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    • 专利摘要:
    COMPOSITIONS OF MOLECULAR CARBON SCREEN BASED ON VINYLIDENE CHLORIDE COPOLYMER AND PROCESSES FOR THE SAME New carbon molecular sieve (CMS) compositions comprising carbonized vinylidene chloride copolymer having micropores with an average size of micropores ranging from 3, 0 Å to 5.0 Å. These materials offer the ability to separate gas mixtures including, for example, propane / propylene; nitrogen / methane; and ethane / ethylene. These can be prepared by a process in which the microspheres of vinylidene chloride copolymer, the extruded fused film or fiber are pre-treated to form a precursor which is finally carbonized at elevated temperature. Does the pre-selection or knowledge of the precursor crystallinity and the maximum pyrolysis temperature obtained allow the pre-selection or knowledge of an average microporous size, according to the equation? = 6.09 + (0.0275 x C) - (0.00233 x T), where? is the average size of the micropores in Angstroms, C is the percentage of crystallinity and T is the maximum pyrolysis temperature obtained in degrees Celsius, since the percentage of crystallinity varies from 25 to 75 and the temperature in degrees Celsius varies from 800 to 1700 Microspheres, fibers or film can be ground, subjected to (...).
    公开号:BR112016029448B1
    申请号:R112016029448-3
    申请日:2015-06-22
    公开日:2021-02-17
    发明作者:Junqiang Liu；Douglas E. Beyer；Edward M. Calverley；Chan Han
    申请人:Dow Global Technologies Llc.；
    IPC主号:
    专利说明:

    [0001] [001] The present application claims the benefit of the United States Provisional Patent Application with Serial No. 62 / 018.828, filed on June 30, 2014, entitled “CARBONIZED VINYLIDENE CHLORIDE COPOLÍMERO-BASED MOLECULAR SIEVE ADSORBENT COMPOSITIONS AND PROCESSES THEREFOR ”, Which is incorporated herein by reference in its entirety.
    [0002] [002] The present invention relates to the field of molecular sieve compositions. More particularly, it relates to carbon molecular sieve compositions based on vinylidene chloride copolymers.
    [0003] [003] Researchers have been looking for ways to separate gas mixtures, either for use as starting materials or as products, for many years. The materials that have been of particular interest as a means of such separations have been carbon molecular sieves (CMSs). These CMS can be prepared from a variety of resins and are pyrolysed at various temperatures and / or under various conditions. Pyrolysis reduces resins to pure carbon, but maintains at least some porosity, in the form of micropores, in the pyrolyzed product. It is known that under some conditions pyrolysis can shrink micropores to a desirable average size. The CMS thus formed can then be used in conventional gas separation equipment, such as packaged beds, columns and the like, where the micropore size determines which gas in a gas mixture is adsorbed and which is not. The adsorption and desorption techniques can be alternated to carry out the separation, according, for example, with the conventional adsorption methods of pressure oscillation or temperature oscillation.
    [0004] [004] However, there is a particular challenge in the technique for preparing CMSs with micropores of the correct size (s) for certain particular separations. Since the use of CMSs to perform separations assumes that the micropores are at least as large as, or larger than, the specified molecule that will enter the micropores, it is necessary to know the "size" of the molecule. The researchers found different ways to determine this molecular size. A commonly used approach has been to determine a given “kinetic diameter” of the molecule. A reference that lists a variety of these kinetic diameters, based on their use in zeolite applications, is DW Breck, Zeolite Molecular Sieves: Structure, Chemistry and Use, John Wiley & Sons, Inc. (New York, NY 1974), 636 , and these determinations are often used even in relation to non-zeolitic carbon molecular sieves that are known to have slit-shaped pores. In view of the above and for the purposes of this document, then, the following kinetic diameters, taken from the Breck reference cited above, are used here as the representative molecular diameters for the following molecules: CO2 (3.3 Angstroms, Å ), N2 (3.64 Å), CH4 (3.8 Å), C2H4 (3.9 Å), C3H8 (4.3 Å), i-C4H10 (5.0 Å), SF6 (sulfur hexafluoride) (5.5 Å), and i-C8H18 (neopentane) (6.2 Å). However, because the reference table does not have a kinetic diameter for ethane, and the kinetic diameter given therein for propene to be considered by at least some researchers to be inaccurate for CMS materials per se, the collision diameters of Lennard-Jones are used here, instead of Breck's kinetic diameters, for these two materials. These Lennard-Jones collision diameters are, respectively, C2H6 (4.1 Å), and C3H6 (4.0 Å). See, for example, Staudt-Bickel C., Koros W.J., "Olefin / paraffin gas separations with 6FDA-based polyimide membranes", J. Membr. Sci. (2000) 170 (2), 205-214 for further discussion. The kinetic diameters and collision diameters of LennardJones are called together as "representative molecular diameters".
    [0005] [005] A particular separation of interest to many for commercial applications is the separation of propane (C3H8) and propylene (C3H6). Since the representative molecular diameter of C3H8 is 4.3 Å, and that of C3H6 is 4.0 Å, the average micropore size of a separation CMS suitable for a mixture of these two gases desirably falls somewhere within the range from 4.0 Å to 4.3 Å. As used here, the "average micropore size" refers to the average micropore opening, that is, the width of a theoretical one-dimensional slit pore, regardless of the actual possible overall configuration of the micropore. Additional desirable separations may include carbon dioxide (CO2, representative molecular size 3.3 Å) and nitrogen ((N2, 3.64 Å); N2 and methane (CH4, 3.8 Å); ethylene (C2H4, 3.7 Å) and ethane (C2H6, 4.1 Å), and n-butane (n-C4H10, 4.3 Å) and iso-butane (i-C4H10, 5.0 Å). All of these separations require an average size of micropore, as defined, generally ranging from approximately 3.0 Å to approximately 5.0 Å.
    [0006] [006] Examples of CMS materials that have been found to be useful for certain separations within the representative molecular diameter range of approximately 3.0 Å to approximately 5.0 Å include the material disclosed in WO 2012/106218 A2 (PCT / US2012 / 023059, Petruska, et al.). This patent application describes a pyrolysed carbon adsorbent having a carbon dioxide (CO2) capacity greater than 105 cubic centimeters per gram (cm3 / g) at a pressure of 1 bar (0.1 megapascals, MPa) and a temperature of 273 Kelvin (K, 0 degrees Celsius, ° C), formed from a polymer or copolymer based on polyvinylidene chloride, or other suitable resin. The separation described there, however, is based on the fact that the CO2 molecule has a stronger affinity for the carbon matrix than certain other molecules, such as nitrogen (N2). Thus, this is not a molecular sieving effect, and the average size of the micropores is, in fact, irrelevant. In view of this fact, the micropores disclosed by Petruska et al. they can, in fact, be of any size that is larger than the size of the CO2 molecule that is adsorbed on them (3.3 Å).
    [0007] [007] Another separation based on molecular size is disclosed in Lamond T.G., et al., “6 Å molecular sieve properties of SARAN-type carbons”, Carbon (1965) 3, 59-63. This article describes the preparation of a CMS, from a polyvinylidene chloride (PVDC) copolymer, which rejects neopentane molecules (6.0 Å), but adsorbs smaller molecules, such as, for example, non-limiting, CO2, butane and iso-butane, not selectively. In view of this, the authors of this article concluded that their CMS had 6 Å micropores.
    [0008] [008] Another example is published in Fuertes A.B., et al., “Molecular sieve gas separation membranes based on poly (vinylidene chloride-co-vinyl chloride)”, Carbon (2000) 38, 1067-1073. This article describes the preparation of a composite carbon membrane using the aforementioned material. The membrane is formed with a thin microporous carbon layer (thickness of 0.8 micrometers, μm) obtained by pyrolysis of the polymeric film, supported on a macroporous carbon substrate (pore size 1 μm, macroporosity 30%,%). Single gas permeation experiments include helium (He), CO2, oxygen (O2), nitrogen (N2) and methane (CH4). Selectivities are described as particularly high for O2 / N2 systems, that is, a selectivity of about 14 to 25 degrees Celsius (° C). From this information it can be deduced that the size of micropores falls somewhere in a range from the representative molecular diameter of O2 (3.46 Å) to that of N2 (3.64 Å). This CMS membrane is prepared by pretreating the film supported at 200 ° C, a temperature at which the PVDC copolymer precursor is melted before carbonization. The fact that the merger is necessary means that the disclosed CMS structures cannot be prepared in unsupported ways.
    [0009] [009] In other research, including, for example, Laredo GC, Meneses E., Castillo J., Marroquin JO, Jimeenez-Cruz F., “Adsorption equilibrium and kinetics of branched octane isomers on a polyvinylidene chloride-based carbon molecular sieve , ”Energy Fuels (2008) 22 (4) 2641-2648, CMSs based on polyvinylidene chloride copolymers have been prepared which exhibit relatively large micropore sizes and pore volumes that are suitable for separating correspondingly large molecules, or that is, those with a representative molecular diameter greater than 5.0 Å. However, previous researchers have not identified CMSs based on polyvinylidene chloride copolymer that are able to effectively and / or efficiently separate gas pairs from much smaller molecules, such separations including, in non-limiting examples, C3H8 / C3H6, C2H6 / C2H4, and / or CH4 / N2.
    [0010] [0010] In this way, it will be observed that the prior art does not identify a carbonized PVDC having an average micropore size, as defined, that is suitable for separations of small molecules, that is, particularly of molecules with representative molecular diameters that vary between 3.0 Å and 5.0 Å. In addition, the prior art does not disclose a process for preparing carbonized PVDC CMSs that can be easily and accurately adapted to a variety of separations of molecules in this range of representative molecular diameters and that, in particular embodiments, also exhibit a geometry stable, whether as granules, pellets, unsupported films, unsupported membrane, sheets of woven fibers or the like.
    [0011] [0011] In one embodiment the present invention provides a molecular sieve composition comprising carbonized polyvinylidene chloride copolymer and having micropores with an average micropore size ranging from 3.0 Å to 5.0 Å.
    [0012] [0012] In another embodiment the present invention provides a molecular sieve composition as defined in the preceding paragraph prepared by a process comprising the pyrolysis of a polyvinylidene chloride copolymer precursor at a maximum pyrolysis temperature obtained in degrees Celsius ranging from 800 to 1700, in which the precursor has a percentage of crystallinity, measured by differential scanning calorimetry, ranging from 25 to 75, to obtain the molecular sieve composition, still characterized according to the equation σ = 6.09 + (0.0275 x C) - (0.00233 x T) (Equation 1) where σ is the average size of the micropores in Angstroms, C is the percentage of crystallinity of the precursor and T is the maximum pyrolysis temperature obtained.
    [0013] [0013] In yet another embodiment, the present invention provides a molecular sieve composition as defined in the previous paragraph which is additionally characterized by having an average volume of micropore according to the equation V = 0.346 + 0.00208 × C - 0.000152 × T (Equation 2) where V is the average volume of micropores in milliliters per gram, C is the percentage of precursor crystallinity and T is the maximum pyrolysis temperature obtained in degrees Celsius, provided that C is 25 to 75 and T is 800 to 1700 .
    [0014] [0014] In yet another embodiment, the present invention provides a process for separating two gases in a mixture thereof, comprising bringing into contact a mixture of two gases, in which at least one gas has a representative molecular diameter ranging from 3.0 Å and 5.0 Å and the molecular sieve composition defined, under conditions suitable to adsorb, in the micropores of the molecular sieve composition, at least 5 weight percent (%) of at least one gas, under conditions such that at least at least 5% by weight of the at least one gas is separated from the other gas; and then desorb the at least one gas.
    [0015] [0015] In general, the present invention provides carbon molecular sieve absorbers (CMS) that are useful for a variety of separations. Such separations may include, but are not necessarily limited to, the following gas pairs in which at least one molecule, and in some embodiments both molecules, has / has a representative molecular diameter within the range of 3.0 Å to 5.0 Å: Propylene (C3H6) and propane (C3H8); carbon dioxide (CO2) and nitrogen (N2); N2 and methane (CH4); ethylene (C2H4) and ethane (C2H6); and n-butane (C4H10) and i-butane (C4H10). The inventive molecular sieves can be conveniently used in the formation of pellets, films, fibers, monoliths and / or sheets, such as fabric sheets, and in certain particular embodiments they can be conveniently used in packaged beds or other typical separation systems, and particularly , in separation systems based, for example, on principles of pressure or temperature oscillation.
    [0016] [0016] The CMSs of the invention can be conveniently prepared from a vinylidene chloride copolymer, comprising a vinylidene chloride monomer and at least one additional comonomer. The comonomer can be selected from a variety of materials, including in particular embodiments a vinyl monomer, vinyl chloride monomer, an acrylate monomer, a methacrylate monomer, a styrenic monomer, acrylonitrile, methacrylonitrile, itaconic acid, chlorotrifluoroethylene and combinations thereof. In more particular embodiments, examples of vinyl monomers include vinyl chloride, vinyl acetate, acrylonitrile and combinations thereof. More particular examples of acrylate monomers include methyl acrylate, ethyl acrylate, butyl acrylate and combinations thereof. More particular examples of methacrylate monomers include methyl methacrylate, butyl methacrylate and combinations thereof. A more particular example of styrenic monomers is styrene itself.
    [0017] [0017] In proportion it is preferred that the vinylidene chloride-based copolymer, which is referred to herein as a polyvinylidene copolymer (PVDC), includes at least 60% by weight of vinylidene chloride based on the total weight of the copolymer, and in more preferential modalities, at least 70%. However, it is still desired that the PVDC contains a maximum of 97% by weight of vinylidene chloride, and therefore, preferably, contains a minimum of at least 3% by weight of the comonomer or comonomer combination; more preferably, from 3% by weight to 40% by weight; even more preferably, from 3% by weight to 30% by weight; and more preferably, from 3% by weight to 20% by weight.
    [0018] [0018] The particular modalities of PVDCs that are suitable for use in the invention are those that include as an comonomer an acrylate, such as methyl acrylate, ethyl acrylate, butyl acrylate, or a combination thereof, in an amount of 3% by weight to 20% by weight, based on the weight of PVDC as a whole; more preferably, from 3.5% by weight to 15% by weight; and more preferably, from 4% by weight to 12% by weight. Another particular embodiment is a PVDC including vinyl chloride in an amount of 3% by weight to 30% by weight; more preferably, from 7% by weight to 28% by weight; and more preferably, from 9% by weight to 25% by weight.
    [0019] [0019] It is also preferred that the total molecular weight average weight (Mw) of the PVDC copolymer varies from 10,000 to 250,000; more preferably, 50,000 to 200,000; and more preferably from 60,000 to 150,000.
    [0020] [0020] The use of additives in the PVDC is also contemplated to be within the scope of the invention. Common additives may include, but are not necessarily limited to, epoxidized oil stabilizers such as expoxidized soybean oil, expoxidified flaxseed oil and bisphenol A diglycidyl ether. Liquid plasticizers such as aliphatic and aromatic esters are also often used, including, for example, dibutyl sebacate, acetyl tributyl citrate, dioctyl phthalate and the like, and combinations thereof. Other common additives may include lubricants, such as polyethylene wax, paraffin wax, oxidized polyethylene wax and combinations thereof. Lubricants can optionally be included and can comprise, for example, high density polyethylene, acrylate copolymers and silicone polymers and combinations thereof. Another group of additives that can be included are acid scavengers, such as epoxy compounds, magnesium hydroxide, magnesium oxide, tetrasodium pyrophosphate, calcium phosphate, magnesium phosphate, DHT 4A (a halogen scavenger similar to synthetic hydrotalcite available from Kyowa Chemical Industry), calcium oxide, calcium carbonate, and combinations thereof. Antioxidants such as phenolics can also be incorporated. Combinations of any or all of these types of additives can be included in the PVDC.
    [0021] [0021] In proportion, it is preferred that the total amount of all additives combined is not more than 8% by weight, and more preferably, not more than 3% by weight. In many applications, however, an amount of all combined additives of at least 2% by weight may be typical, with the use of it preferably ranging from 2% by weight to 8% by weight and, more preferably , from 2% by weight to 3% by weight. Those skilled in the art will be aware of the use of such additives and their indications and contraindications without further guidance in this document.
    [0022] [0022] Those skilled in the art will also be aware of a variety of means and methods for preparing copolymers. However, in general, any of the typical or conventional methods of polymerization can be used, including, but not limited to, mass polymerization, suspension polymerization and emulsion polymerization and, preferably, suspension polymerization or emulsion polymerization. It is generally preferred that the polymerization be carried out at a temperature that ensures the avoidance of degradation of all PVDC components, for example, preferably, from 10 ° C to 120 ° C; more preferably, from 20 ° C to 100 ° C; and more preferably, from 30 ° C to 90 ° C.
    [0023] [0023] Upon completion of copolymerization, the PVDC can be left in its polymerized form, for example, typically microspheres and / or can be extruded by melting to form the PVDC in a film or fine fiber. In particular embodiments, the resin as polymerized (for example, microspheres) or film extruded by fusion or precursor fiber material has a maximum thickness ranging from 10 μm to 1000 μm; preferably from 20 μm to 500 μm; and more preferably, from 50 μm to 200 μm. When films are desired, a conventionally known preparation process, such as a blown film process, for example, a double bubble process or a molten film teterization process, can be especially useful for producing a biaxially oriented film. It is more preferable to use a double bubble process in order to extrude concomitantly, orient biaxially and anneal the PVDC film. The fibers can be produced by uniaxial stretching using known fiber processes for PVDC copolymers and can be hollow round or a combination thereof, or any other desired fiber morphology. It is also contemplated that films and / or precursor fibers can be coextruded with multiple PVDC copolymers and / or with other polymers.
    [0024] [0024] It should be noted that the film or fiber preparation process can optionally include drawing, such as drawing the resin to form a melt extruded film or fiber. This stretching can, in particular embodiments, be particularly effective in inducing faster crystallization and in increasing and therefore improving the alignment of the PVDC crystallites. Desirably the stretch ratio varies from 1 to 8, more desirably from 1 to 6, even more desirably from 1 to 4, and most desirably from 2 to 4.
    [0025] [0025] In general, it is important for the invention that the copolymer precursor, either in its polymerized form (for example, microspheres) or after melt extrusion in a film or fibers, has a desirable level of crystallinity. In the present invention this crystallinity ranges from 25% to 75%, as measured by differential scanning calorimetry (DSC) according to ASTM D3418. It is more preferable for this level to vary from 30% to 55%, and much more preferable for this level to vary from 35% to 50%. Despite the discussion of the significance of the crystallinity of the copolymer, which serves as a precursor of the carbonized microporous composition finally used for separation purposes, to be presented in greater detail below, it is observed at this point that, surprisingly, it was found that the guarantee of a given level of crystallinity within the designated range is essential to obtain the average micropore size and the average volume of micropores desired, after pyrolysis, in the final CMS. It is noted that the homopolymerized PVDC generally has a polymerized crystallinity greater than 75% and that surprisingly it was found to be significant that the PVDC is either copolymerized with an adequate amount of at least one of the listed monomers, or extruded by melting (with or without stretch), or both, in order to ensure the designated level of precursor crystallinity (ie, prepyrolysis) (ie, 25% to 75%) specified here. Thus, the inclusion of a comonomer generally helps to reduce the crystallinity of the precursor to ensure the desired range, and also helps to reduce the melting temperature and thus improve the processability of the resulting copolymer. In general, the inclusion of the more bulky monomers may tend to reduce the total crystallinity of the copolymer by an amount greater than the inclusion of less bulky monomers. Thus, for example, butyl acrylate will tend to reduce crystallinity more than, for example, methyl acrylate or ethyl acrylate, assuming it is / are used in the same molar percentage (mol%) based on the final composition copolymer.
    [0026] [0026] The next step in the preparation of the CMS adsorbent compositions of the present invention is preferably a pretreatment that can be used to stabilize, or "block", the copolymer structure prior to its carbonization. In this step, the microspheres as polymerized or the extruded film or fiber, referred to as "precursor" materials, at this point, are / are heated, below their melting temperature (typically below about 180 ° C, depending on the exact composition of the precursor), so that at least 10% of them are dehydrochlorinated. As used herein, the term "at least 10% dehydrochlorinated" means that the microspheres, film or fiber has been / have been pre-treated, removing hydrogen chloride, to a point where the copolymer precursor no longer melts and, in fact, begins to become infusible. It is well accepted in the art that such a change in molecular kinetics begins to occur at a point of approximately 10% dehydrochlorination and is completed or maintained as the level of dehydrochlorination increases above that point. This step is called "pre-treatment" because it occurs before a pyrolysis step, which is the treatment step in which carbonization is carried out.
    [0027] [0027] During the pretreatment the temperature of the copolymer structure is preferably maintained in a range of 100 ° C to 180 ° C, more preferably, from 120 ° C to 160 ° C, and more preferably, from 130 ° C to 150 ° C. That is, preferably made of air for convenience, but other atmospheres, such as N2 and other inert gases or oxidizing gases, such as CO2, or combinations thereof, can also or alternatively be used, since generally only lower levels oxidation rates of the copolymer are anticipated within the given global temperature range. Achieving the desired dehydrochlorination, which is responsible for the formation of the blocked structure, can be achieved by exposure to a high-energy irradiation source, such as gamma rays, an electron beam, ultraviolet light or a combination thereof. The time can vary from 1 hour (h) to 48 hours, preferably from 1 hour to 24 hours, and more preferably, from 1 hour to 12 hours, as necessary to reach the dehydrochlorination point of at least 10%, in which the copolymer begins to become infusible, that is, it is no longer capable of being melted. The degree of dehydrochlorination can vary from 10% to 100%, depending on the temperature and pre-treatment time. While it is desirable that substantially all of the copolymer is dehydrochlorinated to the desired extent, it will be recognized that the presence of a lesser amount, desirably less than 2% by weight of precursor that is not at least 10% dehydrochlorine may be acceptable. When more than visual confirmation of the start of the infusion is desired, additional confirmation of the percentage of dehydrochlorination can be obtained through, for example, Thermogravimetric Analysis (TGA), using standard and well-known methods and equipment.
    [0028] [0028] After pre-treatment by dehydrochlorination, the polymerized copolymer, typically still in the form of microspheres, film or fiber, now called pretreated microspheres, pretreated film or pretreated fiber, or pretreated CMS material , is pyrolysed. Preferably, such pyrolysis results in at least 90% by weight of the copolymer becoming carbonized, more preferably at least 95% by weight and, more preferably, at least 99% by weight. As already mentioned above, this pyrolysis is also called "carbonization", because its result is that the copolymer is converted only to the carbon skeleton, or to carbon close to its copolymer structure, that is, all or virtually all the atoms with the exception of carbon have been removed, but the carbon-carbon bonds remain substantially intact and the CMS can now be designated as "carbonaceous". Pyrolysis can be carried out using any means generally known to those skilled in the art, but it can be carried out at a maximum temperature reached within the range of 800 ° C to 1700 ° C, more preferably, from 1000 ° C to 1500 ° C, and more preferably, from 1100 ° C to 1300 ° C. More particularly, however, the pyrolysis temperature is an important aspect of the present invention, as explained below below.
    [0029] [0029] A particular and important advantage of the present invention is that an average micropore size, within a range of 3.0 Å to 5.0 Å, can be pre-selected according to a desired separation utility. The pre-selection of the desired average micropore size can then be correlated with a crystallinity of the known and / or also pre-selected (pre-pyrolysis) preform and a maximum pyrolysis temperature obtained to obtain a molecular sieve composition with the average size of micropores desired, through the use of a surprisingly discovered relationship represented by the equation σ = 6.09 + (0.0275 x C) - (0.00233 x T) (Equation 1) where σ is the average microporous size in Angstroms, ranging from 3.0 Å to 5.0 Å; C is the percentage of crystallinity of the precursor; and T is the maximum pyrolysis temperature obtained in degrees Celsius; provided that the crystallinity varies from 25% to 75% and the maximum pyrolysis temperature obtained varies from 800 ° C to 1700 ° C. It should be understood that the percentage of crystallinity is expressed as a rational number greater than zero, for example, the number representing 45% of crystallinity that will be inserted in Equation 1 will be 45 and not 0.45. The discovery of this surprising characterization relationship allows for convenient and accurate preparation and production of the desired small pore microporous compositions and therefore also facilitates the various desired gas separations for which the microporous compositions of the invention can be used. TABLE 1 illustrates the relationships reflected by the equation.
    [0030] [0030] As will be seen from TABLE 1, as the maximum temperature reached increases, the effective crystallinity window, which is necessary to ensure that an average final micropore size in the range of 3.0 Å to 5.0 Å is obtained, correspondingly narrows. For example, at 800 ° C, the crystallinity should be approximately 25%, in order to obtain an average size of micropores within the range of 3.0 Å to 5.0 Å. However, at 1400 ° C, crystallinity can be anywhere from 25% to 75% to ensure a given range of average micropore sizes, and at 1700 ° C, crystallinity can be anywhere from 35% to 75%. It should be noted, however, that crystallinities significantly greater than 75% may require such high pyrolysis temperatures obtained high, in order to produce a CMS with a pore size equal to or slightly less than 5.0 Å, which must be considered to be effectively impractical. In addition, such high crystallinities can even prevent the formation of micropores that are significantly smaller than 5.0 Å, that is, closer to 3.0 Å, even at maximum pyrolysis temperatures obtained in excess of 1700 ° C.
    [0031] [0031] As is also observed from TABLE 1, it is possible to pre-select the desired average micropore size simply by knowing or selecting the crystallinity of the precursor and then using a maximum pyrolysis temperature obtained which, in together with the known or selected crystallinity, will produce the desired average micropore size.
    [0032] [0032] In addition to the average micropore size, it is also often desirable in the technique to improve the total micropore volume, which can be measured by the Brunauer-Emmett-Teller (BET) method at the temperature of liquid N2. This can also be confirmed through the adsorption of helium (He) and the intrusion of mercury (Hg). For most separation applications, a total micropore volume of at least 0.10 ml / g, preferably at least 0.15 ml / g, more preferably at least 0.20 ml / g, of according to the BET method at the temperature of liquid N2, it is necessary to commercially guarantee the desirable and efficient gas adsorption. Again, the present invention provides, in certain particular embodiments, a process by which a composition that has a pre-selected property, i.e., a pre-selected micropore volume, can be prepared. In this case, the same two parameters, that is, the percentage of precursor crystallinity and the maximum pyrolysis temperature reached, can also or alternatively be used to pre-select, or to predict or characterize the microporous volume of the composition after pyrolysis. . The relationship between these three aspects is represented by the equation V = 0.346 + 0.00208 × C - 0.000152 × T (Equation 2) where V is the average volume of micropores in milliliters per gram (mL / g), C is the percentage of crystallinity of the precursor and T is the maximum pyrolysis temperature obtained in degrees Celsius, provided that C is 25% to 75% and T is 800 ° C to 1700 ° C.
    [0033] [0033] It will be understood from Equation 2 that any reduction in the crystallinity of the precursor (again, as in Equation 1, inserted in Equation 2 as a rational number greater than zero) will decrease the volume of micropores in the resulting CMS. However, a relatively lower crystallinity, within the range of 25% to 75%, in the precursor may be preferable in order to obtain a composition with the desired average micropore size within the range of 3.0 Å to 5.0 Å through pyrolysis at a relatively lower temperature within the range of 800 ° C to 1700 ° C. This leads to the conclusion that the average volume of the micropores and the average size of the micropores are desirably balanced and that a relatively narrower range of crystallinities, preferably ranging from 35% to 55%, can often be preferred for industrial manufacturing processes. wherein the maximum desirable operating pyrolysis temperatures are rarely greater than 1200 ° C. It is noted that, although it is desirable, in many cases to treat both the average size of micropores and the average volume of micropores simultaneously, those skilled in the art will recognize that the combination of the two equations (Equation 1 and Equation 2) in a single equation it would require an assumption that there is a standard micropore geometry, an assumption that may not be correct in any given system and that may therefore introduce undesirable error in the calculation. Thus, the application of the two individual equations to any given system is preferable.
    [0034] [0034] In the present invention, the average volume of general micropore can also be increased in particular modalities by applying tension to the film or fiber, during pretreatment, pyrolysis, or both. This tension is preferably applied to maintain the film or fiber, in its largest dimension displayed, or in some percentage of them, before pretreatment and / or pyrolysis. For example, it may be desirable to apply sufficient tension to keep the film or fiber at, for example, 80%, or 75%, or 90% of the largest dimension exhibited by the fiber before its pre-treatment and / or pyrolysis. Such tension can vary from 0.01 MPa to 10 MPa, preferably from 0.1 to 1 MPa, and more preferably, from 0.1 to 0.5 MPa.
    [0035] [0035] It is of particular importance that the average size of the micropores and / or average volume of the micropores of the compositions of the invention appear to suffer little, if any, change when additional factors, including, but not limited to, ramp rate to achieve maximum pyrolysis temperature obtained, and / or the retention time at the maximum pyrolysis temperature reached, are introduced and / or considered. For example, for industrial purposes, ramp rates ranging from 2 ° C / min to 10 ° C / min are typical, and retention times that can vary from 0 minutes (min) (that is, increasing the maximum temperature reached followed by immediate reduction of passive or active temperature) up to 60 minutes (ie, maintaining the maximum pyrolysis temperature obtained for up to 60 minutes before reducing active or passive temperature) are typical. However, when inventive compositions are prepared under conditions in which these parameters are changed, the average size of micropores and / or average volume of micropores can still be reliably preselected or predicted according to the characterization equations given.
    [0036] [0036] After pyrolysis, a modality of the inventive CMS compositions, having an average micropore size ranging from 3.0 Å to 5.0 Å, is completed. In particular modalities of the same, the average micropore size ranges from 4.0 Å to 4.3 Å, and is therefore capable of admitting propylene molecules with the exception of propane gas molecules. In another preferred embodiment, the average size of micropores ranges from 3.7 Å to 4.1 Å, and is thus capable of admitting ethylene molecules while with the exception of ethane molecules. In yet another preferred modality, the average size of micropores ranges from 3.64 Å to 3.8 Å, and is thus capable of accepting nitrogen molecules with the exception of methane molecules. In yet another preferred embodiment, the average size of micropores ranges from 3.0 Å to 3.64 Å, and is thus capable of accepting carbon dioxide molecules with the exception of nitrogen molecules. In yet another preferred embodiment, the average size of micropores ranges from 4.3 Å to 5.0 Å, and is thus capable of admitting n-butane molecules with the exception of iso-butane molecules. Thus, the compositions of the invention are particularly desirable for these particular separations, but may, in other non-limiting embodiments, be useful in certain other separations.
    [0037] [0037] The final CMS will generally appear as a finely divided powder, having a surface area of BrunauerEmmett-Teller (BET) ranging from 300 square meters per gram (m2 / g) to 1500 m2 / g and an average particle size ranging from 10 µm to 1000 µm, preferably from 30 µm to 300 µm. As will be well known to those skilled in the art, however, such powders may be unsuitable for use in applications in typical separations, such as in conventional packaged beds, including, for example, fixed beds. This is because the packaging geometries can, in such applications, be dense enough to severely inhibit the flow of passage and thus create unacceptable transit times and pressure drops.
    [0038] [0038] In order to combat these problems, inventive CMSs can be used as a basis to form CMS pellets or CMS fabric fiber sheets or monoliths that offer significantly more convenient handling, such as greatly improved structural integrity, when compared with powders. In some embodiments, such pellets or sheets of woven fibers may also offer more easily controlled and desirable transit times. This can be prepared in a variety of ways that can be, or will henceforth, become known to those skilled in the art. In certain particularly preferred embodiments, however, the following processes of the invention have been found to be particularly effective.
    [0039] [0039] In the case of microspheres, fiber or pyrolysed CMS film, these can be first crushed to an average particle size ranging between 10 µm and 300 µm, preferably from 20 µm to 200 µm, and more preferably, from 30 µm to 100 µm. The grinding can be carried out using conventional grinding equipment, including, for example, a laboratory scale mortar and pestle, or commercial grinding equipment, such as, but not limited to, a jet mill or an impact mill. The crushed pyrolyzed CMS fiber or film can then be combined with a binder. This binder can, in certain embodiments, be a cellulosic binder, such as cellulose itself, or a cellulose ether or cellulose ester. In one embodiment, it can be methylcellulose. In certain embodiments, a water ratio is also included with the binder in order to form a paste. Therefore, it is generally desirable for the binder to be a relatively hydrophilic material, which is defined here as referring to a binder that is more attracted to water than the crushed CMS film or fiber, such that the coating or pore filling of the CMS film or fiber by the binder is reduced or minimized. This helps to avoid at least some of the reduction in the average volume of micropores that may result from such a pore coating or filling, and is the reason why the desirable binder is defined herein as a substantially "non-coating" binder. The term "substantially" as used here, means that there is less than a 10% reduction, preferably less than a 5% reduction, and more preferably less than a 2% reduction, in the average volume of micropores, compared to the average volume of micropores of the film or CMS fiber crushed without the presence of any binder. Thus, without intending to stick to any theory, it is speculated that in the binder / water / CMS system, the CMS material may be relatively hydrophobic, which contributes to the "non-coating" activity of the binder / water combination. At the same time, the binder as used preferably here provides structural integrity and mechanical strength to the pellet after water is removed from it.
    [0040] [0040] In the proportion in which it is desirable that the weight ratio of the non-coating binder to the pyrolysate, the microspheres, fibers or CMS films crushed in the paste, is less than 0.5: 1, more preferably, less than 0.25: 1, and more preferably, less than 0.05: 1. The binder / water ratio is preferably in the range of 1:10 to 1: 3, to ensure that the paste can be conveniently extruded.
    [0041] [0041] Once a suitable binder formulation is prepared, it can preferably be extruded with a piston to form any desired shape, but for many purposes, an essentially linear shape is convenient. Piston extrusion allows for the formation of relatively large pellets while not significantly reducing the ability of the non-coating binder to minimize water migration during high-resistance transmission after extrusion moisture. It is desirable that the final pellets have a distribution of relatively narrow length and a diameter that preferably ranges from 1 millimeter (mm) to 10 mm, more preferably from 2 mm to 5 mm. The diameter / length aspect ratio preferably ranges from 1: 1 to 1: 5. Note that extrusion by means of a conventional 5 mm die can result in relatively pellet agglomerates, which can then be conveniently cut to the desired length, which are then suitable for drying, for example, in a drying oven at a temperature ranging from 50 ° C to 100 ° C, for a time ranging from 1 h to 24 h, to form pellets that contain mechanically strong CMS. It is preferable that the pellets themselves have a macroporosity, that is, the presence of pores having an average diameter greater than 50 nanometers (nm), which varies from 10 percent in volume (% vol) to 50% in volume, with more preference , from 20% by volume to 40% by volume, and more preferably from 25% by vol to 35% by vol.
    [0042] [0042] In an alternative embodiment, a useful CMS configuration can be prepared first by forming PVDC precursor fibers by means of melt extrusion, as described above, having given approximate preferred thickness, diameters or transverse widths, as applicable, that is, ranging from 10 µm to 1000 µm, preferably from 20 µm to 500 µm, and more preferably, from 30 µm to 300 µm. In separate embodiments these precursor fibers can first be woven together to form a sheet of fabric, then pretreated, as described here above, and finally pyrolysed to form a fabric fiber adsorbent; or the precursor fibers can first be pretreated, then the woven fibers are pretreated to form a fabric fiber sheet, and finally, the fabric fiber sheet is pyrolyzed to form the fabric fiber adsorbent. Of these two modalities, it is often preferable to first weave the precursor fibers, before pretreatment, since the pre-treatment tends to make the fibers more rigid and, therefore, more difficult to weave afterwards. Any approach can allow the inclusion of desired levels of voids, also known as macrovazios or macropores (that is, having average diameters greater than 50 nm), whenever the fibers cross each other, which can serve a function that is equivalent that offered by pellet packing geometries, that is, to ensure desirable mass transport speed and, therefore, a desirable performance for packaged bed applications on a relatively large scale. In some embodiments, it is desirable that the total void space represented by such a fabric fiber sheet varies from 10 to 50% by volume, more desirably from 20% by volume to 40% by volume, and more desirably, 25% by volume to 35% by volume, as measured by mercury porosimetry. A suitable method for this is described, for example, in Liu J., Han C, McAdon M., Goss J., Andrews K., "High throughput development of one carbon molecular sieve for many gas separations", Microporous Mesoporous Mater. (2015) 206, 207-216, which is incorporated herein by reference in its entirety. Note that these ranges of preferential empty volumes correlate substantially with the ranges of macroporosity preferred for pellets.
    [0043] [0043] Once the CMS pellet structure or fabric fiber sheet structure has been prepared and pyrolysis is completed, it is ready to be used in an actual separation process. However, it should be understood that, alternatively, it is possible to use the pyrolyzed CMS powder (which has not been pelletized or formed in a fabric fiber sheet structure) for separation purposes as described hereinafter. Those skilled in the art will be well versed in the means and methods for preparing a packed bed or column, or for making a laminar adsorbent structure comprising sheets of fabric fiber, through which the desired mixture of gases can be passed to carry out the separation. of the same. As noted, a particular, but not limiting, gas mixture that can be conveniently separated in the present invention is a mixture comprising C3H6 and C3H8. In this case, the mixture and the CMS structure can be brought into contact under suitable conditions to adsorb at least 5% by weight, preferably at least 8% by weight, more preferably at least 10% by weight, of at least at least one first gas (in the present case, C3H6), such that the first gas is separated from at least a second gas (in the present case, C3H8); recover the second gas (C3H8); desorb the first gas (C3H6); and finally recovery of the first gas (C3H6). A similar approach can be used with an unlimited number of other gas pairs, having representative molecular diameters differentiated in such a way that at least one of which is within the range of 3.0 Å and 5.0 Å, and in which the average size of the CMS micropores was selected to be part of some point between the two different representative molecular diameters. This separation can be effectively accomplished using traditional pressure oscillation techniques, where the adsorption and desorption cycles are alternated. Other means may include, for example, temperature oscillation adsorption processes, and the adsorption of a gas, for example, propylene from the propylene / propane mixture, followed by desorption, which is achieved by purging with an inert gas. In particular embodiments, it is desirable for the selected gas separation factor to be at least 10, preferably at least 20, more preferably, at least 40, and most preferably, at least 50. Examples 1-17 and Comparative Examples 1-16
    [0044] [0044] A series of sample samples (ES) and comparative samples (CS) are prepared from vinylidene chloride which is copolymerized with a selected monomer of methyl acrylate (MA), ethyl acrylate (EA), or acrylate of butyl (BA), the monomer being present in each case, in an amount shown in TABLE 2. In each case, copolymerization is carried out by suspension polymerization. In general, this includes mixing the selected monomers according to their weight ratio with a polymerization initiator and then carrying out the polymerization reaction in aqueous dispersion. The copolymer powder is then dried to remove water and any unreacted monomers. The powder is then sieved and the US 30-50 mesh portion of it is selected, to ensure uniformity, for the preparation of CMS.
    [0045] [0045] The precursor powder is then dehydrochlorinated to pre-treat it, at a temperature of 130 ° C for 24 hours, followed by 150 ° C for 24 hours, in an oven purged by 2 liters per minute (L / min). air.
    [0046] [0046] After pre-treatment with dehydrochlorination, the pre-treated powder is then pyrolyzed in a three-stage pyrolysis process. The first stage comprises loading samples of 300 grams (g) of vinylidene chloride resin (copolymer) in a low temperature oven. A purifier connected to this oven contains a 10% by weight aqueous solution of sodium hydroxide. The loaded oven is first heated at a ramp rate of 1 ° C / min to 130 ° C and maintained for 24 h, then heated at a ramp rate of 1 ° C / min to 150 ° C and maintained for 24 hours h under 2 L / min air purge, before cooling to room temperature.
    [0047] [0047] Then, the second pyrolysis stage includes loading the precursor powder into a cubic foot retort furnace. A purifier connected to this oven contains a 10% by weight aqueous solution of sodium hydroxide. The loaded oven is heated to 650 ° C at a ramp rate of 5 ° C / min and maintained for 15 min, with less than 2 L / min of nitrogen, before cooling to room temperature.
    [0048] [0048] The third stage of pyrolysis is then carried out in a graphite oven. The precursor powder samples (10 g each) from the second transformation stage in the retort furnace are loaded, in turn, into a graphite boat measuring 4 inches by 4 inches by 0.5 inches (4 "x 4 "x 0.5"). The boat containing each sample is heated according to the conditions indicated for the inventive and comparative samples in TABLE 2, with a nitrogen purge of 10 l / min (one rotation volume every 12 After completing the third pyrolysis stage for each, the oven is cooled at a ramp rate of 10 ° C / min to 450 ° C, below which the oven is allowed to cool to room temperature at a slower rate due to heat transfer limitations.
    [0049] [0049] TABLE 2 also shows the properties of the CMS compositions formed based on six process variables: 1) Maximum pyrolysis temperature obtained; 2) Retention time at the maximum pyrolysis temperature obtained; 3) Ramp rate for the maximum pyrolysis temperature obtained; 4) Type of comonomer; 5) Comonomer content; and 6) Precursor crystallinity. The total micropore volume is measured using an N2 t-plot BET method, which is typically used in the art.
    [0050] [0050] The average micropore size, alternatively, designated as the effective micropore size or the average effective micropore size, is also measured using a kinetic adsorption method using several probe molecules. To estimate the effective micropore size of each CMS adsorbent, first, all probe gas pairs with selectivity greater than 10 are determined for each CMS adsorbent. For each pair of gases with a selectivity greater than or equal to 10, the smallest rejected molecule and the largest adsorbed molecule are selected as the defining molecule pair. Next, the average of the representative molecular diameters of this pair of defining molecules is considered to be the effective micropore size of the particular CMS adsorbent.
    [0051] [0051] For example, the smallest and largest gas molecules that are rejected and accepted by Example 1 (EX 1) adsorbent are C3H8 (4.3 Å) and C2H6 (4.1 Å), respectively. Consequently, the effective micropore size of the EX 1 adsorbent is estimated and understood to be 4.2 Å.
    [0052] [0052] ** Retention time at maximum pyrolysis temperature reached
    [0053] [0053] *** Crystallinity of the precursor (that is, of pre-pyrolysis composition)
    [0054] [0054] **** Micropore volume too low to measure by the BET method of N2. Example 18
    [0055] [0055] Four (4) Sample samples (EX), denoted as ES 1, ES 6, ES 8 and ES 13, shown in Table 2 as having an effective micropore size of 4.2 Å, are used for an experiment to compare high performance kinetic adsorption in propylene and propane separations. To calculate selectivity, the formula presented in Equation (3) is used.
    [0056] [0056] In the equation "ΔP" represents the pressure drop (from 45 psi, 0.31 MPa, the starting pressure to the equilibrium pressure) due to adsorption, which is proportional to the amount of adsorption according to the law of ideal gases. The half-time adsorption ("t0.5") represents the time in which 50% of the head loss (adsorption) occurs, which corresponds to the diffusion speed. Selectivity ("Alpha-PD") is defined in the following equation to take into account both balance and kinetic selectivities. The results for the four sample samples tested are shown in TABLE 3. TABLE 3: Summary of kinetic adsorption of C2H4 / C2H6 from CMS samples: ES 1, 6, 8 and 13
    [0057] [0057] * 1 psi = approximately 0.007 MPa
    [0058] [0058] Note that researchers previously believed that zeolite 4A, with an effective micropore size of about 4.2 Å, offered the best potential for use in propylene / propane separations. However, the volume of Zeolite 4A micropores is known to be 0.20 mL / g. See, for example, Da Silva F.A., Rodrigues A.E., “Adsorption Equilibria and Kinetics for Propylene and Propane over 13X and 4A Zeolite Pellets” Ind. Eng. Chem. Res. (1999) 38, 2051-2057, which is incorporated herein by reference in its entirety. Thus, certain embodiments of the present invention can offer a significant increase in the volume of micropores, and the greater volume generally results in greater yield. It is also noted that the "effective micropore size" refers to pore sizes that are effective in resulting in separation, but this may offer higher or lower rates of diffusion dependent, in part, on geometry. Example 19
    [0059] [0059] A measure of ethylene / ethane selectivity is performed using ES 11 in a high yield kinetic adsorption. The results of this separation are shown in TABLE 4. These results show that not only does ethane adsorb to a much lesser extent in the inventive CMS than ethylene, due to the pressure drop resulting from adsorption, but it also absorbs much more slowly, by a factor of about 10. Thus, the two molecules can be easily and effectively separated using the compositions of the invention. TABLE 4: Summary of Kinetic Adsorption of C2H4 / C2H6 from the CMS sample: ES 11
    [0060] [0060] A measure of nitrogen / methane selectivity is performed using ES 16 in a high yield kinetic adsorption. The results of this separation are shown in TABLE 5. These results show that, although nitrogen is adsorbed to a lesser extent than methane, due to the pressure drop resulting from adsorption, it absorbs almost 40 times faster than methane. Thus, the inventive CMS composition provides an effective kinetic separation of these two molecules. TABLE 5: Summary of kinetic adsorption of N2 / CH4 from the CMS sample: ES 16
    [0061] [0061] A measure of the selectivity of propane (representative of a straight chain paraffin) and isobutane (representative of a branched chain paraffin) is performed using ES 15 in a high yield kinetic adsorption. The results of this separation are shown in TABLE 6. These results show that propane absorbs both to a greater degree and also almost 4 times faster than iso-butane. Thus, the inventive CMS composition provides an effective separation of these two molecules. In addition, it should be noted that, due to the microporous volume of this CMS (ie 0.312 mL / g) being significantly greater than that of Zeolite 5A (that is, 0.198 mL / g), it is currently being used for certain separations of commercial straight / branched chain paraffin, such as nbutane / i-butane separations, the inventive CMS can offer a significant and comparative advantage. TABLE 6: Summary of kinetic adsorption of C3H8 / i-C4H10 from the CMS sample: ES 15
    [0062] [0062] Three exemplary fused extruded copolymer tapes, designated as ES 22, ES 23, and ES 24, comprising vinylidene chloride monomer and, as comonomers with them, methyl acrylate (MA) 4.8% by weight , 8.5 wt% MA or 17.6 wt% vinyl chloride (VC), respectively, are prepared. Approximately 5 g of PVDC tapes are fixed in aluminum (Al) crucibles and allowed to shrink freely during the pretreatment step. PVDC films are kept in a one-cubic foot oven purged with approximately 10 L / min of air. The oven temperature is increased to 130 ° C, with a ramp of 1 ° C / min and maintained for 24 h, then increased to 150 ° C, with a ramp rate of 1 ° C / min and maintained for an additional 24 h , before cooling to room temperature. The crystallinity of each of the tapes is shown in TABLE 7. As compared to the crystallinity of the polymerized resins as in TABLE 2, the crystallinity of the tapes after melt extrusion is reduced by an amount ranging from 10% to 30% . TABLE 7: Crystallinity of various PVDC precursors
    [0063] [0063] Samples of approximately 2 g of each of the pretreated films are loaded into a one-inch diameter quartz tube oven. The tube furnace loaded with the resin samples is then raised from 550 ° C to 1000 ° C, at a ramp rate of 5 ° C / min or 10 ° C / min, respectively, to end the release reaction of HCl. The carbonized film obtained from the first pyrolysis step is then placed in an ASTROTM oven (ASTRO is a trademark of Astro thermal Tec Ltd.) with electric heating, water-cooled and with argon (Air) purge. The temperature is raised from 1000 ° C and the final temperature (ie maximum temperature obtained) of 1500 ° C at a ramp of 10 ° C / min, and maintained at the final temperature for 15 min. The pyrolysis conditions are shown in the sample names as follows: end of ramp temperature retention time. Thus, for example, the notation "5C-1000-15min" defines a ramp of 5 ° C / min, a final temperature of 1000 ° C and a retention time of 15 min during pyrolysis.
    [0064] [0064] High performance kinetic adsorption is performed in a high performance reactor (HTR) system installed in a triple dry box. The adsorbent gases (C3H6 propylene and C3H8 propane) can be injected into each cell at a controlled pressure and temperature. The kinetic adsorption measurements are carried out in the following sequence: (1) Load of approximately 0.5 g of CMS sample for high-performance 14 cm3 cells; (2) degassing at 140 ° C for 4 hours with a semi-continuous N2 purge; (3) Introduce the C3H6 gas at a pressure of 45 pounds per square inch (psi, 0.31 MPa) and monitor the pressure drop for 8 hours at 35 ° C; (4) degassing at 140 ° C for 24 hours by purging N2; and (5) introduce the C3H8 gas at 45 psi (0.31 MPa) pressure and monitor the pressure drop for 96 hours at 35 ° C.
    [0065] [0065] TABLE 8 shows the results of high yield kinetic adsorption on the pyrolysed carbon tapes. Because each of the adsorption cells contains (1) the same amount of CMS adsorbent (0.5 g); (2) the same volume (14 milliliters, mL); and (3) be pressurized to the same 45 pounds per square inch (psi, 0.31 MPa) of initial pressure; the pressure drop (ΔP) is, therefore, an indicator of the amount of gas adsorbed by the adsorbent. The results show that, for CMS adsorbents prepared from the same type of precursor, ΔP of C3H6 and C3H8 is approximately the same at low pyrolysis temperature. The ΔP of both adsorption gases increases slightly and then decreases as the pyrolysis temperature increases. When pyrolyzed at 1500 ° C, the 4.8% by weight precursor MA CMS film shows C3H6 / C3H8 selectivity as high as 50. In addition, when pyrolyzed above 1000 ° C, CMS films of both MA at 8.5% by weight and VC at 17.6% by weight of precursor show some selectivity of C3H6 / C3H8.
    [0066] [0066] From the results above, it can then be concluded that the selective propylene / propane materials can be more conveniently prepared in the form of melt-extruded tapes than in the form of resins as polymerized, because the tapes melt-extruded can be pyrolysed at a lower temperature than the comparable selectivity resins obtained. The final pyrolysis temperature for the 4.8 wt% MA resin decreases from about 1700 ° C for the resin as polymerized at approximately 1500 ° C in the melt extrusion tape. Likewise, the final pyrolysis temperature for the 8.6 wt% MA resin decreases from about 1300 ° C for the resin as polymerized at approximately 1000 ° C on the melt extruded tape. This shows that melt extrusion reduces the crystallinity of the PVDC copolymers, which in turn allows the formation of selective propylene / propane micropores at lower pyrolysis temperatures. TABLE 8: Summary of Kinetic Adsorption of C3H6 / C3H8 from CMS films
    [0067] [0067] ** 1 psi = about 0.007 Mpa Examples 25-41
    [0068] [0068] Two types of CMS fibers of 0.28 mm (mm) in diameter (obtained from SATTITM, Germany, and denoted as "Doll's Hair" due to the fact of the greater application for the hair fiber used in dolls) children's toy) are pre-treated according to two methods: Method A, in which the fiber is kept at constant length during the pre-treatment step, and Method B, in which the fiber is allowed to shrink freely during the pre-treatment. Both methods are performed under the same temperature profiles shown in Example 1. It is noted that the fiber always breaks in the pre-treatment medium when attempts are made to keep the length constant. The broken fibers then shrink in a similar way to those allowed to shrink freely. The crystallinity of the precursor fibers is shown in TABLE 9. TABLE 9: Crystallinity of 0.28 mm PVDC fiber
    [0069] [0069] The fibers are then subjected to pyrolysis at different temperatures. TABLE 10 shows the results of kinetic adsorption of the fibers corresponding to the pyrolysis at each temperature. There is a pyrolysis temperature window that ranges from about 850 ° C to 1000 ° C for both types of CMS fibers to obtain optimum C3H6 / C3H8 selectivity. The temperature window is significantly lower than the 1500 ° C pyrolysis temperature that is required for the CMS film, despite the fact that both fibers and films are prepared from the same 4.8% MA precursor in Weight. The main difference between the film and the fibers is in their respective crystalline morphologies, which depend heavily on the melt extrusion process used. The 4.8 wt% MA film is extruded with an insignificant amount of stretch applied and allowed to slowly crystallize over approximately a two day time period. In contrast, when a stretch ratio as high as 4 is used to fuse the spinning fibers, the crystallization process takes place within a few seconds. It is noted that the crystallites in the stretched fiber are generally much smaller and more highly aligned than those in the films, even though the crystallinity levels of the film and fiber precursors are approximately the same, as shown in TABLE 7 and TABLE 9. Without wishing to stick to any theory, it is speculated that increasing the alignment of crystallites in the precursor, due to stretching, may reduce crosslinking and, through pyrolysis, may increase graphitization, which may, in turn, result in need for, or tolerance of, a lower pyrolysis temperature. The lower pyrolysis temperature for the production of CMS fiber also results in a more economical pyrolysis production process for scaling purposes. TABLE 10: Summary of High Yield Kinetic Adsorption of C3H6 / C3H8 for CMS fibers]
    [0070] [0070] The CMS fiber is obtained by pyrolysis of a 170 µm outer diameter (OD) fiber of vinylidene chloride / methyl acrylate copolymer (SARANTM, obtained from FUGAFILTM in Germany), using the two-step process steps described below. The composition and crystallinity of the precursor fiber are shown in TABLE 11. TABLE 11: Crystallinity of 0.17mm PVDC fiber
    [0071] [0071] In a pre-treatment step, 100 g of PVDC fibers are preheated in an air convection oven at 130 ° C for one day and at 150 ° C for another day, to form the precursor of Stabilized CMS. The pretreated fiber is then pyrolyzed at 550 ° C under N2 purging (ramp of 5 ° C / min, maintained for 15 min at 550 ° C) to complete the chemical decomposition. The CMS fiber is denoted as "0.17mm CF" with "CF" meaning "carbon fiber". The obtained CMS fiber is then ground to an average particle size in the range of 30 µm to 200 µm. Example 43
    [0072] [0072] A paste is made by manually mixing three components: 10 g of crushed CMS fiber (Example 42), 1 g of METHOCELTM A4M (METHOCEL is a trademark of The Dow Chemical Company), and 10 g of deionized water (DI ). The paste is extruded through a 5 mm die and cut into pellets of approximately 5 mm short cylindrical. The pellets are dried in a purged N2 oven at 50 ° C overnight. The pellet is denoted as "10% METHOCEL-CF 0.17mm" with "%" representing% by weight. Examples 44
    [0073] [0073] The CMS fiber is prepared using the protocol of Example 42, except that the pulp components include 5 g of METHOCELTM A4M. Further processing is continued as in Example 43, with the final pellet sample being indicated as "50% 0.17 mm Metocel-CF".
    [0074] [0074] The transient gravimetric adsorption of the CMS fiber and the pellet adsorbents prepared in Examples 42, 43, 44 are performed on a modified thermogravimetric analysis instrument (TGA). Approximately 200 milligrams (mg) of CMS material is loaded into a TGA crucible and heated to 90 ° C (10 ° C / min ramp and 30 min retention time) under 25 standard cubic centimeters per minute (sccm) purging of helium (He). The He purge gas is then transferred to 25 sccm of mixing gas containing 50 mole percent (mol%) He and 50 mol% C3H6. The weight gain of the samples (due to the adsorption of C3H6) over time is recorded. C3H6 capacity is recorded as the percentage of weight gain in equilibrium compared to freshly prepared CMS samples. Half-time adsorption is the time required to achieve 50% of the equilibrium weight variation, which is used as a parameter for the rate of kinetic adsorption. The results are shown in Table 12. TABLE 12: Propylene capacity and adsorption in half the time for pellets and CMS fiber
    [0075] [0075] The results show that a significant variation in the amount of cellulose ether (10% by weight compared to 50% by weight of METHOCELTM) does not significantly reduce the diffusion rate of C3H6. In fact, the release to the pellet is very similar to the diffusion for the 0.17 mm CMS fiber that has not been pelleted at all. The fact that the speed of mass transport does not seem to be significantly affected either by the fact of pelletizing, or by the proportion of binder when the CMS adsorbent was pelletized, is unexpected. Without sticking to the theory, it is speculated that the highly hydrophilic nature of cellulose ether, that is, the fact that it is non-coating, when used in combination with the hydrophobic CMS film or fiber, may result in the conservation of an interface filled void, which ensures efficient mass transportation. Examples 46-47
    [0076] [0076] A type of SARANTM fabric cloth (obtained from FUGAFILTM, Germany, denoted as "SARAN cloth") is pre-treated according to temperature profiles similar to those described in Example 34-41. The SARANTM cloth is allowed to shrink freely during the pre-treatment and the subsequent pyrolysis step according to the maximum pyrolysis temperatures obtained shown in TABLE 13.
    [0077] [0077] The TGA kinetic adsorption test includes testing using C3H6 and C3H8. For the kinetic adsorption test, approximately 200 mg of the tissue is first placed in a TGA pan and heated to 90 ° C (10 ° C / min ramp and 30 min retention time) under 25 sccm purge of He. The He purge gas is then transferred to 25 sccm of mixture gas containing 50 mol% of He and 50 mol% of C3H6. Then, 200 mg of the fresh sample is loaded into a TGA crucible and heated to 90 ° C (10 ° C / min ramp and 30 min retention time) under 25 sccm of He purge. The He purge gas is then transferred to 25 sccm of mixing gas containing 50 mol% of He and 50 mol% of C3H8. For separation based on kinetic adsorption, a cycle time to achieve 50% faster gas equilibrium (C3H6) is desirable to maximize selectivity. Therefore, the selectivity of this gravimetric method (Alpha-L) is defined as the weight gain ratio for C3H6 and C3H8 in half the time of adsorption of C3H6.
    [0078] [0078] TABLE 13 shows the kinetic adsorption results for cloth samples that were carbonized by pyrolysis at different temperatures. There is a temperature window that ranges from 1100 ° C to 1200 ° C to form CMS with selective pores of propylene / propane, which is similar to that found in CMS derived from SARAN fiber. TABLE 13: Summary of High Performance Kinetic Adsorption of C3H6 / C3H8 from CMS cloth.
    权利要求:
    Claims (8)
    [0001]
    Molecular sieve composition, characterized by the fact that it comprises the carbonized polyvinylidene chloride copolymer and having an average micropore size ranging from 3.0 Å and 5.0 â.
    [0002]
    Molecular sieve composition according to claim 1, characterized by the fact that it is used to separate a selected mixture from: (a) propane and propylene; (b) nitrogen and methane; (c) ethane and ethylene; (d) carbon dioxide and nitrogen; and (e) n-butane and iso-butane; the molecular sieve composition having been prepared in such a way that it has an average micropore size which is suitable to allow separation of the selected mixture.
    [0003]
    Process for preparing a molecular sieve composition, comprising carbonized polyvinylidene chloride copolymer and having micropores having an average micropore size ranging from 0.4 nm to 0.43 nm (4.0 Å to 4.3 Å), said method being characterized by the fact that it comprises - pyrolysis of a polyvinylidene chloride copolymer precursor at a maximum pyrolysis temperature obtained in degrees Celsius ranging from 800 to 1700, with the precursor having a percentage of crystallinity, as measured by differential scanning calorimetry , according to ASTM D3418, ranging from 25 to 75, to obtain the molecular sieve composition; the precursor of crystallinity and the maximum pyrolysis temperature obtained being selected according to the correction of the desired average microporous size given by the equation: σ = 6.09 + (0.0275 x C) - (0.00233 x T) where σ is the average micropore size in Angstroms, C is the percentage of precursor crystallinity expressed as a rational number greater than zero, and T is the maximum pyrolysis temperature obtained in degrees Celsius.
    [0004]
    Process according to claim 3, characterized in that the polyvinylidene chloride polymer precursor is pre-treated, before pyrolysis, to dehydrochlorine it by at least 10 percent, to form a pre-treated precursor.
    [0005]
    Process according to claim 4, characterized in that the polyvinylidene chloride copolymer precursor is prepared by polymerization or extrusion with fusion to form a precursor microsphere, a precursor film or a precursor fiber, the polyvinylidene chloride copolymer precursor, optionally comprising vinylidene chloride and at least one additional monomer selected from a vinyl monomer, a vinyl chloride monomer, an acrylate monomer, a methacrylate monomer, a styrene monomer, acrylonitrile, methacrylonitrile, itaconic acid, chlorotrifluoroethylene, and mixtures thereof; and extrusion with melt being optionally carried out at a stretch ratio of 1 to 8, the precursor microsphere, the precursor film or the precursor fiber having, optionally, an average thickness or average diameter of the cross section or average width, as applicable, ranging from 10 micrometers to 1000 micrometers.
    [0006]
    Process according to either of claims 4 or 5, characterized by the fact that: - the pre-treatment is carried out at a temperature ranging from 100 ° C to 180 ° C for a time ranging from 1 hour to 48 hours and, optionally, in the case of the precursor film or the precursor fiber, applying tension, simultaneously with pretreatment, in an amount of 0.01 MPa to 10 MPa.
    [0007]
    Process according to either of claims 5 or 6, characterized by the fact that it further comprises: - weave the precursor fiber to form a sheet of precursor tissue, before pyrolysis; and - pre-treat the precursor fabric sheet, before or after weaving; pyrolysis of the precursor woven sheet forming a fabric fiber adsorbent being characterized as having voids representing 10 percent to 50 percent, as measured by mercury porosimetry, of their total volume.
    [0008]
    Process according to any one of claims 3 to 7, characterized by the fact that it also comprises: - crush the composition of molecular pyrolyzed sieve to form particles having an average size ranging from 10 micrometers to 1000 micrometers; - combining the particles with at least one non-coating binder and water to form a pellet precursor material; and - pellet the pellet precursor material to form a structured pellet adsorbent.
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    NL7111508A|1971-08-20|1971-10-25|High and low branched hydrocarbons molecular|
    EP0394350B1|1987-12-24|1995-05-03|AlliedSignal Inc.|Hydrophobic carbon molecular sieves|
    US5292707A|1992-11-25|1994-03-08|Allied-Signal Inc.|Improving the density of carbon molecular sieves for the storage of natural gas|
    JP3725196B2|1995-03-01|2005-12-07|日本エンバイロケミカルズ株式会社|Nitrogen-containing molecular sieve activated carbon, its production method and use|
    US8003179B2|2002-06-20|2011-08-23|Alcan Packaging Flexible France|Films having a desiccant material incorporated therein and methods of use and manufacture|
    AU2012212537A1|2011-01-31|2013-08-15|Entegris, Inc.|Carbon pyrolyzate adsorbent having utility for CO2 capture and methods of making and using the same|
    TWI583445B|2012-04-13|2017-05-21|恩特葛瑞斯股份有限公司|Storage and stabilization of acetylene|
    US9073039B2|2012-07-13|2015-07-07|Adavanced Fuel Research, Inc.|Carbon sorbent for reversible ammonia sorption|
    CN104045753A|2014-06-19|2014-09-17|浙江衢州巨塑化工有限公司|Polyvinyl dichloride composition for carbon molecular sieve|WO2017160815A1|2016-03-16|2017-09-21|Dow Global Technologies Llc|Separation of gases via carbonized vinylidene chloride copolymer gas separation membranes and process for the preparation of the membranes|
    EP3541507B1|2016-11-17|2020-12-09|Solvay SA|Advanced porous carbon adsorbents for co2 capture and separation|
    US20190388872A1|2016-11-30|2019-12-26|Solvay Sa|Advanced porous carbonaceous materials and methods to prepare them|
    EP3606649A1|2017-04-06|2020-02-12|Dow Global Technologies LLC|Asymmetric polyvinylidine chloride membranes and carbon molecular sieve membranes made therefrom|
    EP3638407A1|2017-06-15|2020-04-22|Dow Global Technologies LLC|Supported carbon molecular sieve membranes and method to form them|
    EP3661643A1|2017-08-02|2020-06-10|Solvay SA|A method for forming an adsorptive carbonaceous shaped body and shaped green body and adsorptive carbonaceous bodies obtained therefrom|
    JP2020530811A|2017-08-14|2020-10-29|ダウ グローバル テクノロジーズ エルエルシー|Improved method for making carbon molecular sieve hollow fiber membranes|
    MX2017012563A|2017-09-29|2019-04-01|Mexicano Inst Petrol|Microporous carbon materials to separate nitrogen in associated and non-associated natural gas streams.|
    CN110102257A|2019-04-30|2019-08-09|贵州大学|Adsorbent is used in a kind of enrichment of coal bed gas methane separation|
    CN110711456B|2019-09-12|2021-06-22|浙江大学|Application of PVDC resin derived microporous carbon material in adsorption separation of xenon and krypton|
    CN110604999B|2019-09-12|2021-05-07|浙江大学|Application of PVDC resin derived microporous carbon material in adsorption separation of methane and nitrogen|
    CN110793888A|2019-11-20|2020-02-14|国网电力科学研究院武汉南瑞有限责任公司|SF6/N2Mixed gas diffusion characteristic experimental method|
    WO2021133596A1|2019-12-27|2021-07-01|Dow Global Technologies Llc|Carbon molecular sieve adsorbent monoliths and methods for making the same|
    CN113019318A|2021-02-26|2021-06-25|华南理工大学|Preparation method and application of carbon molecular sieve for separating olefin and alkane|
    法律状态:
    2018-03-27| B15K| Others concerning applications: alteration of classification|Ipc: B01J 20/20 (2006.01), B01D 53/02 (2006.01), B01J 2 |
    2019-12-31| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|
    2020-11-24| B09A| Decision: intention to grant|
    2021-02-17| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 22/06/2015, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US201462018828P| true| 2014-06-30|2014-06-30|
    US62/018,828|2014-06-30|
    PCT/US2015/036866|WO2016003680A1|2014-06-30|2015-06-22|Vinylidene chloride copolymer-based carbon molecular sieve adsorbent compositions and processes therefor|
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