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    • 专利摘要:
    There is provided a catalyst for the production of ethylene oxide with high efficiency and high selectivity, as well as stable for a long period of time. The catalyst for the production of ethylene oxide comprises silver and a reaction promoter selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, thallium, sulfur, chromium, molybdenum, tungsten and rhenium supported on a porous support comprising α-alumina wherein the amount of α-alumina in the support is greater than or equal to 90% by mass with respect to the total mass, 100% by mass of the support, characterized in that a relative standard deviation of the silver loading degree of each particle of the catalyst is 0.001 or more and 0.1 or less.
    公开号:BE1019674A5
    申请号:E2011/0187
    申请日:2011-03-28
    公开日:2012-09-04
    发明作者:Hirota Hiroyuki；Yunoki Hiromi；Ochiai Kenichi
    申请人:Nippon Catalytic Chem Ind；
    IPC主号:
    专利说明:

    CATALYST FOR THE PRODUCTION OF ETHYLENE OXIDE AND METHOD FOR THE
    PRODUCTION OF ETHYLENE OXIDE
    BACKGROUND OF THE INVENTION
    FIELD OF THE INVENTION
    This invention relates to a catalyst for the production of ethylene oxide and a process for the production of ethylene oxide. More in detail, this invention relates to a catalyst for the production of ethylene oxide that is superior in selectivity to ethylene oxide and the life of the catalyst, and is capable of producing the ethylene oxide with high selectivity for a long period of time, and a process for the production of ethylene oxide using this catalyst for the production of ethylene oxide.
    Description of the relevant state of the art
    Ethylene oxide is produced industrially on a large scale by catalytic vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst. For the use of the silver catalyst in this catalytic vapor phase oxidation, various technologies have been proposed with regard to a carrier thereof, a loading method, and a reaction promoter or the like.
    Catalytic activity, selectivity and service life of the silver catalyst have already reached a high level, but even more improvement of its catalytic activity is required. For example, with regard to selectivity, due to the large-scale production of ethylene oxide, even only a 1% improvement in selectivity results in an extreme saving on the use of quantities of ethylene as a raw material, and its economic effect is large. Under such circumstances, the development of the silver catalyst with a more superior catalytic performance and the search for high efficiency or improvement of the selectivity of the catalytic vapor phase oxidation reaction in a multi-tube type reactor have been using the same, continuous themes of researchers in the relevant technical area.
    For example, WO 2004/101144 describes a catalyst with silver on a support with α-alumina as a main component, and describes the appropriate catalyst size, amount of silver on the support, as well as the amount of silver loaded into a catalyst layer, obtained by packing the catalyst into a reactor. In addition, for example, JP-A-2002-306953 discloses that a catalyst can be uniformly packed and stably used for a long time by packing the catalyst into a reaction tube of a support multi-tube type reactor at a prescribed speed. Further, for example, JP-A-2010 - 36115 describes a method for packing a catalyst with a prescribed outer diameter or length into a reaction tube with a prescribed inner diameter, and describes the amount of silver that the catalyst layer contains.
    SUMMARY OF THE INVENTION
    However, there is still room for improvement in the sense that conversion and selectivity of the response remain insufficient, even using the methods described in the aforementioned patent literature. Moreover, although the development of a catalyst for the production of ethylene oxide, which is capable of satisfying both the requirement of catalyst selectivity and the service life of the catalyst, this is still not realized.
    Accordingly, it is an object of this invention to provide a catalyst for the production of ethylene oxide that is capable of producing stable ethylene oxide with high efficiency and high selectivity for a long period of time.
    In addition, it is another object of this invention to provide a process for the production of ethylene oxide using this catalyst.
    We have intensively studied a way to solve the problem described above, in particular the distribution of the silver loading in the catalyst for the production of ethylene oxide. As a result, we have found that in the catalyst comprising silver and a reaction promoter supported on a porous support comprising α-alumina as the main component, a desired performance cannot be obtained when the content (degree of loading) of silver in each catalyst particle is uneven. Furthermore, we have also found that by uniformly distributing silver on a porous support comprising α-alumina as a major component, ethylene oxide can be produced with a higher efficiency and a higher selectivity and also the service life of the catalyst is longer compared to that of wherein the silver is worn under conditions other than the above, and thus the invention is practiced.
    That is, this invention is a catalyst for the production of ethylene oxide comprising silver and a reaction promoter supported on a porous support comprising α-alumina as a main component, characterized in that a relative standard deviation of the silver charge degree of each particle of the catalyst is determined by the following formula (1), 0.001 or more, and 0.1 or less.
    (1) wherein the standard deviation of the silver loading degree is determined by the following formula (2):
    (Standard deviation from the (2) silver loading degree) (where N stands for the number of catalyst particles for which the silver loading degree is measured, and Xn represents the silver loading degree of each particle); and the average silver charge degree is an arithmetic mean of the silver charge levels of N particles.
    In addition, this invention relates to a method for producing ethylene oxide which comprises subjecting ethylene to catalytic vapor phase oxidation with a molecular oxygen-containing gas in the presence of the ethylene oxide production catalyst.
    The ethylene oxide production catalyst of this invention can suitably be used as a ethylene oxide production catalyst using a multi-tube supportive reactor, and exhibits high efficiency and high selectivity, as well as superior catalyst life ( durability). For this reason, ethylene oxide can be stably produced using the catalyst of this invention for a long period of time.
    DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
    Below, an explanation will be given of embodiments of the present invention.
    An aspect of this invention is a catalyst for the production of ethylene oxide comprising silver and a reaction promoter supported on a porous support comprising α-alumina as a main component, characterized in that a relative standard deviation of the silver charge degree of each particle of the catalyst is 0.001 or more and 0.1 or less.
    The relative standard deviation of the silver loading degree is a value determined by the following formula (1).
    (1) wherein the standard deviation of the silver loading degree is determined by the following formula (2):
    (Standard deviation from the (2) silver loading degree) (where N stands for the number of catalyst particles for which the silver loading degree is measured, and Xn represents the silver loading degree of each particle); and the average silver charge degree is an arithmetic mean of the silver charge levels of N particles.
    A composition of the support used for the ethylene oxide production catalyst of this invention is not particularly limited as long as it contains α-alumina as the main component. Here, the carrier "includes α-alumina as a major constituent" means that it may partially contain alumina of various other forms other than α-alumina, such as γ-alumina and amorphous alumina. The alumina content in the carrier is preferably equal to or higher than 90 mass%, more preferably equal to or higher than 95 mass%, and even more preferably equal to or higher than 98 mass mass% relative to the total mass, 100 mass%, of the carrier. Another composition is also possible, as long as it is only one that comprises α-alumina as a major constituent; however, the support may contain, for example, an oxide of an alkali metal or an alkaline earth metal, or an oxide of a transition metal. Its content is also not particularly limited, but the oxide content of the alkali metal or alkaline earth metal is preferably 0 to 5 mass%, and more preferably 0.01 to 4 mass%, as converted to an oxide. In addition, the content of the transition metal oxide is preferably 0 to 5 mass%, and more preferably 0.01 to 3 mass%, as converted to an oxide.
    In addition, the support usually contains silica (silica). The silica content in the support is not particularly limited, but preferably 0.01 to 10.0 mass%, more preferably 0.1 to 5.0 mass%, and even more preferably 0.2 to 3.0 mass%.
    It should be noted that the composition of the above carrier or the content of each component can be determined using an X-ray fluorescence analysis method.
    The particle diameter of an α-alumina as a raw material of the support is not particularly limited, but a primary particle diameter of the α-alumina is preferably 0.01 to 100 µm, more preferably 0.1 to 20 µm, with even more preferably 0.5 to 10 µm, and particularly preferably 1 to 5 µm. Moreover, the secondary particle diameter of the α-alumina is preferably 0.1 to 1000 µm, more preferably 1 to 500 µm, even more preferably 10 to 200 µm, and particularly preferably 30 to 100 µm.
    The shape of the carrier is not particularly limited, and in addition to a ring shape, a spherical shape, a cylindrical shape, a pellet shape, and the shape of a hollow cylinder, reference can also be made to general knowledge. In addition, the size (average diameter) of the support is not particularly limited, but preferably 3 to 20 mm, and more preferably 4 to 10 mm.
    The specific surface of the support is also not particularly limited, however, preferably 0.03 to 10 m2 / g, more preferably 0.3 to 5.0 m2 / g, and even more preferably 0.5 to 3, 0 m2 / g. When the specific surface of the support is equal to or higher than 0.03 m 2 / g, loading of the necessary amount of catalyst component becomes possible, and as the specific surface of the support becomes larger, well-distributed loading of the catalyst component becomes easier. In addition, the specific surface area is preferably equal to or higher than 0.03 m2 / g because the surface area of the catalyst component, which is an active site of the catalytic reaction, becomes larger. On the other hand, when the specific surface area of the support is equal to or lower than 10 m 2 / g, the pore diameter of the support can be maintained at a certain high level, and sequential oxidation of ethylene oxide during the production of ethylene oxide with the catalyst obtained can be suppressed. It should be noted that as a value for the specific surface of the support, a value is used which is obtained by a method described in the examples which will be described later.
    Preferably, the support has a breaking strength of at least 40 N. The breaking strength of the support is preferably equal to or higher than 50 N, and more preferably equal to or higher than 60 N. The breaking strength within the above-mentioned range is capable of to provide sufficient mechanical strength. The upper limit value of the breaking strength of the support is not particularly limited. It should be noted that if the value for the breaking strength of the support is used, a value is obtained which is obtained by a method described in the examples which will be described later.
    The bulk density of the carrier is preferably 0.5 to 1.0 kg / L, more preferably 0.5 to 0.9 kg / L, and even more preferably 0.5 to 0.80 kg / L. bulk density of the carrier within the above range is capable of providing a suitable packing density and thus producing a catalyst with sufficient strength. It should be noted that, for a value of the bulk density of the carrier, a value is used which is obtained by a method described in the examples which will be described later.
    The pore volume of the support is also not particularly limited, however, preferably 0.2 to 0.6 cm 3 / g, and more preferably 0.3 to 0.5 cm 3 / g. A pore volume of the support that is equal to or greater than 0.2 cm 3 / g is preferred in view of facilitating the loading of the catalyst component. On the other hand, a pore volume of the support that is equal to or less than 0.6 cm 3 / g is preferred in view of ensuring the strength of the support at a practical level. It should be noted that as a value for the pore volume of the support, a value obtained by mercury porosimetry is used.
    The pore size of the support is also not particularly limited, but the median pore diameter is preferably 0.1 to 10 µm, more preferably 0.2 to 4.0 µm, and even more preferably 0.3 to 3.0 µm . A median pore diameter equal to or greater than 0.1 µm is capable of suppressing sequential oxidation of ethylene oxide accompanied by the presence of the generated gas in the production of ethylene oxide. On the other hand, a median pore diameter equal to or less than 10 µm is capable of ensuring the strength of the support at a practical level. It should be noted that as a value of the median pore diameter, a value obtained by mercury porosimetry is used.
    The water absorption of the carrier is also not particularly limited, but preferably 10 to 70%, more preferably 20 to 60%, and even more preferably 30 to 50%. A water absorption of the support equal to or higher than 10% facilitates the loading of the catalyst component. On the other hand, a water absorption of the carrier equal to or lower than 70% can ensure the strength of the carrier at a practical level. It should be noted that, as a value for the water absorption of the support, a value is obtained which is obtained by a method described in the examples which will be described later.
    The wear rate of the carrier is preferably equal to or lower than 5.0%, more preferably equal to or lower than 4.0%, even more preferably equal to or lower than 3.0%, and in particular at preferably equal to or lower than 2.0%. The wear rate of equal to or lower than 5.0% is advantageous from the point of view of equipment and use, since the cracking and pulverization of the catalyst in the gasket of the catalyst in a reaction tube is difficult to occur and the pressure loss is low. It should be noted that, as a value for wear of the wearer, a value is used which is obtained by a method described in the examples which will be described later.
    The ethylene oxide production catalyst of this invention has a composition comprising silver as a catalyst component supported on the above support. In addition, a catalyst component that is generally used as a reaction promoter can be supported by the support, not being silver. A typical example of the reaction promoter comprises an alkali metal, in particular lithium, sodium, potassium, rubidium and cesium or the like. Unlike an alkali metal, thallium, sulfur, chromium, molybdenum, tungsten, rhenium or the like can also be used as the reaction promoter. These reaction promoters can only be used as one species, or two or more species may be used in combination. Of these, cesium can suitably be used as the reaction promoter.
    In the catalyst of this invention, silver and a reaction promoter are supported by a porous support comprising α-alumina as a major component. Here, silver and the reaction promoter can be supported such that the relative standard deviation of silver loading rate in each catalyst particle determined by the above formula (1) for N catalyst particles is 0.001 or more and 0.1 or less. The relative standard deviation is more preferably 0.001 or more and 0.05 or less, even more preferably 0.001 or more and 0.03 or less, and particularly preferably 0.001 or more and 0.02 or less. When the relative standard deviation of the silver loading degree exceeds 0.1, the selectivity and stability of catalyst life are reduced due to the increased variation of the silver content. It should be noted that the number of catalyst particles N used for the silver loading degree measurement is equal to or greater than 30.
    The degree of loading of silver or the reaction promoter is not particularly limited, as long as the relative standard deviation of the silver loading degree, respectively, is within the above-described range, and silver or the reaction promoter can be carried in an amount effective in producing ethylene oxide. For example in the case of silver, an average degree of loading of N catalyst particles is 1 to 30 mass%, and preferably 5 to 20 mass%, based on the mass of the catalyst for the production of ethylene oxide. In this case, the value of the average silver loading degree (relative to the mass of the catalyst) is given by an arithmetic mean of the silver loading degrees of the N-catalyst particles. In addition, the degree of loading of the reaction promoter is usually 0.001 to 2 mass%, preferably 0.01 to 1 mass%, and more preferably 0.01 to 0.7 mass%, based on the mass of the catalyst for the production of ethylene oxide. In particular, an optimum degree of loading of the reaction promoter is different, depending on the difference in properties of the carrier or a combination of the reaction promoters. Therefore, it is preferable that catalysts with different loading degrees of the reaction promoter are prepared in advance, and after evaluation of the performance of the respective catalysts, the loading degree is determined of the reaction promoter that exhibits the best performance and an amount of the reaction promoter having such highest performance is charged to the catalyst, and thus the catalyst is prepared. It should be noted that in the following examples and controls, the catalyst was prepared after predetermining the loading degree of the highest performance reaction promoter in this manner.
    The ethylene oxide production catalyst of this invention can be prepared by a known production method for preparing a ethylene oxide production catalyst.
    Explanation will be given below on an example of a process for producing a catalyst for producing ethylene oxide of this invention using the support described above, however, the technical scope of this invention must be determined on the basis of the claims, and should not be limited to the following method only.
    Firstly, the carrier is prepared. As for a preparation method for the carrier, it is known that by using the following preparation method, the size or the properties of the carrier can be controlled. That is 1) a method for adding a pore-forming agent with a desired size and amount in a base powder with α-alumina as the main ingredient, 2) a method for formulating at least two types of base powders with different properties in a desired mixing ratio, and 3) a method for calcining the support at a desired temperature for a desired time or the like, and a method for combining it is also known. For example, to the α-alumina, a casting aid that influences the improvement of formability, a reinforcing agent or a binder for improving the strength of the catalyst, and a pore-forming agent for forming fine pores in the catalyst, added and mixed. As to a substance being added, it is preferred that it does not have a bad influence on the catalytic performance due to the addition. For example, an inorganic binder such as silica, alumina, silica-alumina, glass fiber, silicon carbide, silicon nitride can be added. An organic binder such as ethylene glycol, glycerin, propionic acid, maleic acid, benzyl alcohol, propyl alcohol, butyl alcohol, cellulose, methyl cellulose, starch, polyvinyl alcohol or phenol is added if necessary. In addition, a shell or seed of a peach, an apricot, a chestnut or the like with a uniform particle diameter or a substance with a uniform particle diameter which disappears by calcining can be added as the pore-forming agent. After sufficient mixing using a mixing machine such as a kneader by further adding water, it is poured into the desired shape with the aid of a suitable mold by extrusion molding or the like, granulated, dried and then calcined. These methods of preparation are described, for example, in "Property of porous substances and application technologies" edited by Yoh Takeuchi, and published by Fujitec Corporation (1999). In addition, reference may be made to JP-A-5-329368, JP-A-2001-62291, JP-A-2002-136868, JP-B-2983740, JP-B-3256237, JP-B-3295433 or the like.
    In the meantime, a solution is prepared for making silver supported on the support. In particular, a silver compound alone or together with a complexing agent to form a silver complex or a compound containing a reaction promoter is added, if necessary, to a solvent such as water, methanol and ethanol. Water is the preferred solvent.
    Here, a silver compound includes, for example, silver nitrate, silver carbonate, silver oxalate, silver acetate, silver propionate, silver actate, silver citrate, silver neodecanoate or the like. Among these, silver oxalate and silver nitrate are preferred. In addition, a complexing agent includes, for example, monoethanolamine, diethanolamine, triethanolamine, ethylene diamine, propylene diamine or the like. These silver compounds or complexing agents can be used only if only one type, or two or more types can be used in combination. The addition of the amount of the silver compound can be suitably determined to become the prescribed average loading degree described above.
    The carrier obtained above is then impregnated with or immersed in the solution that was also obtained above. In this step, the reaction promoter can be simultaneously impregnated by dissolving a compound comprising the reaction promoter in a solution containing the silver compound, prior to the step when the support is impregnated with or immersed in the solution, or it can be applied after silver was charged. Preferably, the reaction promoter is simultaneously impregnated by dissolving it in the solution containing the above silver compound. When cesium is used as the reaction promoter, nitrate salt, nitrite salt, carbonate salt, oxalate salt, halide, acetate salt, sulfate salt, perrhenate salt, molybdate salt and the like of cesium are preferably used. Among these, cesium nitrate, cesium perrhenate and cesium molybdate are particularly preferred. When molybdenum is used as the reaction promoter, preferably molybdenum oxide, molybdic acid, molybdate salt, as well as heteropolyacid such as silica molybdenic acid, phosphomolybdenic acid and / or heteropolyacid salt, and the like are used. Among these, ammonium paramolybdate, cesium paramolybdate, ammonium phosphomolybdate, cesium phosphomolybdate, ammonium silicon molybdate, and cesium silicon molybdate are particularly preferred. These compounds containing the reaction promoter can be used alone or in combination of two or more types.
    In this invention, in order to charge the catalyst component, so that the relative standard deviation of the silver loading degree in each catalyst particle becomes 0.001 or more and 0.1 or less, preferably the support prepared above is impregnated with the above solution with stirring, for example with the aid of a mixer. As a mixer to be used for impregnating the above solution, for example, a V type, a double cone type, a spherical type, a cylinder type, and the like can be used. To homogeneously impregnate the liquid, a mixer is preferably used which, in addition to the structures as described above, has a mixing system such as turning, shaking, and the like to improve the mixing efficiency of the solution, and preferably the carrier is used. Even when the support is impregnated with the solution by dipping, the absorbed solution is dried after once removal from the support by heating, and sometimes the silver is unevenly distributed. To avoid such uneven distribution, a mixer with a structure and a rotation system is preferably used that is capable of achieving superior mixing efficiency.
    The rotation speed (number of revolutions) varies depending on the shape and volume of the treatment container, the carrier and the solution being loaded, however, is generally set at 0.1 to 20 revolutions / minute, preferably 0.1 to 15 revolutions / minute , and further preferably 0.1 to 10 revolutions / minute. When the speed of rotation is equal to or higher than 0.1 revolutions / minute, a high stirring efficiency can be obtained. When the revolution speed is equal to or lower than 20 revolutions / minute, the problem that the carrier is pulverized by repeated collisions hardly occurs. Moreover, when a container capable of shaking is used, the shaking speed is determined, for example, from 1 to 12 bpm, preferably from 1 to 10 bpm, and further more preferably from 1 to 5 bpm. In this case, the unit of spm means the number of shaking movements per minute, provided that one shaking movement is 1. When the shaking speed is equal to or higher than 1 bpm, the shaking effect is high. When the shaking speed is equal to or lower than 12 bpm, a high mixing efficiency can be obtained because the contents of the container migrate sufficiently in the direction of the axis of rotation before the container tilts in the reverse direction, and an efficient migration of the content in the direction of the axis of rotation. Moreover, the maximum range of the angle of inclination of the container relative to the axis of rotation is preferably 5 ° or more. The container can also turn. The maximum range of the inclination angle of the container with respect to the axis of rotation of 5 ° or more is able to efficiently improve the effect of mixing by shaking.
    It is then dried and calcined. The drying is preferably carried out in the atmosphere of air, oxygen or an inert gas (e.g. nitrogen), at a temperature of 80 to 120 ° C. In addition, the calcination is preferably carried out in an atmosphere of air, oxygen, superheated steam or an inert gas (e.g. nitrogen), at a temperature of 150 to 700 ° C and preferably 200 to 600 ° C. It should be noted that the calcination can be performed in one phase alone or can be performed in two phases or more. A preferred calcination condition includes performing the first phase of calcining in an air atmosphere at 150 to 250 ° C for 0.1 to 10 hours, and performing the second phase of calcining in the air atmosphere at 250 to 450 ° C for 0.1 to 10 hours. Even more preferably, after these two phases of calcination, the third phase of calcination can be carried out under an inert gas atmosphere (e.g. nitrogen, helium, argon or the like) at 450 to 700 ° C for 0.1 to 10 hour.
    It should be noted that as the content (silver loading degree) of silver in each particle of the catalyst obtained by the above process, a value is used as analyzed according to the process described in the examples.
    Another aspect of this invention is a method for producing ethylene oxide which comprises subjecting ethylene to catalytic vapor phase oxidation with a molecular oxygen-containing gas in the presence of the catalyst for producing ethylene oxide.
    The process for producing ethylene oxide of this invention is carried out in accordance with a conventional process, except that the catalyst for producing ethylene oxide of this invention is used as a catalyst. For example, a method can be used in which ethylene is subjected to catalytic vapor phase oxidation with a molecular oxygen-containing gas, such as air, oxygen and oxygen-enriched air, using a reactor for producing ethylene oxide with a reaction tube packed with the catalyst for the production of ethylene oxide.
    The ethylene oxide production reactor to be used in this invention can be either a single-tube type reactor or a multi-tube type reactor, but a multi-tube type multi-tube reactor is preferably used for industrial purposes. The ethylene oxide production reactor is not particularly limited, and a conventionally known reactor, such as a solid-state reactor, vortex-bearing reactor, a moving-bearing reactor can be used, but preferably a solid-state reactor is used, and in particular is preferably a multi-tube solid state reactor. As the reaction tube of the ethylene oxide production reactor, it is used with an inner diameter of preferably 15 to 50 mm. The inner diameter of the reaction tube is more preferably 18 to 45 mm, and further preferably 20 to 40 mm. When the inside diameter of the reaction tube is 15 mm or more, the manufacturing cost of the reactor can be reduced because the number of reaction tubes does not increase excessively. Meanwhile, when the inside diameter of the reaction tube is 50 mm or less, the heat dissipation effect is improved and accumulation of heat in a catalyst layer hardly occurs.
    In the ethylene oxide production reactor to be used in this invention, the ethylene oxide production catalyst has a value for the outer diameter or length, which of the two is the largest, preferably 10 to 50%, more preferably preferably 15 to 45%, and even more preferably 20 to 40%, with respect to the inner diameter of the reaction tube. When the value of the outer diameter or the length, whichever is larger, of the catalyst is 10% or more relative to the inner diameter of the reaction tube, the reaction is advantageous from both the equipment point of view and use , because the packing density and the pressure loss become low.
    Meanwhile, when the value of the outer diameter or length, whichever is larger, of the catalyst is 50% or less relative to the inner diameter of the reaction tube, the activity and life of the catalyst can be improved because the silver content becomes high in the catalyst layer.
    In addition to the conditions described above, by grasping the catalyst such that the silver content as a catalyst component to be included in a catalyst layer is 30 to 140 kg / m 3, the activity and life of the catalyst is improved. In addition, the packing density is adjusted by controlling the packing speed, with which the content of silver to be incorporated in the catalyst layer can be easily adjusted.
    When the silver content to be incorporated in the catalyst layer is 140 kg / m 3 or less, the reaction is favorable in view of the equipment and use because the packing density and pressure loss are low. Meanwhile, when the silver content to be included in the catalyst layer is 30 kg / m3 or more, the silver content in the catalyst layer becomes high and the activity and life of the catalyst can be improved. The silver content to be included in the catalyst layer is more preferably 60 to 135 kg / m3, and further preferably 100 to 130 kg / m3. As a value of the silver content to be included in the catalyst layer, a value is used that is calculated with the following formula (3). Here, the packing density, when the catalyst was packed in a reaction tube, is calculated by the formula (5) described below. In addition, as an average silver loading degree, a value is used that was analyzed by a method described in the examples.
    (3)
    Preferably, to control the silver content to be included in the catalyst layer, the ethylene oxide production catalyst described above is packed in the above reaction tube at a packing speed of 0.3 to 5 L / min. The packing speed is more preferably 0.5 to 4 L / min, and further preferably 1.0 to 3.0 L / min.
    By controlling the packing speed in a range of 0.3 to 5 L / min, the activity and the service life of the catalyst is improved and ethylene oxide can be produced with high efficiency and high selectivity, since the catalyst layer has a suitable amount. catalyst component is formed. As a value for the packing speed, the value is used which is calculated by measuring the packing time required when the catalyst is packed in a reaction tube with a desired inner diameter, and the length of a packed catalyst layer; and calculating the value by the following formula (4).
    (4)
    In this invention, the ethylene oxide production catalyst is preferably packed into a reaction tube of the polyethylene oxide production reactor so that the packing density is at least 0.5 kg / L, more preferably 0.6 to 0.9 kg / L , and further more preferably 0.65 to 0.85 kg / L. When the packing density is 0.5 kg / L or more, ethylene oxide can be produced with high efficiency and high selectivity. It should be noted that if a packing density of the catalyst is used, the packing density value calculated by measuring the packed mass of the catalyst and the length of the packed catalyst layer is used when packing the catalyst in a reaction tube with a desired inner diameter, and calculating the value by the following formula (5).
    (5)
    A method of packing the ethylene oxide production catalyst into a reaction tube with a prescribed inside diameter of the ethylene oxide production reactor is not particularly limited, and known packing methods can be used, for example, a method using a packing machine, a a method using a template, a method of manual packing for each reaction tube, and the like. In this regard, however, when the catalyst is packed into a reaction tube of a multi-tube type reactor for producing ethylene oxide, it is preferable to keep the packing speed at a constant speed for each tube, because the silver content in the catalyst layer and the pressure loss for each reaction tube can be checked for a value in a certain range.
    The method for producing ethylene oxide of this invention can be carried out according to the conventional method, except that the catalyst for producing ethylene oxide of this invention is used. Preferably a method can be used in which ethylene is subjected to catalytic vapor phase oxidation with a molecular oxygen-containing gas, such as air, oxygen, oxygen-enriched air.
    For example, general reaction conditions on an industrial production scale, i.e., a reaction temperature of 150 to 300 ° C, preferably 180 to 280 ° C, a reaction pressure of 0.2 to 4.0 MPaG, preferably 1.0 to 3.0 MPaG, a space velocity of 1,000 to 30,000 hours (STP), preferably 3,000 to 8,000 hours (STP) can be used. Natural gas as a raw material to be contacted with the catalyst includes this gas composed of 0.5 to 40 volume% ethylene, 3 to 10 volume% oxygen, 0.5 to 20 volume% carbon dioxide, and the balance of inert gas such as nitrogen argon, steam and lower hydrocarbons such as methane, ethane, and further 0.1 to 10 ppm (volume) of halides such as ethylene dichloride, diphenyl chloride as a reaction inhibitor are included.
    EXAMPLES
    An explanation will be given on the effect of this invention with reference to the following examples and controls. However, the technical scope of the present invention should not be limited to these examples. It should be noted that in these examples, the measurements of various parameters were performed by the following methods. As for an ethylene oxide production reactor, a multi-tube type reactor was used industrially, but in these examples the performance evaluation was performed using a single tube-type reactor.
    Bulk density of the carrier
    By packing the carrier in a 1 L measuring cylinder (inner diameter: 66 mm) at a speed of 2 L / min to a clear 1 L measuring line to measure the mass, the density of the carrier can be calculated by the following formula (6 ).
    (6)
    Specific surface of the carrier
    After pulverizing the carrier, about 0.2 g of a sieved substance with a particle diameter of 0.85 to 1.2 mm was weighed accurately. The weighed sample was vented at 200 ° C for at least 30 minutes to measure the specific area by the B.E.T. (Brunauer-Emmert-Teller) method.
    Water absorption from the carrier
    The water absorption of the support was measured by the following method in accordance with the method described in Japanese Industrial Standards (JIS R 2205 (1998)).
    a) the carrier before crushing was placed in a dryer that was kept at 120 ° C to weigh the mass when a constant mass was achieved (dry weight: W1 (g)).
    b) The support weighed according to the above a) was immersed in water, and after boiling for 30 minutes or longer, the support was cooled in water at room temperature to obtain a sample saturated with water.
    c) The sample saturated with water obtained in the above b) was taken out of the water, the surface was quickly wiped off with a wet cloth, and after the removal of water drops the mass was weighed (weight of the sample saturated with water: W2 (g)) d) The water absorption was calculated according to the following formula (7) using W1 and W2 as obtained above.
    (7)
    Breaking strength of the carrier
    Using an accurate dynamograph (manufactured by Marubish Science Machine Manufacturing Co., Ltd.), a breaking strength in a lateral direction of the support (a vertical direction relative to the length) was measured, and the average value of 50 pieces was used as the breaking strength.
    Wear rate of the wearer
    The wear rate was measured by the following procedures.
    a) 100 ml of the support was placed in a 300 ml conical cup.
    b) pure water was added to the conical beaker from above to 250 ml.
    c) b) as above was heated with an electric heater and cooked for 30 minutes.
    d) After cooking, the following operation was repeated five times: pure water remaining in the conical cup was poured out, pure water was added again, and only pure water was poured out.
    e) Washing from b) to d) above was repeated three times.
    f) The carrier was dried overnight in a dryer at 120 ° C after washing.
    g) The carrier was cooled to room temperature after drying to allow weighing (mass before a test: W3 (g)).
    h) The support obtained in g) above was milled in a stainless steel ball mill (outer diameter: 90 mm, height: 90 mm) at 106 rpm for 30 minutes.
    i) The total amount of the carrier after grinding was transferred to a stainless steel screen (inner diameter: 150 mm, screen with a mesh width: 1.7 mm) for sieving, and then weighed (mass after sieving: W4 (g )).
    j) The wear rate was determined according to the following formula (8) using W3 and W4 obtained above.
    (8)
    Analysis method for the silver loading degree
    The silver loading degree (mass%) based on the mass of the catalyst was measured by the following procedures.
    a) weight of a catalyst (a particle) was weighed, and placed in a 100 ml conical beaker.
    b) Nitric acid was added to the above conical beaker to 20 ml.
    c) After stirring the nitric acid until the silver in the catalyst was completely dissolved, pure water was added to 50 ml.
    d) c) above was heated with an electric heater and cooked for 10 minutes.
    e) After boiling, the remaining pure water in the conical cup was collected in a 200 ml large cup, and pure water was added to 100 ml.
    f) The silver content in the above solution e) was measured by an automatic potentiometric titrator (COM-1600, manufactured by Hiranuma Sangyo Corp). It should be noted that, as a titrant, a 0.1 mol / L NaCl aqueous solution was used.
    Calculation for the average silver loading degree
    For 30 particles of a randomly selected catalyst, the silver loading degree was measured by the method described above for the analysis of the silver loading degree, and an arithmetic mean of the silver loading degree for 30 particles of the catalyst was determined.
    Relative standard deviation of the silver loading degree
    For 30 particles of a randomly selected catalyst, the silver loading degree was measured by the above-described method for analyzing the silver loading degree, and the relative standard deviation was determined according to the above formulas (1) and (2). Conversion and selectivity of the ethylene oxide production catalyst Conversion and selectivity when ethylene oxide production is started and after one year were calculated according to the following formulas (9) and (10), respectively. The performance when ethylene oxide production was started is referred to as "initial performance", and the performance after one year is referred to as "lifetime performance".
    (9)
    (10)
    Example 1
    For 4L of a support with α-alumina as main component (8 mm ring, bulk density: 0.72 kg / L, water absorption: 41.1%, specific surface area: 1.37 m2 / g), the cooking processes were of distilled water (4 L) repeated three times for 30 minutes or more. The support was then sufficiently dried in a dryer at 120 ° C.
    Meanwhile, to an aqueous suspension comprising 520 g of silver oxalate (water content in the aqueous suspension: 150 g), 100 ml of water and a solution with 3.7 g of cesium nitrate dissolved in 250 ml of water were added to obtain a sludge-like mixture. Then 250 ml of ethylenediamine was added thereto and dissolved by sufficient stirring to prepare an impregnating solution.
    The resulting impregnating solution was impregnated on 2,000 g of the support which was pre-heated to approximately 100 ° C. The impregnation was carried out using a mixer (inner diameter 20 cm x length 38 cm, shaker mixer manufactured by Aichi Electric Co., Ltd.), with a volume of 10 L and cylindrical shape that was able to mix by turning and shaking, at a number of revolutions of 8 rpm and a shaking speed of 2 rpm. After the impregnation, the support was then concentrated and dried by heating, and then removed from the mixer. It was then activated at 400 ° C for 20 minutes in an air stream using a hot air dryer to obtain a catalyst precursor. The resulting catalyst precursor was packed in a sealed container made of stainless steel, into which inert gas can be introduced from outside, and subjected to a heat treatment at a high temperature of 530 ° C in a catalyst low temperature for 3 hours in an electric oven, while nitrogen gas was supplied to prepare catalyst A for the production of ethylene oxide. The average silver loading degree of this catalyst was 15.0 mass% and the relative standard deviation of the silver loading degree was 0.021.
    Catalyst A for the production of ethylene oxide was packed in a reaction tube (inner diameter: 25 mm, tube length: 7,500 mm), provided in an external heating double-pipe-type reactor made of stainless steel to form a packed layer. A mixed gas was then composed of ethylene (21 volume%), oxygen (7.5 volume%), carbon dioxide (6.5 volume%), and the balance [methane (50.5 volume%), argon (12 volume%) ), the balance (nitrogen, ethane and the like) (2.5 volume%)], further comprising ethylene dichloride (2.5 ppm per volume) introduced into the respective catalyst layer to produce ethylene oxide under conditions of reaction pressure of 2.0 MPaG and space velocity of 5,500 hr'1. The performance when ethylene oxide production was started (initial performance) and the performance after one year (lifetime performance) are shown in Table 1.
    Example 2
    Catalyst B for the production of ethylene oxide was prepared according to the same procedures as in Example 1, except that the impregnation was carried out using a double cone-type mixer (inner diameter 27 cm χ height 41 cm) with a volume of 10 L at a number of revolutions of 0.5 rpm. The average silver loading degree of this catalyst was 15.0 mass% and the relative standard deviation of the silver loading degree was 0.093. In addition, using catalyst B for the production of ethylene oxide, ethylene oxide was produced under the same conditions as in Example 1. The performance when the production of ethylene oxide was started (initial performance) and the performance after one year (lifetime performance) are shown in Table 1.
    Check 1
    Catalyst "a" for the production of ethylene oxide was prepared according to the same procedure as in Example 1, except that the impregnation was carried out using a spherical mixer (inner diameter: 27 cm) with a volume of 10 L at a number of revolutions of 0, 1 rpm. The average silver loading degree of this catalyst was 15.0 mass% and the relative standard deviation of the silver loading degree was 0.118. In addition, using catalyst "a" for the production of ethylene oxide, ethylene oxide was produced under the same conditions as in Example 1. The performance when the production of ethylene oxide was started (initial performance) and the performance after one year (lifetime performance) are displayed in Table 1.
    From the results shown in Table 1 above, it can be deduced that catalysts A and B of this invention, each having a relative standard deviation of the silver charge degrees in each catalyst particle of 0.1 or less, exhibit not only a higher initial selectivity and activity but also the reduction in selectivity after one year is lower compared to that of catalyst "a" with a relative standard deviation of the silver loading degree of more than 0.1.
    From the above results, it can be deduced that, according to this invention, a catalyst for the production of ethylene oxide can be provided that is superior in selectivity and lifetime performance.
    This invention provides a catalyst for the production of ethylene oxide that is superior in selectivity to ethylene oxide and thereby capable of producing ethylene oxide with high selectivity, and a method for producing ethylene oxide using the catalyst for producing ethylene oxide. By using the method of this invention, it is possible to remarkably save on the amount of ethylene used as a raw material and an enormous economic effect can be obtained in the production of ethylene oxide on a large production scale, because a high selectivity can be maintained for a long period of time of time.
    This application is based on Japanese patent application no. 2010-084467 filed March 31, 2010, and the disclosure is incorporated herein by reference in its entirety.
    权利要求:
    Claims (6)
    [1]
    A catalyst for the production of ethylene oxide comprising silver and a reaction promoter selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, thallium, sulfur, chromium, molybdenum, tungsten and rhenium, supported on a porous support comprising α -alumina, wherein the content of α-alumina in the carrier is greater than or equal to 90 mass% relative to the total mass, 100 mass% of the carrier, characterized in that a relative standard deviation of the silver charge degree of each particle of the catalyst defined by the following formula (1), is 0.001 or more and 0.1 or less:

    [2]
    The ethylene oxide production catalyst according to claim 1, wherein the relative standard deviation of the silver loading degree is 0.001 or more and 0.05 or less.
    [3]
    The catalyst for the production of ethylene oxide according to claim 1 or 2, wherein the average silver loading degree is 1 to 30 mass%.
    [4]
    A method for producing ethylene oxide comprising subjecting ethylene to catalytic vapor phase oxidation with a molecular oxygen-containing gas in the presence of the ethylene oxide production catalyst as set forth in any of claims 1 to 3.
    [5]
    A process for the production of a catalyst for the production of ethylene oxide comprising impregnating a porous support comprising α-alumina, wherein the content of α-alumina in the support is greater than or equal to 90 mass% with respect to the total mass, 100 mass% of the support, with a solution comprising silver and a reaction promoter selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, thallium, sulfur, chromium, molybdenum, tungsten and rhenium, under stirring at a speed of rotation of 0.5 to 20 revolutions / minute.
    [6]
    A process for the production of a catalyst for the production of ethylene oxide as set forth in any of claims 1 to 3, comprising impregnating a porous support comprising α-alumina, wherein the content of α-alumina in the support is greater is equal to or equal to 90 mass% relative to the total mass, 100 mass% of the support, with a solution comprising silver and a reaction promoter selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, thallium, sulfur, chromium, molybdenum, tungsten and rhenium, with stirring at a speed of 0.5 to 20 revolutions / minute.
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    同族专利:
    公开号 | 公开日
    JP5570277B2|2014-08-13|
    JP2011212614A|2011-10-27|
    US8765633B2|2014-07-01|
    US20110245518A1|2011-10-06|
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    法律状态:
    2018-03-07| MM| Lapsed because of non-payment of the annual fee|Effective date: 20170331 |
    优先权:
    申请号 | 申请日 | 专利标题
    JP2010084467A|JP5570277B2|2010-03-31|2010-03-31|Catalyst for producing ethylene oxide and method for producing ethylene oxide|
    JP2010084467|2010-03-31|
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