CA2551499A1 - Mixed matrix membranes with low silica-to-alumina ratio molecular sieves and methods for making and using the membranes - Google Patents

Abstract

A mixed matrix membrane is provided which comprises a continuous phase organic polymer and small pore alumina containing molecular sieves dispersed therein.
The molecular sieves have a silica-to-alumina molar ratio of less than 1.0, more preferably, less than 0.3, and most preferably less than 0.1. In some cases, the molecular sieves have no appreciable amounts of silica. Exemplary compositions include aluminophosphates (AIPO) and silicoaluminophosphates (SAPO). When these molecular sieves are properly interspersed with a continuous phase polymer, the membrane will exhibit a mixed matrix membrane effect, i.e., a selectivity increase of at least 10% relative to a neat membrane containing no molecular sieves. The molecular sieves have pores with a largest minor crystallographic free diameter of 4.0 Angstroms or less. The molecular sieves may be selected from the group having IZA structure types including AEI, CHA, ERI, LEV, AFX, AFT, and GIS. Examples of preferred molecular sieves include: AIPO-18, SAPO-18, AIPO~-34, SAPO-34, SAPO-44, SAPO-47, AIPO-17, SAPO-17, CVX-7, SAPO-35, SAPO-56, ALPO-52, and SAPO-43. Finally, methods for making and using such mixed matrix membranes to separate gases from a mixture containing two or more gases are also disclosed.

Description

TECHNICAL FIELD

7 This invention relates generally to gas separation membranes and to methods 8 of making and using the same, and more particularly, to mixed matrix 9 membranes which use molecular sieves to enhance gas separation properties of the membranes.

14 Numerous references teach using mixed matrix membranes which comprise a continuous polymer phase carrier with molecular sieves dispersed therein.
16 Examples include U.S. Patent No. 4,925,459 to Rojey et al. and U.S. Patent 17 No. 5,127,925 to Kulprathipanja et al. The membranes are particular useful 18 for separating gases from a mixture or feedstock containing at least two gas 19 components, generally of differing effective diameters.
21 Membrane performance is characterized by the flux of a gas component 22 across the membrane. This flux can be expressed as a quantity called the 23 permeability (P), which is a pressure- and thickness-normalized flux of a given 24 component. The separation of a gas mixture is achieved by a membrane material that permits a faster permeation rate for one component (i.e., higher 26 permeability) over that of another component. The efficiency of the 27 membrane in enriching one component over another component in the 28 permeate stream can be expressed as a quantity called selectivity.
Selectivity 29 can be defined as the ratio of the permeabilities of the gas components across the membrane (i.e., PA/PB, where A and B are the two components). A
31 membrane's permeability and selectivity are material properties of the 32 membrane material itself, and thus these properties are ideally constant with 33 feed pressure, flow rate and other process conditions. However, permeability 1 and selectivity are both temperature-dependent. It is desirable for membrane 2 materials to have a high selectivity (efficiency) for the desired component, 3 while maintaining a high permeability (productivity) for the desired component.

Under the proper conditions, the addition of molecular sieves may increase 6 the relative effective permeability of a desirable gas component through the 7 polymeric membrane (and/or decrease effective permeability of the other gas 8 components), and thereby enhance the gas separation (selectivity) of the 9 polymeric membrane material. If the selectivity is significantly improved, i.e., on the order of 10% or more, by incorporating molecular sieves into a 11 continuous phase polymer, the mixed matrix membrane may be described as 12 exhibiting a mixed matrix effect. A selectivity enhancement test will be 13 described in detail below.

One common choice of molecular sieves includes zeolites. Zeolites are a 16 group of hydrous tectosilicate minerals characterized by an aluminosilcate 17 tetrahedral framework, ion-exchangeable large cations, and loosely held 18 water molecules permitting reversible dehydration.

U.S. Patent No. 4,925,562 to Hennepe et al., entitled "Pervaporation Process 21 and Membrane", teaches incorporating zeolites into a membrane with the 22 zeolites preferably being as hydrophobic as possible. Zeolites with a high 23 silicon/aluminum (Si/AI) molar ratio exhibit hydrophobic behavior in that they 24 sorb a less polar component from a mixture also including a more polar component. The hydrophobic zeolites are less likely to be fouled by water 26 while separating gas components in a feedstock than are more hydrophilic 27 zeolites.

29 The preferred zeolites of Hennepe et al. have a high SilAl ratio, and more particularly, have a Si/AI molar ratio of 12 or more and a silica-to-alumina 31 (Si021A1203~ molar ratio of 35 or more. These ratios can be determined by 32 known processes, such as atomic absorption spectroscopy (AAS), X-ray 33 spectroscopy and classical techniques, such as volumetric and titration 1 methods. Hennepe et al. describes using polyfunctional organosilicon 2 compounds to provide a desired interfacial adhesion between zeolites and 3 continuous phase polymers. Poor adhesion between the zeolites and the 4 continuous phase polymer may permit gas components to pass there between without separation. Without such adhesion, mixed matrix 6 membranes containing these high silica-to-alumina molar ratio zeolites often 7 fail to achieve a mixed matrix effect.

9 Another exemplary patent which utilizes zeolite molecular sieves in a mixed matrix membrane is U.S. Pat. No. 6,508,860 to Kulkarni et al., entitled "Gas 11 Separation Membrane with Organosilicon-Treated Molecular Sieves". This 12 patent is incorporated by reference herein in its entirety. Kulkarni et al.
reacts 13 a monofunctional organosilicon compound at the site of a displaceable radical 14 with free silanol on the molecular sieve surface. This step, often referred to as "silanation" of the sieve, typically results in substitution of the displaceable 16 radical of the compound by the silanol of the molecular sieve. A molecular 17 sieve having been treated in this fashion is said to be "silanated". The 18 monofunctional organosilicon compound thus becomes chemically bonded via 19 a single silicon atom bond site formerly occupied by a displaceable radical prior to silanation. Kulkarni et al. further suggests that these silanated mixed 21 matrix membranes provide an improved combination of permeability and 22 selectivity as compared to polymer only membranes and non-silanated mixed 23 matrix membranes.

A drawback to such silanation of molecular sieves is that compounds used in 26 silanation, such as 3-aminopropyldimethylethoxysilane, 27 3-isocyanopropyldimethylchlorosilane, or allyldimethylsilane are prohibitively 28 expensive. Another drawback is that when the molecular sieves are 29 silanated, excess silane must be removed so the silane will not block pores.
Further, the silanation process is usually performed in an organic (ethanol) 31 rather than water solution from which the silanated molecular sieves must be 32 recovered. The silanation and recovery steps increase the time and effort 33 needed to prepare molecular sieves for incorporation into a continuous phase 1 polymer. Accordingly, the cost of making membranes having silanated 2 molecular sieves can be very high and thus commercially disadvantageous.

4 There is a need for additional choices of molecular sieves for incorporation into polymeric carriers to create membranes exhibiting significant mixed 6 matrix effects. Ideally these membranes should provide enhanced selectivity 7 and permeability, foulant resistance, and durability compared to currently 8 available membranes. Further, it is desirable to avoid the expensive and time 9 consuming steps of silanating the molecular sieves prior to their being dispersed into a polymeric carrier. The present invention overcomes many of 11 the aforementioned shortcomings of membranes which utilize such high silica-12 to-alumina molar ratio silanated zeolite molecular sieves. Furthermore, 13 methods of making and utilizing these membranes for gas separation are also 14 taught.

18 A mixed matrix membrane is provided which comprises a continuous phase 19 organic polymer with small pore alumina containing molecular sieves dispersed therein. The molecular sieves ideally have a silica-to-alumina 21 molar ratio ranging from 0-1.0, preferably less than 0.5, more preferably less 22 than 0.3, and even more preferably, less than 0.2. Generally, the lower the 23 content of the silica in the alumina containing molecular sieves the better.
24 Exemplary compositions of such low silica-to-alumina molar ratio molecular sieves include, but are not limited to, non-zeolitic molecular sieves (NZMS) 26 including certain aluminophosphates (AIPO's), silicoaluminophosphates 27 (SAPO's), metallo-aluminophosphates (MeAPO's), 28 elementaluminophosphates (EIAPO's), metallo-silicoaluminophosphates 29 (MeAPSO's) and elementalsilicoaluminophosphates (EIAPSO's).
31 When these molecular sieves are properly interspersed with a continuous 32 phase polymer, the membrane ideally will exhibit a mixed matrix effect even 33 without silanation. Silanation is typically used when conventional high silica-1 to-alumina molar ratio zeolitic molecular sieves are used in membranes. The 2 molecular sieves ideally have pores with a largest minor crystallographic free 3 diameter of 4.0 Angstroms or less. The minor crystallographic free diameter 4 of pores of these molecular sieves may be as small as 3.8 A, 3.6 A, 3.4 A, or even as small as 3.0 A or less. In some instances, it is advantageous to have 6 pores which are generally elliptical or oblong in cross-section rather than 7 circular. Exemplary molecular sieves may include, but are not limited to, the 8 following IZA (International Zeolite Association) structure types: AEI, CHA, 9 ERI, LEV, AFX, AFT, and GIS. Examples of preferred molecular sieves include: AIPO-18, SAPO-18, ALPO-34, SAPO-34, SAPO-44, SAPO-47, 11 MeAPSO-34, AIPO-17, SAPO-17, MeAPSO-17, CVX-7, AIPO-35, SAPO-35, 12 SAPO-56, AIPO-52, and SAPO-43. The more preferable molecular sieves 13 are AIPO-34, SAPO-34, CVX-7, SAPO-17 and MeAPSO-17 with CVX-7 being 14 the most preferred molecular sieve.
16 In other aspects of this invention, a method for making a mixed matrix 17 membrane with low silica-to-alumina molar ratio molecular sieves with small 18 pores is also taught. Finally, methods for using such mixed matrix 19 membranes to separate gases from a mixture containing two or more gas components will also be described. Gases that differ in size, for example 21 nitrogen and oxygen or ethylene and ethane, can be separated using the 22 membranes described herein. In one preferred embodiment, a gaseous 23 mixture containing methane and carbon dioxide can be enriched in methane 24 by a gas-phase process through the mixed matrix membrane. In other cases, by way of example and not limitation, the membranes can be used to 26 separate helium, hydrogen, hydrogen sulfide, oxygen andlor nitrogen from 27 gas mixtures.

29 It is an object of the present invention to provide mixed matrix membranes which utilize small pore alumina containing molecular sieves having a low 31 silica-to-alumina molar ratio wherein no silanation is required to produce a 32 membrane which still exhibits a mixed matrix effect.

1 Another object is to provide mixed matrix membranes which have alumina 2 containing molecular sieves which are low in or devoid of silica content and 3 which have pores sizes which lead to selectivities which are substantially 4 better than conventional membranes used to separate gas components from a feedstream.

9 FIG. 1 is a schematic drawing of a separation system used to test the permeability and selectivity of a particular membrane.

12 BEST MODES) FOR CARRYING OUT THE INVENTION

14 Mixed matrix membranes, made in accordance with the present invention, include small pore silica containing molecular sieves dispersed into a 16 continuous phase polymer. The molecular sieves have a silica-to-alumina 17 molar ratio of 1.0 or less. In some cases, the molecular sieves may contain 18 no appreciable amounts of silica. The molecular sieves preferably do not 19 require silanation to create effective adhesions between molecular sieves and a continuous phase polymer in order for the membranes to exhibit substantial 21 mixed matrix effects.

23 Ideally, the molecular sieves of the present invention have pores with a 24 largest minor crystallographic free diameter of less than 4.0 Angstroms, and more preferably, between 3.0-4.0 ~. Descriptions of crystallographic free 26 diameters of pores of molecular sieves are published, for example, in "Atlas of 27 Zeolite Framework Types," edited by C. Baerlocher et al., Fifth Revised 28 Edition (2001 ). This reference is hereby incorporated by reference in its 29 entirety, particularly for its teachings regarding the crystallographic free diameters of zeolites and other like non-zeolitic molecular sieves.

32 Continuous phase polymers which can support the molecular sieves will first 33 be described. Then, exemplary molecular sieves to be incorporated into the 1 continuous phase polymer will be taught. A method of making mixed matrix 2 membranes utilizing the polymers and molecular sieves will next be 3 described. Finally, examples will show that mixed matrix membranes, made 4 in accordance with the present invention, can be made which have high selectivity and permeability relative to conventional membranes. In a 6 preferred embodiment, the membranes are useful for separating a gaseous 7 mixture containing carbon dioxide and methane.

9 I. Polymer Selection 11 An appropriately selected polymer can be used which permits passage of the 12 desired gases to be separated, for example carbon dioxide and methane.
13 Preferably, the polymer permits one or more of the desired gases to permeate 14 through the polymer at different diffusion rates than other components, such that one of the individual gases, for example carbon dioxide, diffuses at a 16 faster rate than methane through the polymer.

18 For use in making mixed matrix membranes for separating C02 and CH4, the 19 most preferred polymers include Ultem° 1000, Matrimid° 5218, 6FDAlBPDA-DAM, 6FDA-6FpDA, and 6FDA-IPDA (all polyimides). 6FDA/BPDA-DAM and 21 6FDA-IPDA are available from E.I. du Pont de Nemours and Company of 22 Wilmington, Delaware and are described in U.S. Patent No. 5,234,471.
23 Matrimid° 5218 is commercially available from Advanced Materials of 24 Brewster, New York. Ultem° 1000 may be obtained commercially from General Electric Plastics of Mount Vernon, Indiana.

27 Examples of suitable polymers include substituted or unsubstituted polymers 28 and may be selected from polysulfones; poly(styrenes), including 29 styrene-containing copolymers such as acrylonitrilestyrene copolymers, styrene-butadiene copolymers and styrene-vinylbenzylhalide copolymers;
31 polycarbonates; cellulosic polymers, such as cellulose acetate-butyrate, 32 cellulose propionate, ethyl cellulose, methyl cellulose, nitrocellulose, etc.;
33 polyamides and polyimides, including aryl polyamides and aryl polyimides;

1 polyethers; polyetherimides; polyetherketones; poly(arylene oxides) such as 2 poly(phenylene oxide) and poly(xylene oxide); poly(esteramide-diisocyanate);
3 polyurethanes; polyesters (including polyarylates), such as polyethylene 4 terephthalate), poly(alkyl methacrylates), poly(acrylates), poly(phenylene terephthalate), etc.; polypyrrolones; polysulfides; polymers from monomers 6 having alpha-olefinic unsaturation other than mentioned above such as poly 7 (ethylene), poly(propylene), poly(butene-1 ), poly(4-methyl pentene-1 ), 8 polyvinyls, e.g., poly(vinyl chloride), polyvinyl fluoride), poly(vinylidene 9 chloride), poly(vinylidene fluoride), polyvinyl alcohol), polyvinyl esters) such as polyvinyl acetate) and polyvinyl propionate), polyvinyl pyridines), 11 polyvinyl pyrrolidones), polyvinyl ethers), polyvinyl ketones), polyvinyl 12 aldehydes) such as polyvinyl formal) and polyvinyl butyral), polyvinyl 13 amides), polyvinyl amines), polyvinyl urethanes), polyvinyl ureas), polyvinyl 14 phosphates), and polyvinyl sulfates); polyallyls; poly(benzobenzimidazole);
polyhydrazides; polyoxadiazoles; polytriazoles; poly (benzimidazole);
16 polycarbodiimides; polyphosphazines; etc., and interpolymers, including block 17 interpolymers containing repeating units from the above such as terpolymers 18 of acrylonitrile-vinyl bromide-sodium salt of para-sulfophenylmethallyl ethers;
19 and grafts and blends containing any of the foregoing. Typical substituents providing substituted polymers include halogens such as fluorine, chlorine and 21 bromine; hydroxyl groups; lower alkyl groups; lower alkoxy groups;
22 monocyclic aryl; lower acyl groups and the like. It is preferred that the 23 membranes exhibit a carbon dioxide/methane selectivity of at least about 10, 24 more preferably at least about 20, and most preferably at least about 30.
26 Preferably, the polymer is a rigid, glassy polymer as opposed to a rubbery 27 polymer or a flexible glassy polymer. Glassy polymers are differentiated from 28 rubbery polymers by the rate of segmental movement of polymer chains.
29 Polymers in the glassy state do not have the rapid molecular motions that permit rubbery polymers their liquid-like nature and their ability to adjust 31 segmental configurations rapidly over large distances (>0.5 nm). Glassy 32 polymers exist in a non-equilibrium state with entangled molecular chains with 33 immobile molecular backbones in frozen conformations. The glass transition _g_ 1 temperature (Tg) is the dividing point between the rubbery or glassy state.
2 Above the Tg, the polymer exists in the rubbery state; below the Tg, the 3 polymer exists in the glassy state. Generally, glassy polymers provide a 4 selective environment for gas diffusion and are favored for gas separation applications. Rigid, glassy polymers describe polymers with rigid polymer 6 chain backbones that have limited intramolecular rotational mobility and are 7 often characterized by having high glass transition temperatures (Tg >150°C).

9 In rigid, glassy polymers, the diffusion coefficient tends to dominate, and glassy membranes fiend to be selective in favor of small, low-boiling 11 molecules. The preferred membranes are made from rigid, glassy polymer 12 materials that will pass carbon dioxide (and nitrogen) preferentially over 13 methane and other light hydrocarbons. Such polymers are well known in the 14 art and are described, for example, in U.S. Pat. Nos. 4,230,463 to Monsanto and 3,567,632 to DuPont. Suitable membrane materials include polyimides, 16 polysulfones and cellulosic polymers.

18 II. Molecular Sieves Molecular sieves are believed to improve the performance of the mixed matrix 21 membrane by including selective holes/pores with a size that permits a gas 22 such as carbon dioxide to pass through, but either not permitting another gas 23 such as methane to pass through, or permitting it to pass through at a 24 significantly slower rate. The molecular sieves should have higher selectivity for the desired gas separation than the original polymer to enhance the 26 performance of the mixed matrix membrane. For the desired gas separation 27 in the mixed matrix membrane, it is preferred that the steady-state 28 permeability of the faster permeating gas component in the molecular sieves 29 be at least equal to that of the faster permeating gas in the original polymer matrix phase.

32 Molecular sieves may be characterized as being "large pore", "medium pore"
33 or "small pore" molecular sieves. As used herein, the term "large pore"
refers _g_ 1 to molecular sieves which have greater than or equal to 12-ring openings in 2 their framework structure, the term "medium pore" refers to molecular sieves 3 which have 10-ring openings in their framework structure, and the term "small 4 pore" refers to molecular sieves which have less than or equal to 8-ring openings in their framework structure. In addition, the term "unidimensional"
6 or "unidimensional pores" refers to the fact that the pores in the molecular 7 sieves are essentially parallel and do not intersect. The term 8 "multidimensional" or "multidimensional pores" refers to pores which intersect 9 with each other. The molecular sieves of the present invention may be 2-dimensional, but most preferably are 3-dimensional. It is believed that this 11 multi-dimensional character will allow for better diffusion through the sieves 12 and the membrane.

14 A pore system is generally characterized by a major and a minor dimension.
For example, molecular sieves having the IUPAC structure of ERI has a major 16 diameter 5.1 A and a minor diameter of 3.6 ~. In some cases, molecular 17 sieves can have 1, 2 or even three different pore systems. While not wishing 18 to be restricted to a particular theory, it is believe that the pore system with the 19 largest minor free crystallographic diameter will effectively control the diffusion rate through the molecular sieves. As an example, molecular sieves having a 21 GIS structure have two pore systems with major and minor diameters of 4.5 x 22 3.1 A and 4.8 x 2.8 A. In this case, the controlling effective minor diameter is 23 believed to be that of the pore system having the largest minor diameter, i.e., 24 the pore system having the major and minor crystallographic free diameters of 4.5 x 3.1 A. Accordingly, for the purposes of this invention, the largest minor 26 crystallographic free diameter for the GIS structure is 3.1 A.

28 Ideally, the overall particle size of the molecular sieves will be small as well.
29 Size refers to a number average particle size. As used herein, the symbol ",u"
represents a measure of length in microns or, in the alternative, micrometers.
31 In terms of particle size of the small particles described herein, this measure 32 of length is a measure of the nominal or average diameters of the particles, 1 assuming that they approximate a spherical shape, or, in the case of 2 elongated particles the length is the particle size.

4 A variety of analytical methods are available to practitioners for determining the size of small particles. One such method employs a Coulter Counter, 6 which uses a current generated by platinum electrodes on two sides of an 7 aperture to count the number, and determine the size, of individual particles 8 passing through the aperture. The Coulter Counter is described in more detail 9 in J. K. Beddow, ed., Particle Characterization in Technology, Vol 1, Applications and Microanalysis, CRC Press, Inc, 1984, pp. 183-6, and in T.
11 Allen, Particle Size Measurement, London: Chapman and Hall, 1981, pp.
12 392-413. A sonic sifter, which separates particles according to size by a 13 combination of a vertical oscillating column of air and a repetitive mechanical 14 pulse on a sieve stack, can also be used to determine the particle size distribution of particles used in the process of this invention. Sonic sifters are 16 described in, for example, T. Allen, Particle Size Measurement, London:
17 Chapman and Hall, 1981, pp. 175-176. The average particle size may also 18 be determined by a laser light scattering method, using, for example, a 19 Malvern MasterSizer instrument. An average particle size may then be computed in various well-known ways, including:

n ~ ~Zi xLi ) 22 Number Average = i=1 h ~ Zi E=1 23 wherein z; is the number of particles whose length falls within an interval L~.
24 For purposes of this invention, average crystal size will be defined as a number average.

27 The size is ideally between 0.2-3.0 microns, more preferably between 0.2-1.5 28 microns, and even more preferably between 0.2-0.7 microns. Smaller particle 29 sizes are believed to facilitate better adhesion between the molecular sieves and the polymer. Preferably, the molecular sieves are synthesized to have a 1 number average particle size of less than 1 micron and more preferably, less 2 than 0.5. Although less preferred, the particle size can be reduced after 3 synthesis such as by high shear wet milling or by ball milling.

The present invention uses molecular sieves which contain alumina and have 6 a composition which has a low silica-to-alumina molar ratio. This molar ratio 7 should be less than 1.0, more preferably less than 0.5, and even more 8 preferably less than 0.2 or 0.1. In some cases, the alumina containing 9 molecular sieves may have no significant amounts of silica. The low silica-to-alumina molar ratio of the molecular sieves accommodates adhesion between 11 the molecular sieves and polymer phase carrier without the need for 12 expensive silanation of the molecular sieves.

14 Molecular sieve structure types can be identified by their structure type code as assigned by the IZA Structure Commission following the rules set up by the 16 IUPAC Commission on Zeolite Nomenclature. Each unique framework 17 topology is designated by a structure type code consisting of three capital 18 letters. Preferred low silica-to-alumina molar ratio molecular sieves used in 19 the present invention include molecular sieves having IZA structural designations of AEI, CHA, ERI, LEV, AFX, AFT and GIS. Exemplary 21 compositions of such small pore alumina containing molecular sieves include 22 non-zeolitic molecular sieves (NZMS) comprising certain aluminophosphates 23 (AIPO's), silicoaluminophosphates (SAPO's), metallo-aluminophosphates 24 (MeAPO's), elementaluminophosphates (EIAPO's), metallo-silicoaluminophosphates (MeAPSO's) and elementalsilicoaluminophosphates 26 (EIAPSO's).

28 More particularly, the preferred non-zeolite molecular sieves may have the 29 following compositions: AIPO-18, SAPO-18, AIPO-34, SAPO-34, SAPO-44, SAPO 47, AIPO-17, SAPO-17, CVX-7, MeAPSO-17, SAPO-35, SAPO-56, 31 AIPO-52, and SAPO-43. In the case where these molecular sieves can be 32 synthesized with varying ranges of molar ratio for silica-to-alumina, this molar 33 ratio should not exceed 1Ø

1 U.S. Pat. No. 4,440,871, issued on April 3, 1984 to Lok et al., the entire 2 disclosure of which is incorporated herein by reference, describes a class of 3 silicon-substituted aluminophosphate non-zeolitic molecular sieves (SAPO's) 4 which are both microporous and crystalline. These materials have a three-s dimensional crystal framework of [POD], [A102] and [Si02] tetrahedral units 6 and, exclusive of any alkali metal or calcium which may optionally be present, 7 an as-synthesized empirical chemical composition on an anhydrous basis of:

9 mR:(SiXAIy PZ)02 11 wherein "R" represents at least one organic templating agent present in the 12 intracrystalline pore system; "m" represents the moles of "R" present per mole 13 of (SiX AIyPZ)02 and has a value of from zero to 0.3, the maximum value in 14 each case depending upon the molecular dimensions of the templating agent and the available void volume of the pore system of the particular 16 silicoaluminophosphate species involved; and "x", "y", and "z" represent the 17 mole fractions of silicon, aluminum and phosphorus, respectively, present as 18 tetrahedral oxides. The minimum value for each of "x", "y", and "z" is 0.01 and 19 preferably 0.02. The maximum value for "x" is 0.98; for "y" is 0.60; and for "z"
is 0.52. These silicoaluminophosphates exhibit several physical and chemical 21 properties which are characteristic of both aluminosilicate zeolites and 22 aluminophosphates.

24 The silica-to-alumina molar ratio of these molecular sieves can range from slightly more than 0 to 10 or more. Those skilled in the art will appreciate that 26 this molar ratio can be readily adjusted by controlling the amounts of silica 27 available for the synthesis of the SAPO's to reach the desired silica-to-28 alumina ratio of 1.0 or less used in this invention. Similarly, the molar ratio of 29 other molecular sieves (MeAPO's and EIAPSO's) may also be determined by limiting the available silica during their synthesis.

32 U.S. Pat. No. 4,310,440, to Wilson et al., which is hereby incorporated by 33 reference in its entirety, teaches the synthesis of aluminophosphates 1 (ALPO's). The teachings of this reference are hereby incorporated by 2 reference in its entirety. The generic class of aluminophosphates have an 3 essential crystalline framework structure whose chemical composition 4 expressed in terms of molar ratios of oxides, is 6 AI2 03:1Ø~0.2 P2 05;

8 the framework structure being microporous in which the pores are uniform 9 and in each species have nominal diameters within the range of from 3 to 10 Angstroms; an intracrystalline adsorption capacity for water at 4.6 torr and 11 24°C. of at least 3.5 wt. %, the adsorption of water being completely 12 reversible while retaining the same essential framework topology in both the 13 hydrated and dehydrated state. By the term "essential framework topology"
is 14 meant the spatial arrangement of the primary AI-O and P-O bond linkages.
No change in the framework topology indicates that there is no disruption of 16 these primary bond linkages.

18 The aluminophosphates are prepared by hydrothermal crystallization of a 19 reaction mixture prepared by combining a reactive source of phosphate, alumina and water and at least one structure-directing or templating agent 21 which can include an organic amine and a quaternary ammonium salt. In the 22 as-synthesized form the structure-directing agent is contained within the 23 framework structure of the aluminophosphate in amounts which vary from 24 species to species but usually does not exceed one mole per mole of AI203 thereof. This structure-directing agent is readily removed by water washing or 26 calcination and does not appear to be an essential constituent of the product 27 aluminophosphate as evidenced by essentially complete absence of ion-28 exchangeability of the as-synthesized compositions and also the absence of 29 any internally-contained organic molecules in the as-synthesized form of at least one species of the generic class. Evidence that a structure-directing 31 agent is a critical constituent is contained in certain of the illustrative examples 32 appearing hereinafter, wherein reaction mixtures otherwise identical to those 33 which yield products of the present invention except for the presence of 1 templating agents, yield instead the previously known aluminophosphate 2 phases AIPO4 -tridymite, AIPO4-quartz and AIP04-cristobalite.

4 Broadly the preparative process comprises forming a reaction mixture which in terms of molar ratios of oxides is 7 AI203:1~0.5P205:7-100H~0 9 and containing from about 0.2-2.0 moles of templating agent per mole of AI203. The reaction mixture is placed in a reaction vessel inert toward the 11 reaction system and heated at a temperature of at least about 100°C, 12 preferably between 100°C and 300°C, until crystallized, usually a period from 13 two hours to two weeks. The solid crystalline reaction product is then 14 recovered by any convenient method, such as filtration or centrifugation, washed with water and dried at a temperature between ambient and 110°C
in 16 air.

18 U.S. Pat. No. 4,567,029, issued on January 28, 1986 to Wilson et al., the 19 entire disclosure of which is incorporated herein by reference, describes a class of crystalline metal aluminophosphate non-zeolitic molecular sieves 21 (designated therein as "MeAPO") having three-dimensional microporous 22 framework structures of [M02,] [A102] and [P02] tetrahedral units and having 23 an empirical chemical composition on an anhydrous basis expressed by the 24 formula:
26 mR:(MxAIyPZ)02 28 wherein "R" represents at least one organic templating agent present in the 29 intracrystalline pore system; "m" represents the moles of "R" present per mole of (MXAIYPz)02 and has a value of from zero to 0.3; "M" represents at least one 31 metal of the group magnesium, manganese, zinc and cobalt; and "x", "y", and 32 "z" represent the mole fractions of the metal "M", aluminum and phosphorus, 33 respectively, present as tetrahedral oxides.

1 U.S. Pat. No. 4,973,785, issued on November 27, 1990 to Lok et al., the 2 entire disclosure being incorporated herein by reference, discloses a class of 3 crystalline non-zeolitic molecular sieves, designated therein as "EIAPSO".
The 4 EIAPSO compositions are formed with elements capable of forming framework oxide units in the presence of [A102], [Si02] and [P02] tetrahedral 6 units where element "EI" is at least one element capable of forming a three-? dimensional oxide framework in the presence of aluminum, phosphorus and 8 silicon oxide units and is capable of forming stable EI-O-P, EI-O-AL, and EI-O-9 EI bonds in crystalline three-dimension al oxide structures.
11 When these molecular sieves are properly interspersed within a continuous 12 phase polymer, the membrane will exhibit a mixed matrix effect even without 13 silanation. The molecular sieves have pores with a largest minor 14 crystallographic free diameter of 4.0 Angstroms or less. The minor crystallographic free diameter of pores of these molecular sieves may be as 16 small as 3.8 A, 3.6 A, 3.4 A, or even as small as 3.0 A. In some instances, it 17 is advantageous to have pores which are generally elliptical or oblong in 18 cross-section rather than circular.

By way of example rather than limitation, examples of small pore alumina 21 containing molecular sieves which may be used in the present invention are 22 included in Table 1 below. Table 1 includes U.S. patents and literature 23 references which describe how the molecular sieves may be synthesized.
24 These U.S. Patents and the literature references are hereby incorporated by reference in their entireties.

27 The most preferred molecular sieves for use in this invention is that of CVX-7, 28 which is a ERI structured silicoaluminophosphate molecular sieve. A more 29 detailed description of the synthesis of the preferred CVX-7 is described below in Example 4. Also, highly preferred sieves include SAPO-17, 31 MeAPSO-17, SAPO-34, SAPO-44 and SAPO-47. The MeAPSO-17 32 molecular sieves can have, by way of example and not limitation, metal constituents including titanium, magnesium, chromium, nickel, iron, cobalt, 2 and vanadium.

4 Table 1 Exemplary Molecular Sieves IZA Material Major and Minor Synthesis Structure Crystallographic Described Free Type Diameters of Pores in Reference (Angstroms) AEI AIPO-18 3.8 x 3.8 U.S. Pat. No.

4,310,440 AEI SAPO-18 3.8 x 3.8 U.S. Pat. No.

4,440,871;

5,958,370 CHA AIPO-34 3.8 x 3.8 Acta Crystallogr., C50, CHA SAPO-34 3.8 x 3.8 U.S. Pat. No.

4,440,871 CHA SAPO-44 3.8 x 3.8 U.S. Pat. No.

4,440,871 CHA SAPO-47 3.8 x 3.8 U.S. Pat. No.

4,440,871; Pluth, J.J.

& Smith, J.V. J.

Phys. Chem, 93, ERI AIPO-17 ~ 5.1 x 3.6 U.S. Pat. No.

4,503,023 ERI SAPO-17 5.1 x 3.6 U.S. Pat. No.

4,778,780 and 4,440,871 ERI CVX-7 5.1 x 3.6 Described below in Example 4 LEV SAPO-35 4.8 x 3.6 U.S. Pat. No.

4,440,871 AFX SAPO-56 3.6 x 3.4 U.S. Pat. No.

5,370,851 AFT AIPO-52 3.8 x 3.2 U.S. Pat. No.

4,851,204 GIS SAPO-43 4.5 x 3.1 U.S. Pat. No.

4.8 x 2.8 4,440,871 1 III. Methods of Forming Mixed Matrix Membrane 3 The molecular sieves can optionally, but preferably, be "primed" (or "sized") 4 by adding a small amount of the desired matrix polymer or any suitable "sizing agent" that will be miscible with the organic polymer to be used for the matrix 6 phase. Generally, this small amount of polymer or "sizing agent" is added 7 after the molecular sieves have been dispersed in a suitable solvent and 8 sonicated by an ultrasonic agitator source. Optionally, a non-polar non-9 solvent, in which the polymer or "sizing agent" is insoluble, may be added to the dilute suspension to initiate precipitation of the polymer onto the molecular 11 sieves. The "primed" molecular sieves may be removed through filtration and 12 dried by any conventional means, for example in a vacuum oven, prior to re-13 dispersion in the suitable solvent for casting. The small amount of polymer or 14 "sizing agent" provides an initial thin coating (i.e., boundary layer) on the molecular sieve surFace that will aid in making the particles compatible with 16 the polymer matrix.

18 In a preferred embodiment, approximately 10% of total polymer material 19 amount to be added for the final mixed matrix membrane is used to "prime"
the molecular sieves. The slurry is agitated and mixed for preferably between 21 about six and seven hours. After mixing, the remaining amount of polymer to 22 be added is deposited into the slurry. The quantity of molecular sieves and 23 the amount of polymer added will determine the "loading" (or solid particle 24 concentration) in the final mixed matrix membrane. Wifihout limiting the invention, the loading of molecular sieves is preferably from about 10 vol. %
to 26 about 60 vol. %, and more preferably, from about 20 vol. % to about 50 vol.
27 %. To achieve the desired viscosity, the polymer solution concentration in the 28 solvent is preferably from about 5 wt. % to about 25 wt. %. Finally, the slurry 29 is again well agitated and mixed by any suitable means for about 12 hours.
31 This technique of "priming" the particles with a small amount of the polymer 32 before incorporating the particles into a polymer film is believed to make the 33 particles more compatible with the polymer film. It is also believed to promote 1 greater affinity/adhesion between the particles and the polymers and may 2 eliminate defects in the mixed matrix membranes.

4 The mixed matrix membranes are typically formed by casting the homogeneous slurry containing particles and the desired polymer, as 6 described above. The slurry can be mixed, for example, using homogenizers 7 and/or ultrasound to maximize the dispersion of the particles in the polymer or 8 polymer solution. The casting process is preferably performed by three steps:

(1 ) pouring the solution onto a flat, horizontal surface (preferably 11 glass surface);

13 (2) slowly and virtually completely evaporating the solvent from the 14 solution to form a solid membrane film; and 16 (3) drying the membrane film.

18 To control the membrane thickness and area, the solution is preferably 19 poured into a metal ring mold. Slow evaporation of the solvent is preferably effected by covering the area and restricting the flux of the evaporating 21 solvent. Generally, evaporation takes about 12 hours to complete, but can 22 take longer depending on the solvent used. The solid membrane film is 23 preferably removed from the flat surface and placed in a vacuum oven to dry.
24 The temperature of the vacuum oven is preferably set from about 50°C
to about 110°C (or about 50°C above the normal boiling point of the solvent) to 26 remove remaining solvent and to anneal the final mixed matrix membrane.

28 The final, dried mixed matrix membrane can be further annealed above its 29 glass transition temperature (Tg). The Tg of the mixed matrix membrane can be determined by any suitable method (e.g., differential scanning calorimetry).
31 The mixed matrix film can be secured on a flat surface and placed in a high 32 temperature vacuum oven. The pressure in the vacuum oven (e.g., 33 Thermcraft~ furnace tube) is preferably between about 0.01 mm Hg to about 1 0.10mm Hg. Preferably, the system is evacuated until the pressure is 2 0.05mm Hg or lower. A heating protocol is programmed so that the 3 temperature reaches the Tg of the mixed matrix membrane preferably in about 4 two to three hours. The temperature is then raised to preferably about 10°C
to about 30°C, but most preferably about 20°C, above the Tg and maintained 6 at that temperature for about 30 minutes to about two hours. After the heating 7 cycle is complete, the mixed matrix membrane is allowed to cool to ambient 8 temperature under vacuum.

The resulting mixed matrix membrane is an effective membrane material for 11 separation of one or more gaseous components from gaseous mixtures 12 including the desired components) and other components. In a non-limiting 13 example of use, the resulting membrane has the ability to separate carbon 14 dioxide from methane, is permeable to these substances, and has adequate strength, heat resistance, durability and solvent resistance to be used in 16 commercial purifications.

18 IV. Separation Systems Includine~ the Membranes The membranes may take any form known in the art, for example hollow 21 fibers, tubular shapes, and other membrane shapes. Some other membrane 22 shapes include spiral wound, pleated, flat sheet, or polygonal tubes.
Multiple 23 hollow fiber membrane tubes can be preferred for their relatively large fluid 24 contact area. The contact area may be further increased by adding additional tubes or tube contours. Contact may also be increased by altering the 26 gaseous flow by increasing fluid turbulence or swirling.

28 For flat-sheet membranes, the thickness of the mixed matrix selective layer is 29 between about 0.001 and 0.005 inches, preferably about 0.002 inches. In asymmetric hollow fiber form, the thickness of the mixed matrix selective skin 31 layer is preferably about 1,000 Angstroms to about 5,000 Angstroms. The 32 loading of molecular sieves in the continuous polymer phase is between about 33 10% and 60%, and more preferably about 20% to 50% by volume.

1 The preferred glassy materials that provide good gas selectivity, for example 2 carbon dioxidelmethane selectivity, tend to have relatively low permeabilities.
3 A preferred form for the membranes is, therefore, integrally skinned or 4 composite asymmetric hollow fibers, which can provide both a very thin selective skin layer and a high packing density, to facilitate use of large 6 membrane areas. Hollow tubes can also be used.

8 Sheets can be used to fabricate a flat stack permeator that includes a 9 multitude of membrane layers alternately separated by feed-retentate spacers and permeate spacers. The layers can be glued along their edges to define 11 separate feed-retentate zones and permeate zones. Devices of this type are 12 described in U.S. Pat. No. 5,104,532, the contents of which are hereby 13 incorporated by reference.

The membranes can be included in a separation system that includes an 16 outer perforated shell surrounding one or more inner tubes that contain the 17 mixed matrix membranes. The shell and the inner tubes can be surrounded 18 with packing to isolate a contaminant collecfiion zone.

In one mode of operation, a gaseous mixture enters the separation system via 21 a containment collection zone through the perforations in the outer perforated 22 shell. The gaseous mixture passes upward through the inner tubes. As the 23 gaseous mixture passes through the inner tubes, one or more components of 24 the mixture permeate out of the inner tubes through the selective membrane and enter the containment collection zone.

27 The membranes can be included in a cartridge and used for permeating 28 contaminants from a gaseous mixture. The contaminants can permeate out 29 through the membrane, while the desired components continue out the top of the membrane. The membranes may be stacked within a perforated tube to 31 form the inner tubes or may be interconnected to form a self-supporting tube.

1 Each one of the stacked membrane elements may be designed to permeate 2 one or more components of the gaseous mixture. For example, one 3 membrane may be designed for removing carbon dioxide, a second for 4 removing hydrogen sulfide, and a third for removing nitrogen. The membranes may be stacked in different arrangements to remove various 6 components from the gaseous mixture in different orders.

8 Different components may be removed into a single contaminant collection 9 zone and disposed of together, or they may be removed into different zones.
The membranes may be arranged in series or parallel configurations or in 11 combinations thereof depending on the particular application.

13 The membranes may be removable and replaceable by conventional retrieval 14 technology such as wire line, coil tubing, or pumping. In addition to replacement, the membrane elements may be cleaned in place by pumping 16 gas, liquid, detergent, or other material past the membrane to remove 17 materials accumulated on the membrane surface.

19 A gas separation system including the membranes described herein may be of a variable length depending on the particular application. The gaseous 21 mixture can flow through the membranes) following an inside-out flow path 22 where the mixture flows into the inside of the tubes) of the membranes and 23 the components which are removed permeate out through the tube.
24 Alternatively, the gaseous mixture can flow through the membrane following an outside-in flow path.

27 In order to prevent or reduce possibly damaging contact between liquid or 28 particulate contaminates and the membranes, the flowing gaseous mixture 29 may be caused to rotate or swirl within an outer tube. This rotation may be achieved in any known manner, for example using one or more spiral 31 deflectors. A vent may also be provided for removing and/or sampling 32 components removed from the gaseous mixture.

1 V. Purification Process 3 A mixture containing gases to be separated, for example carbon dioxide and 4 methane, can be enriched by a gas-phase process through the mixed matrix membrane, for example, in any of the above-configurations.

7 The preferred conditions for enriching the mixture involve using a temperature 8 between about 25°C and 200°C and a pressure of between about 50 psia and 9 5,000 psia. These conditions can be varied using routine experimentation depending on the feed streams.

12 Other gas mixtures can be purified with the mixed matrix membrane in any of 13 the above configurations. For example, applications include enrichment of air 14 by nitrogen or oxygen, nitrogen or hydrogen removal from methane streams, or carbon monoxide from syngas streams. The mixed matrix membrane can 16 also be used in hydrogen separation from refinery streams and other process 17 streams, for example from the dehydrogenation reaction effluent in the 18 catalytic dehydrogenation of paraffins. Generally, the mixed matrix 19 membrane may be used in any separation process with gas mixtures involving, for example, hydrogen, nitrogen, methane, carbon dioxide, carbon 21 monoxide, helium, and oxygen. Also, the membranes can be used to 22 separate ethylene from ethane and propylene from propane. The gases that 23 can be separated are those with kinetic diameters that allow passage through 24 the molecular sieves. The kinetic diameter (also referred to herein as "molecular size") of gas molecules are well known, and the kinetic diameters 26 of voids in molecular sieves are also well known, and are described, for 27 example, in D.W. Breck, Zeolite Molecular Sieves, Wiley (1974), the contents 28 of which are hereby incorporated by reference.

VI. Membrane Evaluation 32 Permeability measurements of the flat mixed matrix membrane films can be 33 made using a manometric, or constant volume, method. The apparatus for 1 performing permeation measurements on dense, flat polymeric films are 2 described in O'Brien et al., J. Membrane Sci., 29, 229 (1986) and Costello et 3 al., Ind. Eng. Chem. Res., 31, 2708 (1992), the contents of which are hereby 4 incorporated by reference. The permeation system includes a thermostated chamber containing two receiver volumes for the upstream and downstream, 6 a membrane cell, a MKS Baratron~ absolute pressure transducer (0-10 tort or 7 0-100 tort range) for the downstream, an analog or digital high pressure 8 gauge (0-1000 psia) for the upstream, welded stainless steel tubing, Nupro~
9 bellows seal valves, and Cajon VCR~ metal face seal connections. The chamber temperature can be regulated for permeation measurements ranging 11 from 25°C to 75°C.

13 The schematic of the permeation testing apparatus is shown in FIG. 1, where 14 1 is a heated chamber, 2 is a supply gas cylinder, 3 is a vacuum pump, 4 is the feed receiver volume, 5 is the permeate receiver volume, 6 is a pressure 16 transducer, 7 is a membrane cell, 8 is a thermostat- controlled heater, 9 is a 17 fan and 10 is a pressure gauge.

19 Flat membrane films can be masked with adhesive aluminum masks having a circular, pre-cut, exposed area for permeation through the membrane.
21 Application of five minute epoxy at the interface between membrane and the 22 aluminum mask is also used to prevent non-selective gas flow between the 23 aluminum mask adhesive and membrane. Membrane thickness (by high-24 resolution micrometer) and membrane permeation surface area (by image scanning and area-calculating software) are measured.

27 After drying the epoxy for approximately 12 to about 24 hours, the masked 28 membrane can be placed in a permeation cell and the permeation system.
29 Both the upstream and downstream sections of the permeation system were evacuated for about 24 hours to 48 hours to remove ("degas") any gases or 31 vapors sorbed into the membrane. Permeation tests of the membrane can be 32 performed by pressurizing the upstream with the desired gas (pure gas or gas 33 mixture) at the desired pressure. The permeation rate can be measured from 1 the pressure rise of the MKS Baratron° absolute pressure transducer over 2 time and using the known downstream (permeate) volume. The pressure rise 3 data are logged by high-precision data acquisition hardware/software (or 4 alternatively, plotted on a speed-regulated strip chart recorder). When testing gas mixture feeds, the permeate stream is analyzed by gas chromatography 6 to determine composition. Following the permeation testing of a given gas, 7 both the upstream and downstream sections were evacuated overnight before 8 permeation testing of the next gas.

For the purposes of this invention, a mixed matrix membrane shall be referred 11 to as exhibiting a mixed matrix effect if it enhances the selectivity of gas 12 separation by at least 10 per cent relative to a neat membrane. A test can be 13 prepared to verify that the molecular sieves have been properly and 14 successfully made to produce mixed matrix membranes with enhanced permeation properties. This test involves preparation of a sample mixed 16 matrix membrane film using a test polymer and a specified loading of 17 molecular sieve particles, and comparing the C02/CH4 permeation selectivity 18 versus a membrane film of the same test polymer without added sieve. The 19 C02 /CH4 permeation selectivity is determined by taking the ratio of the permeability of C02 over that of CH4. The permeability of a gas penetrant "i"
21 is a pressure- and thickness-normalized flux of the component through the 22 membrane and is defined by the expression:

24 pi=Qi~l Pi 26 where P; is permeability of component i, I is thickness of the membrane layer, 27 N; is component i's flux (volumetric flow rate per unit membrane area) through 28 the membrane, and 0 pi is the partial pressure driving force of component i 29 (partial pressure difference between the upstream to the downstream).
Permeability is often expressed in the customary unit of Barrer (1 Barrer=10-x°
31 cm3 (STP)~ cm/cm2~s~cm Hg). Perr~ieability measurements can be made 1 using a manometric, or constant volume, method. The apparatus for 2 performing permeation measurements in films are described in O'Brien et al., 3 J. Membrane Sci., 29, 229 (1986) and Costello et al., Ind. Eng. Chem. Res., 4 31, 2708 (1992), the contents of which are hereby incorporated by reference.
6 In the Mixed Matrix Enhancement Test, permeation tests of pure gases of 7 C02 and CH4, or gas mixture (e.g., 10% C02/ 90% CH4) are performed on the 8 mixed matrix membrane. The mixed matrix membrane film is separately 9 tested with each gas using an upstream pressure of about 50 psia and a vacuum downstream. A temperature of about 35°C is maintained inside the 11 permeation system. Similar permeation tests of pure gases of C02 and CH4 12 or gas mixture (e.g., 10% C02/ 90% CH4) are performed on a prepared 13 membrane film of the same test polymer without added sieve particles. To 14 confirm that the molecular sieve particles have been properly produced and prepared by the methods described herein, the mixed matrix membrane film 16 should exhibit a CO~/CH4 selectivity enhancement in the Mixed Matrix 17 Enhancement Test, of 10% or more over the C021CH4 selectivity of the pure 18 test polymer membrane alone.

The method for forming the sample mixed matrix membrane for use in the 21 Enhancement Test is as follows:

23 (1 ) The fine particles are preconditioned at high temperature in a 24 vacuum oven at a temperature of about 300°C under vacuum for at least 12 hours. After the preconditioning treatment, these 26 sieve particles can be used to prepare a sample mixed matrix 27 membrane film. For the purpose of the Enhancement Test, the 28 particles are dispersed in the solvent dichloromethane (CH2CI2).

(2) After dispersal in CH2C12, the sieve particles are sonicated in 31 solution for about one minute with an ultrasonic rod in the vial 32 and are well-mixed, as described previously. Large sieve 33 particles in the slurry are separated from the fine particles by 1 any conventional means, for example, decantation or 2 centrifugation. After sonication and isolation of finer sieve 3 particles, the sieve particles are ready for "priming" (or "sizing") 4 with the matrix polymer. For the purpose of the Enhancement Test, the polymer to be used for the matrix phase is Ultem~
6 1000 (GE Plastics).

8 Prior to use, the Ultem~ 1000 polymer is dried at a temperature of about 9 100°C under vacuum for at least 12 hours in a vacuum oven. For "priming"
the sieve particles, typically 10 wt. % of the total amount of matrix polymer 11 (Ultem~ 1000) to be added to the slurry is used. For the Enhancement Test, it 12 is desired to prepare the final slurry of sieve particles and polymer with the 13 following properties: a weight ratio of Ultem~ 1000 to particles of about 4 to 1 14 (i.e., a "loading" of about 20 wt. % of sieve particles in the final mixed matrix membrane) and a slurry concentration of about 15 to about 20 wt. % solids 16 (sieve particles and polymer) in CH2CI2 solvent. After "priming" the sieve 17 particles with Ultem~ 1000, the slurry is well-mixed by any conventional 18 means for about 12 hours. The remaining amount of Ultem~ 1000 polymer is 19 added to the slurry, and the final slurry is again well-mixed by any conventional means for about 12 hours.

22 (3) The polymer/sieve particle slurry is poured onto a flat, leveled, 23 clean horizontal glass surface placed inside a controlled 24 environment (e.g., plastic glove bag). To decrease the evaporation rate, the controlled environment is near-saturated 26 with CH2C12 solvent. A stainless steel film applicator (Paul N.
27 Gardner Co.) is used to draw/spread the sieve particle/polymer 28 slurry to a uniform thickness. An inverted glass funnel was used 29 to cover the solution. The tip of the funnel is covered with lint-free tissue paper to further control the evaporation rate. The 31 solvent from the polymer film slowly evaporates over about a 12-32 hour time period. The dried film approximately has a thickness 33 of about 30 to about 60 microns. After drying, the membrane 1 film is annealed at a temperature of about 100°C for about 12 2 hours in vacuum.

4 (4) To perform the Enhancement Test, permeability measurements of the flat mixed matrix membrane films are required. The 6 measurements can be made using a manometric, or constant 7 volume, method. The apparatus is described in references 8 previously cited in this section. A sample film area from final 9 mixed matrix film is masked with adhesive aluminum masks having a circular, pre-cut, exposed area for permeation through 11 the membrane. The masked membrane can be placed in a 12 permeation cell and the permeation system. Both the upstream 13 and downstream sections of the permeation system are 14 evacuated for about 24 hours to 48 hours to remove ("degas") any gases or vapors sorbed into the membrane. Permeation 16 tests of the membrane can be performed by pressurizing the 17 upstream side with the desired gas at the desired pressure. The 18 permeation rate can be measured from the pressure rise of a 19 pressure transducer and using the known downstream (permeate) volume. Following the permeation testing of a given 21 gas, both the upstream and downstream sections are evacuated 22 for at least 12 hours before permeation testing of the next gas.

24 With the above procedure, the C02 and CH4 permeabilities are measured for the test mixed matrix membrane and the pure test polymer (Ultem~ 1000).
26 The C02/CH4 selectivity of the mixed matrix membrane is compared to the 27 C02 /CH4 selectivity of the pure test polymer (Ultem~ 1000) alone. A
28 C02/CH4 selectivity enhancement of 10% or more should be observed in the 29 mixed matrix membrane film.

1 VII. EXAMPLES

3 COMPARATIVE EXAMPLE 1: Neat Polymer Membrane Film Ultem~ 1000 is a polyetherimide and is commercially available from General 6 Electric Plastics of Mount Vernon, Indiana. Its chemical structure is shown 7 below:

O H3C\ /CH3 O
\ \ C \ /
N
/ ~ / ~ / \ ~ N
~O O v \\
n 11 A neat Ultem~ 1000 membrane film was formed via solution casting. Ultem~
12 1000 was first dried in a vacuum oven at 110°C for overnight. Next, 0.55 13 , grams of the dried Ultem~ 1000 polymer were added to 5mL of CH2CI2 solvent 14 in a 40mL vial. The vial was well-agitated and mixed on a mechanical shaker for about 1 hour to ensure that polymer was dissolved in solution. The 16 polymer solution was poured onto a flat, clean, horizontal, leveled glass 17 surface placed inside a controlled environment (e.g., plastic glove bag). A
18 casting/doctor blade was used to draw down or "cast" the solution, forming a 19 uniform-thickness wet film. The liquid film was covered with an inverted glass cover dish to slow evaporation and to prevent contact with dust, etc. The 21 solvent from the polymer film slowly evaporated over about a 12-hour time 22 period. The dried film, measuring about 30 microns in thickness, was 23 removed from the glass substrate. The resulting neat Ultem~ 1000 film was 24 dried for about 12 hours in a vacuum oven at 150°C.
26 The permeation properties of a neat polymer film of Ultem~ 1000 were 27 determined using the apparatus and procedure described in the previous 28 "Membrane Evaluation" section. A gas mixture containing 10% COZ/90% CH4 29 was used as the feed gas during the permeation testing. The upstream side 1 of the neat Ultem~ 1000 film was exposed to this gas mixture at a pressure of 2 50 psia. The downstream side of the neat Ultem~ 1000 was maintained at a 3 vacuum, resulting in a differential pressure driving force of 50 Asia across the 4 neat Ultem~ 1000 membrane film. With the permeation system maintained at a constant temperature of 35°C, the permeation rate of gases through the 6 membrane was measured with a pressure-rise method and the composition of 7 the permeate gas was analyzed with gas chromatography (HP 6890). Results 8 are shown in Table 2 with the individual gas permeabilities and overall 9 selectivity between the gases.
11 Table 2 12 Neat Ultem~ 1000 Membrane Gas Component Permeability ~10- cm (STP)Selectivity cm/cm scm Hg) CH4 0.038 C02/CH4= 39.2 C02 1.49 From the permeability values in Table 2, the permeability ratios (selectivity) of 16 the neat Ultem~ 1000 membrane film for CO~/CH4 at 35°C was 39.2.

18 COMPARATIVE EXAMPLE 2: Mixed Matrix Membrane Containing 19 Silanated SSZ-13 21 SSZ-13 zeolite particles were prepared in accordance with the method 22 described in U.S. Pat. No. 4,544,538. The silica-to-alumina molar ratio of 23 these molecular sieves was about 25 as measured by ICP bulk elemental 24 analysis. The SSZ-13 has an IUPAC structure of CHA with major and minor crystallographic free diameters comprising 3.8 x 3.8 ~. Because of this 26 relative high molar ratio of silica-to-alumina, the SSZ-13 zeolite particles were 27 surface-modified with a silane coupling agent. The silane coupling agent 28 used was 3-aminopropyldimethylethoxysilane (APDMES) and has the 29 following chemical structure:

~H3 NH2(CH2)3 Si-OCH2CH3 2 The silanation procedure was performed as follows. A 200mL solution was 3 prepared with 95:5 ratio (by volume) of isopropyl alcohol (ACS certified grade) 4 and distilled water. In a separate 500mL container, 4.0 grams of the silane coupling agent (3-aminopropyldimethylethoxysilane or APDMES) was added 6 to 2 grams of SSZ-13 zeolite. The isopropanol solution prepared in the first 7 step was added to this 500mL container to form a slurry. The SSZ-8 13/APDMES/isopropanol/water slurry was sonicated with an ultrasonic horn 9 (Sonics and Materials) in five minute intervals (5 minutes sonication followed by 5 minutes of resting) for a total time of 30 minutes sonication/30 minutes 11 resting.

13 After sonication, the slurry was centrifuged at a high velocity (9000 rpm) for 14 one hour, leaving precipitated solids at the bottom and an isopropanol/water liquid mixture on top. Once the centrifuging was completed, the 16 isopropanol/water liquid was decanted, leaving behind precipitated solid 17 (APDMES-silanated SSZ-13) at the bottom. 100mL of fresh isopropanol was 18 added to the precipitated solid forming a slurry which was sonicated for one 19 hour according to the third step above (30 minutes sonication/30 minutes resting.) After sonication, the slurry was centrifuged at high velocity (9,000 21 rpm) for one hour, leaving precipitated solids (APDMES-silanated SSZ-13) at 22 the bottom and isopropanol liquid on top. The above centrifugation procedure 23 was repeated with two additional aliquots of isopropanol. The APDMES-24 silanated SSZ-13 particles were scraped from the container onto an aluminum foil-lined Petri dish and dried in a vacuum oven for overnight at 150°C. The 26 sieves were set aside until ready to incorporate into a film.

28 A mixed matrix membrane film was prepared with the APDMES-silanated 29 SSZ-13 particles (prepared from the above steps) as the disperse phase.
Ultem° 1000, as described in Comparative Example 1, was used as the 31 polymer matrix phase in the mixed matrix membrane. In this Example, the 1 mixed matrix membrane film contained 18 wt. % APDMES-silanated SSZ-13 2 particles within the Ultem~ 1000 matrix.

4 The mixed matrix membrane film was formed in the following steps. A total of 0.249 grams of the APDMES-silanated SSZ-13 particles (prepared from the 6 silanation above) were added to a 40mL vial containing about 5mL of CH2CI2 7 solvent. The particles in the slurry were sonicated for about two minutes with 8 a high-intensity ultrasonic horn (VibraCeIIT"", Sonics & Materials, Inc.) in the 9 vial. The slurry was well agitated and mixed for about one hour on a mechanical shaker.

12 A total of 0.123 grams of the dried Ultem~ 1000 polymer was added to the 13 slurry in the vial. The vial was well mixed for about two hours on a 14 mechanical shaker. Next, 1.008 grams of dried Ultem~ 1000 polymer was added to the slurry solution to form a solution with 18 wt. % loading of 16 APDMES-silanated SSZ-13 particles. The vial was well mixed again for about 17 16 hours on a mechanical shaker. An enclosable plastic glove bag 18 (Instruments for Research and Industry~, Cheltenham, PA) was setup and 19 near-saturated with about 200mL of CH2CI2 solvent. The Ultem/APDMES-silanated SSZ-13 slurry solution was poured onto a flat, clean, horizontal, 21 leveled glass surface placed inside the plastic glove bag. The near-saturated 22 environment slows down the evaporation of CH2C12.

24 A casting/doctor blade was used to draw down or "cast" the solution, forming a uniform-thickness wet film. The resulting liquid film was covered with an 26 inverted glass cover dish to further slow evaporation and to prevent contact 27 with dust, etc. The CHZCI2 solvent from the polymer film slowly evaporated 28 over about a 12-hour time period. The dried film, measuring about 35 microns 29 in thickness, was removed from the glass substrate. The resulting mixed matrix membrane film was dried for about 12 hours in a vacuum oven at 31 150°C.

1 A section from the Ultem~ 1000-SSZ-13 mixed matrix film (18 wt. % SSZ-13) 2 in this Example was cut to an appropriate size and dimension and used in a 3 permeation testing cell (as described in the "Membrane Evaluation" section) to 4 measure the permeabilities and separation factor for a mixed gas mixture containing 10% C02/90% CHa. The upstream side of the Ultem~ 1000-SSZ-6 13 mixed matrix membrane film was exposed to this gas mixture at a pressure 7 of 50 psia. The downstream side of the Ultem~ 1000-SSZ-13 mixed matrix 8 membrane was maintained at a vacuum, resulting in differential pressure 9 driving force of 50 psia across the Ultem~ 1000-SSZ-13 mixed matrix membrane. With the permeation system maintained at a constant 11 temperature of 35°C, the permeation rate of gases through the membrane 12 was measured with a pressure-rise method and the composition of the 13 permeate gas was analyzed with gas chromatography (HP 6890). Results 14 are shown in Table 3 with the individual gas permeabilities and the overall selectivity.

17 Table 3 18 Uitem~ 1000-SSZ-13 Mixed Matrix Membrane Gas Component Permeability (10-"' cm~ Selectivity (STP) cm/cm2scm Hg) CH4 0.055 C02/ CH4=51.1 C02 2.81 21 From the permeability values in Table 2, the permeability ratios (selectivity) of 22 the Ultem~

mixed matrix membrane for is 51.1.
Both 23 the selectivity and permeability of the Ultem~

24 mixed matrix membrane were enhanced over those measured for the neat Ultem~

polymer membrane film, which was examined in Comparative 26 Example 1.

28 For the Ultem~ 1000-SSZ-13 mixed matrix membrane, the C02/CH4 selectivity 29 was 30% higher and the C02 permeability is 90% higher than such 1 corresponding values in the neat Ultem~ film of Comparative Example 1.
2 Thus, this mixed matrix membrane exhibits a mixed matrix effect. Addition of 3 these APDMES-silanated SSZ-13 zeolite particles provided beneficial 4 performance enhancement to the mixed matrix membrane over the neat membrane.

7 COMPARATIVE EXAMPLE 3: Mixed Matrix Membrane Containing Non-8 silanated SSZ-13 The SSZ-13 zeolite particles as prepared in Comparative Example 2 were 11 used to prepare another mixed matrix membrane film. Unlike Comparative 12 Example 2, these SSZ-13 particles were used "as synthesized" and were not 13 further surface-modified with any silane coupling agent.

As before, Ultem~ 1000, as described in Comparative Example 1, was used 16 as the polymer matrix phase in the mixed matrix membrane. The mixed 17 matrix membrane film containing 18 wt. % "non-silanated" SSZ-13 particles 18 within the Ultem~ 1000 matrix was prepared in a similar fashion as described 19 in Comparative Example 2.
21 In contrast to the mixed matrix film prepared in Comparative Example 2, the 22 resulting mixed matrix film using these "non-silanated" SSZ-13 particles had a 23 markedly different morphology and physical appearance. The mixed matrix 24 film employing the "non-silanated" SSZ-13 particles contained numerous, large agglomerates that gave its texture similar to that of sandpaper, whereas 26 the mixed matrix film employing the APDMES-silanated SSZ-13 particles 27 (Comparative Example 2) was physically smooth and free of agglomerates.

29 For the mixed matrix film employing the "non-silanated" SSZ-13 particles, the permeation rate was not measurable because of its high rate. Further, gas 31 chromatography analysis of the permeate stream indicated no compositional 32 difference versus that of the feed mixture. Both results are indicative of a 33 defective mixed matrix film providing virtually no separation of gases.
Thus, 1 these "non-silanated" SSZ-13 particles appear to be poor candidates as the 2 sieve phase in mixed matrix membrane materials. While not wishing to be 3 held to a particularly theory, it is believed that alumina containing molecular 4 sieves with high silica-to-alumina molar ratio need to be silanated in order to effect satisfactory adhesion between the molecular sieves and the continuous 6 polymer phase. Without satisfactory adhesion, the addition of the molecular 7 sieves to the polymer will result in a mixed matrix membrane which does not 8 exhibit a "mixed matrix effect."

EXAMPLE 4: Synthesis of CVX-7 12 The silicoaluminophosphate molecular sieve, CVX-7, with Erionite framework 13 structure was synthesized according to the following procedure. Initially, 14 grams of aluminum isopropoxide (Chattem Chemical, Inc), ground to 100(US) mesh, were added to 1,600 grams of de-ionized water with vigorous agitation.
16 This mixture was stirred for two hours. Next; 352 grams of Orthophosphoric 17 acid (85 wt. % in water, EMS) were slowly added to the aluminum 18 isopropoxide/water mixture with intense agitation. The resulting mixture was 19 blended vigorously for 30 minutes.
21 In the next step, 31.2 grams of Colloidal silica, LUDOX AS-30 (Du Pont), were 22 added to the mixture with agitation followed by 64.8 grams of 48 wt.
23 Hydrofluoric acid, (Baker). The resulting mixture was stirred for one hour.
24 Finally, 155 grams of cyclohexylamine, (Aldrich) were added to the mixture followed by stirring for 30 minutes. The preparation was seeded with 7 grams 26 of as-made SAPO-17. This material was made according to U.S. Pat. No.
27 4,440,871. The pH of the final mixture was 4.8. 2,000 grams of the mixture 28 were transferred into a one gallon stainless steel liner and the liner was 29 placed into a stirred reactor. The material was synthesized at 200°C
with 150 rpm stirring over 42 hours.

32 The pH of the product mixture was 7.1. The product was separated from its 33 mother-liquor by vacuum filtration followed by washing with 1.5 gallon of 1 HCI/Methanol solution (1 part of mefihanol to 5 parts of 0.05M HCI) and rinsed 2 with two gallons of water. The product was dried at room temperature 3 overnight. Thereafter, the product was calcined with the temperature being 4 ramped from room temperature to 630°C at 1 °C/minute. The mixture was held at 630°C for six hours and then allowed to cool to room temperature.
6 The PXRD pattern of the resulting product was of Erionite-type material. The 7 product had a silica-to-alumina molar ratio of 0.1, as measured by ICP bulk 8 elemental analysis.

The synthesis of CVX-7 differs from the normal synthesis of SAPO-17 in a 11 number of ways. First, a small amount of SAPO-17 was used as seeds. The 12 SAPO-17 seeds were phase pure according to PXRD and SEM. The term 13 "pure phase" by PXRD means that at the conditions of the experiment (X-ray 14 wavelength, beam intensity that is defined by anode voltage and current, slit sizes, and scan range) no lines in a diffraction pattern were detected that can 16 not be attributed to erionite-type crystal structure.

18 The hydrolysis of aluminum isopropoxide was completed under vigorous 19 agitation at room temperature. The SAPO-17 mixture is usually heated before it goes to an autoclave to remove isopropyl alcohol produced by the alumin-21 um isopropoxide hydrolysis process. In the case of the CVX-7 synthesis, this 22 step was omitted. The presence of isopropyl alcohol in the reaction mixture 23 helps to reduce an average crystal size of the product from about 10 microns 24 to about 1.5 microns and significantly reduce the aspect ratio of the crystals, as evident by SEM. To reduce the size of CVX-7 crystals, it is preferred to 26 use good surface complexing agents that among others include organic 27 species such as alcohols, amines, esters or glycols. While not wishing to be 28 held to a particular theory, it is believed reduced aspect ratio aids in 29 preventing the sieve particles from agglomerating, which is particularly valuable in fiber spinning operations. Smaller crystals aid in formation of 31 relatively defect-free fibers.

1 Based on SEM results a maximum aspect ratio for CVX-7 was about 5:1 2 (length to width or diameter of a crystal). A typical ratio is about 2-2.5 to 1.
3 For SAPO-17 a typical aspect ratio is about 10:1. Erionite crystals typically 4 have needle-type morphology and thus very high aspect ratios. Ideally the aspect ratio for the sieve particles is less than 10, more preferably, less than 5 6 and most preferably, between 1 and 3.

8 EXAMPLE 5: Mixed Matrix Membrane Containing Non-silanated CVX-7 A mixed matrix membrane was prepared using the non-silanated CVX-7 11 particles, as prepared from Example 4, as the disperse phase. As before, 12 Ultem~ 1000, as described in Comparative Example 1, was used as the 13 polymer continuous matrix phase in the mixed matrix membrane. The mixed 14 matrix membrane film containing 18 wt. % non-silanated CVX-7 particles within the Ultem~ 1000 matrix was prepared in a similar fashion as described 16 in Comparative Example 3. In other words, the CVX-7 particles were used 17 "as synthesized" and were not further surface-modified with any silane 18 coupling agent (i.e., non-silanated).

The mixed matrix membrane film was formed in the following steps.
21 Initially, 0.250 grams of the non-silanated CVX-7 particles were added to a 22 40mL vial containing about 5mL of CH2CI2 solvent to create a slurry. The 23 particles in the slurry were sonicated for about two minutes with a high-24 intensity ultrasonic horn (VibraCeIIT"", Sonics & Materials, Inc.) in the vial. The slurry was well agitated and mixed for about one hour on a mechanical 26 shaker. 0.160 grams of the dried Ultem~ 1000 polymer was added to the 27 slurry in the vial. The vial was then well mixed for about two hours on a 28 mechanical shaker. 1.003 grams of dried Ultem~ 1000 polymer was added to 29 the slurry solution to form a solution with 18 wt. % loading of non-silanated CVX-7 particles. The vial was well mixed again for about 16 hours on a 31 mechanical shaker. An enclosable plastic glove bag (Instruments for 32 Research and Industry~, Cheltenham, PA) was setup and near-saturated with 33 about 200mL of CH2CI2 solvent.

1 The Ultem/non-silanated CVX-7 slurry solution was poured onto a filat, clean, 2 horizontal, leveled glass surface placed inside the plastic glove bag. The 3 near-saturated environment slows down the evaporation of CH2CI2. A
4 casting/doctor blade was used to draw down or "cast" the solution, forming a uniform-thickness wet film. The resulting liquid film was covered with an 6 inverted glass cover dish to further slow evaporation and to prevent contact 7 with dust, etc. The CH2C12 solvent from the polymer film slowly evaporated 8 over about a 12-hour time period. The dried film, measuring about 35 microns 9 in thickness, was removed from the glass substrate. The resulting mixed matrix membrane film was dried for about 12 hours in a vacuum oven at 11 150°C.

13 A section from the Ultem~ 1000-CVX-7 mixed matrix film (18 wt. % non-14 silanated CVX-7) was tested as described in Example 2. Results are shown in Table 4 with the individual gas permeabilities.

17 Table 4 18 Ultem~ CVX-7 Mixed Matrix Membrane Gas, Component Permeability (10-' cm Selectivity (STP) cm/cm2scm Hg) CH4 0.049 C02/CH4 = 62.9 C02 3.08 21 The permeability ratio (selectivity) of the Ultem~

mixed matrix 22 membrane for was 62.9.
Both the selectivity and 23 permeability of the Ultem~

mixed matrix membrane were 24 enhanced over those measured for the neat Ultem film, which was examined in Comparative Example 1. Thus, this mixed matrix membrane 26 exhibits a mixed matrix efFect.

28 For this Ultem~ 1000-CVX-7 mixed matrix membrane containing 18 wt.
29 CVX-7 zeolite, the C02/CH4 selectivity is 60% higher and the C02 permeability was 107% higher than such corresponding values in the neat 1 Ultem~ 1000 film. Addition of these CVX-7 zeolite particles provided 2 beneficial performance enhancement in membrane. Thus, these CVX-7 3 zeolite sieve particles are good candidates as the disperse phase ("inserts") in 4 a mixed matrix membrane.
6 Note that these CVX-7 sieve particles, which had a relative low silica-to-7 alumina molar ratio (0.1 ) were non-silanated; hence, they did not require 8 silane coupling agents to achieve the significant mixed matrix effect. In 9 contrast, SSZ-13 sieves, which had a high silica-to-alumina ratio, did not provide a satisfactory mixed matrix effect without silanation (see Comparative 11 Examples 2 and 3). Thus, CVX-7 sieve particles offer an advantage over 12 SSZ-13 sieve particles as silanation was not necessary to achieve a mixed 13 matrix effect.

EXAMPLE 6: Preparation and testing of SAPO-17 17 SAPO-17 was prepared as follows. 48.8 grams of aluminum isopropoxide 18 (Aldrich) were added to 64.6 grams of de-ionized water with vigorous mixing.
19 This mixture was then mixed with 17.58 grams of orthophosphoric acid (85 wt.
%) using a blender, and blended vigorously for ten minutes. Then, 1.56 21 grams of colloidal silica (Ludox AS-30, DuPont) were added followed by 3.24 22 grams of hydrofluoric acid HF (48 wt. %, Aldrich), and the mixture stirred for 23 ten minutes. Next, 7.74 grams of cyclohexylamine (Aldrich) were added and 24 the mixture stirred for five minutes. The mixture was placed in a plastic container and the container into a water bath at 80C° in order to remove iso-26 propanol, a decomposition product from the isopropoxide. The volume of the 27 mixture was reduced by about 40% as the result of this procedure.

29 The mixture was placed into a Teflon lined reactor and heated in the oven at 200°C for 24 hours without agitation. The product was separated from its 31 mother-liquor by vacuum filtration. It was washed with 300mL of a 0.1 N
32 solution of HCI in methanol followed by 2.0 liters of deionized water. The 33 product was dried at room temperature over night. The diffraction pattern of 1 the product matched that of the SAPO-17 erionite available from the literature.

3 The material was calcined in air according to the following method. The 4 temperature was ramped from room temperature to 630°C at the rate of 1 °C/minute. The sample was kept at 630°C for six hours and then cooled to 6 room temperature overnight. Micropore volume of the molecular sieves was 7 0.233 cc/g, and BET surface area 414 m2/g.

9 The silica-to-alumina ratio for these molecular sieves was approximately 0.1.
The molecular sieves were used to prepare a mixed matrix film with 11 polyvinylacetate (PVAc), with the molecular sieve loading at 15 wt. %, after 12 which the film was dried at 75°C. The film was tested for 02, N2 and 13 permeability at 35°C and 50 psi, giving an oxygen permeability of 0.54 14 Barrers, a 02/N2 selectivity of 7.2, and a C02/N2 selectivity of 47.4.
16 Table 5 17 (PVAc) SAPO-17 Mixed Matrix Membrane Gas Component Permeability ~10- cm' Selectivity (STP) cm/cm scm H

02 0.54B 0 /N
= 7 N2 0.075B 2 .

C02 3.54B C02/N~ = 47.2 By contrast, the oxygen permeability of a neat PVAc membrane alone was 21 measured at 0.53 Barrers, with a 02/N2 selectivity of 5.91, and the C02/N2 22 selectivity was 34.7.

1 Table 6 2 Neat (PVAc) Mixed Matrix Membrane Gas Component Permeability (10-"' cm Selectivity (STP) cm/cm2scm Hg) 02 0.53B 0 /N

N2 0.09B 2 .

C02 3.12B C02/N2 = 34.7 EXAMPLE 7: Mixed Matrix Membrane with SAPO-34 6 SAPO-34 was prepared as follows. 46 grams of 86% H3P04 were placed in a 7 beaker in a cold bath. To this were added 120 grams of water and 81.8 8 grams of aluminum isopropoxide with stirring using a Polytron. Then 6.6 9 grams of silica (Cab-o-Sil M-5, Cabot) were added and mixed until homogeneous. To this were added 84.2 grams of a 35% aqueous solution of 11 TEAOH (tetraethylammonium hydroxide) with mixing. The mixture was 12 placed in a Teflon bottle in a stainless steel autoclave, and heated at 165°C
13 for three days at autogenous pressure. The product was filtered, washed 14 three times with water, dried overnight in a vacuum oven at 120°C, then calcined in air at 550°C for six hours. X-ray diffraction analysis showed the 16 material to be SAPO-34. The Si02/A12O3 molar ratio, by ICP bulk elemental 17 analysis, was 0.5.

19 The sieve, unsilanated, was then used to make a mixed matrix PVAc membrane at 15.1 wt. % loading, and the membrane tested at 50 psi and 21 35°C for both 02/N2 separation and C02/N2 separation. The 02/N2 selectivity 22 was 7.0 versus 5.9 for a neat PVAc membrane, and the C02/N2 selectivity 23 was 39.4 versus 34.7 for the neat membrane.

1 Table 7 2 PVAc SAPO-34 Mixed Matrix Membrane Gas Component Permeability ~10- cm Selectivity (STP) cm/cm scm Hg) /N
= 7 .

C02 COZ/N2 = 39.4 EXAMPLE 8: Mixed Matrix Membrane with SAPO-44 7 SAPO-44 was prepared as follows. 19.91 grams of Catapal B (Vista 8 Chemicals) were dispersed in 60.6 grams of water. Then 33.08 grams of 9 H3P04 (85°l°) were added slowly to the dispersion while mixing. The contents were blended to a homogeneous paste for ten minutes. 16.88 grams of 11 Ludox AS-40 (DuPont) were blended into the above mixture until a 12 homogeneous mixture was obtained. 3.89 grams of KN03 were dissolved in 13 60.6 grams of water and 31.5 grams of cyclohexylamine (Aldrich) were added 14 with stirring to the solution. Finally, the above solution was added to the mixture with rapid agitation. The pH of the final gel was 6.02. The mixture 16 was loaded into a Teflon-lined reactor and heated at 180°C for four days in an 17 oven equipped with a tumbler.

19 The product was separated from its mother-liquor by vacuum filtration. It was washed with 400mL of 1 N solution of HCI in methanol followed by 1.5L of 21 deionized water. The product was dried at room temperature over night. The 22 diffraction pattern of the product matched that of SAPO-44. The Si02/AI203 23 ratio, by by ICP bulk elemental analysis, was 0.7.

The material was calcined in air according to the following method. The 26 temperature was ramped from room temperature to 500°C at the rate of 27 2Clmin. The sample was kept at 500°C for six hours and then cooled to room 28 temperature overnight. The PXRD pattern of the calcined material again 1 matched that of calcined SAPO-44. The BET surface area for the sample 2 was 349 m2/g.

4 The sieve, unsilanated, was then used to make a mixed matrix PVAc membrane at 15.3 wt. % loading, and the membrane tested at 50 psi and 6 35°C for both 02/N~ separation and C02/N2 separation. The 02/N2 selectivity 7 was 6.4 versus 5.9 for a neat PVAc membrane, and the C02/N2 selectivity 8 was 46.5 versus 34.7 for the neat membrane.

Table 8 11 PVAc SAPO-44 Mixed Matrix Membrane Gas Component Permeability ~10-"' cm' Selectivity (STP) cm/cm scm H

/N
= 6 ~
.

C02 C02/N2 = 46.5 14 While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have 16 been set forth for purpose of illustration, it will be apparent to those skilled in 17 the art that the invention is susceptible to alteration and that certain other 18 details described herein can vary considerably without departing from the 19 basic principles of the invention.

Claims (23)

1. A mixed matrix membrane comprising:
a continuous phase organic polymer and small pore alumina containing molecular sieves dispersed therein, the molecular sieves having a silica-to-alumina molar ratio of less than 1Ø

2. The mixed matrix membrane of claim 1 wherein:
the silica-to-alumina molar ratio is less than 0.5.

3. The mixed matrix membrane of claim 1 wherein:
the silica-to-alumina molar ratio is less than 0.2.

4. The mixed matrix membrane of claim 1 wherein:
the mixed matrix membrane is made without silanation of the molecular sieves.

5. The mixed matrix membrane of claim 1 wherein:
the membrane exhibits a mixed matrix effect.

6. The mixed matrix membrane of claim 1 wherein:
the molecular sieves have pores with a minor crystallographic free diameter of 3.8 .ANG., or less.

7. The mixed matrix membrane of claim 1 wherein:
the molecular sieves have pores with a minor crystallographic free diameter of 3.6 .ANG., or less.

8. The mixed matrix membrane of claim 1 wherein:
the molecular sieves have a number average particle size of less than 2 microns.

9. The mixed matrix membrane of claim 1 wherein:
the molecular sieves have a number average particle size of less than 0.5 microns.

10. The mixed matrix membrane of claim 1 wherein:
the molecular sieves are non-zeolitic molecular sieves.

11. The mixed matrix membrane of claim 10 wherein:
the composition of the molecular sieves includes at least one of an aluminophosphate (AIPO), a silicoaluminophosphate (SAPO), a metallo- aluminophosphate (MeAPO), an elementaluminophosphate (EIAPO), a metal silicoaluminophosphate (MeAPSO) and an elementalsilicoaluminophosphate (ELAPSO).

12. The mixed matrix membrane of claim 1 wherein:
the composition of the molecular sieves includes a SAPO.

13. The mixed matrix membrane of claim 1 wherein:
the composition of the molecular sieves includes a MeAPSO.

14. The mixed matrix membrane of claim 1 wherein:
the molecular sieves have an IZA structure type of at least one of AEI, CHA, ERI, LEV, AFX, AFT and GIS.

15. The mixed matrix membrane of claim 1 wherein:
the molecular sieves include at least one of ALPO-18, SAPO-18, AIPO-34, SAPO-34, MEAPSO-34, SAPO-44, SAPO-47, AIPO-17, SAPO-17, CVX-7, MeAPSO-17, SAPO-35, SAPO-56, AIPO-52, and SAPO-43.

16. The mixed matrix membrane of claim 1 wherein:
the molecular sieves have an IZA structure type of at least one of ERI, LEV, AFX, AFT and GIS.

17. The mixed matrix membrane of claim 1 wherein:
the molecular sieves include at least one of AIPO-17, SAPO-17, CVX-7, MeAPSO-17, SAPO-35, SAPO-56, AIPO-52, and SAPO-43.

18. The mixed matrix membrane of claim 1 wherein:
the molecular sieves have an IZA structure type of at least one of AFX, AFT and GIS.

19. The mixed matrix membrane of claim 1 wherein:
the molecular sieves include at least one of SAPO-56, AIPO-52, and SAPO-43.

20. The mixed matrix membrane of claim 1 wherein:
the molecular sieves include SAPO-17 and MeAPSO-17 and CVX-7.

21. The mixed matrix membrane of claim 1 wherein:
the polymer is selected from the group compromising polyetherimides and polyimides.

22. A method of making a mixed matrix membrane comprising:
providing a continuous phase organic polymer;
providing small pore alumina containing molecular sieves having a silica-to-alumina molar ratio of less than 1.0;
dispersing the molecular sieves into a continuous phase organic polymer; and allowing the continuous phase organic polymer to solidify about the molecular sieves to produce a mixed matrix membrane;
whereby the mixed matrix membrane exhibits a mixed matrix membrane effect.

23. A process for separating two gas components having different molecular sizes from a feed stream including the two gas components, the process including:

(a) providing a mixed matrix membrane that has small pore alumina containing molecular sieves that have a silica-to-alumina molar ratio of less than 1.0 interspersed into a continuous phase polymeric carrier, the membrane including feed and permeate sides; and (b) directing a feedstream including first and second gas components to the feed side of the membrane and withdrawing a retentate stream depleted in the first gas component from the retentate side and withdrawing a permeate stream enriched in the first gas component from the permeate side of the membrane;
wherein the selectivity of the first gas component through the molecular sieves is greater than the selectivity of the first gas component through the polymer.