium based catalyst reduction system according to the modalities of the present techniques.
[0018] FIG. 3B is a diagrammatic representation of an inlet arrangement using the duct extension of FIG. 3A according to the modalities of the present techniques.
[0019] FIG. 4 is an exemplary flow index bar graph in a laboratory paste phase polymerization reactor as a function of the inlet arrangement for the reducing agent for an upstream pilot plant catalyst mixing container according to modalities of the present techniques.
[0020] FIG. 5 is an exemplary flow index bar graph in a pilot plant gas phase reactor as a function of the inlet arrangement for the reducing agent for an upstream pilot plant catalyst mixing container according to the modalities of the present techniques .
[0021] FIG. 6 is a graph of an adjusted curve of sample data of the flow index in a laboratory paste polymerization reactor as a function of the catalyst drying temperature in an upstream pilot plant catalyst mixing container according to modalities of the present techniques.
[0022] FIG. 7 is a graph of an adjusted curve of sample flow rate data in a pilot plant gas phase reactor as a function of the drying temperature of the catalyst in an upstream pilot plant catalyst mixing container according to the modalities of the technical gifts.
[0023] FIG. 8 is a block diagram of a method of preparing a chromium-based catalyst including adjusting the drying temperature of the catalyst for the polymerization of an olefin to a polyolefin according to the modalities of the present techniques.
[0024] FIG. 9 is a block diagram of a method of preparing a chromium-based catalyst for the production of polyolefin, including the method of introducing a reducing agent through an inlet arrangement into a mixing vessel having the catalyst based chromium according to the modalities of the present techniques.
[0025] FIG. 10 is a block flow diagram of a polymerization reactor system having an in-line reduction system for mixing a reducing agent with a substantially continuous supply of chromium-based catalyst according to the modalities of the present techniques; and
[0026] FIG. 11 is a block diagram of a method of operating a polyolefin reactor system, including feeding a chromium-based catalyst through an in-line reduction system to a polymerization reactor according to the modalities of the present techniques. Detailed description
[0027] Before the present compounds, components, compositions and / or methods are disclosed and described, it should be understood that, unless otherwise indicated, this invention is not limited to compounds, components, compositions, reagents, reaction conditions , linked or the like, as such may vary, unless otherwise specified. It is also to be understood that the terminology used here is for the purpose of describing particular modalities only and is not intended to be limiting.
[0028] As discussed below, the present embodiments include techniques for adjusting the drying temperature of a reduced chromium-based catalyst in a mixing vessel to give a desired catalyst flow index response. An inlet arrangement in the mixing vessel can also be used to direct the flow of the reducing agent into the mixing vessel to improve dispersion of the reducing agent and to increase the flow rate response prior to drying of the catalyst. In addition, some embodiments may use an in-line mixer instead of the mixing vessel, for the in-line reduction of the chromium-based catalyst en route to the polyolefin polymerization reactor.
[0029] The modalities of the techniques can be directed to control and adjust the flow index response. The techniques can facilitate the increase and decrease in the flow index response beyond the typical process variety of a given chromium-based catalyst. The modalities provide for the adjustment of the catalyst flow index response in the production of chromium-based catalysts for use in the polymerization of olefin to polyolefin. In other words, the chromium-based catalyst compositions can be used in the polymerization of olefins, wherein the chromium-based catalyst composition has a flow index response within a selected or desired range. In addition, the techniques described herein can also beneficially maintain or increase the productivity of the catalyst.
[0030] Generally, the modalities described here refer to controlling or adapting the flow index response of catalysts based on supported chromium. In the production of the chromium-based catalyst, the catalyst can be contacted with a reducing agent at an adjustable rate of reduction agent during an adjustable period and with an adjustable stirring rate, and then drying the catalyst at a temperature adjustable drying time (and drying time) to give a reduced chromium based catalyst, having a flow index response within a desired range. These reduced chromium based catalysts can then be employed to polymerize olefins into polyolefins having a flow index correlative with the flow index response. In fact, a catalyst with a higher flow index response generally gives a polyolefin with a higher flow index, and a catalyst with a lower response flow index generally gives a polyolefin with a lower flow index.
[0031] In the reduction of the catalyst before polymerization, the rate of addition of a reducing agent (for example, DEAlE) to a chromium-based catalyst (for example, silyl chromate or chromium oxide catalysts) and the rate stirring of the reduction reaction mixture influences the response to the catalyst flow index. As discussed below, according to current techniques modalities, the catalyst flow rate response can still be controlled or adjusted by adjusting the drying temperature of the catalyst after the reduction reaction, just as in place in the mixing vessel you performed the reduction reaction. As used herein, "flow index response" means that, under a given set of polymerization reaction conditions, the catalyst produces a polymer within a given molecular weight range.
[0032] In the subsequent polymerization with the catalyst, the molar ratio of DEAlE / Cr in the catalyst or the percentage by weight of DEAlE in the catalyst, the polymerization temperature, the residence time of the catalyst in the polymerization reactor, the trace concentration of addition of oxygen introduced or present in the reactor, and the comonomer and hydrogen ratios in ethylene can each affect the molecular weight of the polymer produced with the catalyst. When the catalyst is prepared consistently, and the subsequent polymerization process variables are kept constant or generally constant, a catalyst of a given formulation must produce the same polymer. Even with small variations in the preparation and process variables, such as within a certain control tolerance, a similar polymer must be formed. Thus, the control of the flow index response of a catalyst in the production of the catalyst can be implemented to give a certain variety of molecular weights for the polymer in the downstream polymerization according to the modalities disclosed herein.
[0033] The flow index of the polymer is inversely related to the molecular weight of the polymer. The flow rate response can be modified here using terms such as "high", "medium" or "low" to indicate the relative range of flow rate of the resulting polymer produced in a given set of polymerization conditions compared to compositions of similar chromium catalyst produced using varying rates of reducing agent feed, periods for adding the reducing agent, inlet arrangements of the reducing agent, stirring rates and / or drying temperature or drying line outlet temperature. For example, for a given chromium-based catalyst composition produced using two different selected DEAlE feed rates over a given period, a catalyst may have a low flow rate response, producing a higher molecular weight polymer, while the other can have a high flow, producing a low molecular weight polymer. These relative terms should not generally be used to compare different chromium-based catalysts, but they can be used to differentiate the flow index response for a given chromium-based catalyst.
[0034] The melt index of the polymer is another indicator of the molecular weight of the polymer. The melt index is a measure of the polymer's fluidity and is also inversely related to molecular weight. A high melt index may indicate a higher termination of active polymer chains in relation to propagation, and thus a lower molecular weight.
[0035] As discussed in Moorhouse et al., US Patent Publication 2011/0010938, which is incorporated herein by reference in its entirety, the present inventors have found that reducing the agent feed rate, in some examples, or that the reduction of the agent feed rate and the agitation rate, in other examples, during the addition and reaction of the reducing agent with the catalyst can affect the flow index response of the catalysts. It can be beneficial to maintain control over these parameters to produce catalyst batches with a consistent or desired flow index response. In addition, according to the modalities of the present techniques, the drying temperature (and in some cases, the drying time) of the catalyst can be adjusted to give a desired catalyst flow rate response. Consequently, the flow index response can be beneficially varied to produce catalysts for the production of polyethylene for different applications by adjusting or selecting rates of addition of reducing agent and stirring rates and the drying temperature of the catalyst.
[0036] For a selected or specified reducing agent / Cr ratio, the flow index response of a chromium-based catalyst can be affected by the addition of the reducing agent, including the feed rate and the period during which the reducing agent is added. For example, the flow index response generally increases at a lower rate of addition of the reducing agent. In addition, the flow rate response generally increases with a faster rate of agitation during addition and reaction of the reducing agent, or a combination of a slower rate of addition and a faster rate of agitation. Consequently, in applications where the desired flow index response is low, the reducing agent can be added at a high feed rate over a short period or the agitation rate decreased. On the other hand, for applications where the desired flow index response is high, the reducing agent can be added at a lower feed rate over a long period or an increased agitation rate.
[0037] In addition, according to the modalities of the present techniques, the flow index response of a chromium-based catalyst can be affected by adjusting the temperature of the drying catalyst (and drying time). For example, it has been found that the flow index response increases with a reduced drying temperature. Consequently, in applications where a higher flow index response is desirable, the drying temperature can be reduced (for example, such as from 80 ° C to 60 ° C in an example). On the other hand, for applications where a low flow rate response is desirable, the drying temperature can be increased. In addition, it has been found that reducing the drying temperature of the catalyst can also increase the productivity of the catalyst in downstream polymerization. The productivity of the catalyst is the ratio of the polyolefin mass (for example, polyethylene) produced by the catalyst mass used in the polymerization, that is, in the downstream polymerization reactor. In cases where the drying temperature is reduced, it may be advantageous to slightly extend the drying time to reach the same low residual solvent level. For example, at a drying temperature of 70 ° C, the drying time can be 18 hours in one example, but if the drying temperature is reduced to 60 ° C, then the drying time can be 21 hours in that example to reach the same residual solvent level. Of course, other drying temperatures, drying times, and pairs of these temperatures and drying times are applicable.
[0038] Although modalities disclosed herein include chromium oxide and silyl chromate catalysts, the scope of the disclosure should not therefore be limited. One skilled in the art will appreciate that the addition of the reducing agent can be adapted to produce a desired flow index response from other chromium-based catalysts.
[0039] Catalysts useful in embodiments disclosed herein include catalysts based on chromium, such as chromium oxide and catalysts based on silyl chromate. The catalyst system chosen for polymerization often determines the properties of the polymer, such as molecular weight, molecular weight distribution and flow index.
[0040] Chromium oxide-based catalysts, for example, Phillips-type catalysts, can be formed by impregnating a Cr + 3 species in silica, followed by calcination of the silica support under oxidizing conditions at about 300 ° C at 900 ° C and at about 400 ° C to 860 ° C in other embodiments. Under these conditions, at least part of Cr + 3 is converted to Cr + 6. The Phillips catalyst is also commonly referred to in the prior art as Cr + 6 supported with inorganic oxide.
[0041] Silyl chromate catalysts are another type of Cr + 6 catalysts supported with inorganic oxide that tend to produce polyethylenes with improved properties for various applications. The silyl chromate catalyst can be formed by dehydrating silica at about 400 ° C to 850 ° C in air or nitrogen, followed by contact for a specified time of a silyl chromate compound, such as bis (triphenylsilyl) chromate ), with the silica paste in an inert hydrocarbon solvent, then reacting the resulting product with an aluminum alkyl alkoxide, such as diethyl aluminum ethoxide (DEAlE), for example, and then drying the resulting catalyst product to remove the solvent at from it.
[0042] Cann et al., In US Publication 2005/0272886, teaches the use of alkyl aluminum activators and cocatalysts to improve the performance of chromium-based catalysts. The addition of aluminum alquis to allow for variable side branch control, and desirable productivities, and these compounds can be applied directly to the catalyst or added separately to the reactor. The addition of the alkyl aluminum compound directly to the polymerization reactor (in situ) eliminates induction times.
[0043] Advantageously, adjusting the addition of a reducing agent (including the feed rate and the period over which the reducing agent is added), such as DEAlE, to the chromium-based catalyst and optionally the stirring rate , the flow index response can be adapted. According to the modalities of the present techniques, the flow index response can also be adapted by adjusting the drying temperature of the catalyst.
[0044] As described herein, the flow rate is typically an important parameter for polyolefin applications. The flow rate is a measure of the ease of flow of the melt product of a thermoplastic polymer. The flow index, or I21, as used herein, is defined as the weight of polymer in grams flowing in 10 minutes through a capillary of specific diameter and length by a pressure applied through a load of 21.6 kg at 190 ° C and is usually measured according to ASTM D-1238. The indices I2 and I5 are similarly defined, in which the applied pressure is a load of 2.16 kg, or 5 kg, respectively. I2 and I5 are also referred to as fusion indices.
[0045] The flow index is therefore a measure of a fluid's ability to flow under pressure and temperature. The flow index is an indirect measure of molecular weight, with a high flow index corresponding to low molecular weight. At the same time, the flow index is inversely proportional to the melt viscosity under the test conditions and the ratios between a flow index value and a melting index value such as the ratio of I21 to I2 for a material are often used as a measure for the breadth of a molecular weight distribution.
[0046] The flow index is, therefore, a very important parameter for polyolefins. Different flow rates may be desirable for different applications. For applications, such as lubricants, injection molding, and thin films, a higher polyolefin flow rate may be desired, while for applications such as piping, large drums, buckets or gasoline tanks for automobiles, it may be desired a lower flow index polyolefin. Polyolefins for a given application must therefore have a sufficiently high flow rate to easily form the polymer in the molten state for the intended article, but also low enough that the mechanical strength of the final article is suitable for its intended use. .
[0047] Reactor process variables can be adjusted to obtain the desired polymer flow index and melt index when using prior art chromium based catalysts for which the flow index response has not been adapted in any way. according to the modalities disclosed here. For example, it is known that the increase in polymerization temperature intensifies the termination rate, but has a comparatively lesser effect on the rate of propagation, as reported in M. P. McDaniel, Advances in Catalysis, vol. 33 (1985), p. 47-98. This can result in more short-chain polymers and an increase in melt index and flow index. Catalysts with a low flow rate response, therefore, often require higher reactor temperatures, higher oxygen addition and higher concentrations of hydrogen to produce a polymer of a given flow index.
[0048] However, there are limits to the range in which the reactor process variables can be adjusted, such as, for example, the reactor temperature, hydrogen and oxygen levels, without negatively affecting the polymerization process or the catalyst productivity. For example, excessively high temperatures can approach the softening or melting point of the formed polymer. This can then result in polymer agglomeration and blockage of the reactor. Alternatively, low reactor temperatures can lead to a lower temperature differential in relation to cooling water, less efficient heat removal and, ultimately, reduced production capacity. In addition, high concentrations of oxygen addition can lead to reduced catalyst productivity, smaller average particle size of the polymer and higher fines that can contribute to reactor clogging. In addition, variations in hydrogen concentrations can affect the properties of the polymer, such as, for example, the swelling of the matrix which, in turn, can affect the suitability of a polymer for its desired application. Consequently, adjusting the reactor variables to approach operating limits can result in operational problems that can lead to premature reactor shutdowns and downtime due to extensive cleaning procedures, as well as unwanted gels and other unwanted properties of the resulting polymeric product. .
[0049] The ability to adapt the catalyst flow rate response by adjusting the feed rate and / or the period for adding the reducing agents alone or in combination with adjusting the stir rate during the addition and reaction of the agent reduction, as well as adjusting the temperature and time of the catalyst can therefore avoid operational difficulties, reactor shutdowns and less economical polymerization conditions. This ability to adapt the flow rate response of the catalyst can facilitate the production of catalysts that give polymers with the desired properties to be more easily produced. In fact, the modalities of the techniques described here relate to increasing the dispersion or mixing the reducing agent with the catalyst in a reduction mixing vessel, adjusting the drying temperature of the catalyst in the mixing vessel and the alternative inline catalyst reductions can improve flow rate control in viable operating regimes.
[0050] The chromium-based catalyst compositions disclosed herein may include chromium-based catalysts and reducing agents. Chromium-based catalysts used in embodiments of the present invention can include chromium oxide catalysts, silyl chromate catalysts or a combination of both chromium oxide and silyl chromate catalysts.
[0051] The chromium compounds used to prepare chromium oxide catalysts can include CrO3 or any compound convertible to CrO3 under the activation conditions used. Many compounds convertible to CrO3 are disclosed in US Patents 2,825,721, 3,023,203, 3,622,251, and 4,011,382 and include chromic acetylacetonate, chromic halide, chromium nitrate, chromium acetate, chromium sulfate, ammonium chromate, ammonium dichromate or other soluble salts containing chromium. In some modalities, chromic acetate can be used.
[0052] The silyl chromate compounds used to prepare the silyl chromate catalysts disclosed herein may include bis-triethylsilyl chromate, bis-tributylsilyl chromate, bis-triisopentylsilyl chromate, bis-tri-2-ethylhexylsilyl chromate, bis-tridecylsilicate chromate, bis-tri (tetradecyl) silyl chromate, bis-tribenzylsilyl chromate, bis-triphenylethylsilyl chromate, bis-triphenylsilyl chromate, bis-tritolylsilyl chromate, bis-trixylsilyl chromate, bis-chromate trinaftilsilil, bis-triethylphenylsilyl chromate, bis-trimethylnaphthylsilyl chromate, polydiphenylsilyl chromate and polydiethylsilyl chromate. Examples of such catalysts are described, for example, in US Patent 3,324,101, 3,704,287 and 4,100,105, among others. In some embodiments, bis-triphenylsilyl chromate, bis-tritolylsilyl chromate, bis-tri-xylylsilyl chromate and bis-trinaftylsilyl chromate can be used. In other embodiments, bis-triphenylsilyl chromate can be used.
[0053] In some embodiments of the present description, silyl chromate compounds can be deposited on conventional catalyst supports or bases, for example, inorganic oxide materials. In some embodiments of the present description, the chromium compound used to produce a chromium oxide catalyst can be deposited on conventional catalyst supports. The term "support", as used herein, refers to any support material, a porous support material, in an exemplary embodiment, including inorganic or organic support materials. In some embodiments, desirable vehicles may be inorganic oxides that include Group 2, 3, 4, 5, 13 and 14 oxides, and more particularly, inorganic oxides of Group 13 and 14 atoms. The group element notation in this specification it is as defined in the Periodic Table of Elements according to the IUPAC 1988 notation (IUPAC Nomenclature of Inorganic Chemistry 1960, Blackwell Publ., London). Groups 4, 5, 8, 9 and 15 correspond respectively to Groups IVB, VB, IIIA, IVA and VA of the Deming notation (Chemical Rubber Company Chemistry and Physics Manual, 48th edition) and to IVA, VA, IIIB, IVB Groups and VB of the IUPAC 1970 notation (Kirk-Othmer Encyclopedia of Chemical Technology, 2nd edition, Vol. 8, p. 94). Non-limiting examples of support materials include inorganic oxides such as silica, alumina, titania, zirconia, thorium, as well as mixtures of such oxides such as, for example, silica-chromium, silica-alumina, silica-titania and the like.
[0054] The inorganic oxide materials that can be used as a support in the catalyst compositions according to the present invention are porous materials having varying surface area and particle size. In some embodiments, the support may have a surface area in the range of 50 to 1000 square meters per gram and an average particle size of 20 to 300 micrometers. In some embodiments, the support may have a pore volume of about 0.5 to about 6.0 cm3 / g and a surface area of about 200 to about 600 m2 / g. In one embodiment, the support can have a pore volume of about 1.1 to about 1.8 cm3 / g and a surface area of about 245 to about 375 m2 / g. In other embodiments, the support can have a pore volume of about 2.4 to about 3.7 cm 3 / g and a surface area of about 410 to about 620 m2 / g. In still other embodiments, the support can have a pore volume of about 0.9 to about 1.4 cm3 / g and a surface area of about 390 to about 590 m2 / g. Each of the above properties can be measured using conventional techniques as they are known in the art.
[0055] In some embodiments, the support materials include silica, amorphous silica in particular, and more particularly the high surface area of amorphous silica. Such support materials are commercially available from a variety of sources. Such sources include W.R. Grace and Company which markets silica support materials under the trade names of Sylopol 952 or Sylopol 955 and PQ Corporation, which markets silica support materials under various trade names, including ES70. Silica is in the form of spherical particles, which are obtained by a spray drying process. Alternatively, PQ Corporation markets silica support materials under trade names like MS3050 that are not spray dried. As acquired, all of these silicas are not calcined (that is, not dehydrated). However, the silica that is calcined before purchase can be used in catalysts of the present disclosure.
[0056] In other embodiments, supported chromium compounds that are commercially available, such as chromium acetate, can also be used. Commercial sources include W.R. Grace and Company which markets chromium in silica support materials under trade names, such as Sylopol 957, Sylopol 957HS or Sylopol 957BG and PQ Corporation, which markets chromium in silica support materials under various trade names, such as ES370. The chromium in the silica support is in the form of spherical particles, which are obtained by a spray drying process. Alternatively, PQ Corporation markets silica support materials under trade names such as C35100MS and C35300MS that are not spray dried. As acquired, all of these silicas are not activated. However, if available, the chromium supported on silica that is activated before purchase can be used in catalysts of the present disclosure.
[0057] The activation of the supported chromium oxide catalyst can be carried out at almost any temperature of about 300 ° C up to the temperature at which the substantial sintering of the support takes place. For example, activated catalysts can be prepared in a fluidized bed, as follows. The passage of a stream of dry air or oxygen through the supported chromium-based catalyst during activation helps in the displacement of any water from the support and converts, at least partially, the chromium species into Cr + 6.
[0058] The temperatures used to activate the chromium-based catalysts are often high enough to allow the rearrangement of the chromium compound in the support material. Maximum activation temperatures of about 300 ° C to about 900 ° C are acceptable for periods of more than 1 hour to 48 hours. In some embodiments, the supported chromium oxide catalysts are activated at temperatures from about 400 ° C to about 850 ° C, from about 500 ° C to about 700 ° C and from about 550 ° C to about 650 ° C. Examples of activation temperatures are about 600 ° C, about 700 ° C and about 800 ° C. The selection of an activation temperature can take into account the temperature restrictions of the activation equipment. In some embodiments, the supported chromium oxide catalysts are activated at a chosen peak activation temperature over a period of about 1 to about 36 hours, from about 3 to about 24 hours, and from about 4 to about 6 hours. Examples of peak activation times are about 4 hours and about 6 hours. Activation is typically carried out in an oxidative environment; for example, very dry air or oxygen is used and the temperature is kept below the temperature at which substantial support sintering occurs. After the chromium compounds are activated, a free flowing powdered chromium oxide catalyst is produced.
[0059] The cooled activated chromium oxide catalyst can then be slurried and placed in contact with a reducing agent, fed at a selected feed rate for a selected period, to result in a catalyst composition with a response of flow index within a selected range. The solvent can then be substantially removed from the slurry to result in a dry, free flowing catalyst powder, which can be fed to a polymerization system as is or slurried into a suitable liquid prior to feeding.
[0060] In a class of modalities, because the organometallic components used in the preparation of the catalysts and catalyst compositions of the present disclosure can react with water, the support material should preferably be substantially dry. In embodiments of the present description, for example, when the chromium based catalysts are silyl chromates, the untreated supports can be dehydrated or calcined prior to contact with the chromium based catalysts.
[0061] The support can be calcined at high temperatures to remove water, or to effect a chemical transformation on the surface of the support. The calcination of the support material can be carried out using any procedure known to those skilled in the art, and the present invention is not limited by the calcination method. Such a method of calcination is disclosed by T. E. Nowlin et al., "Ziegler-Natta Catalysts on Silice for Ethylene Polymization", J. Polym. Sci., Part A: Polymer Chemistry, vol. 29, 1167-1173 (1991).
[0062] For example, calcined silica can be prepared in a fluidized bed, as follows. A silica support material (eg Sylopol 955) is heated in stages or steadily from room temperature to the desired calcination temperature (eg 600 ° C) during the passage of dry nitrogen or dry air through or on the support material. The silica is maintained at approximately this temperature for about 1 to about 4 hours, and then it is allowed to cool to room temperature. The calcination temperature mainly affects the number of OH groups on the support surface; that is, the number of OH groups on the support surface (silanol groups, in the case of silica) is approximately inversely proportional to the drying or dehydration temperature: the higher the temperature, the lower the content of hydroxyl groups.
[0063] In some embodiments of the present disclosure, support materials are calcined at a peak temperature of about 350 ° C to about 850 ° C, in some embodiments, between about 400 ° C to about 700 ° C , in other modalities, and from about 500 ° C to about 650 ° C, in still other modalities. Examples of calcination temperatures are about 400 ° C, about 600 ° C, and about 800 ° C. In some embodiments, the total calcination times are from about 2 hours to about 24 hours, from about 4 hours to about 16 hours, from about 8 hours to about 12 hours. Exemplary times at peak calcination temperatures are about 1 hour, about 2 hours and about 4 hours.
[0064] In some embodiments, the silyl chromate compound can be brought into contact with the calcined support to form a "bonded catalyst". The silyl chromate compound can then be brought into contact with the calcined support material in any of the forms known to those skilled in the art. The silyl chromate compound can be contacted with the support by any suitable means, such as in a solution, paste or solid form, or some combination thereof, and can be heated at any desirable temperature for a sufficient specified period. to effect a desirable chemical / physical transformation.
[0065] This contact and this transformation are generally carried out in a non-polar solvent. Suitable non-polar solvents can be materials that are liquid in contact and temperature transforming and in which some of the components used during the preparation of the catalyst, that is, silyl chromate compounds and reducing agents, are at least partially soluble . In some embodiments, non-polar solvents are alkanes, particularly those containing about 5 to about 10 carbon atoms, such as pentane, isopentane, hexane, isohexane, n-heptane, iso-heptane, octane, nonane and decane . In other embodiments, cycloalkanes may also be used, particularly those containing about 5 to about 10 carbon atoms, such as cyclohexane and methylcyclohexane. In still other embodiments, the non-polar solvent can be a mixture of solvents. Examples of non-polar solvents are isopentane, isohexane and hexane. In some embodiments, isopentane can be used due to its low boiling point which makes its removal quick and convenient. The non-polar solvent can be purified before use, such as by degassing under vacuum and / or heat or by percolation through silica gel and / or molecular sieves, to remove traces of water, molecular oxygen, polar compounds and other materials capable of adversely affect the activity of the catalyst.
[0066] The mixture can be mixed for a time sufficient to support or react the silyl chromate compound on the silica support. The reducing agent can then be brought into contact with this suspension, where the reducing agent is fed at a selected feed rate for a selected period to result in a catalyst with a flow index response within a selected range. Alternatively, after supporting the silyl chromate compound on the support and before adding the reducing agent, the solvent can then be substantially removed by evaporation, to produce a free flowing supported silyl chromate on the support. The silyl chromate thus supported can again be slurried in it or in a different non-polar solvent and contacted with a reducing agent to result in a selected flow index response.
[0067] Once the catalyst is supported, and in the case of activated chromium oxide catalysts, the chromium-based catalyst composition can then be slurried in a non-polar solvent, prior to the addition of the reducing agent . The supported catalyst can be supported chromium oxide catalysts, silyl chromate catalysts or a mixture of both. This paste is prepared by mixing the supported catalyst with the non-polar solvent. In some embodiments, the supported silyl chromate compound is not dried prior to the addition of the reducing agent, but is instead left as a paste in the non-polar solvent, for reasons such as reduced costs.
[0068] The chromium-based catalysts of the present invention are then brought into contact with a reducing agent. The reducing agents used can be composed of organoaluminium, such as aluminum alkyds and alkyl aluminum alkoxides. Alkyl aluminum alkoxides, of the general formula R2AlOR, may be suitable for use in the modalities of this disclosure. The R or alkyl groups of the previous general formula may be the same or different, they may have from about 1 to about 12 carbon atoms in some embodiments, about 1 to about 10 carbon atoms in other embodiments, about 2 to about 8 carbon atoms in still other embodiments, and about 2 to about 4 carbon atoms in other embodiments. Examples of alkyl aluminum alkoxides include, but are not limited to, aluminum diethyl methoxide, aluminum diethyl ethoxide, aluminum diethyl propoxide, aluminum diethyl isopropoxide, aluminum diethyl tert-butoxide, aluminum dimethyl ethoxide, aluminum diisopropyl ethoxide , isobutyl aluminum ethoxide, methyl ethyl aluminum ethoxide and mixtures thereof. Although the examples use diethyl aluminum ethoxide (DEAlE), it should be understood that the disclosure is not so limited. In the following examples, in which DEAlE is used, other aluminum alkynes (for example, trialkylalumin, triethylalumin or TEAL, etc.) or alkyl aluminum alkoxides, or mixtures thereof, may be used.
[0069] The reducing agent can be added to a mixture of a supported silyl chromate catalyst with a non-polar solvent in a catalyst mixing vessel or other catalyst preparation vessel. The reducing agent can be added to a mixture of an activated chromium oxide catalyst with a non-polar solvent in a catalyst mixing vessel. The reducing agent can be added to a mixture of silyl chromate catalysts and catalyst based on chromium oxide activated in a non-polar solvent in a catalyst mixing vessel. When both chromium oxide-based catalysts and silyl chromate-based catalysts are used together in this description, each catalyst is typically deposited on a separate support and receives different calcination or activation treatments before mixing together. Again, the reducing agent can include an organoaluminium compound, an aluminum alkyl, an aluminum alkyl alkoxide, such as diethylaluminium ethoxide (DEAlE), a trialkylaluminium, such as triethylaluminium (TEAL), a mixture of DEAlE and TEAL and other organoaluminium compounds and so on.
[0070] The addition of the reducing agent to the catalyst paste can be carried out at elevated temperatures and under an inert atmosphere, such as up to 7 bar (100 psig) of nitrogen head pressure. For example, the paste can be kept at a temperature between about 30 ° C and 80 ° C during mixing of the reducing agent. In other embodiments, the mixture can be maintained at a temperature between about 40 ° C and about 60 ° C. In other embodiments, the mixture can be maintained at a temperature between about 40 ° C and about 50 ° C, such as about 45 ° C.
[0071] To achieve a catalyst or reduced catalyst composition, having a desired flow index response, or a flow index response within a selected range, and which produces polymers with desired attributes, the reducing agent may need be well dispersed through the catalyst mixture and throughout each particle. Alternatively, to obtain a catalyst composition with a different response flow index or polymer with other attributes, the reducing agent may need to be dispersed non-uniformly over the catalyst particles and / or within each particle. The degree of non-uniformity can be determined by the desired polymer attributes (such as the molecular weight and the range of the molecular weight distribution) and the desired catalyst flow index response under a given set of reactor conditions. To this end, the reducing agent is added at a selected feed rate over a selected period to the chromium-based catalyst slurry, where the slurry can be stirred at a selected stir rate. For example, to achieve a catalyst composition with a low response flow index, the total amount of reducing agent to be combined with the catalyst paste can be added over a short period and / or at a slow stirring rate. . On the other hand, to achieve a catalyst composition with a higher flow index response, the total amount of reducing agent can be added over a longer period. In this case, the stirring speed can be slow, medium or fast, in order to further adapt the flow index response. In some examples, the reducing agent can be added over period intervals of 5 seconds to 120 minutes, 1 to 5 minutes, 5 to 15 minutes, 10 to 110 minutes, 30 to 100 minutes, and so on. against. For example, where the catalyst composition includes a silyl chromate, the reducing agent can be added over a period ranging from about 30 seconds to about 10 minutes. After adding the reducing agent, the reducing agent can be allowed to react with the catalyst slurry for a specified reaction time. In some embodiments, the reducing agent can be allowed to react with the catalyst slurry for a reaction time at intervals of about 5 minutes to about 240 minutes, or about 30 minutes to about 180 minutes, and so on. .
[0072] As mentioned, the flow index response can be influenced by agitation. Catalyst preparations with similar ratios or fillers of chromium reducing agent or catalyst and made with equivalent rates and addition times can result in catalysts with different flow index responses, resulting from different degrees of agitation in the catalyst mixing vessel. during the addition and reaction of the reducing agent. Agitators useful for performing agitation during the catalyst preparation methods disclosed herein may include agitators and helical tape and conical agitators. In some embodiments, agitators may include a combination-type agitator, such as the combination of a helical ribbon-type agitator or a conical agitator with a drill, turbine impeller, paddle or other type of mixing device, in that the different types of agitators can be operated at the same or different rpms.
[0073] Increased agitation rates can provide catalysts with a higher flow index response compared to decreased agitation rates that provide catalysts with a lower flow index response. A particular benefit for some embodiments is that higher agitation rates can be used to facilitate the rate of addition of reducing agent to be increased (and the time of addition to be decreased), while resulting in a catalyst having a response of equivalent response flow index. As used herein, "agitation rate" generally refers to the specific rotation of the impeller for a ribbon mixer or other agitation devices where the diameter of the agitator does not play an important role in the degree of agitation achieved, and refers to the peak impeller speed for agitators where the agitator diameter affects the degree of mixing, as for a turbine impeller. The agitation rates useful in this context can be dependent on the size of the reactor and the type of impeller. In some embodiments, such as when using a helical ribbon impeller, the rate of agitation can be in the range of about 5 to about 200 rpm, from about 10 to about 180 rpm, from about 15 rpm to about 50 rpm, and the like.
[0074] Other techniques, such as using jet streams of fluid introduced into the container, mixing and other mixing techniques can be used in addition to or in place of the impeller stirrer to agitate or mix the paste in the mixing container. In embodiments employing a rotary stirrer having a shaft and impeller (s), a smaller batch size in certain embodiments can lead to a higher flow rate response of DEAlE-reduced chromium oxide catalysts. While not wishing to be confined by theory, this may be due to one or more of the following: better mixing on the paste surface of any aggregates or gels that form and / or the DEAlE being added due to the paste surface being below the top of the impeller; lower total height of the batch, thus improving the top-down mixture of DEAlE with the solids; greater penetration speed of the DEAlE stream added to the paste surface due to the fall from a greater height; or differences in drying profiles that may result from a smaller batch size.
[0075] During the reduction reaction, for a relatively larger batch size, the level of the paste mixture in the mixing vessel can be maintained above the impeller region along the agitator axis. For a relatively smaller batch size, the level of the paste mixture in the mixing vessel can be maintained at or in the rotor region along the agitator axis. As can be appreciated, agitators including the aforementioned helical ribbon agitators and other agitators generally have an impeller (s) arranged along the axis of the agitator. In the examples, the upper portion of the agitator shaft may be free of an impeller. Thus, for a larger batch size, the level of the paste in the mixing vessel can rise to this impeller-free region in the upper portion of the agitator shaft. On the other hand, for a small batch size in certain examples, the level of the slurry in the mixing vessel may be below this impeller-free region and, instead, in an impeller region of the agitator.
[0076] However, the reducing agent is usually added to the paste surface in the mixing vessel. Other locations for the addition of the reducing agent can be used to further adjust the flow rate response of the catalyst. Selected feed rates and selected addition times can be interrupted briefly to allow refilling of a reducing agent supply container or when an empty reducing agent supply container is replaced. A brief interruption in the flow of the reducing agent is not believed to significantly affect the flow index response resulting from the catalyst. In addition, the supply system may have a reducing agent loading container large enough to avoid interruption while a reducing agent supply container or shipping container is replaced. As discussed in detail below, the reducing agent can be added to the mixing vessel so that the dispersion of the reducing agent in the slurry mixture of the reducing reaction is increased.
[0077] In some embodiments, contact of the reducing agent and chromium-based catalyst can occur at a selected rate of reduction agent supply for a selected time at a selected agitation rate, followed by an outlet temperature of drying line of the specified catalyst, resulting in a catalyst composition with a flow index response within a selected range. For example, in a commercial scale catalyst manufacturing equipment, increased agitation can provide a catalyst with a higher flow index response, while allowing the reducing agent to be added at faster rates, reducing cycle time of the lot and the manpower needs. In another example, where existing commercial scale catalyst manufacturing equipment is limited in the rate of agitation, the reducing agent can be added slowly to obtain a desired adaptation to a high flow rate response. In addition, the drying temperature or drying line outlet temperature of the catalyst can be decreased (for example, by 10 ° C, 15 ° C or 20 ° C, as can the drying temperature decrease to 60 ° C 70 ° C, 75 ° C or 80 ° C in certain examples) to achieve a desired adaptation to a high flow rate response.
[0078] In some exemplary embodiments, the chromium-based catalyst can be a silicon-supported chromium oxide catalyst. This silica-supported chromium oxide can be prepared from chromium acetate in silica precursors, commercially available under trade names such as Sylopol 957HS, from W.R. Grace and Company, and C35100MS, or C35300MS, from PQ Corporation. Chromic acetate in silica precursors can be heated at temperatures of about 600 ° C for about six hours, under oxidation conditions to produce a chromium oxide catalyst. Rates of temperature rise during heating can be specified, for example, in the range of 40 to 120 ° C per hour, and various retentions at specified temperatures can be conducted for purposes such as allowing moisture and other surface species to be released and purged from the container to increase the higher conversion of Cr + 3 to Cr + 6. In examples, the fluidizing gas is often nitrogen initially, until the end of a retention at a temperature of 300 to 500 ° C in which some of the organic fragments are decomposed. Then, switching to air as a fluidizing gas can occur in which the remaining organic compounds are burned and a temperature exotherm occurs. In embodiments, after the oxidation step, the activated chromium oxide catalyst is cooled and transferred to a stirred catalyst mixture vessel. An amount of non-polar hydrocarbon solvent, such as isopentane, can be added to form a paste in which the solids are sufficiently suspended.
[0079] A selected amount of DEAlE can then be added to the chromium oxide catalyst during an addition period in the range of about 30 seconds to about 500 minutes, while stirring the resulting mixture at a stirring speed in the range of about 15 rpm to about 200 rpm. In other modalities, the selected period can be within the range of about 30 minutes to about 240 minutes; from about 60 minutes to about 180 minutes in other modalities; and from about 90 to about 120 minutes in still other modalities. In some embodiments, a selected amount of DEAlE can be added to the chromium oxide catalyst over a period in the range of about 40 to about 80 minutes, while stirring the resulting mixture at a stirring speed of 30-40 rpm. The mixture can then be allowed to react for a reaction time in the range of about 30 minutes to about 180 minutes.
[0080] In other embodiments, the chromium-based catalyst can be a silyl chromate catalyst supported on silica. This silica-supported silyl chromate catalyst can be prepared from a calcined silica support at temperatures of about 600 ° C for a period ranging from about one hour to about four hours and subsequently allowed to react with silica chromate. bis (triphenylsilyl), for example, in a paste in a non-polar hydrocarbon solvent such as isopentane. A selected amount of DEAlE can then be added to the silyl chromate catalyst slurry over an addition period in the range of about 0.5 to about 10 minutes, while stirring the resulting mixture at a rate of stirring in the range of about 15 rpm to about 50 rpm. In a particular embodiment, a selected amount of DEAlE can be added to the silyl chromate catalyst over a period in the range of about 1 to about 3 minutes, while stirring the resulting mixture at a speed of stirring in the range of 30- 40 rpm. The mixture can then be allowed to react for a reaction time in the range of about 30 minutes to about 180 minutes.
[0081] In several embodiments, the selected agitation rate can be less than 70 rpm and the addition time of the selected reducing agent can be less than 20 minutes. In other embodiments, the stirring rate selected may be greater than 70 rpm and the time for adding the selected reducing agent may be less than 20 minutes. In yet other embodiments, the stirring rate selected may be greater than 70 rpm and the addition time of the selected reducing agent may be greater than 20 minutes.
[0082] After the addition of the reducing agent followed by a suitable period to allow the reaction, such as 0 to 2 hours, the catalyst slurry is further heated to remove the non-polar solvent. Drying can result in the slurry transition from a viscous slurry to a partially dried slurry or slurry to a free flowing powder. Accordingly, helical ribbon stirrers can be used in vertical cylindrical mixing vessels to accommodate varying mixing viscosities and stirring requirements. The agitators can have single or double helical strips and can optionally include a central axis drill or other more complex secondary agitator. Drying can be conducted at pressures above, below, or at normal atmospheric pressure, provided that contaminants, such as oxygen, are generally strictly excluded. Exemplary drying temperatures can range from 0 ° C to as much as 100 ° C, from about 40 ° C to about 85 ° C, from about 50 ° C to about 75 ° C, from about 55 ° C at about 65 ° C and the like. Examples of drying times can vary from about 1 to about 48 hours, from about 3 to about 26 hours, from about 5 to about 20 hours, and so on. In a particular example of a drying temperature of about 60 ° C, the drying time is extended to about 21 hours or more, in that particular example. Following the drying process, the catalyst can be stored under an inert atmosphere until use.
[0083] As described above, the flow index response of chromium-based catalysts can be adapted to meet various commercial needs by the controlled addition of a reducing agent to a paste of a chromium solid supported in a non-polar solvent under controlled agitation. For a given chromium-based catalyst, the supported chromium solid can be made into slurry, brought into contact with a selected amount of a reducing agent fed at a selected feed rate over a selected period at a rate of agitation selected, resulting in a chromium reducing agent for the reducing agent or a desired chromium load on the catalyst. The solvent used to slurry the catalyst can then be removed, such as by drying at an adjustable drying temperature, to give a free flowing dry catalyst composition. The chromium-based catalyst has a flow index response of selected to do with polymer with desired polymer attributes. This catalyst composition can then be fed to a polymerization reactor as it is, or slurried into a suitable liquid prior to feeding into a polymerization reactor.
[0084] Although the general procedure outlined above may apply to chromium catalysts in general, the procedure can be changed according to the particular type of chromium-based catalyst to be used. For example, the above procedure can be manipulated for catalysts based on silyl chromate and for catalysts based on chromium oxide, the latter typically requiring an activation step or an oxidation step to generate Cr + 6 species. before reduction. In addition, the process can be adjusted depending on whether the complete catalyst preparation is conducted, or whether a supported chromium compound is purchased and treated according to the modalities described herein.
[0085] Chromium-based catalysts formed by the processes described above can have a chromium load on the support that varies from about 0.15 to about 3 weight percent in modalities; from about 0.2 to about 0.3 weight percent in other embodiments; from about 0.4 to about 0.6 weight percent in other modalities; and from 0.7 to about 1.2 weight percent in other modalities. Chromium-based catalysts formed by the processes described above can have a molar ratio of chromium reducing agent ranging from about 0.5 to about 8, in some embodiments; from about 2 to about 7, in other modalities; and from about 3.0 to about 5.5, in still other modalities. Exemplary reduction of chromium-based catalyst
[0086] In view of the above, including the aforementioned materials, equipment and techniques, FIG. 1 is an exemplary catalyst reduction system 100 having a mixing vessel 102 for treating a chromium-based catalyst 104 to give a reduced chromium-based catalyst 106 that can be used in the polymerization of olefin to polyolefin. Inlet catalyst 104 can generally be a catalyst supported, for example, supported on silica, such as silica dioxide or SiO2. Of course, other catalyst supports are applicable. In addition, catalyst 104 can already be activated. In certain embodiments, the chromium-based catalyst 104 is activated in an activation system upstream of the catalyst (not shown) before being fed into the mixing vessel 102.
[0087] The catalyst stream 104 fed to the mixing vessel 102 may be a dry catalyst 104 or a mixture of catalyst 104 and an inert solvent or mineral oil, and so on. The inert solvent can be an alkane, such as isopentane, hexane, and the like. Catalyst 104 can be provided from an upstream storage container, the feed tank, or container, for example. In particular, catalyst 104 can be pumped (via a pump) or transferred under pressure (via nitrogen or solvent pressure, for example) through the tubing of the storage container, the supply tank or the container to the container of mixing 102.
[0088] In one example, catalyst 104 is a dry catalyst powder and is transported with nitrogen from a storage container. The storage container can be in weighing cells to indicate the amount or weight of catalyst fed to the mixing vessel 102. The amount (for example, pounds) of catalyst 104 transported to the mixing vessel 102 can be specified for the load . A solvent 107 (e.g., non-polar hydrocarbon solvent), such as isopentane, is added to form a slurry in mixing vessel 102 in which at least a majority of the catalyst solids 104 are suspended. A specified amount of solvent 107 can be added for a given batch reduction in mixing vessel 102. Solvent 107 can be introduced directly into mixing vessel 102, as shown, or can be added, for example, via the same inlet. feed or nozzle used by the reducing agent 108, typically before the reducing agent is fed.
[0089] Although the reduction system 100 may be a continuous, semi-batch or batch system, the illustrated embodiment is generally a batch system in a sense where a charge from catalyst 104 is fed to mixing vessel 102, a solvent loading 107 is fed to mixing vessel 102, stirring is initiated, and a load of reducing agent 108 is fed over time to mixing vessel 102 for a given catalyst loading 104. Of course, other settings and actions are applicable. The residence time of the catalyst load 104 in the mixing vessel 102 gives the reaction of substantially all of the reducing agent present 108 with the catalyst 104 to produce the reduced catalyst 106.
[0090] The reducing agent 108 supplied to the mixing vessel 102 can generally be an organoaluminium compound and can be either pure or diluted in a non-polar solvent. As discussed above, a variety of reducing agents and inert solvents can be employed. In addition, the additional solvent can be added to the mixture in the mixing vessel 102. In a particular example, the reducing agent is DEAlE 108, and the current of the reducing agent 108 is 25 weight percent DEAlE in isopentane. Naturally, DEAlE can be diluted in other concentrations and in other solvents.
[0091] In operation, a charge of the activated catalyst 104 is fed to the mixing vessel 102. A solvent charge 107 may be fed to the mixing vessel 102 and stirring started, including before the introduction of the reducing agent 108. In embodiments, catalyst 104 can be fed in solvent to mixing vessel 102. In a particular example, activated catalyst 104 is fed at an isopentane rate to mixing vessel 102. A reducing agent 108, also optionally diluted in the solvent, an adjustable feed rate is added to the mixing vessel 102 to react with catalyst 104. Note that for embodiments with reducing agent 108 diluted in solvent, additional solvent 107 can be added additionally, including before adding the reducing agent stream 108 to a given batch. In one example, the reaction or reduction reaction in the mixing vessel is conducted at a temperature of about 45 ° C, or at 2 ° C of about 45 ° C, and a pressure of about 30 pounds per square inch (psig). Other temperatures and pressures are applicable.
[0092] In certain embodiments, the length of time to feed the reducing agent 108 into the mixing vessel 102 can be as long as 40 minutes, and longer. At the end of the feed of the reducing agent 108, the contents of the mixing vessel 102 can receive additional residence time for the reaction of the reducing agent 108 with the catalyst in the mixing vessel 102. The catalyst can be subsequently dried, as in place in the mixing vessel 102, to expel the solvent 110 to give a (reduced) product catalyst 106 which is substantially dry. The reduced chromium-based catalyst 106 can be discharged into a collection container 112, such as a storage container or container (e.g., a cylinder) and the like. Generally, the collection vessel 112 can have a substantially inert atmosphere.
[0093] Furthermore, as indicated in the discussion throughout this disclosure, the mixing vessel 102 can typically have an agitator, for example, an agitator 210 in FIG. 2, to stir and mix the contents (catalyst, reducing agent, solvent, etc.) in the mixing vessel 102. Both the feed rate (for example, mass per time or volume per time) of the reducing agent 108 to the mixing vessel 102, and the stirring speed (for example, in revolutions per minute or rpm) of the mixing vessel 102 stirrer can be adjusted to give a desired or specified flow index response of the reduced chromium-based catalyst 106.
[0094] Furthermore, after the reaction of the reducing agent 108 with the catalyst 104 in the mixing vessel 102, the produced reduced catalyst 106 can be dried as in place in the mixing vessel 102. Indeed, after the reaction of the agent reduction pressure 108 with the catalyst (in an example, at a reaction temperature of 45 ° C), the drying temperature of the catalyst (for example, 55 ° C, 60 ° C, 65 ° C, 70 ° C, 75 ° C, 80 ° C, 85 ° C, etc.) or the drying line outlet temperature can be adjusted to give a desired or specified flow index response of the reduced chromium-based catalyst 106.
[0095] In the illustrated embodiment, a heat transfer system 114 provides a means of transferring heat from a coating of the mixing vessel 102 to heat or cool the contents of the mixing vessel 102 to obtain the desired temperature, including the temperature reaction temperature and the drying temperature of the subsequent catalyst or the drying line outlet temperature of the contents of the mixing vessel 102. As discussed below with reference to FIG. 2, the heat transfer system 114 may include heat exchangers to provide cooling and heating of the heat transfer medium. Furthermore, as would be clearly understood by one skilled in the art with the benefit of the present disclosure, the contents of the mixing vessel 102 including the catalyst may be at the reaction temperature or at the drying temperature, or may approach and reach close (for example, within 4 ° C) of the reaction temperature or the drying temperature, depending on the temperature control scheme used.
[0096] In some embodiments, the heat transfer system 114 and the control system 116 can directly control the temperature of the contents of the mixing vessel 102. In other words, a temperature setpoint can be specified and the input for the contents of the mixing vessel 102, and the operating temperature of the contents of the mixing vessel 102 controlled to adjust the temperature set point of the heat transfer medium to the coating of the mixing vessel 102. Thus, for a reaction temperature example of 45 ° C, the temperature setpoint is indicated as 45 ° C and the contents of the mixing vessel measured and maintained at 45 ° C during the reduction reaction. Likewise, for an exemplary drying temperature of 60 ° C, the temperature setpoint is specified at 60 ° C and the contents of the mixing vessel measured and maintained at 60 ° C. In such embodiments, the temperature controller for the contents of the mixing vessel 102 that receives the set of inserted points for the reaction temperature and the drying temperature can be a master controller. This master controller can provide a secondary setpoint to a slave temperature controller that adjusts the temperature of the heat transfer medium supply to the lining of the mixing vessel 102 to maintain the contents of the mixing vessel 102 at the primary setting point. reaction temperature or drying temperature.
[0097] However, in other modalities, a master / slave control configuration is not used. Instead, the temperature of the heat transfer medium (for example, supply to the coating) is designated with a specified set point and entered as the coating temperature for the reaction temperature or drying temperature. Thus, for an exemplary reaction temperature of 45 ° C, the coating temperature set point of mixing vessel 102 is specified as 45 ° C, the coating temperature measured and maintained at 45 ° C during the reduction reaction and the temperature of the contents of the mixing vessel 102 is at about 45 ° C at steady state during the reduction reaction. The steady-state temperature of the contents of the mixing vessel 102 with the coating temperature setpoint as the reaction temperature can generally be the reaction temperature. In other words, due to the exothermic nature of the reduction reaction, the temperature of the contents of the mixing vessel 102 can generally be the same or similar to or slightly higher than the temperature of the coating during the steady state of the reduction reaction. However, for an exemplary drying temperature of 60 ° C, the setpoint of the coating temperature of the mixing vessel 102 is specified as 60 ° C, the coating temperature measured and maintained at 60 ° C during drying of the catalyst. reduced 106 and the temperature of the contents of the mixing vessel 102 including the catalyst 106 reaches close to 60 ° C (e.g., about 64 ° C) at steady state during drying. The steady-state temperature of the contents of the mixing vessel 102 for the coating temperature setpoint as the drying temperature is here defined as the drying line outlet temperature. Altogether, for a coating temperature of the mixing vessel 102 as a primary setpoint, the contents of the mixing vessel 102 may reach a line outlet temperature close to (for example, within 4 ° C) the coating temperature . It should be noted that when controlling the coating temperature adjustment bridge as the drying temperature, the drying line outlet temperature (eg, catalyst temperature 64 ° C) may exceed the drying temperature (for example, coating temperature of 60 ° C) due to the contribution of heat added by the mechanical energy of the agitator or agitation, for example,
[0098] In certain embodiments, during drying of catalyst 106, the pressure of mixing vessel 102 may be decreased, including incrementally, to values as low as about 1 psig, or even at a vacuum to facilitate drying of catalyst 106 in the mixing vessel 102. During drying, including when the pressure is reduced, such as at 1 psig or in a vacuum, the temperature of the reduced catalyst can drop substantially below the coating temperature and below the drying or outlet temperature of line for drying the contents in the mixing vessel 102. As drying proceeds and nears completion, the temperature of the contents of the mixing vessel 102 may rise close to the coating temperature and reach a substantially constant temperature. As mentioned, this substantially constant temperature of the solid material can be referred to as the drying line outlet temperature and is the temperature that can be manipulated to adjust the flow rate response of the catalyst. In general, the line outlet drying temperature can be within a few degrees of the coating temperature for a heat transfer system, which controls the coating temperature to the set point. For example, again, a drying temperature of 60 ° C (coating temperature) can give a drying line outlet temperature of about 64 ° C (temperature of the contents in the mixing vessel) in a particular example. As regards the behavior of the drying process in certain examples, the pressure in the mixing vessel 102 can be reduced at the start of drying and the coating temperature adjusted (for example, high) to the drying temperature of 60 ° C, for example. However, the slurry temperature of the catalyst 106 in the mixing vessel 102 may initially decrease to as low as about 30 ° C or below, for example, due to evaporative solvent cooling. Generally, once the free liquid outside the catalyst pores and on the catalyst surface is evaporated, the temperature of the catalyst can begin to rise towards and beyond the drying temperature (coating temperature of 60 ° C in these examples) to a exit temperature of drying line (eg 64 ° C). The time for the catalyst in the mixing vessel 102 to reach 60 ° C and the eventual drying line outlet temperature of 64 ° C can be several hours. Thus, in certain cases, a reported drying time of 18 hours, for example, can represent 6-9 hours of the catalyst at a drying line outlet temperature (for example, 64 ° C) near (within 4 ° C) ) of the drying temperature of 60 ° C (coating temperature). Naturally, other temperatures and times of drying and drying out of line and behavior of the drying process are applicable.
[0099] A control system 116 can provide control and adjustment of the process variables mentioned above in the preparation and reduction of the catalyst. Process variables can include the rate of reduction agent feed 108 and the agitation rate (rpm) of the agitator. Process variables can include the reaction temperature, pressure and retention time in the mixing vessel 102, and the drying temperature, pressure and time in the mixing vessel 102, and so on. The control system 116 can include any number of units, such as a distributed control system (DCS), a programmable logic controller (PLC) and the like.
[0100] In some embodiments, a filter / paste system 118 can optionally be installed and employed in addition to, or instead of, evaporating the solvent to dry catalyst 106. In particular embodiments, no significant thermal drying of the catalyst 106 in mixing vessel 102. Instead, catalyst paste 106 in a solvent is discharged from mixing vessel 102 to the optional filter / paste system 118. In certain embodiments, the temperature of mixing vessel 102 may be reduced, such as at 25 ° C in one example, prior to the discharge of catalyst slurry 106 into the filter / slurry system 118. Of course, other filtration temperatures can be used, such as in the range of 30 ° C to 70 ° C, or higher.
[0101] In the filter / paste system 118, the catalyst paste 106 can be filtered to remove the solvent to give a catalyst 106, with residual solvent, which is sent to the collection vessel 112. As an additional alternative, the catalyst 106 after filtration can again be slurried with another alkane solvent or mineral oil, for example, before being sent to the collection vessel 112. Avoid such hot drying of the catalyst in the mixing vessel 102 and instead further filtering catalyst 106 can provide a reduced catalyst 106 with a different flow index response. In certain filtration modalities, the flow rate response is greater than if heat drying, which can be beneficial when a higher flow rate response is desired.
[0102] FIG. 2 is a more detailed view of the exemplary catalyst reduction system 100 having the stirred mixing container 102. The identical numbered items are as discussed with reference to FIG. 1. The metallurgy or construction material of the mixing vessel 102 may include carbon steel, stainless steel, nickel alloys, and so on. In certain embodiments, the mixing vessel 102 has a nominal diameter in the exemplary range of 60 to 80 inches (152 to 203 cm) and a volume in the exemplary range of 1,000 to 3,000 gallons (3,785 to 11,355 liters). These ranges are only given as examples and are not intended to limit the modalities of the present techniques. In addition, mixing vessel 102 may be a coated vessel having a coating 200 for a heat transfer medium used to facilitate control of both the reaction temperature and drying temperature for mixing vessel 102, as discussed below.
[0103] In the illustrated embodiment to perform the reduction, a charge of chromium-based catalyst 104 enters an upper portion or top surface of mixing vessel 102. A charge of non-polar hydrocarbon solvent 107, such as as isopentane, and the stirrer begins to form a paste in which the solids are at least partially suspended. The solvent 107 can be introduced through a dedicated feed inlet, as shown. On the other hand, the addition of solvent 107 may share the same orifice or nozzle with the reducing agent 108, typically in sequence. Reducing agent 108 (eg, pure DEAlE, solvent-diluted DEAlE, etc.) is added to an upper portion (eg, top surface or top head) of mixing vessel 102. A 202 level of the solid and liquid contents are perceived in the mixing vessel 102 during the reaction.
[0104] The rate of addition of human or animal feed (for example, by mass per unit of time or volume per unit of time) of reducing agent 108 can be manipulated by a control valve 204 (for example, control valve flow control) under the control system 116 or other control system. A feed speed set point can be specified in the control system 116 based on or in response to the desired catalyst reduced flow rate response value or range 106. A flow sensor 206, such as a mass meter, orifice flow (ie, with differential pressure tapping), and so on, can measure the flow rate of reducing agent 108. A transmitter associated with flow sensor 206 can send a signal to the control system 116 indicating the measured flow rate. The flow control circuit implemented through the control system 116, for example, as a control block in a DCS 116 control system, can adjust the opening position of the control valve 204 to maintain the flow rate of the control agent. reduction 108 at the set point, the desired rate of addition of the reducing agent 108 to the mixing vessel 102. The control system 116 and the instrumentation associated with the flow sensor 206 can total the mass of the reducing agent solution (for example , DEAlE) powered and the control system 116 closes the control valve 204 when the desired amount of load is fed. Alternatively, the desired volume of reducing agent 108 can be introduced in advance into a reducing agent loading container from which the reducing agent solution 108 is fed to mix container 102 through flow sensor 206 and the control valve 204.
[0105] Catalyst 104 and reducing agent 108 generally react in mixing vessel 102 during the addition of reducing agent 108. In addition, catalyst 104 and reducing agent 108 may be given longer residence time (i.e. , a waiting time) to react in the mixing vessel 102 after the addition of the reducing agent 108 is complete. In certain embodiments, the waiting time can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, and so on. A valve 208 in the bottom discharge of the mixing vessel 102 or in the bottom discharge pipe as shown, can retain the catalyst in the mixing vessel 102 during the addition of the reducing agent 108, during any additional reaction time or wait and also during subsequent drying of the reduced catalyst 106 in the mixing vessel 102. The valve 208 can be a manual or automatic shut-off valve, or other type of valve.
[0106] Mixing vessel 102 may include an agitator 210 to stir the contents of mixing vessel 102. Stirring may promote mixing and contact of the reducing agent 108 with the catalyst 104 to facilitate the reaction of the reducing agent 108 with the catalyst 104. In the illustrated embodiment, the agitator 210 has an axis 212 and an impeller 214. While the process symbol for the agitator 210 is represented as an axis with a single paddle impeller, the agitator 210 can be an agitator helical tape or conical stirrer, among others. In some embodiments, the stirrer 210 may include a combination-type stirrer, such as the combination of a helical ribbon-type stirrer or a conical stirrer with an impeller, turbine impeller, paddle or other type of mixing device.
[0107] In addition, agitator 210 may include a motor 216 to drive the rotation or rotation of shaft 212 and impeller 214. Motor 216 may include, for example, a variable speed drive or a variable frequency drive ( VFD), to facilitate the adjustment of the agitation speed or agitation, for example, the rpms of the axis 212 and the impeller 214. The VFD of the motor 216 in the manipulation of the agitator speed can operate under the direction of the control system 116 or another control system. A speed or feed rate (rpm) setpoint can be specified in the control system 116 based on or in response to the desired catalyst reduced flow rate response value or range 106.
[0108] As mentioned, the reaction of the reducing agent 108 with the catalyst 104 to give the reduced catalyst 106 can be carried out at a specified pressure in the mixing vessel and a specified temperature in the mixing vessel 102. The reaction pressure can be maintained (for example, by means of an inert gas or head pressure steam) at exemplary values of 15 psig, 30 psig, 50 psig, 75 psig, 100 psig, and the like. The reaction temperature can be maintained at exemplary values of 20 ° C, 25 ° C, 30 ° C, 35 ° C, 40 ° C, 45 ° C, 50 ° C, 55 ° C, 60 ° C, and so on. against. This reaction temperature can be either the temperature of the contents of the mixing vessel 102 or the temperature of the coating of the mixing vessel 102. In addition, the desired or adjusted drying temperature value (for example, 60 ° C, 65 ° C , 70 ° C, 75 ° C, 80 ° C, etc.) can be entered as the set point of a temperature controller in the mixing vessel 102 or entered as the set point of the temperature controller 222 in the medium supply heat transfer 218.
[0109] To maintain and control the reaction temperature and the drying temperature as the temperature of the contents in the mixing vessel 102 or as the temperature of the heat transfer medium supply 218, the catalyst reduction system 100 may include a heat transfer system 114 which is coupled with the liner 200 of the mixing vessel 102. The heat transfer system 114 can include heat exchangers (heaters, cooler, condensers, etc.), containers, pumps, pipes, valves and the like, to provide a supply of heat transfer medium 218 at a desired or specified temperature for the liner 200 of the mixing vessel 102. The heat transfer system 114 can also receive and process a return of heat transfer medium 220 from the liner 200 of the mixing vessel 102. Examples of a heat transfer medium include tempered water, treated water, water demineralized, cooling water tower, steam condensate, steam, glycols, and other heat transfer fluids.
[0110] A temperature controller 222 can have a temperature sensor to measure and indicate the temperature of the heat transfer medium supply 218. Temperature controller 222 can be represented by a logic control block in the control system 116 or another control system. The temperature sensor associated with temperature controller 222 (and other temperature sensors in system 100) can include a thermocouple housed in a thermowell, or a resistance temperature detector (RTD) and the like. The detected temperature values can be transmitted or otherwise indicated to the hardware and logic of a control system (for example, control system 116). In response, the control system (via the controllers) can send output signals to manipulate or modulate the operation of various equipment and process valves to maintain the temperature measured at the set point.
[0111] In the illustrated mode, temperature regulator 222 maintains the temperature of the supply of heat transfer medium 218 to an inserted setpoint. In fact, the temperature controller 222 can direct the adjustment of the operation of equipment and valves in the heat transfer system 114 to give the desired temperature setpoint of the heat transfer medium supply 218. This medium supply temperature heat transfer temperature 218 can be marked as the temperature of the coating 200 of the mixing vessel 102 or it can approximate the temperature of the coating 200 of the mixing vessel 102. In addition, in embodiments, the reaction temperature and the drying temperature above mentioned can be the temperature set point of the controller 222 (for example, the temperature of the heat transfer medium supply 218 or the coating temperature 200) during the catalyst reduction reaction and subsequent drying of the reduced catalyst, respectively . The temperature of the contents of the mixing vessel 202 may be the reaction temperature and the drying line outlet temperature, respectively, and may approach (for example, at 4 ° C) the coating temperature 200. For example, an operator can introduce a target coating temperature 200 into the temperature controller 222 of the coating 200 which then acts to maintain a constant coating temperature 200 during drying of the catalyst allowing the drying catalyst to gradually approach close to the coating temperature 200. In the illustrated embodiment, the temperature of the contents of the mixing vessel 102 can be indicated by the temperature indicator 224 having a temperature sensor 226 that extends into the mixing vessel 102. The temperature controller 222 and other temperature controllers in the system 100 can be logic control blocks of a control system 116, such as a DCS, and can be associated with appropriate field hardware, such as a transmitter, sensor, and so on. Again, the outlet temperature of the controller 222 can direct the equipment in the heat transfer system 114.
[0112] In alternative embodiments, the temperature indicator 224 in the mixing vessel 102 can instead be configured as a temperature controller that maintains the contents of the mixing vessel 102 at an adjusted temperature point. In such embodiments, temperature controller 222 of the heat transfer medium supply 218 can be the secondary or slave controller that facilitates temperature control of the heat transfer medium supply 218. As mentioned, temperature controller 222 can send one or more output signals to adjust the position of one or more valves (and / or pumps, etc.) in the heat transfer system 114. In operation, the output of the primary temperature controller to the contents of the mixing vessel 102 can specify the temperature controller 222 setpoint as a secondary or slave in the heat transfer medium supply 218. The temperature controller 222 setpoint as a secondary or slave controller for the heat transfer medium supply. heat 218 can be greater or less than the temperature setpoint of the primary temperature controller of the recipient's content and mixing 102. This may depend on the fact that heating or cooling of the contents of the mixing vessel 102 is being implemented to maintain the desired temperature of the contents of the mixing vessel 102 at the set point. In operation, a control scheme can direct the heat transfer system 114 to maintain the temperature of the contents in the mixing vessel 102 at a desired set point. Temperature control can involve a cascade control system or, in other words, a primary controller (for example, temperature controller 224) that maintains the temperature of the mixing vessel 102 and directs a slave controller (for example, temperature controller). temperature 222) which adjusts the temperature of the heat transfer medium supply 218. To implement and maintain a desired temperature of the contents of the mixing vessel 102, the desired value of the reaction temperature (for example, 45 ° C) or temperature of drying (for example, 60 ° C) can be specified as the setpoint of the primary temperature controller in the mixing vessel 102. Other temperature controllers and temperature sensors can be arranged elsewhere in the system 100, including in the cooking vessel. mixture 102 and the heat transfer system 114.
[0113] In general, temperature instrumentation can include a sensor or sensing element, a transmitter and so on. For a temperature element or instrument, the sensing element can include a thermocouple, RTD, and the like. A transmitter can convert an analog signal received from the sensing element to a digital signal for power or transmission to a control system, such as control system 116. A control block in control system 116 can use such measured data. As mentioned with reference to FIG. 1, the heat transfer system 114 can operate, at least in part, under the direction of the control system 116.
[0114] Control system 116 and associated control schemes can be used to change the temperature of the contents of the mixing vessel 102 or the supply of heat transfer medium 218 of the reaction temperature (for example, in the range of 35 ° C to 55 ° C) to the drying temperature (for example, in the range of 55 ° C to 85 ° C). In certain embodiments, the temperature of the contents in the mixing vessel 102 and the supply of heat transfer medium 218 generally increases when the reaction temperature is transitioned to the drying temperature.
[0115] After the reaction of substantially all of the reducing agent 108 with the catalyst 104 to give the reduced catalyst 106, the catalyst 106 can be dried in the mixing vessel 102, i.e., the evaporated solvent 110 and conducted from the vessel mixture 102. The evaporated solvent 110 can be discharged above the mixing vessel 102 and collected in a recovery system, for example. The drying temperature or drying line outlet temperature of catalyst 106 in mixing vessel 102 can be adjusted in response to (or to adjust) the desired or specified flow index response of catalyst 106. The Catalyst flow 106 may be a function of the drying temperature of the catalyst or outlet temperature of the drying line in the mixing vessel 102. See the examples of FIGS. 6 and 7 representing the flow rate of the polymer subsequently polymerized as a function of the drying temperature of the upstream catalyst or the drying line outlet temperature. In the illustrated embodiment of FIG. 2, the setpoint of the temperature controller 222 in the heat transfer supply means 218 can be specified and adjusted as the drying temperature (to give a desired flow index response).
[0116] Control system 116 may include control hardware, a processor, and memory storage of code executable by the processor to implement control schemes. As mentioned in relation to FIGs. 1 and 2, the control system 116 can direct and control the aforementioned process variables of the feed rate of addition of the reducing agent 108, the speed of the stirrer 210, the drying temperature of the catalyst 106 and other process variables . In the control system 116, computer-readable media can store executable code by control to be executed by associated processors including central processing units and the like. Such code executable by the processor (s) may include logic to facilitate the operations described here.
[0117] Actually, the 116 control system can include the appropriate hardware, software logic and code, to interface with the various process equipment, control valves, ducts, instrumentation, etc., to facilitate measurement and the control of process variables, to implement control schemes, to perform calculations and so on. A variety of instrumentations known to those skilled in the art can be provided to measure process variables, such as pressure, temperature, flow rate and so on, and to transmit a signal to the control system 116, where the measured data can be read by an operator and / or used as input to various control functions 116. Depending on the application and other factors, the indication of process variables can be read locally or remotely by an operator, and / or used for a variety of purposes through the 116 control system.
[0118] As discussed in relation to controlling an entered setpoint of the coating temperature such as drying temperature, a temperature controller "TC" can be located in the coating supply, for example, and a temperature indicator "TI" "on the contents of the paste in the container 102. By controlling the coating temperature as the drying temperature, a coating temperature setpoint (for example, the supply of heat transfer medium) can be inserted as the heating temperature. drying. Thus, the temperature of the contents in the container 102 can be a drying "exit line" temperature that is a few degrees different from the coating temperature. In these examples of coating temperature such as the drying temperature, the directly controlled operating temperature can be a variable of operation of the container (coating temperature) but not the actual temperature of the contents of the container when controlling the coating temperature. Therefore, when controlling and adjusting the coating temperature directly as a drying temperature, the coating temperature (for example, supply of heat transfer medium) can be the reaction temperature (for example, 45 ° C) and also the drying temperature (for example, 60 ° C). Thus, in modalities, the reaction temperature and the drying temperature can be the coating temperature, which is a variable of operation of the container 102 and with the understanding that the temperature of the contents in the container 102 can get out of line close, but at a different temperature level than the coating temperature. An alternative is to control the temperature of the paste contents in container 102, for example, with master and slave temperature controllers operating on the contents of the mixing container and on the coating of the mixing container, respectively.
[0119] In short for certain examples, when controlling the coating temperature, the operating variable of the direct temperature of the container 102 may be the coating temperature. The set point you enter can be the coating temperature. Therefore, for a reaction temperature of 45 ° C, for example, the temperature of the coating (supply) can be maintained at 45 ° C and the paste temperature of the contents of container 102 approaches and ends at about 45 ° C, for example. However, for a drying temperature of 60 ° C, for example, the coating temperature (supply) is maintained at 60 ° C and the line outlet temperature of the contents of container 102 is about 64 ° C, for example (for example, exceeding the coating temperature due to the heat from the mechanical energy transmitted by the stirrer over the substantially dry catalyst). On the other hand, when directly controlling the temperature of the contents of the container 102, the operating variable of the direct temperature of the container may be the temperature of the contents of the container (paste, catalyst). The setpoint you enter can be the temperature of the paste content of the container. Therefore, for a reaction temperature of 45 ° C, for example, the temperature of the paste content of the container rises to and is maintained at 45 ° C. For a drying temperature of 60 ° C, the temperature of the container contents rises to and is maintained at 60 ° C. Naturally, as drying proceeds, the contents in container 102 during the drying phase become essentially solid as the solvent is evaporated and discharged above.
[0120] To facilitate the discharge of the reduced dry solid catalyst 106, the bottom portion of the mixing vessel 102 can be a conical shape with at least a 45 ° inclination of the cone walls and up to an inclination of 60 ° or more . In addition, to facilitate drying of the reduced catalyst 106, an inert gas 223 (e.g., nitrogen) can be introduced into the mixing vessel 102, such as in the lower cone (as shown) or in the outlet tubing. This inert gas supply purge 223 can flow upward through the solid bed of catalyst 106 in the mixing vessel once the free liquid outside the pores of the catalyst support 106 has evaporated. A manual or automatic valve 225 is provided so that the inert gas purge 223 can be closed and not introduced during the reduction reaction before drying, for example. A restriction orifice may be provided to limit the flow rate of the inert gas 223.
[0121] As mentioned in relation to alternative modalities, a filter / suspension system 118 can optionally be employed instead of significant heat drying (solvent evaporation) of catalyst 106. A suspension of catalyst 106 with solvent is discharged from the container mixture 102 for the filter / paste system 118, such as, for example, at room temperature in the range of 20 ° C to 30 ° C. The catalyst paste 106 can be filtered through the filter / suspension system 118 to partially remove the solvent to give a filtered catalyst 106 sent to the collection vessel 112. As an additional alternative, an alkane solvent or a mineral oil, for example, can be added to the filtered catalyst prior to collection 106 in the collection vessel 112. In this way, the collection vessels 112 can maintain under an inert atmosphere, for example, a filtered catalyst 106 and / or a paste catalyst 106. Avoid such drying by significant heat of the catalyst in the mixing vessel 102, combined with subsequent filtration, it can provide a reduced catalyst 106 with a relatively higher flow rate response which can be beneficial when a higher flow rate response is desired.
[0122] Furthermore, according to the modalities of the present techniques, the mixing vessel 102 may include an inlet arrangement 228 for the inlet reducing agent 108. Inlet arrangement 228 can facilitate the inlet of the 108 reducing agent in the mixing vessel 102. In particular, the inlet arrangement 228 can direct the inlet reducing agent out of the inner side wall of the mixing vessel 102, for example.
[0123] In the examples, the reducing agent 108 can generally be fed to the mixing vessel 102 at a relatively low flow rate. Conventionally, the reducing agent 108 can be introduced through a simple nozzle or fitting on the top head of the mixing vessel 102. However, with such a nozzle or simple fitting and especially when gradually reducing agent 108 is added over a specified period , the inlet reducing agent 108 can flow totally or partially along the bottom of the top head and down the side of the mixing vessel 102 instead of flowing directly to the surface of level 202 in the mixing vessel 102. Consequently , dispersion of the reducing agent 108 in the reaction mixture can be inhibited. This lack of dispersion can be more accentuated with the aggregation of particles induced by the reducing agent 108, giving rise to a viscous paste that approaches the gel-like behavior, which can be a problematic phenomenon on the paste surface near the wall outside. This phenomenon can inhibit a good dispersion of the reducing agent 108 throughout the slurry.
[0124] Thus, the modalities can provide a new inlet arrangement 228 with a duct or duct extension 230 that extends into the mixing vessel 102 to direct the flow of the reducing agent 108. In the embodiment illustrated in FIG. 2, the duct extension 230 can be an insert positioned in or through a nozzle 232 in an upper portion (e.g., top head 234) of the mixing vessel 102, for example. In embodiments, the conduit or conduit extension 230 can be a pipe or tube that extends into the nozzle 232 and also into the container 102.
[0125] This extension of duct or duct 230 may result in an increase in the mixing and dispersion of the reducing agent 108 in the contents of the mixing vessel 102 by directing the inlet reducing agent 108 more directly to the stirred mixture or to a further portion. of the stirred mixture. The extension of the conduit 230 can prevent the inlet reducing agent 108 from flowing on the underside of the top head 234 and down the container side 102, for example. In certain embodiments, extension 230 may direct inlet reducing agent 108 to desirable positions on the surface of the reaction mixture in mixing vessel 102. For example, in some embodiments, the extension of conduit 230, for example, a pipe or tube insert, directs the reducing agent 108 to a surface location of the mixing level 202 which is 20-80% or 50-70% of the horizontal (perpendicular) distance 236 from the vertical center line of container 102 or the center line of stirrer 204 for the inner surface 238 of the outer wall. The directed flow and thus the improved dispersion of the reducing agent 108 due to the extension of the duct 230 can increase the flow index response of the catalyst 106 and also increase the productivity of the catalyst 106. In some embodiments, the extension of the duct 230 as a insert can be removed or a door used that does not have a duct extension 230 when a low flow rate response is desired.
[0126] Examples of chromium-based catalysts 104 that may be applicable to the use of a 230 duct extension or pipe to inject a reducing agent 108 (for example, DEAlE) may include at least chromium oxide on silica supports , such as forms activated at high temperatures of: PQ Corporation C35300MS, C35300MSF (with grinding of large support particles), C36300MS and ES370; Grace Sylopol 957HS; KD Corporation KDC11C31 and KDC120120; And AGC Sci-Tech Company D-70-120A (LV) silica with chromium and other catalysts. Of course, other classes and types of catalysts are relevant and applicable. Finally, further improvements can be implemented to reduce the agglomeration of particles in the mixture and thus increase the dispersion of the reducing agent 108 in the mixture and, therefore, to increase the contact and reaction of the reducing agent 108 with the catalyst. For example, in some embodiments, the catalyst support can be specified as an unground support. This can reduce the aggregation of particles in the reaction paste exacerbated by ground supports in certain examples.
[0127] In particular, taking an example as representative of some modalities, catalyst 104 is a PQ Corporation C35300MSF class of chromium oxide supported on silica that was activated at high temperature in an oxidizing atmosphere. In this representative example, the use of grade PQ C35300MSF in which the oversized fraction was ground to form smaller particles exacerbates the aggregation of particles in the reaction paste, such that particle aggregation can occur long before the addition of DEAlE is complete. This early aggregation with the ground C35300MSF grade may result from the presence of a substantial number of broken, irregular particles that may experience a greater surface area than the predominantly smooth spheres of the unground milled C35300MSF. In contrast, the use of the un-ground C35300MS class in certain examples can delay the significant occurrence of particle aggregation phenomena until after the addition of DEAlE is complete or close to being complete. Notably, a variant in the class of C35300MS unground with a smaller fraction of large particles can be beneficial. Altogether, the combination of (1) improved nozzle inlet arrangement 228 for the reducing agent 108 and (2) choice of support class can increase the dispersion and reaction of the reducing agent 108 in the mixture in the container 102.
[0128] FIGS. 3A and 3B describe an embodiment of an example 228 inlet arrangement (Figure 3B) with an exemplary conduit extension (Figure 3A). In particular, FIG. 3A is an example of duct extension 230, for example, a simple duct or duct extension, an injector insert, or a tube, among others, for the inlet arrangement 228 in the mixing vessel 102 for the reducing agent 108 FIG. 3B is an exemplary inlet arrangement 228 in the mixing vessel 102 for the reducing agent 108 having the example duct extension insert 230 installed therein.
[0129] In embodiments, the exemplary conduit extension 230 is or has a conduit 240 that extends into the mixing vessel 102 through a neck 242 of a nozzle 232 in the mixing vessel 102. The conduit portion 240 of the extension 230 extending into the mixing vessel 102 may have a dimension of length 244 to provide that the inlet reducing agent 108 does not flow along the underside 258 of the top head 234 of the mixing vessel 102. In examples, the dimension of length 244 is 0.5 ", 1", 2 ", 3", 4 ", 6", 9 ", 12" or 18 "and so on.
[0130] In alternative embodiments, the length of the conduit 230 may extend into the nozzle 232, but not into the mixing vessel 102. In particular, the length of the conduit 230 may extend into the neck 242 of the nozzle. 232, but does not extend beyond the bottom of the inner surface 258 of the top head 234. Thus, the dimension of length 244 can be represented by a negative number (for example, -0.5 "or -1") in the sense that the duct extension 230 is lowered in the nozzle 232 and does not reach the underside of the inner surface 258. Such a lowered duct extension 230 can provide that the inlet reducing agent 108 does not flow along the side of the bottom 258 of the top head 234 of the mixing vessel 102.
[0131] Furthermore, whether it is recessed in the nozzle 232 or extending into the mixing vessel 102, the duct extension 230 can be arranged in such a way that the duct 240 directs the reducing agent 108 to a desired location in the surface of the reaction mixture in the mixing vessel 102. In examples, inlet arrangement 228 directs the reducing agent 108 to an area on the surface of the reaction mixture that is in a percentage range (for example, 20% to 80%, 30% to 60%, 50% to 70%, etc.) from the perpendicular distance from the vertical center line of the mixing vessel 102 or agitator 210 to the vertical inner wall of the mixing vessel 102 (see FIG. 2).
[0132] It should be noted that while the illustrated duct extension 230 has a simple vertical extension, for example, end portion of duct 240, into mixing container 102, duct 240 can extend through various configurations physical, including horizontal and / or inclined orientations, branching, multiple legs or tubes, spreading or spreading holes, and so on. In one embodiment, if a combination agitator is used in which a turbine or other impeller operates at a higher speed than the main helical strip and creates a rapid downward circulation of the paste close to the agitator shaft, it may be advantageous to direct the reducing agent 108 for the flow leading to this impeller. In addition, the duct extension 230 may include a dispensing device such as a dispenser, spray nozzle (s), multiple nozzles in the same or different radial locations, a jet nozzle (s) to give a narrower speed stream and the like, all or some of which may be installed in or through conduit 240. Such incorporation of additional features and different physical arrangements for conduit extension 230 may direct and / or distribute reducing agent 108 to a variety of particular locations in the mixing vessel 102. However, on the other hand, an advantage of the flat vertical flue pipe 240, as illustrated can be simplicity in installation, low cost, less prone to obstructions, ease of maintenance, and so on. In addition, in embodiments, a short, flat straight extension may be able to prevent significant flow of the reducing agent along the underside 258 of the top head and down the inner vertical wall 238 of the mixing vessel 102.
[0133] To deliver the reducing agent 108 to the mixing vessel 102, a tube or conduit 246 routes the reducing agent 108 to the inlet arrangement 228. The conduit 246 ends and couples with the reducing nozzle 232 in the mixing bowl 102 via a spool part 248. In the illustrated embodiment, the end flange 250 of the supply line 246 mates with the inlet flange 252 of the spool part 248. A shut-off valve (not shown) can installed between the two flanges 250 and 252.
[0134] In certain examples, the reduction spool part 248 can provide an increased flange size in the flow direction. In one example, inlet conduit 246 has a nominal diameter of 2 "and ends with a flange 250 which is a 2" flange. A 2 "stop valve 251 is sandwiched between flanges 250 and 252. Continuing in this particular example, the extension duct 240 has a nominal diameter of 1.25", the upstream flange 252 of the reduction spool part 248 is a 2 "by 1.25" reduction flange, the downstream flange 254 of the reduction spool part 248 is a 1.25 "X 3" flange, and the nozzle 232 in the mixing bowl 102 is a nozzle 3 "with a 3" 256 flange and a 3 "neck 242. In this example and in other examples, the reducing agent 108 is introduced through the wall 258 of the top head 234 of the mixing vessel 102 through conduit 240 through nozzle 232. In another example, nozzle 232, neck 242, and flange 256 can be 2 "and flange 254 can be 1.25" by 2 ".
[0135] As mentioned, the reducing agent 108 can be directed away from the wall of the mixing vessel 102 and at the surface level 202 of the reaction mixture in the mixing vessel 102. In addition, the reducing agent 108 can be directed for a relatively higher mixing region of the mixture, such as away from the vessel wall and also away from the proximity of the stirrer axis 212. Finally, it should be noted that various stirring rates can be employed with the stirrer, such as such as 25 rpm, 30 rpm, 37 rpm, 40 rpm, 60 rpm, 70 rpm, greater than 60 rpm, greater than 70 rpm, less than 75 rpm, and so on.
[0136] FIG. 4 is an exemplary bar graph 400 of flow rate 402 in decigrams per minute (dg / min) for polyethylene produced in lab paste polymerizations using reduced chromium-based catalyst. The catalyst was reduced in a stirred mixing vessel in a pilot plant before laboratory polymerizations. Bars 404, 406, 408 are the polyethylene flow index produced in three respective polymerizations carried out under the same polymerization conditions and with the catalyst that had been reduced under the same reduction conditions, except with different DEAlE inlet arrangements for the container mixing plant at the pilot plant.
[0137] The chromium-based catalysts used in the pilot plant's three mixing container reductions had a ground C35300MS support (marked C35300MSF) and were activated at 600 ° C prior to reduction and subsequent laboratory paste polymerizations. To reduce the catalyst before the polymerizations, the catalyst was reduced with DEAlE in hexane solvent in the pilot factory mixing vessel. The catalysts were reduced with DEAlE added over 40 minutes at 45 ° C of reaction temperature with 30 to 37 rpm helical tape stirrer speed in the mixing vessel of the pilot plant to give 1.53 to 1.58% in weight of Al on the catalyst and then dried at 71 ° C of the outlet temperature in the mixing vessel of the pilot plant. To subsequently determine the flow index responses, the olefin was polymerized in the laboratory paste polymerization with the reduced chromium-based catalysts, and the produced polyolefin tested for the flow index. The subsequent three respective polymerizations were carried out to produce polyethylene with the same polymerization conditions. See the example section below for additional details.
[0138] The first bar 404 is the resulting flow index of 20 dg / min of polyethylene produced with a catalyst that had been reduced in the pilot factory mixing vessel, having a DEAlE feeding arrangement without a duct extension or insert. tube in the mixing bowl. In this arrangement without extension or insert, DEAlE was introduced into the mixing vessel through a single inlet and flowed along the underside of the head and down the inner wall for the reduction reaction mixture in the mixing vessel. Thus, the DEAlE flowed into the reaction mixture on the wall, or 100% of the distance from the vertical center line of the mixing vessel to the inner wall of the mixing vessel. As indicated, the reaction mixture included the chromium oxide based catalyst, the DEAlE reducing agent and the hexane solvent.
[0139] The second bar 406 is the resulting flow index of about 76 dg / min for polyethylene produced with a previously reduced catalyst in the pilot plant mixing vessel having a DEAlE feed arrangement in the pilot factory mixing vessel having a conduit extension or tube insert that directed the DEAlE to a location on the surface of the reduction reaction mixture in the mixing vessel. In particular, the duct extension directed the DEAlE to a location 83% of the perpendicular distance from the vertical center line of the mixing vessel to the inner surface of the wall (i.e., inner wall) of the mixing vessel.
[0140] The third bar 408 is the resulting flow index of about 104 dg / min for polyethylene produced with a previously reduced catalyst in the pilot factory mixing vessel having a DEAlE feed arrangement with a duct extension (pipe insert) ) which, as with the second bar 406, also directed the DEAlE to the surface of the reduction reaction mixture. However, the DEAlE with respect to the third bar 408 was directed to a surface location of the reaction mixture that was 67% of the perpendicular distance from the vertical center line of the mixing vessel to the inner surface of the vessel wall.
[0141] FIG. 5 is a bar graph 500 of the flow index 502 (dg / min) of polymerization in a gas-phase fluidized bed in a pilot plant using reduced chromium-based catalysts that had been reduced with different DEAlE feeding arrangements in a container pilot mixing plant. Thus, the basic difference between FIG. 4 and FIG. 5 is that FIG. 4 is a flow index for polyethylene produced in a laboratory paste polymerization, while FIG. 5 is the flow index for polyethylene produced in a pilot phase gas polymerization reactor. As indicated in the Examples section below, the three catalysts represented in FIG. 5 were a similarly reduced catalyst and two of the same three reduced catalysts shown in FIG. 4.
[0142] The first bar 504 is the resulting flow index (dg / min) of about 4.4 dg / min for a DEAlE feed arrangement with no duct extension or tube insert in the pilot factory mixing vessel at reduction before polymerization. DEAlE was introduced into the mixing vessel through a single nozzle and DEAlE flowed along the underside of the mixing vessel's top head and down the inner wall of the mixing vessel for the reduction reaction mixture.
[0143] The second bar 506 is the resulting flow rate of about 5.3 dg / min for a DEAlE feed arrangement in the pilot factory mixing vessel with a duct extension or tube insert that directed the DEAlE to a location on the surface of the reaction mixture. In particular, the duct extension directed the DEAlE to a location 83% of the perpendicular distance from the vertical center line of the mixing vessel (or the vertical center line of the stirrer) to the inner surface of the wall (i.e., inner wall) of the mixing vessel. mixture. The third bar 508 is the resulting flow rate of about 8.2 dg / min for a DEAlE feeding arrangement with a duct extension, which was a tube insert in this example, which directed the DEAlE to the surface of the mixture of reaction at about 67% of the perpendicular distance from the vertical center line of the mixing vessel to the inner surface of the outer wall of the vessel.
[0144] The chromium-based catalyst used in these three pilot factory example reductions represented by FIG. 5 had a support that was ground C35300MS (marked as C35300MSF) and the catalysts were activated at 600 ° C prior to reduction in the mixing vessel and subsequent polymerization. To reduce the catalyst after activation and before polymerisations, the catalyst was reduced with DEAlE in hexane solvent in the pilot factory mixing vessel. The catalysts were reduced with DEAlE added over 40 minutes at 45 ° C of reaction temperature with 30 to 37 rpm helical tape stirrer speed in the mixing vessel of the pilot plant to give 1.53 to 1.58% in weight of Al on the catalyst and then dried at 71 ° C of the outlet temperature in the mixing vessel of the pilot plant. As mentioned, to subsequently determine the flow rate responses, the olefin was polymerized in a pilot plant gas phase reactor with reduced chromium-based catalysts, and the polyolefin produced was tested for flow rate. The three polymerizations to produce polyethylene with the respective three reduced catalysts were carried out under the same polymerization conditions. See the example section below for additional details.
[0145] The examples of FIGS. 4 and 5 demonstrate that for a reduction of the chromium-based catalyst with DEAlE in a mixed or stirred reaction mixture of the catalyst, DEAlE and solvent, the flow index response may be a function of the location at which the reducing agent enters at the surface level of the reaction mixture. In particular, the response flow index may increase as the point of entry of the reducing agent at the surface of the reaction mixture is moved towards the vertical center of the container away from the outer wall. However, the flow index response may decrease as the entry point approaches the agitator axis, which may be a region of lower mixing. In certain examples, the beneficial intervals for the reducing agent to find the surface of the reaction mixture are in the distance range of 20% to 80%, 30% to 70% and 50% to 70% of the distance from the vertical center line of the container mixer or stirrer shaft to the inner surface or wall of the mixing vessel. In addition, for typical alkane solvents, it should be noted that the results of the catalyst flow index response from these exemplary reductions of exemplary chromium-based catalysts are considered to be substantially independent of the particular alkane solvent used in the reduction. For example, the flow index results are not expected to be significantly different in certain embodiments if the isopentane solvent were used instead of hexane. Finally, it should also be noted that while the inlet arrangement for the reducing agent is shown in FIG. 2 on a top portion of the mixing container, the inlet arrangement may also be on one side of the mixing container or on a bottom portion of the mixing container. In one embodiment, the inlet arrangement includes a conduit that extends into a nozzle in a bottom portion of the mixing vessel. In the operation of such a mode, the reducing agent enters directly into the suspension content in the mixing vessel through a duct that extends inward or through the bottom nozzle.
[0146] FIG. 6 is a graph 600 of an adjusted curve 602 of catalyst flow index 604 (dg / min) of polyethylene produced in lab paste phase polymerizations with a catalyst that had been reduced in a pilot factory mixing vessel to a drying line outlet temperature 606 (in ° C). The catalysts were reduced in the mixing vessel of the pilot plant with DEAlE of different charges of the same type (class) of chromium-based catalyst. The chromium-based catalysts were made with C35300MSF support activated at 600 ° C, then reduced in the mixing vessel with DEAlE added for 40 minutes at 45 ° C of reaction temperature with 30 rpm helical tape stirrer speed to give 1.53 to 1.58% by weight of Al on the catalyst. The reductions of the chromium-based catalyst with DEAlE were carried out in a pilot factory mixing vessel, in the presence of an alkane solvent.
[0147] DEAlE was added to the pilot factory mixing vessel, using an insert tube to direct the DEAlE away from the pilot factory mixing vessel wall. The drying of the reduced catalyst in the pilot factory mixing vessel at drying temperature 606 occurred after substantial completion of the DEAlE reaction with the catalyst during a 1 hour reaction wait. To carry out the drying, the pressure in the pilot plant mixing vessel was reduced and the coating temperature increased to slightly above the drying line outlet temperature 606 to evaporate and expel the solvent. In these examples, the drying time represents the period after which the pressure of the container has been reduced and the temperature of the coating of the container has increased until the temperature of the coating has decreased and the pressure of the container has increased.
[0148] To subsequently determine the catalyst flow index values 604, the respective lots of reduced chromium-based catalyst were used in polymerisations of polyolefin olefin laboratory under identical or similar polymerization conditions. The samples of the respective produced polyolefin were tested to determine the flow rate of the polyolefin and thus give comparable flow index values of the same type of catalyst (class) subjected to different drying line outlet temperatures of catalyst 606.
[0149] FIG. 7 is a graph 700 of an adjusted curve 702 of catalyst flow index 704 (dg / min) from gas phase fluidized bed polymerizations in a pilot plant in relation to the drying line outlet temperature of catalyst 706 ( in ° C) with DEAlE of different loads of the same type (class) of chromium-based catalyst. The chromium-based catalysts were made with C35300MSF support activated at 600 ° C, then reduced in the mixing vessel with DEAlE added for 40 minutes at 45 ° C of reaction temperature with 30 rpm helical tape stirrer speed to give 1.53 to 1.58% by weight of Al in the catalyst. These catalysts were the same three catalysts tested in the laboratory polymerizations of FIG. 6.
[0150] The chromium-based catalyst reductions with DEAlE were performed in a pilot factory mixing vessel, in the presence of an alkane solvent. DEAlE was added to the pilot mixing vessel using a tube insert to direct the DEAlE away from the mixer wall. The drying of the catalyst reduced to drying temperature 706 in the pilot mixing vessel occurred after substantial completion of the reaction of the DEAlE with the catalyst during a reaction wait of 1 hour. To carry out the drying, the pressure in the pilot factory mixing vessel was reduced and the temperature of the coating (i.e. the temperature of the heat transfer medium in the coating) of the pilot factory mixing vessel increased to slightly above the temperature drying line outlet 706 to evaporate and expel the solvent. In these examples, the drying time, that is, the period after which the pressure of the container was reduced and the temperature of the coating began to be increased until the coating began to be cooled and the pressure was increased again, was 16 hours. To subsequently determine the catalyst flow index values 704, the respective batches of reduced chromium-based catalyst were used in polymerization of pilot phase olefins in fluidized bed in gas phase in polyolefin under identical or similar polymerization conditions. The samples of the respective produced polyolefin were tested to determine the flow rate of the polyolefin, and thus give values of flow index 704 of the catalyst.
[0151] The examples in FIGs. 6 and 7 demonstrate that, for a reduction of the chromium-based catalyst with DEAlE in a mixed or stirred reaction mixture of the catalyst, DEAlE and solvent, the flow index response may be a function of the drying line outlet temperature of the subsequent catalyst to evaporate and expel the solvent. In particular, the flow index response may increase as the drying line outlet temperature of the catalyst is reduced in certain drying temperature ranges. In the examples, catalyst flow index 604, 704 increased only slightly or negligently when drying temperature 606, 706 was reduced from 80 ° C to 70 ° C. In contrast, catalyst flow index 604, 704 increased significantly when drying temperature 606, 706 was reduced from 80 ° C to 60 ° C or from 70 ° C to 60 ° C.
[0152] FIG. 8 is a method 800 of preparing a chromium-based catalyst for subsequent use in the polymerization of an olefin into a polyolefin. This method 800 of preparing a chromium-based catalyst for the production of polyolefins involves treating the catalyst to reduce the catalyst. As discussed below, method 800 includes adjusting a drying temperature of the catalyst.
[0153] Method 800 begins at block 802, with the contact of a chromium-based catalyst, for example, supported and activated, with a reducing agent in a solvent to reduce an oxidation state of chromium in the catalyst based on chromium to obtain a reduced chromium-based catalyst. The oxidation state can be reduced from +6 (activated) to +2. Chromium +6 can alternatively be reduced to chromium +3. Some of the +6 stickers cannot be reduced, but remain in an oxidation state of +6. Thus, in certain embodiments, the reduced chromium-based catalyst produced as a result of method 800 may include some chromium +6 that has not been reduced, and may include chromium reduced to oxidation states of +2 and / or +3.
[0154] The contact and reaction of the reducing agent with the chromium-based catalyst to reduce the chromium-based catalyst can occur in a mixing vessel. The reducing agent can be an organoaluminium compound (for example, DEAlE). The solvent can be an alkane. The contact of the chromium-based catalyst with the reducing agent can result in the reaction of the chromium-based catalyst with the reducing agent to obtain the reduced chromium-based catalyst. In addition, the chromium-based catalyst can be contacted with the reducing agent in the solvent at a reaction temperature lower than the subsequent drying temperature.
[0155] The reduced chromium-based catalyst can be dried at a drying temperature or drying line outlet temperature, as indicated in block 804. In certain embodiments, the reaction temperature is in the range of 20 ° C to 60 ° C and the drying temperature or drying line outlet temperature is in the range of 50 ° C to 90 ° C. The drying temperature or drying line outlet temperature can be adjusted to change the flow rate response of the reduced chromium-based catalyst, as indicated in block 806. In fact, method 800 may involve specifying the temperature drying time or drying line outlet temperature to give a desired flow index response of the reduced chromium-based catalyst. For a desired high flow rate response, the drying temperature or drying line outlet temperature can be specified at less than 65 ° C or 68 ° C, for example. Other preferred values for the drying temperature or the drying line outlet temperature can be specified at less than 75 ° C or 76 ° C, for example.
[0156] Drying the reduced chromium-based catalyst may involve evaporation and / or filtration of the solvent from the catalyst mixture. Drying may include reducing the pressure of the reduced chromium-based catalyst mixture and the solvent to facilitate evaporation and / or filtration of the solvent from the mixture. For the use of a mixing vessel in reducing the catalyst, evaporation of the solvent through heat drying of the catalyst may include increasing the operating temperature of the mixing vessel from the reaction temperature to the drying temperature or outlet temperature drying line. In addition, evaporation of the solvent may include reducing the operating pressure of the mixing vessel. In all cases, the evaporated solvent can discharge from the mixing vessel. It should be noted that when drying the catalyst includes filtration of the reduced chromium-based catalyst to remove the solvent (instead of significant evaporation of the solvent), the mixture of catalyst and solvent can be filtered at a lower temperature (for example, less than 30 ° C) downstream of the mixing vessel to increase the flow index response in some cases. In addition, the filtered catalyst can then be subjected to drying heat in the alternative examples. Finally, it should be noted that during drying, either by evaporation and / or filtration, most of the solvent can be removed from the catalyst, leaving the residual solvent with the catalyst in certain cases.
[0157] The reduced (and / or filtered) chromium-based catalyst can be collected (block 808) for supply or distribution to a polymerization reactor or polymerization reactor system. In certain embodiments, the reduced chromium-based catalyst can be discharged into a mixing container storage container which performs the reduction and drying of the catalyst. Indeed, the method may also include feeding, in block 810, the chromium-based catalyst reduced to a polymerization reactor. In block 812, an olefin is polymerized to a polyolefin, in the presence of a reduced chromium-based catalyst.
[0158] In summary, one embodiment includes a method of preparing a chromium-based catalyst, such as a chromium oxide catalyst, for the polymerization of an olefin to a polyolefin. The method includes contacting a chromium-based catalyst with a reducing agent (eg, organoaluminium compound, DEAlE, TEAL, etc.) in a solvent, such as alkane to decrease a chromium oxidation state in the catalyst at chromium based to give a reduced chromium based catalyst. The chromium-based catalyst can be an activated and supported chromium-based catalyst. Contact of the chromium-based catalyst with the reducing agent can result in the reaction of the chromium-based catalyst with the reducing agent to give the reduced chromium-based catalyst. In addition, in this embodiment, the method includes drying the reduced chromium-based catalyst to a drying line outlet temperature and adjusting the drying line outlet temperature to alter the catalyst-based flow index response of reduced chromium. Drying may involve evaporation of the solvent, reducing a pressure in the mixture, and so on.
[0159] In examples, the chromium-based catalyst can be brought into contact with the reducing agent in the solvent at a reaction temperature below the drying line outlet temperature and where the reaction temperature is in the range of 20 ° C to 60 ° C and the drying line outlet temperature is in the range of 40 ° C to 90 ° C. In particular examples, drying can be started after substantially all of the reducing agent in contact with the chromium-based catalyst has been consumed in a reaction of the reducing agent with the chromium-based catalyst. In some examples, drying may include filtration or reduced chromium-based catalyst to remove the solvent at a temperature below 30 ° C, for example. The method may include collecting the reduced chromium-based catalyst to supply a polymerization reactor. The method may include feeding the chromium-based catalyst reduced to a polymerization reactor to polymerize an olefin into a polyolefin.
[0160] An additional embodiment includes a method of preparing a chromium-based catalyst for the production of polyolefins, the method including contacting a chromium-based catalyst with a reducing agent in the presence of a solvent in a container of mixture for the production of a reduced chromium-based catalyst. The method includes evaporating the solvent, at a drying temperature to dry the reduced chromium based catalyst, and specifying the drying temperature or drying line outlet temperature to give a desired catalyst flow index response based on reduced chromium. Exemplary specified values for drying temperature or drying line outlet temperature are less than 65 ° C, less than 68 ° C, less than 75 ° C, in the range of 65 ° C to 75 ° C, less at 76 ° C, in the range of 75 ° C to 85 ° C, and so on. Evaporation can be accommodated by increasing the operating temperature of the mixing vessel from a reaction temperature to the drying temperature. Evaporation of the solvent may involve increasing the temperature of the coating of the mixing vessel from a reaction temperature to the drying temperature and / or reducing the operating pressure of the mixing vessel. The method may include the polymerization of an olefin into a polyolefin, in the presence of a reduced chromium-based catalyst in a polymerization reactor.
[0161] Yet another embodiment includes a reduction system catalyst, includes a mixing vessel to stir a mixture of a chromium-based catalyst, a reducing agent and a solvent to produce a chromium-based reduction catalyst for use in the polymerization of an olefin to a polyolefin. In this embodiment, the catalyst reduction system includes a heat transfer system to provide a heat transfer medium to a coating of the mixing vessel to evaporate the solvent and dry the reduced chromium-based catalyst at a drying temperature or exit temperature of drying line. A control system is configured to adjust the drying temperature or drying line outlet temperature in response to a measured flow index response from the reduced chromium-based catalyst. In the examples, the supply temperature of the heat transfer medium to the coating is the drying temperature, and where the temperature of the mixture is an outlet temperature of the drying line. In addition, the control system can be configured to automatically adjust the drying temperature or drying line outlet temperature based on a predetermined ratio of flow index response to the drying temperature or the outlet temperature of drying line.
[0162] Finally, yet another modality is a method that includes the preparation of a chromium oxide catalyst for the polymerization of an olefin into a polyolefin. The preparation includes: (1) mixing the chromium oxide catalyst with a reducing agent (for example, alkyl aluminum, alkyl aluminum alkoxide, etc.) in a solvent (for example, alkane) to give an oxide catalyst reduced chromium; (2) removing the solvent from the reduced chromium oxide catalyst to a specified temperature setpoint; and (3) adjusting the specified temperature setpoint to give a desired flow index response of the reduced chromium oxide catalyst. The method includes collecting the reduced chromium oxide catalyst for distribution to a polyolefin polymerization reactor.
[0163] FIG. 9 is a 900 method for the preparation of a chromium-based catalyst for the production of polyolefins. Method 900 treats the chromium-based catalyst for the polymerization of an olefin to a polyolefin. As discussed below, method 900 includes feeding a reducing agent to a mixing vessel via an inlet arrangement of the mixing vessel to direct the reducing agent to the mixing vessel. The inlet arrangement may include an extension of the conduit or conduit that extends into the mixing vessel.
[0164] In block 902, a chromium-based catalyst is fed to a mixing vessel. Feeding the catalyst may involve loading the catalyst, or adding a batch or loading of the chromium-based catalyst into the mixing vessel. The chromium-based catalyst can be an activated and / or supported chromium-based catalyst. If supported, the support can be an unground support to potentially reduce the agglomeration of particles in the reaction mixture in the mixing vessel, in certain embodiments.
[0165] In block 904, a reducing agent, such as an organoaluminium compound, is introduced (block 904) into the mixing vessel by means of an inlet arrangement having a duct extension or duct extending into the mixing vessel. mixture. The reducing agent can be received in the inlet arrangement of the mixing vessel in a stream with the reducing agent and a solvent, for example. The stream with the reducing agent and solvent can travel through the extension of the duct or ducts to the mixing vessel. The additional solvent can be added to the mixing vessel before, during and / or after the addition of the reducing agent.
[0166] In certain embodiments, the conduit may have a length that extends from at least 0.5 inches, 2 inches, 4 inches, 6 inches, and so on, to the mixing vessel from a surface top of the mixing bowl. The extension of the conduit or conduit may extend through an upper portion of the mixing vessel, and direct the inlet stream having the reducing agent to a surface of the mixing level in the mixing vessel. The conduit can extend into the mixing vessel through a top head of the mixing vessel and terminate in a designated steam space of the mixing vessel.
[0167] In some embodiments, the duct or duct extension is an insert through a mixing vessel nozzle. In particular embodiments, the extension of the conduit or conduit may be a nozzle insert for supplying a tube through a nozzle of the mixing vessel. In some examples, the duct or duct extension extends at least 2 inches into the mixing vessel through a nozzle in the mixing vessel and in which the stream having the reducing agent is introduced into the mixing vessel via an extending duct through the mixing bowl nozzle. In a particular example, the length of duct or duct that introduces the reducing agent into the mixing vessel can direct the inlet reducing agent, or an inlet stream with the reducing agent to a location on the surface of the mixture at an interval from about 20% to 80 or about 50% to 70%, from a perpendicular distance from a vertical center line of the mixing vessel (or vertical center line of the agitator shaft) towards an inner diameter wall ( inner surface of the vertical outer wall) of the mixing vessel.
[0168] Other modalities of the conduit extension are applicable. For example, the conduit extension can be an immersion tube. In particular, the reducing agent can be added via a duct extension which is an immersion tube that extends beyond the vapor space of the mixing vessel to a level below the level of the contents of the mixing vessel. In another embodiment, the duct extension may have a recess in the reducing agent feed injector. In particular, the duct extension may extend into the reducing agent feed nozzle in the mixing vessel, but not into the mixing vessel.
[0169] Finally, with respect to the addition (block 904) of reducing agent to the mixing vessel, the reducing agent may be added to the mixing vessel other than through the aforementioned duct extension. For example, in an alternative embodiment, the reducing agent can be added via a side nozzle or bottom nozzle to the mixing vessel below the level of the reducing reaction mixture. In general, the reducing agent can be added to the mixing vessel in such a way that it does not travel down the inner wall of the mixing vessel, and / or that promotes mixing of the reducing agent with the mixing of the reducing reactor.
[0170] In block 906, the mixture of the chromium-based catalyst, the reducing agent and a solvent in the mixing vessel continue to be agitated to promote contact of the reducing agent with the chromium-based catalyst to give a catalyst based on reduced chromium. The stirring of the mixture can disperse the reducing agent in the mixture, to promote the reaction of the reducing agent with the chromium-based catalyst to obtain a reduced chromium-based catalyst.
[0171] The reduced chromium-based catalyst is dried in the mixing vessel, as indicated by block 908. Drying may include evaporation of the solvent in the mixing vessel and the discharge of the evaporated solvent above the mixing vessel. The reduced chromium-based catalyst can be collected (block 910) to supply a polymerization reactor. In one example, the reduced chromium-based catalyst can be discharged from the mixing vessel to a storage vessel for the delivery of a polymerization reactor system. The reduced chromium-based catalyst can be fed (block 912) to a polymerization reactor to polymerize block (914) an olefin into a polyolefin, in the presence of a reduced chromium-based catalyst.
[0172] In summary, one embodiment provides a method of preparing a chromium-based catalyst for the polymerization of an olefin to a polyolefin. The method includes feeding the chromium-based catalyst to a mixing vessel, introducing a stream with a reducing agent to the mixing vessel through a conduit that extends to a mixing vessel nozzle. In addition, the method includes stirring a mixture of the chromium-based catalyst, the reducing agent and a solvent in the mixing vessel to promote contact of the reducing agent with the chromium-based catalyst to provide a reduced chromium-based catalyst . In certain cases, the conduit extends through the nozzle into the mixing vessel in addition to an inner surface of the mixing vessel. In one example, the duct or duct extension extends at least 0.5 inch into the mixing vessel through a nozzle in the mixing vessel and where the stream with the reducing agent is introduced into the mixing vessel through a duct that extends through the mixing bowl nozzle. In some cases, the conduit may extend at least 2 inches into the mixing vessel through the nozzle. In particular examples, the conduit may have a length that extends at least 6 inches in the mixing vessel from an upper inner surface of the mixing vessel. The conduit may extend through the nozzle into an upper portion of the mixing vessel and direct the stream with the reducing agent to a surface of the mixture in the mixing vessel. In fact, the conduit can extend through the nozzle into a top head of the mixing vessel and end in a vapor space of the mixture. On the other hand, the conduit may be an immersion tube that extends through the nozzle into the mixing vessel at a level below the mixture. The conduit can direct the current that has the reducing agent towards a location on the surface of the mixture, for example, in a range of 20% to 80% of a perpendicular distance from a vertical center line of the mixing vessel to an inner wall of the mixing vessel. In addition, the reducing agent can be introduced into the mixing vessel by means of a second nozzle of a bottom portion of the mixing vessel. The level of the mixture in the mixing vessel may be maintained in or at a region of the impeller of a stirrer in the mixing vessel. On the other hand, prior to drying the reduced chromium-based catalyst in the mixing vessel, the level of mixing in the mixing vessel can be maintained above an impeller region of a stirrer in the mixing vessel. Finally, the method may involve where the duct extending into the mixing vessel nozzle extends into the mixing vessel, comprises a dispenser or spray nozzle, or both. In certain configurations, the conduit that extends to at least the nozzle of the mixing vessel and is configured to direct a jet of the reducing agent to penetrate beneath a surface of a mixture level in the mixing vessel to facilitate mixing of the mixture in the mixing bowl.
[0173] Another embodiment provides a method of treating a chromium-based catalyst for the production of polyolefin, including the method of adding a chromium-based catalyst filler to a mixing vessel and introducing a reducing agent into the mixing vessel through a duct extension that extends at least 0.5 inches into the mixing vessel and ends in a designated steam space of the mixing vessel. The method includes stirring a mixture of the chromium-based catalyst, the reducing agent and a solvent in the mixing vessel to disperse the reducing agent in the mixture to promote the reaction of the reducing agent with the chromium-based catalyst to give a reduced chromium-based catalyst. The conduit extension can be an insert through a mixing vessel nozzle and can direct the reducing agent to a mixture level surface in the mixing vessel. For example, the duct extension directs the reducing agent to a location on the surface of the mixture within a range of 20% to 80% of a perpendicular distance from a vertical center line of the mixing vessel to an inner wall of the mixing vessel. mixture. In addition, the method may include maintaining a level of mixing in the mixing vessel to an impeller region of a shaft of a mixing vessel stirrer. The method may include the discharge of the reduced chromium-based catalyst from the mixing vessel to a storage vessel for distribution to a polymerization reactor system. Finally, the method may include the polymerization of an olefin into a polyolefin, in the presence of a reduced chromium-based catalyst in a polymerization reactor.
[0174] Yet another embodiment includes a reduction system for chromium-based catalyst can include a catalyst feed system to provide a chromium-based catalyst to a mixing vessel, a reducing agent delivery system to provide a reducing agent to the mixing vessel and the mixing vessel to maintain a mixture having the chromium-based catalyst, the reducing agent and a solvent to produce a reduced chromium-based catalyst for use in the polymerization of an olefin into a polyolefin . The mixing container can include an agitator to stir the mixture, and an inlet arrangement for the reducing agent, the inlet arrangement with a conduit or an extension of the conduit for receiving and directs the reducing agent to the mixing container. The reducing agent can include an organoaluminium compound, an alkyl aluminum alkoxide, such as diethylaluminium ethoxide (DEAlE), an alkyl aluminum, such as triethylaluminium (TEAL), a mixture of DEAlE and TEAL, and so on. As indicated, the chromium-based catalyst can be a chromium oxide catalyst.
[0175] In certain cases, the duct extension extends into the interior of the mixing vessel and directs the reducing agent into a vapor space in the mixing vessel. The duct extension can direct the reducing agent away from an interior surface of the mixing vessel towards the mixture, such as to a top surface of the mixture level. In particular examples, the duct extension directs the reducing agent to a location on the surface of the mixture within a range of 20% to 80% or 50% to 70% from a perpendicular distance from a vertical center line of the mixing vessel to an inner wall of the mixing vessel. The vertical axis of the stirrer can be substantially the same as a vertical axis of the mixing vessel. In certain embodiments, the duct extension can be a nozzle insert through a nozzle of the mixing container, the nozzle insert being a tube that ends in a vapor space of the mixing container. On the other hand, the conduit extension could be an immersion tube that extends beyond the vapor space below the level (surface) of the contents of the mixing vessel.
[0176] In general, the reducing agent can be added to the mixing vessel in such a way that the reducing agent does not predominantly go to the aggregate ring around the outer top surface of the paste, and so that the dispersion of the agent reduction in the reduction reaction paste mixture is increased. For example, the reducing agent can be introduced through a duct extension or duct insert into the vapor space of the mixing vessel or below the surface of the sludge away from the interior wall. In the case of the pipe conduit or insert as a dip tube below surface level, the dip tube may extend below the mixing surface between the agitator shaft and the helical strip (s) ) exterior, for example. The dip tube can have multiple outlet holes below the surface level. In another configuration, the tube insert does not extend into the container, but is instead fitted into a feed nozzle on the top head of the mixing container, such that the reducing agent flows to a location the paste surface away from the inner wall of the mixing vessel. In addition, in still other embodiments, the reducing agent can be added to the mixing vessel through a port or nozzle in the bottom portion of the vessel. If so, the supply of reducing agent can be divided between the bottom port or nozzle and a port or nozzle on the top head.
[0177] The catalyst reduction system may include a flow control valve to modulate the flow rate of the reducing agent to the inlet arrangement of the mixing vessel. The system may have a variable drive to modulate a rate of agitation of the mixture by the agitator, wherein the agitation rate comprises rotations per unit time of an agitator axis. In addition, a heat transfer system can provide a heat transfer medium for a coating of the mixing container to maintain a temperature of the heating medium in the coating or to maintain the temperature of the contents of the mixing container. A control system can facilitate the adjustment of the stirring rate, in time rotations of the stirring device to obtain a desired flow rate response of the reduced chromium-based catalyst. The same or different control system can facilitate the adjustment of the flow rate of the reducing agent to the inlet arrangement of the mixing vessel to give a desired flow index response of the reduced chromium-based catalyst and also facilitate the adjustment of the drying temperature of the reduced chromium-based catalyst in the mixing vessel to give a desired flow index response of the reduced chromium-based catalyst. Polymerization processes
[0178] The catalysts formed by the processes described above, as well as the catalyst prepared in line discussed below, can be used in the polymerization of olefins by suspension, solution, paste and gas phase processes, using known equipment and reaction conditions and are not limited to any specific type of polymerization system. Generally, olefin polymerization temperatures can vary from about 0 to about 300 ° C at atmospheric, subatmospheric or superatmospheric pressures. In particular, suspension or solution polymerization systems can use subatmospheric pressures, or alternatively, superatmospheric, and temperatures in the range of about 40 to about 300 ° C.
[0179] Liquid phase polymerization systems, such as those described in US Patent 3,324,095, can be used in the modalities of the present disclosure. Liquid phase polymerization systems generally comprise a reactor to which olefin monomers and catalyst compositions are added. The reactor contains a liquid reaction medium that can dissolve or suspend the polyolefin product. This liquid reaction medium can comprise an inert liquid hydrocarbon that is non-reactive under the polymerization conditions employed, the apparent liquid monomer or a mixture thereof. Although such an inert liquid hydrocarbon cannot function as a solvent for the catalyst composition or the polymer obtained by the process, it usually serves as a solvent for the monomers used in the polymerization. Inert liquid hydrocarbons suitable for this purpose may include isobutane, isopentane, hexane, cyclohexane, heptane, octane, benzene, toluene, and mixtures and isomers thereof. The reactive contact between the olefin monomer and the catalyst composition can be maintained by constant agitation or agitation. The liquid reaction medium containing the olefinic polymeric product and the unreacted olefinic monomer is withdrawn from the reactor continuously. The olefin polymer product is separated and the unreacted olefin monomer and liquid reaction medium are typically recycled and fed back to the reactor.
[0180] Some modalities of this disclosure can be especially useful with gas phase polymerization systems, at superatmospheric pressures in the range of 0.07 to 68.9 bar, from 3.45 to 27.6 bar (50 to 400 psig) in some modalities, from 6.89 to 24.1 bar (100 to 350 psig) in other modalities, and temperatures in the range of 30 to 130 ° C, or from 65 to 110 ° C, from 75 to 120 ° C in other modalities or from 80 to 120 ° C in other modalities. In some embodiments, operating temperatures may be less than 112 ° C. Gas phase polymerization systems in a fluidized or agitated bed can be useful in modalities of this disclosure.
[0181] Generally, a conventional gas phase fluid bed process is conducted by passing a stream containing one or more olefin monomers continuously through a fluid bed reactor under reaction conditions and in the presence of a catalyst composition at a speed enough to keep a bed of solid particles in a suspended state. A stream containing unreacted monomer is continuously withdrawn from the reactor, compressed, cooled, optionally partially or fully condensed and recycled back to the reactor. The product is removed from the reactor and the replacement monomer is added to the recycling stream. Inert gases for the composition of the catalyst and reagents can also be present in the gas stream. The polymerization system can include a single reactor, or two or more reactors in series.
[0182] Feed streams can include olefin monomer, non-olefinic gas such as nitrogen and hydrogen and can also include one or more non-reactive alkanes that can be condensed in the polymerization process to remove reaction heat. Illustrative non-reactive alkanes include, but are not limited to, propane, butane, isobutane, pentane, isopentane, hexane, isomers thereof and derivatives thereof. The feeds can enter the reactor in a single or multiple and different locations.
[0183] In addition, the polymerization process is typically conducted substantially in the absence of catalyst poisons, such as moisture, oxygen, carbon monoxide and acetylene. However, oxygen can be added back to the reactor at very low concentrations to alter the polymer's structure and its product performance characteristics. Oxygen can be added at a concentration to the reactor ethylene feed rate of about 10 to 600 ppbv, and more preferably about 10 to 500 ppbv. Organometallic compounds can be used as sequestering agents to remove poisons from the catalyst, thereby increasing the activity of the catalyst, or for other purposes. Examples of organometallic compounds that can be added include metal alkyds, such as aluminum alkyds. Conventional adjuvants can also be used in the process, as long as they do not interfere with the mechanism of the catalyst composition in forming the desired polyolefin. In some embodiments, hydrogen gas can be added. The use of hydrogen affects the molecular weight of the polymer and the distribution, and ultimately influences the properties of the polymer. For the purposes of polymerization with chromium-based catalysts of the present invention, the mole ratio of hydrogen gas to ethylene in the reactor can be in the range of about 0 to 0.5, in the range of 0.01 to 0.4 and in the range of 0.03 to 0.3.
[0184] An illustrative catalyst reservoir suitable for continuous feed of dry catalyst powder to the reactor is shown and described in US Patent 3,779,712, for example. A gas that is inert to the catalyst, such as nitrogen or argon, is preferably used to transport the catalyst to the bed. In another embodiment, the catalyst is supplied as a slurry in mineral oil or liquid hydrocarbon or mixture such as, for example, propane, butane, isopentane, hexane, heptane or octane. An illustrative catalyst reservoir is shown and described in WO 2004094489. The catalyst paste can be supplied to the reactor with a carrier fluid, such as, for example, nitrogen or argon or a liquid such as, for example, isopentane or another C3 to C8 alkane.
[0185] In order to achieve the desired density ranges in the copolymers, it is necessary to copolymerize enough of the comonomers with ethylene to obtain a level of about 0 to any of 5 to 10 weight percent of the comonomer in the copolymer. The amount of comonomer required to achieve this result will depend on the particular comonomer (s) used, the catalyst composition and, in particular, the aluminum to chromium molar ratio, the catalyst preparation conditions and the reactor temperature. The ratio of the comonomer to ethylene is controlled to obtain the desired resin density of the copolymer product.
[0186] Polymerization conditions vary depending on monomers, catalysts and equipment availability. The specific conditions are known or readily derived by those skilled in the art. In some embodiments of this description, the polyolefins produced may include those made from olefin monomers, such as ethylene and upper linear or branched alpha-olefin monomers containing 3 to about 20 carbon atoms. In other embodiments, homopolymers or interpolymers of ethylene and these higher alpha-olefin monomers can be made, with densities ranging from about 0.905 g / cc to about 0.97 g / cc; densities ranging from about 0.915 to about 0.965 in other modalities. Examples of higher alpha-olefin monomers may include, for example, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 3,5,5-trimethyl-1- hexene. Examples of polyolefins can include ethylene-based polymers (at least 50 mol% of ethylene), including copolymers of ethylene-1-butene, ethylene-1-hexene and ethylene-1-octene, such as high density polyethylene (HDPE ), medium density polyethylene (MDPE) (including ethylene-butene copolymers and ethylene-hexene copolymers), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) or homopolyethylene.
[0187] In certain embodiments, the polymers of the present disclosure may have flow rates (I21) ranging from about 0.1 g / 10 min to about 1000 g / 10 min. In other embodiments, the polymers of the present disclosure may have flow rates (I21) ranging from about 1 g / 10 min to about 300 g / 10 min. In still other embodiments, the polymers of the present disclosure may have flow rates (I21) ranging from about 0.5 g / 10 min to about 60 g / 10 min.
[0188] In some exemplary embodiments, the processes and catalysts disclosed herein can be used to produce polyolefins, such as ethylene / 1-hexene copolymer or ethylene homopolymer under specific reactor conditions. For example, the molar ratio of H2 / C2 can be in the range of about 0.01 to about 0.5. The addition of oxygen can be in the range of about 10 to about 600 ppbv in relation to the ethylene feed rate for the reactor. The operating temperature of the reactor can be in the range of about 75 to about 120 ° C. The reactor can optionally be run in condensation mode. Polymerization conditions vary depending on monomers, catalysts and equipment availability. The specific conditions are known or readily derived by those skilled in the art.
[0189] The following test methods should be used to obtain the numerical values for certain properties and characteristics as disclosed, for example, density, productivity, chromium content or flow rates or melting rates, although it is understood that these values also refer to any results obtained by other test or measurement methods that may not be disclosed here, provided that such other test or measurement methods are published, for example, in at least one patent, patent application or scientific publication. Also, it is understood that the values presented in the claims may have some degree of error associated with their measurement, be it experimental, of equipment or operator error; and that any value in the claim is approximate only, and covers values that are more or less (+/-) 10% or even 20% from the measured value.
[0190] The density values are based on ASTM D1505. The values of the Flow Index (I21) are based on ASTM D1238, performed at 190 ° C, with a weight of 21.6 kg; the standard designation for this measurement is 190 / 21.60. The values of the Fusion Index (I5) are based on ASTM D1238, performed at 190 ° C, with a weight of 5.0 kg; the default designation for this measurement is 190/5. The values of the Fusion Index (I2) are based on ASTM D1238, performed at 190 ° C, weighing 2.16 kg; the standard designation for this measurement is 190 / 2.16.
[0191] The discussion here illustrates, among other things, for reduced chromium oxide catalysts and reduced silyl chromate catalysts, the effect on the flow rate response utilization of different reduction agent addition times and different rates of surprisingly different agitation and drying temperatures in a fluidized bed gas and in a paste polymerization process, for polyethylene copolymers, which included ethylene units as well as other monomer units. These effects can be used to adapt the flow rate response of a catalyst to produce target polymers with high, medium or low flow rates under a variety of polymerization conditions.
[0192] As described above, the flow index response of a chromium-based catalyst can be adapted by contacting the chromium-based catalyst with a reducing agent fed at a selected feed rate during a selected period and optionally to a selected stirring rate and subsequently dried at an adjustable drying temperature (at a specified drying time). The use of the chromium-based catalyst compositions described herein, in which the catalysts have an adapted or selected flow index response, provides a capacity for flexibility of the polymerization process, which has significant commercial application in the polymerization of polyolefins.
[0193] Furthermore, the modalities of the present disclosure provide a process for producing chromium-based catalyst compositions with a selected flow index response. Still other embodiments provide a process for the production of polyolefins comprising forming a chromium-based catalyst composition with a selected flow index response, as described herein, and contacting the chromium-based catalyst composition with olefins under polymerization conditions.
[0194] Advantageously, the embodiments disclosed herein provide a method for adapting the flow index response of chromium-based catalysts. The ability to select the flow index response of a chromium-based catalyst even more advantageously allows for a greater number of polymerization products produced with chromium-based catalysts than was previously possible. In addition, chromium-based catalysts with a low or moderate flow index response advantageously allow the production of low flow index products with chromium-based catalysts at significantly higher reactor temperatures, where cooling is more efficient and higher production rates can be obtained. As another advantage, chromium-based catalysts with a higher flow index response result in lower hydrogen feed rates to the reactor. Chromium-based catalysts that have a higher flow index response can also result in lower oxygen feed rates to the reactor that correlate with improved catalyst productivity and higher fluidized bulk density of the polyethylene particles that can lead to a higher polyethylene production rate for a given equipment. As yet another advantage, the greater flexibility of chromium-based catalysts to produce polymers of various flow rates allows for a better transition of the grades. In-line reduction of chromium-based catalysts for polyolefin production
[0195] The polymerization reactor systems discussed in the above section "Polymerization Processes" and other polymerization reactor systems may employ an in-line reduction of the chromium-based catalyst, as discussed below with reference to FIGs. 10 and 11. In fact, instead of using said upstream mixing vessel to reduce and isolate chromium-based catalyst loads, the chromium-based catalyst can instead be reduced in line (with a reducing agent ) as power for one or more of the polyolefin polymerization reactors discussed above in the "Polymerization Processes" section. In certain embodiments, inline reduction may be part of the polymerization reactor system or its supply system. In-line reduction can be carried out without removing the solvent and thus a stream of the chromium-based catalyst, solvent and any remaining reducing agent can enter the polymerization reactor.
[0196] Advantageously, the modalities of the present inline reduction can prevent a drop (for example, of 4 lb / ft3) in the apparent polymer density values associated with the conventional in situ reduction of the chromium-based catalyst with reducing agent introduced directly into the polymerization reactor and first contacting the chromium-based catalyst in the polymerization reactor. In addition, in some instances, the amount of reducing agent used can be beneficially decreased with in-line reduction, compared to the aforementioned reduction of chromium-based catalyst in a batch mixing vessel in an upstream step. In other words, for the same class or type of catalyst subjected to the same amount of reducing agent (ie, the same reducing agent / Cr ratio), a higher chromium-based catalyst flow rate response can be carried out with in-line reduction in relation to drying and isolation of reduced chromium-based catalyst with a mixing vessel 102, for example. In some cases as discussed below, the flow index response increases significantly for the in-line reduction of the catalyst compared to the dry and reduced isolated isolated catalyst in the same reducing agent / Cr ratio.
[0197] In addition, as discussed below, in-line reduction can also advantageously benefit substantially real-time control of the product properties (for example, the flow rate) of the product's polyolefin by adjusting the rate of addition reduction agent in line reduction. The present in-line reduction may include a static in-line mixer, an in-line agitator vessel, an in-line agitation vessel or the like. The mixer, static mixer, stirred vessel, stirring vessel and / or flue volume can provide a specified dwell time of the contact of the chromium-based catalyst with the reducing agent.
[0198] FIG. 10 is a polymerization reactor system 1000 having an inline reduction system 1002 for mixing a reducing agent 1004 with a substantially continuous supply of chromium-based catalyst 1006. The reduction system 1002 includes an in-line mixer 1008 to mix the reducing agent 1004 with the chromium-based catalyst 1006 en route to a polymerization reactor 1010. The polymerization reactor 1010 polymerizes an olefin into a polyolefin, in the presence of chromium based catalyst 1006.
[0199] The polymerization reactor 1010 can be a liquid phase reactor, such as a closed loop reactor, a boiling liquid pool reactor, an autoclave reactor and the like. The polymerization reactor 1010 can also be a gas phase reactor, such as fluidized bed reactors, horizontally stirred or vertically stirred, and so on. Again, the 1010 reactor may be one of the types of reactor discussed above in the section entitled "Polymerization Processes". In addition, reactor system 1000 can generally include equipment and subsystems associated with reactor 1010, as discussed above. Reactor 1010 can represent more than one reactor arranged in series and / or in parallel.
[0200] The chromium-based catalyst 1006 received in the mixer 1008 and flowing through the mixer 1008 can be of the previously mentioned types of chromium-based catalyst discussed throughout the present disclosure. Catalyst 1006 can be chromium oxide catalysts and / or silyl chromate catalysts, for example. The chromium-based catalyst 1006 can be supported and can be activated just like in an upstream activation system where an oxidation state of chromium in catalyst 1006 is increased from +3 to +6, for example. Chromium-based catalyst 1006 can be received in mixer 1008 as a substantially dry catalyst if feasible, but is typically received in a suspension with an alkane solvent, mineral oil and the like. The amount or rate of catalyst 1006 for the mixer (and finally for reactor 1010) can be controlled and modulated to give a desired rate of polyolefin production in the polymerization reactor 1010, a desired degree of polyolefin property values and polyolefin.
[0201] The reducing agent 1004 can be an organoaluminium compound (for example, DEAlE) and can be diluted in an inert solvent, such as an alkane. The rate of addition of the reducing agent 1004 can be modulated with a control valve 1012, such as a flow control valve. In fact, as discussed below, the flow rate of addition of the reducing agent 1004 can be an operational variable of the polymerization reactor system 1000 to give a desired flow index (and other desired properties) of the polyolefin product discharging from the reactor. polymerization agent 1010. The reducing agent 1004 (with solvent) can be added to catalyst 1006 near or at the inlet of mixer 1008, as shown or can be added directly to mixer 1008.
[0202] In certain embodiments, mixer 1008 is a static mixer or a plurality of static mixers arranged in series and / or in parallel. Mixer 1008 can also be or include a stirred or stirred container instead of or in addition to a static mixer (s). If so, the stirring speed in the mixer (s) 1008 can be adjusted to give good mixing and / or to change the mixing characteristics in response to the change in the operating conditions of the polymerization reactor. Such changes in the operating conditions of the polymerization reactor may include changes in the flow index response and / or changes in the average particle size distribution of the polymer resin, such as an increase in the fraction of resin powders, and so on. Mixer 1008 can also be a plurality of stirred containers. In addition, in-line mixer 1008 can be other types of mixers, and is generally a unit operation to provide contact and mixing of reducing agent 1004 with chromium-based catalyst 1006. Mixer 1008 can be configured and sized based on typical flow rates of catalyst 1006 and reducing agent 1004 to give particular residence times of contact / mixing and reaction of reducing agent 1004 with chromium-based catalyst 1006 in mixer 1008. In certain embodiments, the stay contact of the mixer 1008 is at exemplary intervals of about 2 minutes to 120 minutes, about 18 minutes to 30 minutes, and so on. Other dwell contact time intervals apply. The dwell contact time of the mixer 1008 can be considered the dwell time of the contact of the catalyst 1006 with the reducing agent 1004 through the mixer 1008. The additional contact residence time of the catalyst 1006 with the reducing agent 1004 can be contributed by piping or tubing between the mixer 1008 and the polymerization reactor 1010. The dwell contact time can affect the catalyst flow rate response and thus the polymer flow rate in the downstream polymerization reactor. In fact, differences in the catalyst flow rate response have been observed, for example, between the dwell contact times of about 20 minutes and about 80 minutes.
[0203] The operating temperature of mixer 1008 can be ambient, in some examples. Thus, the reduction of catalyst 1006 in mixer 1008 can occur at room temperature. In other embodiments, the operating temperature of the mixer 1006 can be increased above room temperature, such as by heating the inlet streams 1004 and 1006, as well as heating the mixer 1008. Cooling can also be employed to maintain the desired operating temperature of mixer 1008 to remove heat from the reaction of the reducing agent with the chromium-based catalyst. The operating pressure of the mixer 1008 can be a function of the flow supply pressure of the inlet currents 1004 and 1006, the back pressure of the polymerization reactor 1010, and so on. In addition, the pressure control in the mixer 1008 can be implemented in alternative modalities.
[0204] The 1014-based catalyst composition discharging from mixer 1008 generally includes chromium-based catalyst 1006 (some of which may have been reduced in mixer 1008), solvent and any remaining reducing agent 1004. The composition of catalyst 1014 flows substantially continuously as feed to polymerization reactor 1010. Reduction of chromium-based catalyst 1006 occurs in mixer 1008. This reduction may also continue to occur in the composition of chromium-based catalyst 1014 in the supply pipe or piping from mixer 1008 to reactor 1010, and reactor 1010 in certain embodiments. The reduction may involve reducing at least some of the chromium sites from an oxidation state from +6 to +3 and / or +2, for example. In certain embodiments, the chromium-based catalyst 1006 that enters the in-line reduction system 1002 is not previously contacted with a reducing agent. In other embodiments, the chromium-based catalyst 1006 that enters the line reduction system 1002 is previously contacted with a reducing agent and further reduction can occur through the line reduction system 1002.
[0205] Additional feed components, as discussed above in the "Polymerization Processes" section and as represented by a single arrow 1016 in FIG.10, are fed to the polymerization reactor. Such olefin feed components may include, comonomer, hydrogen, additives, and other components. In the 1010 reactor, the olefin and any comonomer are polymerized into polyolefin in the presence of the 1014 catalyst composition and any hydrogen and / or additives. A stream of product 1018 polyolefin discharges from the polymerization reactor.
[0206] In modalities, the olefin is ethylene, the comonomer is 1-butene or 1-hexene, and the product polyolefin 1018 is polyethylene. In other embodiments, the olefin is propylene, the comonomer is ethylene, if used, and the product polyolefin is polypropylene. As mentioned, polymerization reactor 1010 typically includes associated equipment and subsystems of reactor system 1000. In addition, product polyolefin stream 1018 can be further processed, combined with additives, and polyolefin 1018 extruded into pellets, for example. example, for distribution to customers or end users.
[0207] The feed component addition rates and operating conditions (eg pressure, temperature) of the 1010 reactor can be controlled to give a desired polymerization mix or recipe in the 1010 reactor and thus the desired degree and properties of product polyolefin 1016. Such control can generally impact the productivity of catalyst 1006 or catalyst composition 1014, the production rate of product polyolefin 1018, and so on. According to the modalities of the present techniques, the rate of addition of the reducing agent 1004 to the inline reduction system 1002 can be an additional operational variable of the reactor system 1000 to facilitate control of properties, for example, flow rate, density , etc., of product polyolefin 1018, as well as the productivity of catalyst 1006, the production rate of polyolefin 1018 and the like.
[0208] As mentioned, the addition or flow rate of the reducing agent 1004 to the mixer 1008 can be modulated by a control valve 1012. The modulation and control of the flow rate of the reducing agent 1004 through the control valve 1012 they may be under the direction of a 1020 control system, which may be analogous to the aforementioned control system 116. The flow control circuit in a DCS 1020 control system can supervise the operation (valve position) of the control valve 1012 to give the desired flow rate or setpoint flow rate of the reducing agent 1004 to the mixer 1008.
[0209] The addition or feed rate, for example, in mass per time or volume per time, of the reducing agent 1004 can be manipulated by the control valve 1012 under the direction of the control system 1020 or another control system. A feed rate set point can be specified in the 1020 control system based on or in response to the desired flow index or other property of the 1018 product polyolefin. The feed rate set point of the reducing agent 1004 also can be specified in the control system 1020 to work in conjunction with other operational variables to give certain values of catalyst productivity, production rates of polyolefin 1018 and other operating conditions of reactor 1010 and reactor system 1000.
[0210] A 1022 flow sensor, such as a mass meter, flow measuring orifice (for example, with differential pressure taps), and so on, can measure the flow rate of the reducing agent 1004 and indicate such measured flow rate values for the 1020 control system. A transmitter can send a signal to the 1020 control system indicating the measured flow rate. This flow control circuit implemented through the 1020 control system, for example, as a control block in a DCS 1020 control system, can adjust the valve opening position of the 1012 control valve to maintain the flow rate of the reducing agent 1004 at the set point, that is, the desired rate of addition of the reducing agent 1004 to the in-line reduction system 1002 and its mixer 1008.
[0211] Finally, a solvent 1024 can be added to the mixer 1008 to adjust the residence time or contact residence time of the chromium-based catalyst through the mixer 1008. The solvent 1024 can be added directly to the mixer 1008, to a conduit supplying the catalyst 1006 to the mixer 1008, to a conduit supplying the reducing agent 1004 to the mixer 1008 and the like. In the illustrated embodiments, the solvent addition rate 1024 can be modulated with a control valve 1026 which can operate under the direction of the control system 1020.
[0212] FIG. 11 is an 1100 method of operating a polyolefin reactor system. The method includes feeding a chromium-based catalyst, as indicated in block 1102, through an in-line reduction system for a polymerization reactor. This catalyst feed can be a substantially continuous feed through the in-line reduction system for the polymerization reactor. The inline reduction system may have a mixer that contacts the chromium-based catalyst with a reducing agent. The mixer can be an in-line mixer including a static mixer, an agitator vessel, an agitated vessel, and so on.
[0213] A reducing agent (block 1104) is added to the chromium-based catalyst in the in-line reduction system to reduce an oxidation state of at least a portion of the chromium in the chromium-based catalyst. The reducing agent can be added to the chromium-based catalyst in the mixer or upstream of the mixer, or a combination thereof. The reducing agent can be an organoaluminium compound (for example, DEAlE and / or TEAL) and can be diluted in a solvent, such as an alkane solvent.
[0214] In addition, a solvent can be added (block 1106) to the inline reduction system to adjust the residence time or contact residence time of the chromium-based catalyst and the reducing agent in the mixer. An exemplary contact residence time of the chromium-based catalyst in the mixer can be in the range of about 2 minutes to about 120 minutes, in the range of about 18 minutes to about 30 minutes, and so on.
[0215] In block 1108, an olefin or a mixture of olefins, is polymerized into a polyolefin in the polymerization reactor in the presence of the chromium-based catalyst fed through the in-line reduction system to the polymerization reactor. In certain embodiments, the olefin is ethylene and the polyolefin is polyethylene. The polymerization reactor can be a gas-phase reactor and / or a liquid-phase reactor.
[0216] In block 1110, the rate of addition or flow rate of the reducing agent to the inline reduction system and its mixer can be specified and adjusted to obtain a desired flow index of the polyolefin produced in the polymerization reactor. Adjustment of the rate of addition of reducing agent may be in response to a measured flow rate of the polyolefin. In fact, method 1100 may include adjusting a polyolefin flow index by modulating the rate of addition of the reducing agent to the chromium-based catalyst. In addition, the rate of addition of the reducing agent to the chromium-based catalyst can be adjusted in response to the operating conditions of the polymerization reactor. In some cases, to control the flow rate, the rate of addition of the reducing agent may be based on obtaining or changing a concentration of target aluminum added to the reduced catalyst. In some cases to control the flow rate, the rate of addition of the reducing agent may be based on obtaining or changing a target molar ratio added from aluminum to chromium in the reduced catalyst. The rate of addition of the reducing agent can further be adjusted to maintain a target feed rate in relation to the feed rate of the catalyst or changes in the feed rate of the catalyst as it may be beneficial, for example, to manipulate the rate of production of polymer from the downstream polymerization reactor.
[0217] In summary, one embodiment provides a method of operating a polyolefin reactor system, including the method of feeding a chromium-based catalyst (eg, chromium oxide catalyst) through a reduction system in line for a polymerization reactor, such as a gas phase reactor. The chromium-based catalyst can be fed substantially continuously through the in-line reduction system for the polymerization reactor. The method includes adding a reducing agent to the chromium-based catalyst in the in-line reduction system to reduce an oxidation state of at least a portion of the chromium in the chromium-based catalyst and polymerizing an olefin (for example, ethylene ) in a polyolefin (for example, polyethylene) in the polymerization reactor in the presence of the chromium-based catalyst. The reducing agent can include an organoaluminium compound, an organoaluminium compound diluted in a solvent, and so on. In particular examples, the reducing agent can include DEAlE, TEAL, both DEAlE and TEAL, and so on. The inline reduction system may include a mixer, such as a static mixer or stirring vessel that contacts the chromium-based catalyst and the reducing agent.
[0218] In addition, the method may include adding solvent to the inline reduction system to adjust the contact residence time of the chromium-based catalyst and the reducing agent in the mixer. The rate of addition of solvent to the inline reduction system can be adjusted in response to the operating conditions of the polymerization reactor, in response to a measured flow rate of the polyolefin, to maintain a flow rate of the polyolefin or to give an index different flow than polyolefin. The rate of solvent addition to the mixer can be adjusted in response to a change in the chromium-based catalyst feed rate, to maintain a substantially constant residence time of the chromium-based catalyst through the mixer, or to change the time contact permanence.
[0219] The method may include specifying the rate of addition of the reducing agent to the inline reduction system to give the desired polyolefin flow index. Similarly, the method may include specifying the ratio of the rate of addition of the reducing agent to the feed rate of the chromium-based catalyst through the inline reduction system to give the desired polyolefin flow index. The method may include specifying the rate of addition of the reducing agent to the inline reduction system to give the desired polyolefin flow index. Likewise, the method may include adjusting a ratio of a rate of addition of the reducing agent to a rate of feed of the chromium-based catalyst through the inline reduction system in response to a measured flow rate of polyolefin. The method may include adjusting the concentration of aluminum in the chromium-based catalyst to give a desired flow rate of the polyolefin and / or specifying the molar ratio of aluminum to chromium in the chromium-based catalyst to give the desired flow rate of the polyolefin. . In addition, the method may include adjusting the molar ratio of aluminum to chromium or an aluminum concentration in the chromium-based catalyst in response to changes in the chromium-based catalyst feed rate to maintain the desired flow rate of the polyolefin. The method may include adjusting a ratio of the feed rate of the reducing agent to the feed rate of the chromium-based catalyst through the in-line reduction system to maintain a polyolefin flow index value.
[0220] The method may or may not include contacting the chromium-based catalyst with the additional reducing agent in another system before feeding the chromium-based catalyst through the in-line reduction system. Thus, in certain embodiments, the chromium-based catalyst is not contacted with the reducing agent before feeding the catalyst through the in-line reduction system. On the other hand, in other embodiments, the chromium-based catalyst is contacted with a reducing agent before feeding the chromium-based catalyst through the in-line reduction system.
[0221] Another modality provides a method of operating a polyolefin reactor system, including feeding a chromium-based catalyst through an in-line mixer to a polymerization reactor, adding a reducing agent to contact the catalyst chromium-based through the in-line mixer for the polymerization and polymerization reactor of an olefin in a polyolefin in the polymerization reactor in the presence of the chromium-based catalyst. The chromium-based catalyst can be fed in the form of a paste through the in-line mixer to the polymerization reactor. The reducing agent can be added to the chromium-based catalyst in the mixer or upstream of the mixer, or a combination thereof. The method may include modulating the rate of addition of the reducing agent to the chromium-based catalyst. In fact, the reducing agent can be added to the chromium-based catalyst at a specified flow rate to give a desired polyolefin flow index. For example, the addition of the reducing agent may involve adjusting the rate of addition of the reducing agent to maintain a desired ratio of the rate of addition of the reducing agent at a feed rate of the chromium-based catalyst through the mixer. The method may include adjusting a ratio of a feed rate of the reducing agent to a feed rate of the chromium-based catalyst through the mixer, to give a desired polyolefin flow index. The method may include adjusting the rate of addition of the reducing agent to the chromium-based catalyst in response to the operating conditions of the polymerization reactor. In addition, the method may include adjusting the stirring speed of an in-line mixer agitator in response to the operating conditions of the polymerization reactor. In addition, the method may include adjusting a molar ratio of the reducing agent to the chromium-based catalyst in response to operating conditions of the polymerization reactor. The method may include adjusting a feed rate of the reducing agent to the chromium-based catalyst to maintain a specified molar ratio of the reducing agent to the chromium-based catalyst through the mixer, to give a desired polyolefin flow index .
[0222] The solvent can be added to the chromium-based catalyst through the in-line mixer to maintain or regulate a contact residence time of the chromium-based catalyst and reducing agent. Examples of contact residence times for the chromium-based catalyst and reducing agent in the in-line mixer can be in the range of 2 minutes to 120 minutes, in the range of 18 minutes to 30 minutes, and so on. The method may include adjusting the rate of solvent addition to the mixer in response to the operating conditions of the polymerization reactor or in response to the measured polyolefin flow rate. The method may include adjusting the rate of solvent addition to the mixer in response to a change in the chromium-based catalyst feed rate and maintaining a chromium-based catalyst residence time through the mixer.
[0223] Finally, an embodiment of a polymerization reactor system includes a mixer (for example, static mixer or stirred vessel) to contact a substantially continuous supply of chromium-based catalyst to a polymerization reactor with a reducing agent to form a catalyst feed composition having the chromium-based catalyst en route to the polymerization reactor. A residence time of the chromium-based catalyst through the mixer can be in the range of 2 minutes to 120 minutes in certain examples, or in the range of 18 minutes to 30 minutes in other examples. The reactor system includes a polymerization reactor (for example, a gas phase reactor) that receives the catalyst feed composition and in which an olefin is polymerized to a polyolefin in the presence of the chromium-based catalyst. The reactor system includes a control system for adjusting a rate of addition of the reducing agent to the mixer to give a desired polyolefin flow index. The control system can use a control valve to modulate the rate of addition, for example, a flow rate or mass feed rate by time or volume by time, from the reducing agent to the inline reducing system that has the mixer.
[0224] Furthermore, the modalities of the present disclosure provide a process for producing chromium-based catalyst compositions with a selected flow index response. Still other embodiments provide a process for the production of polyolefins comprising forming a chromium-based catalyst composition with a selected flow index response, as described herein, and contacting the chromium-based catalyst composition with olefins under polymerization conditions.
[0225] Advantageously, the modalities disclosed herein provide a method for adapting the flow index response of chromium-based catalysts. The ability to select the flow index response of a chromium-based catalyst even more advantageously allows for a greater number of polymerization products produced with chromium-based catalysts than was previously possible. In addition, chromium-based catalysts with a low or moderate flow index response advantageously allow the production of low flow index products with chromium-based catalysts at significantly higher reactor temperatures, where cooling is more efficient and higher production rates can be obtained. As another advantage, chromium-based catalysts with a selected flow index response result in lower hydrogen feed rates for the reactor. As yet another advantage, the greater flexibility of chromium-based catalysts to produce polymers of various flow rates allows for a better transition of the grades.
[0226] For the sake of brevity, only certain intervals are explicitly disclosed here. However, intervals from any lower limit can be combined with any upper limit to recite an interval not explicitly mentioned, as well as intervals from any lower limit can be combined with any other lower limit to recite an interval not explicitly recited, in the same way. that any upper limit can be combined with any other upper limit to recite an interval not explicitly recited. In addition, within a range it includes each point or individual value between its end points, although not explicitly recited. Thus, each individual point or value can serve as its own lower or upper limit combined with any other individual point or value or any other lower or upper limit, to recite an interval not explicitly recited.
[0227] All priority documents are hereby fully incorporated by reference for all jurisdictions in which such incorporation is permitted and to the extent that such disclosure is consistent with the description of the present invention. In addition, all documents and references cited here, including test procedures, publications, patents, magazine articles, etc. are hereby incorporated in full by reference for all jurisdictions in which such incorporation is permitted and to the extent that such disclosure is consistent with the description of the present invention.
[0228] Although the invention has been described with respect to a number of modalities and examples, those skilled in the art, benefiting from this disclosure, will understand that other modalities can be devised that do not depart from the scope and spirit of the invention as disclosed herein . EXAMPLE SECTION
[0229] It is to be understood that, although the present invention has been described in conjunction with specific modalities thereof, the foregoing description is intended to illustrate and not to limit the scope of the invention. Other aspects, advantages and modifications will be evident to those skilled in the technique to which the invention belongs.
[0230] Accordingly, the following examples are presented in order to provide those skilled in the art with full disclosure and description of how to prepare and use the compounds of the invention, and are not intended to limit the scope of what the inventors regard as their invention .
[0231] High density polyethylene resin samples were prepared in polymerizations using catalysts made using different locations and arrangements in the mixing vessel for introducing reducing agent feed, different temperatures and drying line exit times, sizes of different batches and in some cases by inline reduction, as noted in Tables 1 to 6 below. The examples in Tables 1 and 5 are chromium oxide catalysts reduced on either a pilot scale or a commercial factory scale. For some of these catalysts, Table 1 includes results from scale laboratory polymerization reactor. The examples in Table 2 are chromium oxide catalysts made on a pilot factory scale and used to polymerize olefin in a pilot phase gas polymerization reactor (fluidized bed). The examples in Tables 3 and 6 are chromium oxide catalysts made on a factory scale and polymerized in a gas phase fluidized bed polymerization reactor. These examples collectively illustrate the control or adaptation of the flow index response of a catalyst using different DEAlE feed arrangements and selected drying line outlet temperatures for the selected drying times and different batch sizes. The examples in Table 4 are chromium oxide catalysts activated on a factory scale and used to polymerize olefin in a pilot phase gas polymerization reactor (fluidized bed) by means of in-line reduction with reducing agent. General Catalyst Preparation (chromium oxide catalysts)
[0232] The catalysts employed in the Examples were activated on a commercial scale, as follows. An adequate amount of a porous silica support containing about 5 weight percent chromium acetate (chromium on silica class C35300MSF, produced by PQ Corporation), which is equivalent to about 1 weight percent Cr content, having a particle size of about 82 microns and a surface area of about 500 square meters per gram, it was loaded into a fluidized bed heating vessel. There, the catalyst precursor (chromium on silica) was slowly heated at a rate of about 50 ° C per hour under dry nitrogen to 200 ° C and maintained at that temperature for about 4 hours. Then, the chromium on silica was heated slowly at a rate of about 50 ° C per hour under dry nitrogen to 450 ° C and maintained at that temperature for about 2 hours. The nitrogen stream was then replaced by a dry air stream and the as on silica was heated slowly at a speed of about 50 ° C per hour to 600 ° C, where it was activated for about 6 hours. The activated catalyst was then cooled with dry air (at room temperature) to about 300 ° C and further cooled from 300 ° C to room temperature with dry nitrogen (at room temperature). The resulting cooled catalyst powder was stored under a nitrogen atmosphere until treated with a reducing agent in a mixing vessel or by in-line reduction as described below.
[0233] In a typical reduction of chromium oxide catalyst, the catalyst was placed in a vertical catalyst mixer with a double helical tape stirrer under an inert atmosphere. Dry hexane or isopentane solvent was added to properly suspend the supported catalyst. All catalysts used C35300MSF starting material in the Examples listed in Tables 1, 2, 3, 5 and 6. The size of the catalyst batch was varied in the Examples performed and used in Tables 5 and 6. For all of these catalysts, about 7, 1 liter of solvent was loaded per kilogram (0.89 gallons per pound) of support. DeAlE, available from Akzo Nobel and obtained as a 25 wt% solution in isopentane or hexane, was then added above the surface of the catalyst suspension at a selected rate over a period of about 40 minutes to obtain a selected weight percentage aluminum over the catalyst. The feeding site of DEAlE was varied radially from the central vertical axis of the container. DEAlE insert tubes were missing or were used with variable tube length below the underside of the top head of the container. The mixture was stirred at a selected rate of stirring at a temperature of approximately 45 ° C during the addition time. The mixture was then stirred at a controlled rate for about 1 hour on a pilot scale or 2 hours on a commercial scale. Then, the solvent was substantially removed by drying at a selected coating temperature for about 16 to 21 hours. The coating temperature was selected to give a material temperature that aligned close to the target of 61, 64, 71 or 81 ° C during the last hours of drying. Pilot scale C35300MSF-based catalysts were generally dried for a total of 16 hours with a progressively stronger vacuum to be applied as the drying time increased. Example 9 was dried for a total of 19 hours. The factory-based C35300MSF-based batches were dried for 18 or 21 total hours at slightly above atmospheric pressure. The only factory-reduced catalysts in these examples that were dried for a total of 18 hours were in Comparative Examples 10, 25 and 26. The total drying time is the lift time and the line exit time. The "drying line exit time" is the time when the bed temperature was within 2 ° C of the final line exit temperature, and ranged from about 6 to about 11 hours, in most of these Examples. The resulting free flowing, dry catalyst powder was then stored under nitrogen until used. General laboratory testing procedures for catalysts
[0234] Certain catalyst samples that were prepared as described above and shown in Table 1 were tested for their response to the flow index in a 1 liter laboratory reactor of pulp. In a typical paste polymerization, the catalyst was loaded into a reactor equipped with a mechanical stirrer and a jacket for internal temperature control. In Examples 8 and 9, an amount of 0.144 to 0.146 g of catalyst was introduced. In the remaining Examples shown in Table 1, an amount of 0.177 to 0.210 g of catalyst was introduced. This was followed by 600 ml of dry purified isobutene and 500 cc of hydrogen were charged, the reactor was brought to the reaction temperature (95 ° C in these examples), during which the ethylene feed and 10 ml of 1- hexene was loaded in batches through a small gas bottle. Ethylene was fed continuously on demand to maintain a partial ethylene pressure of 13.8 bar (200 psi). Ethylene uptake was measured with an electronic flow meter. The polymerizations were carried out until about 180 grams of polyethylene were made. The reactor was opened after depressurization and cooled in order to recover the polymer. After drying, the flow rate of the polymer was measured. General pilot factory testing procedure for reduced and dry catalysts
[0235] Certain catalyst samples that were prepared as described above and shown in Tables 2, 3 and 6 were tested for their response to the flow index by producing ethylene / 1-hexene copolymer in a pilot scale fluidized bed reactor of 14 inches in diameter. The cycle gas was circulated through the reactor and the reaction heat was removed in a heat exchanger. The catalyst powder was introduced continuously into the fluidized bed. Monomers, hydrogen and oxygen were fed into the cycle gas pipeline. The product was transferred intermittently in a product chamber, depressurized, degassed briefly, and then discharged to a drum. The conditions in the fluidized bed reactor were kept at a constant value or in a narrow range for the related experiments within each set of tests that were conducted. The reactor bed temperature was about 98.2 ° C. The partial pressure of ethylene was about 13.8 bar (200 psi). The ratio of molar gas H2 / C2 in the cycle gas was maintained at about 0.04. The molar ratio of 1-hexene to ethylene in the cycle gas was maintained at about 0.0100. The oxygen added to ethylene in the feed gas was maintained at about 25 ppb by volume. The total pressure of the reactor was about 24.8 bar absolute (360 psia). The surface velocity of the gas within the fluidized bed was 1.78 - 1.93 feet / s. The average residence time of the resin in the reactor ranged from 2.08 to 2.28 hours. Tables 2, 3, and 6 summarize the catalyst information and reaction conditions together with the properties of the resulting polymers. Examples 1, 2, 4, 5, 6 and 7
[0236] In Examples 1, 2, 4, 5, 6 and 7, the DEAlE-reduced chromium oxide-based catalysts were prepared on a pilot scale using factory-activated C35300MSF support as described above and then tested for the response flow index in a laboratory polymerization reactor. The conditions of preparation of the catalyst used are shown in Table 1 (agitation rate during the addition and reaction of DEAlE, load in Al by weight, time of addition of DEAlE, arrangement of feeding of DEAlE and temperature and time of exit of line of drying). Batch sizes were about 88% full when filled in the Examples refers to a lot size that only reaches the top of the agitator impeller blades. The results of paste polymerization in the laboratory are shown in Table 1 and in Figures 4 and 6.
[0237] The results show that at a rate of agitation within a narrow range and within a narrow range of Al load by weight, and within a narrow time range of DEAlE addition, the measured flow index response increased when the DEAlE was fed with an inserted tube to substantially prevent the bottom of the container head from sliding down to the container wall. The results also show that the measured flow index response increased further when the tip of the tube was located farther from the wall, which means more towards the center of the container.
[0238] Comparative Examples 1 and 2 show the relatively low measured flow rates (20 and 35 dg / min) obtained for the polymer from two pulp polymerizations in the laboratory with reduced catalyst from the pilot plant, without an insert tube and with DEAlE added about 90% of distance radially from the vertical centerline of the container, thus in a position very close to the wall. During these catalyst preparations, DEAlE was observed to flow completely or almost entirely along the underside of the head and down the side wall where it came into contact with a green viscous agglomeration that was observed to have formed within 20 minutes of the start of the addition. DEAlE and moved more slowly than the mass of the reaction mixture. Examples 5 and 7 compared to Examples 1 and 2 show that when using an insert tube of at least 0.5 inch protrusion below the top head, at a location about 83% of the radial distance from the vertical centerline of the container, the flow rate increased significantly to 76 dg / min, and further increased to 104 when a 1-inch protruding insert was used at a location about 67% of the radial distance from the vertical centerline of the container. Figure 4 shows this effect in a bar chart. The drying line outlet temperature was 70 to 72 ° C in these four examples. Examples 4 to 6 show that when the drying line outlet temperature was reduced from 72 ° C to 82 ° C to about 61 ° C, the measured flow index increased significantly, from about 76 to about 101 dg / min Figure 6 shows this effect graphically. As illustrated by the examples above, it is possible to adapt the flow index response of chromium oxide catalysts based on a pilot scale-reduced DEAlE based C35300MSF, by varying the feed location of DEAlE radially, using a feed tube insert. of DEAlE protruding below the bottom side of the top head of the container and / or varying the temperature and drying time of the catalyst drying line. Examples 8 and 9
[0239] In Examples 8 and 9, chromium oxide based catalysts reduced by DEAlE were reduced on a pilot factory scale using factory activated C35300MSF support as described above. The conditions of preparation of the catalyst used are shown in Table 1 (agitation rate during the addition and reaction of DEAlE, load in Al by weight, time of addition of DEAlE, arrangement of feeding of DEAlE and temperature and time of exit of line of drying). Batch sizes were about 88% full when full refers to a lot size that only reaches the top of the agitator impeller blades. Examples 4 to 6 showed the improved flow index response possible by drying at the bottom line outlet temperature. In order to achieve the same level of residual solvent in the final catalyst, extending the drying time is an option. In Examples 8 and 9, to determine any deleterious effects of increasing drying time on the performance of the catalyst, the catalyst was dried differently than in other examples. The catalyst in Example 8 was dried for 16 hours in total, but the catalyst in Example 9 was dried for 19 hours in total. In both examples, a smoother vacuum was applied to the catalysts during drying to keep the material temperature close to the final drying line outlet temperature for everyone, except during the first hour of drying when evaporation is fast and the batch cools. The measured flow rates resulting from 118 and 114 dg / min, respectively, show total drying times of 16 to 19 hours and the drying line exit times of about 15 to 18 hours have no significant effect on the index response. flow rate of the catalyst. Examples 10 to 14
[0240] In Examples 10 to 14, DEAlE-reduced chromium oxide-based catalysts were prepared on a factory scale using the activated C35300MSF support as described above. The conditions of preparation of the catalyst used are shown in Table 1 (agitation rate during the addition and reaction of DEAlE, load in Al by weight, time of addition of DEAlE, arrangement of feeding of DEAlE and temperature and time of exit of line of drying). The lot size for Comparative Example 10 was about 100% full when full refers to a lot size that only reaches the top of the agitator impeller paddles. The batch size for Examples 11 to 14 was about 95% filled. Table 1. Conditions for preparing the catalyst for Examples 1-14 and results of paste polymerization in the laboratory for Examples 1-9
Examples 15 to 19
[0241] In Examples 15 to 19, DEAlE-reduced chromium oxide-based catalysts were prepared on a support scale of C35300MSF activated as described above and then the flow rate response was tested in a bed polymerization reactor fluidized in gas phase. Specifically, the catalysts prepared in Comparative Example 3 and Examples 4 to 7 were used in these polymerization examples. The conditions of preparation of the catalyst used are indicated in Tables 1 and 2 (agitation rate during the addition and reaction of DEAlE,% by weight of Al charge, time of addition of DEAlE, feeding arrangement of DEAlE and temperature and time of drying line outlet). The polymerization results are shown in Table 2 below and in FIG. 5 above.
[0242] The results show that at a rate of agitation within a narrow range and within a narrow range of wt% Al load and within a narrow time range of DEAlE addition, the flow index response measurement increased when the DEAlE was fed with an insert tube to substantially prevent it from running down from the bottom of the container head to the container wall and the measured flow index response increased further when the tube tip was located farther from the wall, which meant more towards the center of the container.
[0243] Comparative Example 15 shows the relatively low measured flow rate (4.43 dg / min) obtained for the polymer from a polymerization of a pilot fluidized bed in a gas phase with a reduced catalyst from a pilot plant, without a insert tube and with DEAlE added about 90% of the distance radially from the vertical center line of the container, thus in a very close position to the wall. Examples 17 and 19 compared to Comparative Example 15 show that when using an insert tube of at least 0.5 inch protrusion below the top head, at a location about 83% of the radial distance from the line vertical center of the container, the flow rate increased significantly to 5.31 dg / min, and further increased to 8.20 when a 1-inch protruding insert was used at a location about 67% of the radial distance from the line vertical center of the container. FIG. 5 above displays this effect in a bar chart. The drying line outlet temperature was 71 to 72 ° C in these three examples. Examples 16 to 18 show that when the drying line outlet temperature was reduced from 72 ° C to 82 ° C to about 61 ° C, the measured flow index increased significantly, from about 5.1 to 5.3 to about 7.6 dg / min. FIG. 7 above displays this effect graphically. As illustrated by the examples above, it is possible to adapt the flow index response of chromium oxide catalysts based on a pilot scale-reduced DEAlE based C35300MSF, by varying the feed location of DEAlE radially, using a feed tube insert. of DEAlE protruding below the bottom side of the top head of the container and / or varying the temperature of the catalyst drying line outlet (and the time). Table 2. Catalyst information, reaction conditions of the pilot plant and average resin properties for Examples 15-19

Examples 20 to 24
[0244] In Examples 20 to 24, DEAlE-reduced chromium oxide-based catalysts were prepared on a factory scale using activated C35300MSF support as described above and then the flow rate response was tested in a gas reactor. polymerization of fluidized bed in a gas phase of pilot scale. Specifically, the catalysts prepared in Comparative Example 10 and Examples 11 to 14 were used. The conditions of preparation of the catalyst used are indicated in Tables 1 and 3 (agitation rate during the addition and reaction of DEAlE,% by weight of Al charge, time of addition of DEAlE, feeding arrangement of DEAlE and temperature and time of drying line outlet). The polymerization results are shown in Table 3. The polymerization conditions were kept constant. The reactor operated well without cases of resin agglomeration or interruption of the polymerization process.
[0245] The results in Table 3 show that at a rate of agitation within a narrow range and within a narrow range of% by weight of Al charge and within a narrow range of DEAlE addition time, the response of the measured flow index increased when the DEAlE was fed with an insert tube to substantially prevent it from running down from the bottom of the container head to the container wall and the measured flow index response increased further when the tip of the container tube was located farther from the wall, which meant more towards the center of the container. The results in Table 3 further show that at a given rate of agitation, for catalysts with similar wt% Al load and within a narrow time span of DEAlE addition, the measured flow index response increases with decreasing the drying line outlet temperature. Comparative Example 20 shows that without DEAlE feed insert, with DEAlE added ~ 54% of the radial distance from the center line of the container to the wall and at 73 ° C of drying line outlet temperature and about 6 hours of drying time. drying line exit time, a flow rate of 4.48 dg / min was obtained.
[0246] Examples 21 and 22 compared to Example 20 show that without DEAlE feed insert and with DEAlE feed in the same radial location and with about 8 to 9 hours of drying line exit time, as the drying line outlet temperature decreased from 73 ° C to about 65 ° C for the factory reduced activated C35300MSF catalyst, the measured flow index increased from about 13% to 4.48 for the 5.0 range at 5.1 dg / min. It is believed that this increase in the flow rate was due to the decrease in the drying line outlet temperature and not due to the shorter total drying time of 18 hours in Comparative Example 20, nor due to the drying line outlet time. shorter. See Examples 8 and 9. In Example 23 with a DEAlE insert tube that projects 2 inches below the underside of the top head and is about 74% of the radial distance from the vertical center line of the container to at the wall and at a drying line outlet temperature of about 64 ° C, the measured flow rate of 5.19 dg / min increased only slightly compared to Examples 21 and 22, but significantly increased compared to the Comparative Example 20. The location in Example 23 closest to the container wall limited the improvement provided by the DEAlE feed insert. In Example 24 with a DEAlE insert tube that protrudes 2 inches below the underside of the top head and located about 54% of the radial distance from the vertical center line of the container to the wall and at an outlet temperature of drying line of about 63 ° C, the measured flow rate of 5.95 dg / min was increased by about 33% over Comparative Example 20 without insert and higher drying line outlet temperature of 73 ° CO flow rate measured in Example 24 increased 17% over Examples 21 and 22 without DEAlE feed insert, but with a similar low drying line outlet temperature of about 65 ° C. The flow rate measured in Example 24 increased by about 15% above Example 23 in which the DEAlE feed insert of the same length and approximately the same drying line outlet temperature was used, but the DEAlE feed site was significantly closer to the container wall. Table 3. Catalyst information, reaction conditions of the pilot plant and average resin properties for Examples 20-24


[0247] These examples illustrate, among other things, for reduced chromium oxide catalysts, the surprising effect on the utilization flow index response of different DEAlE feed arrangements and different radial DEAlE feed positions from the center line vertical container and different drying line outlet temperatures and times in both a fluidized bed gas polymerization process and in a paste polymerization process for polyethylene copolymers, which included ethylene units as well as other monomer units . These effects can be used to adapt the flow rate response of a catalyst to produce target polymers with high, medium or low flow rates under a variety of polymerization conditions. As described above and illustrated in the Examples, the flow index response of a chromium-based catalyst can be adapted by contacting the chromium-based catalyst with a reducing agent fed at a radial location selected from the vertical centerline of the container and with a feed insert protruding from the bottom side of the container head and, optionally, drying at a drying line outlet temperature below 68 ° C. The use of the chromium-based catalyst compositions described herein, in which the catalysts have an adapted or selected flow index response, provides a capacity for flexibility of the polymerization process, which has significant commercial application in the polymerization of polyolefins. Examples of inline reduction
[0248] Gasified fluidized bed polymerizations were conducted in a similar manner to that employed in previous gas phase Examples. With respect to catalyst systems, Comparative Examples 25 and 26 use DEAlE reduced catalyst prepared on a factory scale using the activated C35300MSF support as described above. The preparation conditions for the catalyst used are indicated mainly in Table 4 and were very similar to those used in Comparative Example 10. DEAlE was added about 54% of the distance radially from the vertical center line of the container and no insert tube was used. . The temperature and the drying line exit time were 73.4 ° C and 5.35 hs. The batch size was about 99% full when full refers to a batch size that only reaches the top of the agitator impeller blades.
[0249] Examples 27-30 use non-reduced activated chromium oxide catalyst C35300MS prepared as described previously in General catalyst preparation. In all cases, the chromium oxide catalysts were activated at 600 ° C in air. In Examples 27-30, the unreduced catalyst and DEAlE reducing agent are fed through a Parr Series 4560 bottom port type mini reactor vessel (Parr Instrument Company, Moline, Illinois, USA), hereinafter referred to as a Parr mixer at temperatures between 14 and 23 ° C prior to addition to the polymerization reactor. The chromium oxide catalyst is fed with 11.2% by weight of mineral oil slurry and the reducing agent is fed as a solution of 0.20% by weight in isopentane. The air driven agitator near the bottom of the Parr mixer includes a four-bladed turbine with no pitch on the blades (0.25 inch high, 0.75 inch in diameter). The chromium oxide catalyst paste enters through an immersion tube at a point immediately above the stirrer. The reducing agent enters the top of the Parr mixer, and the mixed contents come out at the bottom. An optional line for adding additional isopentane to the Parr mixer also enters the top. The Parr mixer operates at a higher pressure than the polymerization reactor. The reduced catalyst is transported to the polymerization reactor with an auxiliary isopentane carrier current, with the possible addition of a nitrogen carrier gas by a T or Y block at a location on the line near the reactor inlet. The catalyst enters the reactor fluidized bed about 1.5 to 2.0 feet above the distributor plate through a section of stainless steel tube that can typically extend about 1/4 to 1/2 the distance along the diameter of the pilot reactor straight section.
[0250] In Comparative Example 25 the catalyst is fed dry to the reactor producing a polymer with a certain flow and density index. In Comparative Example 26, the reduced catalyst is fed to the reactor as a slurry of 11.2% by weight. It can be seen that there is some loss of catalyst productivity and an increase in the polymer flow index value, possibly due to impurities in the oil paste.
[0251] In Example 27, the reducing agent is fed to the mixer, together with the chromium oxide catalyst with approximately the same chromium ratio as that found in the Comparative Examples. It can be seen that the flow rate of the polymer and the productivity of the catalyst have increased significantly. Comparing Examples 26 to 27, the flow rate response increased from about 10 dg / min (isolated catalyst reduced and dried in batches) to about 48 dg / min (linear reduction of the catalyst). Examples 28-30 show that the flow rate of the polymer can be controlled by varying the ratio of the reducing agent to the chromium oxide catalyst. A significantly less reducing agent is required to obtain the same flow index response as that obtained with the reduced catalyst in the mixing tank. In all cases of inline reduction, the polymer morphology is maintained without loss of apparent density of the polymer. Examples 28 and 29 show that at a constant DEAlE feed rate, the reaction temperature and molar ratio of hydrogen to ethylene can be used to adjust the flow rate of the polymer. The average residence time of the mixer listed in Table 4 can be marked as the average residence time of the DEAlE contact with the catalyst in the mixer. The molar ratio of Al added by weight and DEAlE (added) / Cr represents the DEAlE added in the inline reduction and are determined based on the feed rate of DEAlE in line and the feed rate of the catalyst. Table 4. Inline reduction

* Value calculated on the DEAlE line feed
[0252] Within each set, the temperature of the polymerization reactor, the molar ratios from hexene to ethylene in the gas phase and the DEAlE level for these catalysts with different flow index responses were varied to obtain the polymer density and the desired flow rate. Other polymerization conditions were kept constant within each set. The lower reactor temperature consistently leads to a lower flow rate and a lower melt index for a given DEAlE-reduced chromium catalyst. Batch size examples varying from 31 to 35
[0253] In Examples 31 to 35, DEAlE-reduced chromium oxide based catalysts were prepared on a factory scale using the activated C35300MSF support as described above. The conditions of preparation of the catalyst used are indicated in Table 5 (batch size, agitation rate during the addition and reaction of DEAlE, load in Al by weight, time of addition of DEAlE, feeding arrangement of DEAlE and temperature and time of drying line outlet). In Example 31 the batch size was about 95% of the total, such that the pulp surface was close to the top of the double helical ribbon impeller during the addition of DEAlE. In Examples 32, 33, 34 and 35, the lot size was reduced to about 75% of the total. This placed the paste's surface well below the top of the impeller. This is believed to have contributed to a better mixing of the surface where DEAlE is added throughout the DEAlE addition step and thus to a better distribution of DEAlE throughout the batch. In Examples 34 and 35 more DEALE addition time of 62 minutes was used in combination with the smaller lot size and the nozzle insert. In Example 35, a higher drying line outlet temperature was used. Table 5. Conditions for preparing the catalyst for Examples 31-35
Examples 36 to 40
[0254] In Examples 36 to 40, DEAlE-reduced chromium oxide-based catalysts were prepared on a factory scale using activated C35300MSF support as described above and then the flow rate response was tested in a gas reactor. polymerization of fluidized bed in a gas phase of pilot scale. Specifically, the catalysts prepared in Examples 31 to 35 were used. The conditions of preparation of the catalyst used are indicated in Table 5 (batch size, agitation rate during the addition and reaction of DEAlE, load in Al by weight, time of addition of DEAlE, feeding arrangement of DEAlE and temperature and time of drying line outlet). The polymerization results are shown in Table 6. The polymerization conditions were kept constant. The reactor operated well without cases of resin agglomeration or interruption of the polymerization process.
[0255] In Table 6, Example 37 compared to Example 36 shows when a 2-inch protruding insert tube below the top head was used at a location 54% of the radial distance from the vertical centerline of the container, the smaller batch size produced a catalyst with a 66% higher measured flow rate (8.75 dg / min versus 5.27 dg / min respectively). In Example 38, a DEAlE feed tube insert was not used in a small batch, however Table 6 shows that this catalyst gave a significantly higher flow rate (7.46 dg / min) in Example 38 than Example 36 (5.27 dg / min) with catalyst made with larger normal lot size and a DEAlE feed nozzle insert. Only a small portion of this 42% increase in the flow index should be due to the slightly higher weight% of Al (4.2% relatively) in Example 38 over Example 36. In Example 39 vs. Example 37 can be seen how increasing the DEAlE addition time from 42 minutes to 62 minutes further increased the flow rate from 8.75 dg / min to 9.54 dg / min. In Example 40 vs. Example 39 can be seen how the increase in the drying line outlet temperature from 62.1 oC to 70.1 oC decreased the flow rate from 9.54 dg / min to 7.26 dg / min. The results in Table 6 show that at a rate of agitation within a narrow range and within a narrow range of Al weight loading, and within a narrow range of DEAlE addition time, the measured flow index response increased when the lot size was reduced, that the paste surface was well below the top of the impeller throughout the addition of DEAlE. In addition, the combination of smaller batch size with an insertion tube in the DEAlE addition nozzle gave a relatively high increase in the flow index response. The prolongation of the DEAlE addition time from 42 to 62 minutes gave the greatest increase in the flow index response in these tests. The elevated line outlet temperature reduced the flow index response. Table 6. Catalyst information, reaction conditions of the pilot plant and average resin properties for Examples 36-40

权利要求:
Claims (15)
[0001]
1. Method of preparing a chromium-based catalyst to polymerize an olefin into a polyolefin, said method being characterized by the fact that it comprises: - contacting a chromium-based catalyst with a reducing agent in a solvent to reduce a state of oxidation of at least some chromiums in the chromium-based catalyst to obtain a reduced chromium-based catalyst, the chromium-based catalyst comprising a chromium oxide catalyst; - drying the reduced chromium-based catalyst at an outlet temperature of the drying line; and - adjusting the drying line outlet temperature to change the flow rate response of the reduced chromium-based catalyst.
[0002]
Method according to claim 1, characterized in that the reducing agent comprises an organoaluminium compound, and the solvent comprises an alkane.
[0003]
Method according to claim 1, characterized in that the reducing agent comprises diethyl aluminum ethoxide (DEAlE).
[0004]
4. Method according to claim 1, characterized in that the reducing agent comprises triethyl aluminum (TEAL).
[0005]
5. Method according to claim 1, characterized in that the chromium-based catalyst comprises an inorganic oxide support having a pore volume of 1.1 to 1.8 cubic centimeters (cm3) / g and an area of area of 245 to 375 square meters (m2) / g.
[0006]
6. Method according to claim 1, characterized in that the chromium-based catalyst comprises an inorganic oxide support having a pore volume of 2.4 to 3.7 cm3 / g and a surface area of 410 to 620 m2 / g.
[0007]
7. Method according to claim 1, characterized in that the chromium-based catalyst comprises an inorganic oxide support having a pore volume of 0.9 to 1.4 cm3 / g and a surface area of 390 to 590 m2 / g.
[0008]
Method according to claim 1, characterized in that the chromium-based catalyst comprises an activated and supported chromium-based catalyst, and in which the drying comprises the evaporation of at least a major part of the solvent.
[0009]
9. Method according to claim 1, characterized in that the contact of the chromium-based catalyst with the reducing agent allows the chromium-based catalyst to react with the reducing agent to obtain the chromium-based catalyst reduced.
[0010]
10. Method according to claim 1, characterized in that the contact comprises contacting the chromium-based catalyst with the reducing agent in the solvent at a reaction temperature lower than the drying line outlet temperature, and where the reaction temperature is in the range of 20 ° C to 60 ° C, and the outlet drying temperature is in the range of 40 ° C to 90 ° C.
[0011]
11. Method according to claim 1, characterized in that the drying comprises reducing the pressure of a mixture of the reduced chromium-based catalyst and the solvent.
[0012]
12. Method, according to claim 1, characterized in that the drying is started after all the reducing agent placed in contact with the chromium-based catalyst has been consumed in a reaction of the reducing agent with the base-catalyst of chrome.
[0013]
13. Method, according to claim 1, characterized by the fact that it comprises the collection of the reduced chromium-based catalyst for supply to a polymerization reactor.
[0014]
14. Method according to claim 1, characterized by the fact that it comprises feeding the catalyst based on chromium reduced to a polymerization reactor to polymerize an olefin into a polyolefin.
[0015]
15. Method according to claim 1, characterized in that the drying comprises filtering the reduced chromium-based catalyst to remove the solvent at a temperature below 30 ° C.

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引用文献:

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法律状态:
2019-09-10| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-12-01| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-01-19| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 01/09/2015, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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US201462044732P| true| 2014-09-02|2014-09-02|

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US62/044,732|2014-09-02|

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PCT/US2015/047936|WO2016036737A1|2014-09-02|2015-09-01|Polyolefin production with chromium-based catalysts|

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