Gas Separation Membranes

Abstract

The present invention relates to mixed matrix membranes (MMM) for gas filtration and separation, the membranes comprising a glassy polymer matrix comprising at least 20% w / w or 30% w / w (zeolite / polymer), characterized in that the zeolite polymer matrix has no interfacial voids or has voids less than 50 nm, less than 20 nm or less than 10 nm measured in the longest dimension.

Description

[Technical field]

[0001] The present invention relates to membranes comprising zeolites and their use in the separation of gases or liquids. [Background technology]

[0002] Membrane technology has matured into an established commercial technique for CO2 separation over the past 30 years, and is used for natural gas sweetening and syngas processing. In addition, biogas purification, "net-zero CO2" energy vectors, and carbon capture from flue gases may also be important applications of membranes in the near future. While more conventional techniques such as amine absorption, cryogenic separation, and adsorption certainly have certain advantages, membrane technology can offer a more sustainable alternative due to its lower energy consumption, lower environmental impact, and modular design that allows membrane modules to be retrofitted into existing plants. The polymers used to produce commercial CO2-selective membranes are cheap and easy to process, but there is an inherent trade-off between permeability and selectivity, and it is very difficult to obtain membranes that combine high permeability with sufficient selectivity. On the other hand, inorganic membranes made from zeolites or from crystalline microporous hybrid materials such as metal-organic frameworks (MOFs) usually perform better, but have poorer mechanical properties, are expensive, and have problems with processability and scalability. The development of new membrane materials for advanced separations remains necessary to make gas separation processes more sustainable.

[0003] Mixed matrix membranes (MMMs) are hybrid membranes consisting of fillers embedded in a polymer matrix. These membranes combine the advantages of polymer processability, flexibility, and low cost with the excellent gas separation properties of fillers. Many porous materials, including zeolites, MOFs, carbon molecular sieves (CMS), covalent organic frameworks (COFs), graphene, and carbon nanotubes (CNTs), have been investigated as fillers for MMMs. Zeolites are particularly interesting for the development of MMMs because they combine well-defined rigid pores with outstanding thermal, chemical, and mechanical stability. Although zeolites have great theoretical potential in MMMs, polymer-zeolite compatibility presents a major obstacle. Inherently rubbery polymers (e.g., polydimethylsiloxane (PDMS)) have low selectivity and high permeability, which negate the advantages of zeolites, making rigid glassy polymers the key to developing high-performance zeolite-filled MMMs. However, the interfacial adhesion between inorganic zeolites and rigid glassy polymers is very poor, usually resulting in non-selective interfacial voids. As a result, achieving high zeolite loading (>50 wt%) while ensuring a defect-free polymer-zeolite interface, together with the selection of highly selective zeolite and glassy polymer matrices, can be considered as the main method for the successful development of high-performance zeolite-loaded MMMs for various of the most important gas separation challenges of our time. For example, while exhaust gas applications require high-volume feed streams at low pressures, which require highly permeable membranes, the multiple steps currently required for methane upgrading could benefit from at least equally permeable but more selective membranes. Summary of the Invention

[0004] Here, as an embodiment of the present invention, a platelet-shaped 8-ring AEI-type zeolite (SSZ-39) with a long-range ordered 3D connected micropore system along with a gas selective window and excellent CO2 adsorption is incorporated into a Matrimid 5218 polymer matrix.

[0005] The combination of a carefully optimized MMM synthesis procedure and the unique shape and sorption behavior of zeolites circumvents the traditional problem of poor zeolite-polymer adhesion and enables ultra-high zeolite loadings, leading to unprecedented CO2 separation performance that may surpass the performance of all previously reported MMMs and even many of the pure zeolite or MOF membranes.

[0006] As an example, an ultra-high performance zeolite-filled polyimide-based membrane for CO2 removal was developed. The Na-SSZ-39 / Matrimid MMM showed the best CO2 removal performance from both N2 and CH4 so far, which is not only higher than any existing MMM but also higher than pure zeolite membranes. By solving the compatibility issue between the zeolite filler and the glassy Matrimid matrix, a defect-free zeolite / polyimide MMM with a zeolite loading of more than 50 wt% was fabricated. A novel platelet-shaped Na-SSZ-39 zeolite was developed as the filler for this membrane. Its excellent CO2 affinity, outstanding CO2 uptake capacity, desirable competitive gas adsorption behavior, and precise size exclusion of CH4 promote the remarkable gas separation of the membrane. Moreover, thanks to the platelet shape of the Na-SSZ-39 zeolite filler, a unique membrane morphology was obtained, which ensured a quasi-continuous permeation pathway for CO2, dramatically improving the membrane performance. This invention not only relates to ultra-high performance CO2 removal membranes, but also shows a feasible method to fabricate defect-free zeolite-filled membranes using commercially available glassy polymers. This expands the use of zeolites in the membrane field and paves the way for more scalable and economical high performance zeolite-filled membranes that are processable and robust, which is especially beneficial for zeolites that are rather difficult to convert into defect-free thin films. These membranes and their fabrication techniques offer great economic and environmental benefits for a global carbon-neutral future.

[0007] Here, mixed matrix membranes (MMMs) are studied in detail to make energy-intensive separations more efficient by combining the selectivity and permeability performance, robustness, and non-aging characteristics of fillers with the easy processing, handling, and scale-up of polymers. In one embodiment, polyimide is filled with high aspect ratio CO2-affinitive Na-SSZ-39 zeolite at ultra-high loadings to obtain a three-dimensional channel system that precisely separates gas molecules. By engineering both the synthesis of the zeolite and the synthesis of the MMMs, a flexible and age-resistant (>1 year) membrane is obtained. The combination of CO2-CH4 mixed gas selectivity of about 423 and CO2 permeability of about 8300 Barrer outperforms all existing polymer-based membranes and even most zeolite-only membranes.

[0008] The present invention is further summarized in the following description. 1. A mixed matrix membrane (MMM) for fluid filtration and separation, obtainable by the method according to any one of statements 14 to 27, the membrane comprising a glassy polymer matrix containing at least 20% w / w of zeolite, the zeolite polymer matrix having no interfacial voids or having voids less than 20 nm measured in its longest dimension. These MMMs can be equally used for the filtration and separation of fluids, or more generally for the separation of molecules. 2. The MMM of statement 1, wherein the membrane comprises a glassy polymer matrix comprising at least 30% w / w, 40% w / w, or 50% w / w of zeolite. 3. The MMM according to statement 1 or 2, wherein the zeolite is a platelet, cubic, rectangular, spherical or octahedral shaped zeolite. 4. The MMM of any one of statements 1 to 3, wherein the zeolite is in platelet form and has a concentration in the membrane of at least 20% w / w, at least 30% w / w, at least 40% w / w, or at least 50% w / w. 5. The MMM of any one of statements 1-4, wherein the membrane has a concentration of zeolite of at least 40% w / w and has a CO2 permeability of at least 4000 Barrer. 6. The MMM of any one of statements 1-5, wherein the membrane has a zeolite / polymer concentration of at least 20% w / w and has a CO2 / CH4 selectivity of greater than 100. 7. The MMM of any one of statements 1-5, wherein the membrane has a concentration of zeolite of at least 40% w / w and has a CO2 / CH4 selectivity of greater than 400. 8. The MMM of any one of statements 1-7, wherein the zeolite is in the form of platelets. 9. The MMM of any one of statements 1 to 8, wherein the zeolite is an 8-ring or 12-ring. 10. The MMM of any one of statements 1 to 9, wherein the zeolite is of the AEI type. 11. The MMM of any one of statements 1-10, wherein the membrane is flexible and has a flexural modulus of from 2 Gpa up to 9 Gpa. 12. The MMM of any one of statements 1-11, wherein the membrane is flexible and has a flexural modulus of from 3.5 Mpa up to 9 Mpa. 13. The MMM of any one of statements 1-12, wherein the polymer is a polyimide. 14. A method for producing a mixed matrix membrane, comprising: a) providing a mixture of a glassy polymer and a zeolite in a solvent, the solvent comprising at least 5% w / v of the polymer and at least 20% w / w, 30% w / w, 40% w / w or 50% w / w of the zeolite; b) pouring the mixture obtained in step a); c) drying the cast mixture obtained in step b) to obtain a membrane, the drying being carried out at a rate such that 85% to 95% by weight of the solvent is removed in 15 minutes to 24 hours; d) heating the dried film obtained in step c) at a temperature below the glass transition temperature of the polymer, said heating being maintained for a period of 5 minutes to 24 hours and / or carried out at a temperature of 30° C. to 300° C., provided that said temperature is below the glass transition temperature of the polymer; A method comprising: In the preparation of these membranes, no crosslinking of the membrane occurs. Furthermore, as shown in the examples, the drying step c can be carried out while applying a vacuum. 15. The method of claim 14, wherein the solution of the polymer and the dispersion of the zeolite are prepared separately and then mixed. 16. The method according to any one of claims 14 to 15, wherein the drying in step c) is carried out at a rate such that 85% to 95% by weight of the solvent is removed within 5 minutes to 24 hours. 17. The method according to any one of claims 14 to 15, wherein the drying in step c) is carried out at a rate such that 85% to 95% by weight of the solvent is removed in 3 hours to 24 hours. 18. The method of any one of statements 14 to 17, wherein in step d, the membrane is heated to a temperature of from 30° C. to the glass transition temperature of the polymer. 19. The method of any one of statements 14 to 17, wherein in step d, the membrane is heated to a temperature of from 120° C. or 150° C. to the glass transition temperature of the polymer. 20. The method of any one of statements 14 to 19, wherein the heating in step d) is maintained for a period of 4 hours to 24 hours. 21. The method of any one of statements 14 to 19, wherein the heating in step d) is maintained for a period of 8 hours to 24 hours. 22. The method of any one of statements 14 to 19, wherein the heating in step d) is maintained for a period of 8 hours to 24 hours and / or step d) is carried out at a temperature of 150°C to 300°C. 23. The method of any one of statements 14-22, followed by a step of determining whether or not voids are present. 24. The method of statement 23, wherein the absence of voids is determined by microscopic examination. 25. The method of claim 23, wherein the absence of voids is determined by measuring the flow rate of gas over the membrane. 26. The method of any one of statements 14-25, wherein the zeolite is in the form of platelets. 27. The method of any one of statements 14 to 26, wherein the zeolite is of the AEI type. 28. The method of any one of statements 14-27, wherein the polymer is a polyimide. A mixed matrix membrane (MMM) for fluid filtration and separation, the MMM being obtainable by the method according to any one of statements 14 to 27. [Brief description of the drawings]

[0009] [Figure 1-1] A. SEM photograph of platelet shaped Na-SSZ-39 zeolite. B. SEM cross section of Na-SSZ-39 MMM (zeolite loading 20 wt%) not thermally annealed. C. SEM cross section of Na-SSZ-39 MMM (zeolite loading 20 wt%) after thermal annealing at 260°C. D. SEM cross section of Na-SSZ-39 MMM (zeolite loading 40 wt%) after thermal annealing at 260°C. E. SEM cross section of 30 wt% Na-SSZ-39 MMM after oxidation treatment at 800°C. F. SEM top view of membranes with zeolite loadings of 0 wt% to 50 wt%. G. SEM bottom view of membranes with zeolite loadings of 0 wt% to 50 wt%. [Figure 1-2] Same as above [Figure 1-3] Same as above [Figure 2-1]1 shows the gas separation performance of Na-SSZ-39 MMM membranes. A. Selectivity difference between rectangular and platelet-shaped Na-SSZ-39 MMMs. B and C. Temperature and pressure dependence of CO2 / CH4 selectivity and CO2 permeability (from bottom to top: zeolite loading 0 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%). D and E. Literature zeolite-based MMMs [squares] plotted against 2008 CO2 / N2 and CO2 / CH4 Robeson plots, with stars representing data from MMMs with platelet-shaped Na-SSZ-39 fillers (from left to right: zeolite loading 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 55 wt%). F. 2008 CO2 / CH4 Robeson plot comparing pure zeolite membranes from the literature [squares] with 50 wt.% Na-SSZ-39 MMM. [Figure 2-2] Same as above [Figure 2-3] Same as above [Figure 2-4] Same as above [Figure 2-5] Same as above [Figure 3-1] Figure 3.a: Adsorption isotherms of CO2, CH4, and N2 for Na-SSZ-39 and SSZ-39 zeolites at 10 °C based on high pressure physical adsorption experiments. The results show high CO2 affinity and gas uptake capacity. Figure 3.b: Comparison of experimental and GCMC simulation results for single gas adsorption isotherms of CO2, CH4, and N2 for Na-SSZ-39 zeolite at 25 °C. [Figure 3-2]FIG. 3.c: Comparison of the CO2 and CH4 single gas adsorption isotherms and the CO2 / CH4 (50 vol. / 50 vol.) binary gas adsorption isotherms for Na-SSZ-39 zeolite at 25° C. (by GCMC simulation). CO2 adsorption impedes CH4 adsorption, indicating a strong competitive gas adsorption behavior that improves the separation performance of mixed gases. FIG. 3.d: Comparison of the CO2 and N2 single gas adsorption isotherms and the CO2 / N2 (50 vol. / 50 vol.) binary gas adsorption isotherms for Na-SSZ-39 zeolite at 25° C. (by GCMC simulation). CO2 adsorption impedes N2 adsorption, indicating a strong competitive gas adsorption behavior that improves the separation performance of mixed gases. [Figure 3-3] Figure 3.e: 3D CO2 adsorption density plot of Na-SSZ-39, showing isosurfaces of CO2 adsorption at 0.1 bar (section indicated by oval) and 1 bar (general grey cloud area). Figure 3.f: Random and non-ordered packing of zeolite platelets in a polymer matrix with zeolite loadings between 10 wt% and 50 wt%. Figure 3.g: 3D diagram showing random and non-ordered packing of zeolite platelets inside a polymer matrix. [Figure 4] SEM cross-section of Na-SSZ-39 MMM subjected to a thermal annealing program at 260°C for 24 hours revealing a defect-free zeolite / polymer interface with no voids observed, indicating good zeolite and polymer compatibility (no membrane leakage) and promising high membrane performance. [Diagram 5] SEM top view of Na-SSZ-39 MMM subjected to a thermal annealing program at 260° C. for 24 hours revealing a defect-free zeolite / polymer interface with no voids observed. [Figure 6] SEM cross-section of Na-SSZ-39 MMM after thermal annealing at 300°C for 24 hours. Zeolite and matrimid matrix are exfoliated. [Figure 7]SEM cross-section of Na-SSZ-39 MMM after thermal annealing at 350°C for 24 hours, showing further exfoliation of the zeolite and matrimid matrix. [Figure 8] Figure 1 shows XRD results of thermally annealed (260°C program) Na-SSZ-39 MMM with zeolite loadings ranging from 0 wt% (pure matrimid) to 55 wt%. The membrane samples show a strong characteristic XRD signal of AEI zeolite, indicating extremely high zeolite loading in the membranes. [Figure 9] Figure 1 shows FTIR transmission patterns of Na-SSZ-39 zeolite, pristine matrimid membrane and thermally annealed (260°C program) 0 wt% (pure matrimid membrane), 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 55 wt% Na-SSZ-39 MMM. Except for the characteristic peaks of zeolite, no new peaks are observed after zeolite loading and thermal treatment, indicating that no chemical reaction occurs at the zeolite / polymer interface. [Figure 10] Figure 1 shows a comparison of the solubility selectivity of single and equimolar binary CO2 / N2 and CO2 / CH4 gases in Na-SSZ-39 zeolite (at 25°C) based on GCMC simulation. The solubility selectivity of CO2 / N2 and CO2 / CH4 for binary gases is higher than that for single gases, indicating a strong competitive gas adsorption behavior that improves the separation performance of mixed gases. [Figure 11] Carbon dioxide, nitrogen and methane adsorption isotherms for thermally annealed (260° C. program) pure matrimid membrane and 50 wt. % Na-SSZ-39 MMM at 25° C. Zeolite loading significantly improves the gas uptake performance. [Figure 12]Carbon dioxide adsorption isotherms for Na-SSZ-39, SSZ-39 and Na-SSZ-39 MMM in the temperature range of 10°C to 50°C. The dotted lines correspond to the Toth isotherm model. High CO2 adsorption capacity and high CO2 affinity are shown, with Na-SSZ-39 showing improved CO2 gas uptake performance and increased CO2 affinity. [Figure 13] Adsorption isotherms of methane for Na-SSZ-39, SSZ-39 and Na-SSZ-39 MMM in the temperature range of 10°C to 50°C. The dotted lines correspond to the Toth isotherm model. The CH4 adsorption capacity and CH4 affinity are significantly lower than those for CO2. [Figure 14] Nitrogen adsorption isotherms for Na-SSZ-39, SSZ-39 and Na-SSZ-39 MMM in the temperature range of 10°C to 50°C. The dotted lines correspond to the Toth isotherm model. The N2 adsorption capacity and N2 affinity are significantly lower than those for CO2. [Figure 15] Figure 1 shows the elongation vs. load force plot for three-point bending tests for four membrane samples: pure Matrimid membrane (no heat treatment), pure Matrimid membrane thermally annealed at 260°C, 50 wt% zeolite MMM (no heat treatment), and 50 wt% zeolite MMM thermally annealed at 260°C. All membrane coupons showed good flexibility during the test, and all membrane samples returned to their original shape after the load was removed. Both zeolite loading and thermal annealing treatments reduced the flexibility of the membrane coupons, but the annealed 50 wt% MMM still showed high flexibility. Also, the zeolite MMM with a lower zeolite loading may have a higher flexibility than this membrane sample. [Figure 16] Figure 1 shows DSC results for 10 wt% and 30 wt% Na-SSZ-39 MMM subjected to thermal annealing at 260° C. The glass transition temperature (Tg) of the annealed Na-SSZ-39 MMM increases from 320° C. to 330° C., indicating stiffening of the polymer chains at the polymer-zeolite interface, resulting in the coating of the zeolite with polymer. [Figure 17]1 is a Robeson plot of CO2 / CH4 selectivity and permeability. Circles are values ​​for prior art membranes. Stars represent membranes of embodiments of the present invention. [Figure 18] Figure 1 shows the gas separation performance of zeolite-filled MMMs prepared by the method of the present invention. (A) Performance of zeolite-filled MMMs from literature is shown in the CO2-CH4 2008 Robeson plot, with the star representing Na-CHA-10 / Matrimid MMM. (B) Performance of zeolite-filled MMMs from literature is shown in the CO2-N2 2008 Robeson plot, with the star representing Na-FAU-2 / Matrimid MMM. (C) Performance of zeolite-filled MMMs from literature is shown in the CO2-N2 2008 Robeson plot, with the star representing 50 wt% Na-FAU-2 / Polysulfone MMM, and the hollow star representing unfilled polysulfone membrane. In panels A and B, the different stars indicate different zeolite loadings in the MMMs. From left to right, the zeolite is 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, and 60 wt%. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The concentration of zeolite in the membrane can also be expressed as % w / w, since the membrane is composed of only zeolite and polymer. The concentration of zeolite refers to the amount of zeolite in the total of zeolite + polymer, where 20% w / w zeolite is, for example, 2 grams of zeolite and 8 grams of polymer in 10 grams of membrane (2 grams zeolite / 2 grams zeolite + 8 grams of membrane (polymer??)).

[0011] As can be derived from the examples of the present invention, the polymers in the membranes of the present invention are not crosslinked.

[0012] A glassy polymer is a type of polymer that exhibits a highly rigid, glass-like, amorphous solid state at room temperature. The glass transition temperature (Tg) of a glassy polymer is higher than room temperature. That is, unlike rubbery polymers, a glassy polymer can maintain the glassy random alignment of its molecular chains at room temperature with high strength and stability. Examples of glassy polymers are polystyrene, polyimide, polysulfone, polyvinyl acetate, polylactic acid, polyvinyl chloride, polymethyl methacrylate, polysulfone, poly(ether sulfone), polycarbonate, polypropylene, and polyethylene. Mixed matrix membranes (MMMs) consist of fillers embedded in a polymer matrix, combining the intrinsic advantages of polymeric membranes with the excellent gas separation properties of fillers.

[0013] Zeolites are of particular interest for the development of MMMs due to their well-defined rigid pores and outstanding thermal and chemical stability. Rigid glassy polymers are used to develop high-performance zeolite-filled MMMs because the low selectivity and high permeability of inherently rubbery polymers (e.g., polydimethylsiloxane) negate the advantages of zeolites. However, poor adhesion between zeolites and glassy polymers usually results in nonselective interfacial voids. As a result, highly selective zeolites and suitable glassy polymer matrices are required to fabricate high-performance MMMs that address a variety of the most critical separation challenges, while still achieving high zeolite loadings (>50 wt%) while ensuring a defect-free polymer-zeolite interface. In one example, a platelet-shaped, CO2-philic small-pore (8-membered ring) AEI-type zeolite (SSZ-39) with a long-range ordered three-dimensional (3D) channel system and gas-selective windows was incorporated into poly(3,3'-4,4'-benzophenonetetracarboxylic dianhydride diaminophenylindane) (Matrimid 5218) polymer. By combining the zeolite synthesis with the MMM synthesis, high zeolite loadings were obtained with a quasi-continuous zeolite phase throughout the free-standing membrane.

[0014] A first aspect of the present invention relates to a mixed matrix membrane (MMM) for gas filtration and separation, which comprises a glassy polymer matrix having at least 20% w / w or 30% w / w of (zeolite / (zeolite+polymer)).

[0015] Instead of filtration and separation of gases, membranes can be used for filtration of other types of molecules.

[0016] The membrane may be further characterized in that the zeolite polymer matrix has no interfacial voids, or the voids measured in the longest dimension are less than 50 nm, less than 20 nm, or less than 10 nm.

[0017] In these membrane embodiments, the zeolite has the shape of a platelet, cube, rectangular prism, sphere, or octahedron.

[0018] Other examples of commercially available zeolites suitable for use in the membranes of the present invention include CHA, which has a cubic shape, LTA, which has a spherical shape, and FAU, which has an octahedral shape.

[0019] Based on SEM photographs (10,000x-25,000x) of the membranes of the present invention showing top, bottom and cross-sectional views of the membrane, no detectable voids were observed (less than 20 nm). This is supported by the gas separation results with these membranes. Ultra-high selectivity membranes were obtained (gas selectivity of over 420 for a feed stream of CO2 / CH4 gas mixture). In this case, small leaks through voids would significantly reduce the selectivity.

[0020] Instead of specifying membrane properties in terms of permeability or selectivity, membranes can also be characterized with reference to the Robeson upper limit, which represents the performance trade-off between permeability and selectivity. The Robeson upper limit is the limit beyond which state-of-the-art membranes do not perform for a given separation (e.g. CO2 / N2 or CO2 / CH4). The Robeson relationship between selectivity α and permeability P (in Barrers) can be expressed as follows: α.P n =k where n and k are coefficients. Because membrane selectivity and permeability are usually plotted on a logarithmic scale, the Robeson plot is assumed to be linear in shape. The area above the Robeson plot can be expressed as: α.P n > k

[0021] For CO2 / CH4 gas separation by conventional mixed matrix membranes, the Robeson upper limit is a(α).P 0.41 = 550. In the Na-AEI mixed matrix membrane in the current study, a(α).P 0.41 The values ​​of are in the range of 660 to 20,000, and the zeolite concentration is 20% to 55%, i.e., far above 550 (see FIG. 17).

[0022] For CO2 / N2 separation by conventional mixed matrix membranes, the Robeson upper limit is a(α).P 0.34 =250.

[0023] For CH4 / N2 separation by conventional mixed matrix membranes, the Robeson upper limit is a(α).P 0.239 In this study, the inventors measured the a(α).P 0.239 It was demonstrated that values ​​were well above 6.79 and could reach the 50-60 range.

[0024] In an embodiment of the first aspect of the present invention, the zeolite is in platelet form and its concentration in the polymer is at least 10% w / w, at least 15% w / w, at least 20% w / w, at least 25% w / w, at least 30% w / w, at least 40% w / w, or at least 50% w / w (zeolite / polymer).

[0025] It should be noted that a concentration of 30% w / w platelet shaped zeolite corresponds to 25 v / v % of the volume of zeolite within the membrane.

[0026] In an embodiment of the first aspect of the present invention, the zeolite is cubic in shape and its concentration in the polymer is at least 30% w / w, at least 40% w / w, at least 50% w / w, at least 60% w / w (zeolite / polymer).

[0027] In an embodiment of the first aspect of the present invention, the membrane having a zeolite / polymer concentration of at least 30% w / w has a CO2 permeability of at least 600 Barrer.

[0028] In an embodiment of the first aspect of the present invention, a membrane having a zeolite / polymer concentration of at least 40% w / w has a CO2 permeability of at least 4000 Barrer.

[0029] In an embodiment of the first aspect of the present invention, the membrane having a zeolite / polymer concentration of at least 50% w / w has a CO2 permeability of at least 10000 Barrer.

[0030] In an embodiment of the first aspect of the present invention, membranes with a zeolite / polymer concentration of at least 20% w / w have a CO2 / CH4 selectivity of greater than 100.

[0031] In an embodiment of the first aspect of the present invention, a membrane having a zeolite concentration of at least 30% w / w has a CO2 / CH4 selectivity of greater than 300.

[0032] In an embodiment of the first aspect of the present invention, a membrane having a zeolite concentration of at least 40% w / w has a CO2 / CH4 selectivity of greater than 400.

[0033] In an embodiment of the first aspect of the present invention the zeolite is in the form of platelets.

[0034] In an embodiment of the first aspect of the present invention, the zeolites are randomly and non-orderly packed within the polymer.

[0035] In an embodiment of the first aspect of the present invention the zeolite is 8, 10 or 12 ring members.

[0036] Other zeolites suitable for use in the membrane of the present invention are, for example, RRO, RHO, FER and LTA zeolites.

[0037] In an embodiment of the first aspect of the present invention, the zeolite is of the AEI, CHA, LTA or FAU type.

[0038] Here, CHA is cubic, LTA is spherical and FAU is octahedral. It is clear that CHA, LTA and FAU can also be prepared as defect-free zeolite MMM for gas separation.

[0039] In an embodiment of the first aspect of the present invention the zeolite is of the AEI type.

[0040] In an embodiment of the first aspect of the present invention, the AEI structure does not include aluminum species in the outer structure.

[0041] In an embodiment of the first aspect of the present invention, the zeolite is a platelet-shaped 8-membered AEI type SSZ-39 zeolite.

[0042] Changing the type of zeolite structure will result in different pore sizes, which will affect the types of gases that are separated. Similarly, the type of counter cation will affect the interaction with the gas molecules, which will in turn affect the selectivity and pore size. The Si / Al molar ratio will also affect the polarizability and pore size.

[0043] Approximately 10% of the aluminum sites in SSZ-39 zeolite are Na. + and Na-SSZ-39 (completely Na + At least 90% of the aluminum sites in the exchanged SSZ-39 zeolite are saturated with Na. + was occupied by.

[0044] In an embodiment of the first aspect of the present invention, at least 40%, at least 60%, at least 80%, at least 95%, at least 98% or at least 99% of the aluminium sites in the zeolite are occupied by sodium ions.

[0045] The addition of aluminum sites allows for tuning of the polarizability and counter ions of the zeolite filler, which alters the gas adsorption / diffusion properties and affects the overall membrane performance.

[0046] From the data of the present invention, it is clear that the gas separation performance of zeolite MMM is highly dependent on the Si / Al molar ratio of the zeolite filler.

[0047] In an embodiment of the first aspect of the present invention, the platelet zeolite has a thickness of 90 nm to 200 nm.

[0048] In an embodiment of the first aspect of the present invention, the particle size of the zeolite having a cubic or cubic, rectangular, spherical or octahedral shape is from 200 nm to 5 μm.

[0049] In an embodiment of the first aspect of the present invention, the size of the zeolite platelets is between 1x1 μm or 1.25x1.25 μm and 1.75x1.75 μm or 2x2 μm.

[0050] In an embodiment of the first aspect of the present invention, the zeolite has a bulk density of 15 mg / cm 3 , 20 mg / cm 3 or 50 mg / cm 3 to 100 mg / cm 3 , 200 mg / cm 3 , 500 mg / cm 3 Until then.

[0051] In an embodiment of the first aspect of the present invention the membrane is flexible and has a flexural modulus between 3.5 Mpa, 4 Mpa or 4.5 Mpa to 6.0 Mpa, 6.5 Mpa, 7 Mpa, 7.5 Mpa, 8.0 Mpa, 8.5 Mpa up to 9 Mpa.

[0052] In an embodiment of the first aspect of the invention, the polymer is a polyimide. Typically, the glassy polymers used in the present invention have a lower gas permeability than the zeolite filler. The polymer is compatible with the zeolite filler and can encapsulate it but not penetrate into its pores. The polymer does not decompose during thermal annealing and does not shrink by more than 10% by volume.

[0053] A second aspect of the present invention relates to a method for producing a mixed matrix membrane, the method comprising: a) dissolving a glassy polymer in a solvent; b) providing a zeolite dispersion (usually in the solvent of step a); c) mixing the dissolved polymer of a) with the dispersion of b) in an amount such that the mixture contains at least 5% w / v polymer / solvent and the amount of zeolite is at least 20% w / w, 30% w / w, 40% w / w or 50% w / w zeolite / (zeolite+polymer); d) pouring the mixture obtained in step c); e) drying the mixture to obtain a membrane; f) heating the membrane obtained in step e) at a temperature between 120° C. or 150° C. and the glass transition temperature of the polymer; Includes.

[0054] Generally, the upper limit of polymer / solvent that can be used in step c) is 15% to 20% by weight.

[0055] In a particular embodiment of the method, certain zeolites are used in concentrations to obtain MMM, as described above in the aspect relating to the MMM product.

[0056] As can be seen from the Examples section, the method does not involve or require cross-linking of the polymer within the membrane.

[0057] In an embodiment of the second aspect of the present invention, the drying in step e) is carried out at a rate such that 85% to 95% by weight of the solvent is removed within 3 hours to 24 hours.

[0058] In the present process, the rate of solvent removal is monitored to prevent desorption of the hardening polymer from the zeolite.

[0059] In an embodiment of the first (2?) aspect of the present invention, the heating is maintained for 8 hours to 24 hours.

[0060] In these method embodiments, a funnel is used to create an enclosed space above the casting solution film to slow down the rate of solvent removal.

[0061] For example, the boiling point of chloroform is 61.2 °C, so a funnel is used to slow the rate of evaporation of the solvent.

[0062] In other embodiments, the evaporation rate of the solvent is reduced by using a high boiling point (usually above 150° C.) solvent (e.g., Tamisolve, boiling point about 240° C.) or by using a climatic chamber with a solvent vapor atmosphere.

[0063] In an embodiment of the second aspect of the present invention, the reaction is carried out at a temperature of 150°C to 300°C.

[0064] In an embodiment of the first (2?) aspect of the present invention, step f is carried out at a temperature of 180°C to 280°C, or 200°C to 280°C, or 240°C to 280°C, or 250°C to 270°C.

[0065] In an embodiment of the second aspect of the invention, the method further comprises the steps of determining the gas permeability and selectivity of the prepared membranes and selecting membranes having at least 100% higher permeability and at least 50% higher CO2 / CH4 selectivity than the same membrane without zeolite subjected to the same heat treatment.

[0066] In an embodiment of the second aspect of the present invention the zeolite is in the form of platelets.

[0067] In an embodiment of the second aspect of the present invention the zeolite is eight-membered.

[0068] In an embodiment of the second aspect of the present invention the zeolite is of the AEI type.

[0069] In an embodiment of the second aspect of the present invention the polymer is a polyimide.

[0070] In an embodiment of the second aspect of the invention the solvent is chloroform or a dipolar aprotic solvent.

[0071] A third aspect of the present invention relates to a membrane obtainable by the process disclosed above as the second aspect of the present invention and its embodiments.

[0072] The gas separation performance of the MMMs of the present invention can be explained by several factors.

[0073] Zeolites have very high diffusion and dissolution selectivities, resulting in very high selectivity for mixed gases. In certain embodiments, the non-centrosymmetric AEI-type structures allow the preparation of high aspect ratio platelets.

[0074] Furthermore, the sharp increase in the CO2-CH4 separation factor with increasing % loading of zeolite indicates a percolation effect, whereby gas permeating through the membrane passes mainly through the zeolite phase. The zeolite creates a quasi-continuous zeolite phase throughout the membrane that allows percolation of gas molecules while minimizing the effect of the less permeable polymer phase. The zeolite platelets stack from the bottom and emerge at the top of the membrane. The non-aligned randomly oriented distribution provides selective gas permeation highways and realizes the membrane performance. Furthermore, platelet shaped zeolites were found to provide better selectivity and permeability than rectangular shaped zeolites.

[0075] In addition, the overall gas transport through the MMM is a pure result of both the zeolite and the polymer properties and their interactions, and it is important to obtain a defect-free zeolite-polymer interface. Although rubbery polymers such as polydimethylsiloxane (PDMS) facilitate the creation of a defect-free interface, they are inherently less selective and more permeable, thus compromising the beneficial contribution of the zeolite embedded therein. The membrane fabrication method of the present invention prevents the occurrence of non-selective voids at the zeolite-polymer interface and allows ultra-high loadings of zeolite, exceeding 50 wt.%, without chemical modification of the zeolite or the polymer or the use of additives.

[0076] An ultra-high performance zeolite-filled MMM for CO2 separation has been developed, which shows unprecedented CO2 removal performance, not only superior to existing polymeric membranes or MMMs, but even surpassing most zeolite-only membranes. By circumventing the traditional incompatibility of zeolite fillers with glassy polymer matrices, flexible, defect-free zeolite-polyimide MMMs were fabricated with ultra-high (>50 wt%) zeolite loadings. Na-SSZ-39 zeolite proved to be an excellent filler due to its prominent CO2 affinity, precise molecular sieving window, strong competitive sorption behavior, and excellent stability, facilitating strong and age-resistant CO2 separation performance. The high aspect ratio and 3D channel system of the filler dramatically improved the membrane performance by creating gas permeation highways that permeate the entire membrane.

[0077] The fabrication of defect-free zeolite-filled membranes using commercially available glassy polymers using a scalable method paves the way for the development of easy-to-process, robust, and economical high-performance zeolite-filled MMMs for the separation of a variety of gases and liquids, which is particularly beneficial for zeolites that are difficult to engineer into defect-free, all-zeolite films. EXAMPLES

[0078] Example 1 Preparation of mixed matrix membranes on a laboratory scale Mixed matrix membranes (MMMs) containing 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, and 55 wt% zeolite were prepared. First, 0.3 g of Matrimid was dissolved in 2.70 g of chloroform to make a homogenous 10 wt% Matrimid solution. Then, a certain amount of zeolite was added to 1.80 g of chloroform to make a zeolite dispersion. The zeolite dispersion was stirred for 2 h and thoroughly sonicated for 1 h. To each zeolite dispersion, 3 g of 10 wt% Matrimid solution was added. All zeolite / polymer solutions were stirred on a magnetic stir plate for 8 h and sonicated twice (1 h each) at the beginning and end of the stirring process. The final mixture was poured into a Petri dish (d=7 cm) in a nitrogen bag. The polymer concentration was adjusted to around 7 wt % to obtain a viscous solution that was pourable but did not result in significant precipitation of the zeolite during solvent evaporation. A small opening (diameter = 3 mm, internal volume of the funnel ≈ 30 cm) was placed on top of a Petri dish. 3 The evaporation of chloroform was slowed down by placing a glass funnel (200 mm x 200 mm) over the polymer solution layer. The glass funnel created a saturated chloroform vapor phase above the polymer solution layer, slowing down the rate of solvent evaporation. This resulted in the membrane film solidifying in approximately 1 hour. The solidified membrane was placed in a nitrogen bag for 12 hours, removed from the Petri dish, and allowed to air dry for 10 hours before heat treatment. The zeolite loading was calculated using Equation 1: Zeolite loading (wt%) = 100 × (m ゼオライト / (m ゼオライト +m ポリマー )) (In the formula, m ゼオライト and m ポリマー are the weights of zeolite and polymer, respectively).

[0079] For the post-thermal annealing process, the dried membrane was placed between glass supports to prevent curling before being placed in a muffle oven. The muffle oven was heated to 180°C, 260°C (below the glass transition temperature (Tg) of Matrimid), 300°C (below but close to the Tg of Matrimid) and 350°C (above the Tg of Matrimid). The heating protocol consisted of heating from room temperature to the final annealing temperature at 1°C per minute in 30°C increments. At each 30°C increment, the oven was kept isothermal for 2 hours. The membrane was held at the final temperature for 24 hours and removed after the oven had cooled naturally to room temperature. This is because rapid cooling would create voids between the polymer matrix and the filler due to the difference in the thermal expansion coefficients of the two materials. Allowing the MMM to cool naturally preserves good adhesion between the polymer chains and the zeolite.

[0080] Example 2. Characterization of zeolites Powder X-ray diffraction (pXRD) of the Na-SSZ-39 zeolite confirmed a highly crystalline AEI structure, which was in good agreement with previous reports of Na-SSZ-39. N2 adsorption experiments showed that the synthesized Na-SSZ-39 had a microporous content of nearly 100% and a pore size of 0.28 cm 3 / g~0.29 cm 3 It has been demonstrated that the Na-SSZ-39 has a pore volume of approximately 100 nm thick and approximately 1.5 × 1.5 μm in size, which is close to the theoretical maximum accessible volume of AEI-type structures. According to the literature, Na-SSZ-39 synthesis results in an AEI structure that does not contain aluminum species in the external structure, which exhibits a nearly perfect 3D connected channel system, enabling fast gas transport. SEM images show a pore volume of approximately 100 nm thick and approximately 1.5 × 1.5 μm in size. 2 Platelet-shaped Na-SSZ-39 zeolite is shown (Figure 1.a). As a result of the loose packing of the zeolite plates, 20 mg / cm 3 A very low bulk density was obtained.

[0081] The uptake of CO2, CH4 and N2 gases and the isosteric adsorption enthalpy (Q st ) is SSZ-39 (SSZ-39, Na / Al ratio = 0.12) and Na+ Adsorption isotherms for CO2, CH4 and N2 at 10°C to 50°C over the pressure range 0 bar to 8 bar are shown in Figures 12, 13 and 14. For both SSZ-39 and Na-SSZ-39, the gas uptake decreases in the logical order CO2>CH4>N2, which is ascribed to the expected differences in the polarizabilities and quadrupole moments of the adsorbates. The maximum CO2 uptake for Na-SSZ-39 is 10.87 mmol / cm at 10°C. 3 (253.1 cm 3 (STP) / cm 3 ) and SSZ-39 reached 10.66 mmol / cm 3 (248.2 cm 3 (STP) / cm 3 To quantify the CO2 affinity of Na-SSZ-39, the CO2Q st was determined to be -35.1 kJ / mol using the Toth model. The heat of adsorption of CO2 on Na-SSZ39 (-35.1 kJ / mol) was much larger than that of CH4 (-21.4 kJ / mol) and N2 (-19.4 kJ / mol) as a result of the large polarizability and quadrupole moment of CO2 (Table 1). Overall, it was observed that Na-SSZ-39 gave a more negative CO2 sorption enthalpy and higher CO2 uptake compared to SSZ-39. In addition, a significant difference in the adsorption of CO2 in the low pressure region of the isotherm was observed for Na-SSZ-39. + This suggests that the exchange increased the zeolite's affinity for CO2.

[0082] Table 1. Fitted Toth parameters (with 95% confidence intervals) of CO2, CH4, and N2 adsorption isotherms for three samples (Na-SSZ-39, SSZ-39, and 50 wt.% Na-SSZ-39 MMM). [Table 1] Adsorbents

[0083] To further explain the experimental results at the molecular level, Grand Canonical Monte Carlo (GCMC) simulations were used to model the adsorption behavior of pure and mixed gases in Na-SSZ-39. The results from the pure gas adsorption simulations are qualitatively similar to the experimental data (Fig. 3.b), and the enthalpies of adsorption are in good agreement (at 2 bar, GCMC gives -31.6 kJ / mol for CO2, -18.5 kJ / mol for CH4, and -15.8 kJ / mol for N2). The 3D density isosurfaces for CO2 adsorption (Fig. 3.e) show that the CO2 molecules adsorb at 1000 MPa with a 1000 MPa sorption of 1000 MPa. + We find that while CO2 preferentially interacts with Na (especially at low CO2 pressures), the Na-SSZ-39 window remains open for gas transport. + This tendency to approach the site is due to Na + This confirms the enhanced CO2 affinity of the exchanged zeolite, improving the CO2 adsorption in Na-SSZ-39. Furthermore, the CO2 / CH4 mixed gas sorption simulation in Na-SSZ-39 clearly demonstrates that the CH4 uptake is dramatically decreased due to the competitive sorption of CO2 at the expense of CH4 (Fig. 3.c). Compared with the single gas adsorption results (Fig. 3.a), the CH4 uptake in the mixed gas condition is reduced from 1.94 mmol / g to 0.26 mmol / g at 5 bar and 25 °C (Fig. 3.c). In addition, the molecular sieve behavior of Na-SSZ-39 zeolite is further confirmed by ab initio free energy barrier calculations for diffusion inside the zeolite. The largest opening in Na-SSZ-39 zeolite only allows the diffusion of molecules with a diameter of 3.84 Å. This is close to the kinetic diameter of a CH4 gas molecule (3.80 Å) and significantly larger than that of CO2 (3.30 Å), so the free energy barrier for permeation of CH4 through the 8-membered ring of Na-SSZ-39 is approximately twice that of CO2. As a result, the self-diffusion coefficient of CO2 is more than three orders of magnitude larger than that of CH4.

[0084] The adsorption behavior of pure and mixed gases in SSZ-39 was modeled by Grand Canonical Monte Carlo (GCMC) simulations. The results from the pure gas adsorption simulations are in good agreement with the experimental data (Fig. 3.b). Moreover, the 3D density plot of CO2 adsorption (Fig. 3.e) shows that the CO2 adsorption mainly occurs within the zeolite cages and that the CO2 is absorbed by Na + This indicates that while CO2 molecules preferentially interact with Na (especially at low CO2 pressures), the window in Na-SSZ-39 remains open for gas transport. + This is because Na + This explains the enhanced CO2 affinity of the exchanged zeolite, resulting in improved CO2 adsorption on Na-SSZ-39. Most importantly, the CO2 / CH4 mixed gas sorption simulation on Na-SSZ-39 clearly demonstrates that the CH4 uptake is dramatically reduced due to the competitive sorption of CO2 at the expense of CH4 (Figure 3.c). Compared with the single gas adsorption results, the CH4 uptake in the mixed gas condition is 72.3 cm at 5 bar and 25 °C. 3 STP / cm 3 From 7.9 cm 3 STP / cm 3 In addition, the molecular sieve behavior of Na-SSZ-39 zeolite was further confirmed by energy barrier calculations for diffusion inside the zeolite. Since the maximum opening size of Na-SSZ-39 zeolite is 3.84 Å, which is close to the kinetic diameter of a CH4 gas molecule (3.80 Å), the energy barrier for permeation of CH4 through its pores is calculated to be approximately twice that of CO2.

[0085] Example 3 MMM Characterization MMMs were prepared with Na-SSZ-39, the loading of which reached a truly exceptional 55 wt%. XRD confirmed that the zeolite crystallinity was maintained in the MMMs after thermal treatment (Fig. 8). SEM cross-sectional photograph of the membrane (Fig. 1.d) shows that the zeolite platelets are arranged in a random, non-ordered packing within the polymer matrix. This random distribution of SSZ-39 zeolite platelets in the MMMs is attributed to the delicate and carefully optimized interplay of zeolite and solvent properties during the MMM synthesis. More specifically, the good interaction of the Na-SSZ-39 plates with the solvent, the small density difference between the zeolite and the solvent (1.55 g / cm, respectively) and the low density difference between the two are the key factors in the synthesis of the MMMs. 3 and 1.49 g / cm 3 ) prevented particle settling and the high aspect ratio of the platelet-shaped zeolite and the high viscosity of the final casting solution resulted in optimal dispersion of the zeolite in the casting solvent (i.e., chloroform). In addition, slow chloroform evaporation rate during membrane formation prevented the hardening polymer chains from detaching from the zeolite surface during solvent evaporation. After drying the cast film, an annealing protocol further eliminated interfacial defects, which had a significant impact on the final MMM morphology. Several thermal annealing programs were tested at 180°C, 260°C, 300°C, and 350°C. Of these, annealing at 180°C and 260°C gave similar MMM CO2 permeability, while the 260°C program nearly doubled the CO2 / CH4 separation factor (for 50 wt% Na-SSZ-39 MMM, the separation factor increased from about 200 to over 420). Annealing at temperatures above 300° C. resulted in brittle and brittle carbonized films with significant voids at the zeolite-polymer interface (FIGS. 6 and 7).

[0086] Complete removal of the polymer by oxidation treatment at 800 °C resulted in a remarkably stable zeolite-only film (Figure 1.e), with extremely high zeolite loading with random packing and a clear confirmation of a quasi-connected continuous zeolite phase inside the MMM. Figure 1.c clearly shows that the membrane subjected to annealing at 260 °C did not show the cage-intrasieve morphology, which is a traditional major problem of zeolite MMMs (Figure 1.b). Compared to the unannealed membrane (Figure 1.b), a significant improvement in the zeolite-polymer adhesion after annealing can be observed. FTIR shows that the zeolite-polymer adhesion at specific wavenumbers (1050 cm -1 and 1090 cm -1 ), we identified typical zeolite and polymer signals in the polyimide-zeolite interface, but could not find conclusive evidence of covalent interactions between the polymer and zeolite at the annealed interface, even at high zeolite loadings (Figure 9). To investigate the zeolite-polymer interface interactions more deeply, we applied confocal Raman spectroscopy to confirm the absence of chemical reactions between the zeolite and polyimide. Although no indication of covalent bond formation was detected, we could observe the rearrangement of the polymer chains and the improved wrapping around the zeolite particles induced by thermal annealing. Increasing the zeolite loading from 10 to 30 wt% steadily increased the glass transition temperature (Tg) of the thermally annealed Na-SSZ-39 MMM from 320 to 330 °C, indicating the stiffening of the polymer chains at the polymer-zeolite interface (Figure 16). This indicates that the zeolite is wrapped by the polymer, restricting the thermal motion of the polymer and requiring more energy by the movement of the polymer chains. Sorption experiments of CO2, CH4 and N2 were performed on pristine Matrimid membranes annealed at 260 °C and 50 wt% Na-SSZ-39 MMMs to quantify the uptake of each gas. Compared to the pure Matrimid membrane, MMMs showed significantly increased uptake of CO2, CH4 and N2 (Figure 11).

[0087] Example 4 Gas separation performance of the membrane Because SSZ-39 MMM exhibits competitive gas adsorption behavior, its mixed gas selectivity is significantly higher than the ideal gas selectivity (Table 2).

[0088] Table 2. CO2 / CH4 and CO2 / N2 mixed gas selectivity for Na-SSZ-39 MMM at 25°C (for equimolar CO2 / N2 gas mixture and equimolar CO2 / CH4 gas mixture, partial pressures of CO2, CH4, and N2 in the gas mixture are 1 bar) and CO2 / CH4 and CO2 / N2 ideal gas selectivity (pressures of CO2, CH4, and N2 feed streams are 1 bar). [Table 2] Membrane name: Name of membrane Mixed gas selectivity: Ideal gas selectivity: Wt.%: Weight%

[0089] For example, for 50 wt% Na-SSZ-39 MMM, the CO2 / CH4 ideal gas selectivity is about 335 at 1 bar / 25°C, while the CO2 / CH4 mixed gas (CO2 / CH4=50vol% / 50vol%) selectivity reaches about 423 at 2 bar / 25°C (both CO2 and CH4 partial pressures are equal to 1 bar). Similarly, the CO2 / N2 ideal gas selectivity at 1 bar / 25°C is about 32, while the mixed gas selectivity at 2 bar / 25°C increases to about 60. Thus, obviously, when the more strongly adsorbed CO2 occupies the adsorption sites, the zeolite channels become partially inaccessible to other gases, preventing the permeation of CH4 and N2. Based on the MMM sorption and pure gas permeation experiments, the gas solubility and gas diffusivity values ​​for the pristine Matrimid membrane and 50 wt% Na-SSZ-39 MMM were calculated (Table 3).

[0090] Table 3. Single component CO2, CH4, and N2 gas uptake (cm) for 50 wt% Na-SSZ-39 MMM and pristine Matrimid membranes (both those subjected to a 260 °C thermal annealing program) at 25 °C and 1 bar. 3 STP / cm 3), ideal permeability P(Barrer), solubility S(10 + cm 3 (STP) / cm 3 cmHg), diffusive D(10 8 cm 2 / s), and comparison of these values [Table 3] Gas: Gas Uptake: Pristine Matrimid membrane: Pristine Matrimid membrane Uptake:

[0091] Relative to the unfilled polymer membrane, MMM showed 4.6 times greater CO2 solubility, while the solubility of CH4 and N2 in Na-SSZ-39 MMM increased by 7.5 and 3.4 times, respectively. Compared to the unfilled Matrimid membrane, the CO2 diffusivity increased by 220 times, while the diffusivities of CH4 and N2 increased by 14 and 148 times, respectively, in Na-SSZ-39 MMM. Thus, the enhanced MMM CO2 / CH4 diffusion selectivity (+1104%) appears to be the basis for the significant improvement in the gas separation capacity of MMM. This can be explained by the strict size sieving effect of Na-SSZ-39 on CH4, since the zeolite pore size (3.84 Å) is almost equal to the kinetic diameter of CH4 (3.80 Å). The increase in the CO2 / N2 diffusion selectivity is less pronounced due to the smaller kinetic diameter of N2 (3.64 Å), which is consistent with the observed CO2 / N2 permeation behavior of the SSZ-39 MMM. The separation performances of the mixed gases CO2 / CH4 and CO2 / N2 are shown in Figures 2.D and 2.E. For CO2 / CH4, a continuous increase in the separation factor is observed with higher Na-SSZ-39 loading. The unloaded Matrimid membrane has a CO2 / CH4 separation factor of about 45 and a CO2 permeability of about 8 Barrer, whereas the best MMM performance was obtained with 50 wt% Na-SSZ-39 loading, which gave an impressive separation factor of about 423 at 2 bar / 25°C. At the same time, a CO2 permeability of about 8280 Barrer was obtained (an increase of about 1037 times). Similar results were obtained for the MMM CO2 / N2 separation performance. Here, 50 wt% MMM combines a CO2 permeability of about 8300 Barrer with a CO2 / N2 separation factor of about 60. Figures 2.b and 2.c show the temperature and pressure dependences of the CO2 / CH4 separation factor and CO2 permeability of Na-SSZ-39 MMM with different zeolite loadings. With increasing temperature, the CO2 adsorption in the zeolite decreases (Figure 12), the CO2 permeability decreases, but the CH4 permeability increases slightly and the CO2 / CH4 selectivity decreases. Similar behavior was observed with increasing feed pressure, where both the CO2 permeability and the CO2 / CH4 selectivity decreased.This can be explained by the high CO2 affinity of the Na-SSZ-39 zeolite filler, which is already saturated with CO2 molecules at low feed pressures (Figure 12). Further increasing the pressure has a much smaller impact on the CH4 permeability compared to the CO2 permeability. For the same reason, when the membrane is exposed to a feed with reduced CO2 partial pressure, the Na-SSZ-39 MMM shows superior performance compared to the tests with equimolar gas mixtures. For example, 50 wt% Na-SSZ-39 MMM showed a CO2 permeability of over 10,000 Barrers and a CO2 / CH4 separation factor of over 460 for a 20 vol% CO2 / 80 vol% CH4 feed.

[0092] When shown in the selectivity vs. permeability trade-off plot, the Na-SSZ-39 MMM already exceeds the trade-off line for CO2 / CH4 from only 20 wt.% zeolite loading (Fig. 2E) and for CO2 / N2 from 30 wt.% zeolite loading (Fig. 2D). Finally, it achieves an unprecedented rise towards the upper right corner of the MMM Robeson plot, ending up beyond the performance region dominated by pure zeolite membranes (Fig. 2F). The superior performance over pure zeolite membranes is likely related to the outstanding properties of the Na-SSZ-39 filler and the unique morphology of the membranes with ultra-high zeolite loading. Moreover, compared to pure zeolite membranes, the Na-SSZ-39 MMM shows better upscaling potential since it also maintains flexibility due to the presence of the polymer matrix. From an application point of view, the exceptional combination of very high flux and selectivity can significantly reduce both operational and capital costs. This is because simplified and more energy-efficient operating schemes with less recycle and gentler (re)compression stages can be applied, as well as the membrane area being reduced.

[0093] The exceptional gas separation performance of Na-SSZ-39 MMM can be explained by a combination of several factors. +The synthesis of exchanged SSZ-39 zeolite created a more CO2-friendly adsorption environment, leading to increased CO2 uptake and increased CO2 affinity. GCMC modeling and calculations of the gas diffusion selectivity of the membrane revealed a strong competitive sorption of CO2 at the expense of CH4 and N2, along with a highly accurate CO2 / CH4 size sieve effect. This effect is clearly confirmed by mixed-gas GCMC simulations (Figures 3C and 3D). In other words, under mixed-gas conditions, the geometric constraints of the zeolite pores, combined with the competitive advantage of sorption in the zeolite over CO2, prevent CH4 from entering the zeolite cage, further restricting the access of CH4. The significant difference in the separation factors of CO2 / CH4 and CO2 / N2 (about 423 and about 60, respectively, for 50 wt. % Na-SSZ-39 MMM at 2 bar and 25 °C) is almost a direct consequence of the smaller kinetic diameter of N2 compared to CH4, thus confirming the central role of the size-sieving mechanism.

[0094] Second, the sharp increase in the CO2 / CH4 separation factor from 20wt% to 30wt% loading suggests a percolation effect; i.e., the permeation of gas through the membrane from this loading onwards is mainly determined by the zeolite phase. The reason for this change in phase dominance is sought due to the practicality of being able to incorporate higher than usual loadings of zeolite within the polymer matrix. This results in a unique membrane morphology consisting of a quasi-connected continuous zeolite phase within the polymer matrix, starting from 20wt% to 30wt% zeolite loading, allowing percolation of gas molecules with minimal influence of the polymer phase. SEM top (Fig. 1.E(F?)) and bottom (Fig. 1.F(G?)) views of membranes with different zeolite loadings show that zeolite platelets stack from the bottom and appear at the top of the membrane when the zeolite loading reaches 30wt%.

[0095] In this context, the non-aligned and random platelet-like Na-SSZ-39 distribution within the MMM polymer matrix (a result of the zeolite shape and optimized MMM synthesis) is identified as the main driving force and prerequisite for the exceptional performance of the membrane. The random zeolite packing ensures the overall connectivity between the zeolite particles that determines the permeation pathways of the gas molecules. This was confirmed by comparing the CO2 / CH4 separation performance of MMMs containing platelet-shaped Na-SSZ-39 with that of MMMs with rectangular shaped Na-SSZ-39. As can be seen in Figure 2.A, a sudden increment in CO2 / CH4 selectivity was observed only for the platelet-shaped zeolite, but not for the rectangular shaped Na-SSZ-39. Moreover, the platelet-shaped Na-SSZ39 MMMs show much better CO2 / CH4 selectivity and CO2 permeability compared to the rectangular shaped Na-SSZ-39 MMMs with the same zeolite loading. Third, since the overall gas transport through the MMM is a pure result of both the zeolite and the polymer properties and their interactions, it is important to obtain a defect-free interface between Matrimid and Na-SSZ-39. The thermal annealing protocol minimizes the occurrence of non-selective voids at the zeolite-polymer interface, allowing ultra-high loadings of zeolite, exceeding 50 wt%, without chemical modification of the zeolite or the polymer or the use of additives. This was visualized by SEM cross-sectional images.

[0096] Example 5. Three-point bending test For the measurement of flexural modulus, three-point bending tests were performed on an Instron 5943. The support span was set at 20 mm and the maximum extension distance was 10 mm. Four samples were tested: pure Matrimid membrane (without heat treatment), pure Matrimid membrane thermally annealed at 260 °C, 50 wt. % zeolite MMM (without heat treatment), and 50 wt. % zeolite MMM thermally annealed at 260 °C. All membrane coupons were prepared with a size of 60 mm x 20 mm (thickness 800 μm to 100 μm), and each membrane coupon was tested four times at the maximum load extension. The flexural modulus was calculated based on Equation 1: Eflex=L 3 F / 4wh 3d (1) w: width of membrane coupon, h: thickness of the membrane coupon, L: distance between support spans, d: load elongation, F: Load force applied at the center of the beam.

[0097] The flexural modulus of the four membrane samples is shown in Table 1. None of the membrane coupons broke during testing, and all of the membrane samples were able to return to their original shape after the load was removed. As shown by the flexural modulus, both the zeolite loading and the thermal annealing treatment reduced the flexibility of the membrane coupons and increased the flexural modulus.

[0098] Table 4. Flexural modulus of membrane coupons [Table 4] Membrane name: Name of membrane Flexural Modulus: Flexural modulus Annealed: Annealed Wt.%: Weight%

[0099] Example 6. Further embodiments of mixed matrix membranes Three further membranes were prepared. Na-CHA-10 Zeolite with Polyimide Polymer Na-FAU-2 Zeolite with Polyimide Polymer Na-FAU-2 zeolite with polysulfone (Ultrason™ S2010) polymer

[0100] Here, Na-CHA-10 is Na + It is a cubic shaped 8-membered ring (8MR) CHA-type structure zeolite filler containing counter ions, and the Si / Al molar ratio is about 10.

[0101] Here, FAU is Na + It is an octahedral 12-membered ring (12MR) FAU-type structure zeolite filler containing counterions, and the Si / Al molar ratio is about 2.

[0102] These additional films were prepared using the same solvents and the same conditions as disclosed in Example 1, except for the final heating step.

[0103] Na-CHA-10 / Matrimid MMM and Na-FAU-2 / Matrimid MMM were then heated at 260° C. for 24 hours.

[0104] The Na-FAU-2 / polysulfone MMM was then heated at 50° C. for 12 h.

[0105] FIG. 18 shows the permeability and selectivity of these membranes compared to prior art membranes, showing similar but superior properties compared to the prior art. [Explanation of symbols]

[0106] Drawing translation Figure 2A CO2 / CH4selectivity Zeolite loading (wt%) Cuboid Filler Plate Filler Figure 2B CO2 / CH4selectivity Temperature Pressure (bar) Figure 2C CO2 permeability (Barrer) CO2 permeability (Barrer) Temperature Pressure (bar) CO2permeability CO2 permeability Figure 2D CO2 / N2selectivity CO2 permeability (BARRER) CO2 permeability (BARRER) 2008 upper bound Figure 2E CO2 / CH4selectivity CO2 permeability (BARRER) CO2 permeability (BARRER) 2008 upper bound Figure 2F CO2 / CH4selectivity CO2 permeability (BARRER) CO2 permeability (BARRER) 2008 upper bound Silicalite Silicalite-1 / SSZ-13 Silicalite-1 / SSZ-13 wt.% Weight% Figure 3A Gas uptake (mmol / g) Pressure (bar) Figure 3B Gas uptake (mmol / g) Pressure (bar) Simulated Na-SSZ-39 CO2-25℃ Simulated Na-SSZ-39 CO2-25℃ Simulated Na-SSZ-39 CH4-25℃ Simulated Na-SSZ-39 CH4-25℃ Simulated Na-SSZ-39 N2-25℃ Simulated Na-SSZ-39 N2-25℃ Figure 3C Gas uptake (mmol / g) Pressure (bar) Simulated binary CO2-25℃ Simulated binary CO2-25℃ Simulated binary CH4-25℃ Simulated binary CH4-25℃ Simulated unary CO2-25℃ Simulated single component CO2-25℃ Simulated unary CH4-25℃ Simulated single component CH4-25℃ Figure 3D Gas uptake (mmol / g) Pressure (bar) Simulated unary CO2-25℃ Simulated single component CO2-25℃ Simulated uary N2-25℃ Simulated single component N2-25℃ Simulated binary CO2-25℃ Simulated binary CO2-25℃ Simulated binary N2-25 ℃ Simulated binary N2-25℃ Figure 8 Intensity (-) Intensity (-) wt.% Weight% Pure matrimid (260℃) Figure 9 Transmittance (-) Wavelength (cm -1 ) Wavelength (cm -1 ) wt.% Weight% Pristine Matrimid (without annealing) Pristine Matrimid (without annealing) Pure Na-SSZ-39 zeolite Figure 10 Simulated Na-SSZ-39 solubility selectivity Pressure (bar) Unary CO2 / CH4-25℃ Single component CO2 / CH4-25℃ Unary CO2 / N2-25℃ Single component CO2 / N2-25℃ Binary CO2 / CH4-25℃ Binary CO2 / CH4-25℃ Binary CO2 / N2-25℃ Binary CO2 / N2-25℃ Figure 11 Loading (mmol / g) Pressure (bar) Pure matrimid CO2-25℃ Pure matrimid CO2-25℃ Pure matrimid CH4-25℃ Pure matrimid CH4-25℃ Pure matrimid N2-25℃ Pure matrimid N2-25℃ Figure 12 Gas uptake (mmol / g) Pressure (bar) Figure 13 Gas uptake (mmol / g) Pressure (bar) Figure 14 Gas uptake (mmol / g) Pressure (bar) Figure 15 Load (N) Extension (mm) 50 wt.% MMM 50 wt.% MMM Annealed Matrimid Annealed Matrimid Annealed 50% by weight MMM Annealed 50% by weight MMM Figure 16 Heat flow / weight (W g -1 ) Heat flow / weight (W g -1 ) Temperature (℃) Temperature (℃) Figure 17 selectivity Permeability (Barrer) Permeability (Barrer) Figure 18A CO2 / CH4selectivity CO2 permeability (Barrer) CO2 permeability (Barrer) Prior art MMMs Figure 18B CO2 / N2selectivity CO2 permeability (Barrer) CO2 permeability (Barrer) Prior art MMMs Figure 18C CO2 / N2selectivity CO2 permeability (Barrer) CO2 permeability (Barrer) Prior art MMMs Pure polysulfone Na-FAU-2 / polysulfone MMM Na-FAU-2 / polysulfone MMM

Claims

1. A mixed matrix membrane (MMM) for gas filtration and separation, obtainable by the method according to any one of claims 14 to 27, said MMM comprising a glassy polymer matrix containing at least 20% w / w of zeolite, said zeolite polymer matrix having no interfacial voids or having voids less than 20 nm measured in its longest dimension.

2. 10. The MMM of claim 1, wherein the membrane comprises a glassy polymer matrix comprising at least 30% w / w, 40% w / w, or 50% w / w of zeolite.

3. 3. The MMM of claim 1 or 2, wherein the zeolite is a platelet, cubic, rectangular, spherical or octahedral shaped zeolite.

4. 4. The MMM of any one of claims 1 to 3, wherein the zeolite is in platelet form and has a concentration in the membrane of at least 20% w / w, at least 30% w / w, at least 40% w / w, or at least 50% w / w.

5. The membrane has a concentration of zeolite of at least 40% w / w and is resistant to CO of at least 4000 Barrer. 2 5. The MMM of any one of claims 1 to 4, which has permeability.

6. The membrane has a zeolite / polymer concentration of at least 20% w / w and has a CO 2 / CH 4 The MMM of any one of claims 1 to 5, which has selectivity.

7. The membrane has a zeolite concentration of at least 40% w / w and has a CO 2 / CH 4 The MMM of any one of claims 1 to 5, which has selectivity.

8. 8. The MMM of any one of claims 1 to 7, wherein the zeolite is in the form of platelets.

9. 9. The MMM of any one of claims 1 to 8, wherein the zeolite has 8 or 12 ring members.

10. 10. The MMM of any one of claims 1 to 9, wherein the zeolite is of the AEI type.

11. 11. The MMM of any one of claims 1 to 10, wherein the membrane is flexible and has a flexural modulus of from 2 Gpa up to 9 Gpa.

12. 12. The MMM of any one of claims 1 to 11, wherein the membrane is flexible and has a flexural modulus of from 3.5 Mpa up to 9 Mpa.

13. The MMM of any one of claims 1 to 12, wherein the polymer is a polyimide.

14. 1. A method for producing a mixed matrix membrane, comprising: a) providing a mixture of a glassy polymer and a zeolite in a solvent, said solvent comprising at least 5% w / v of polymer and at least 20% w / w, 30% w / w, 40% w / w or 50% w / w of zeolite; b) pouring the mixture obtained in step a); c) drying the cast mixture obtained in step b) to obtain a membrane, said drying being carried out at a rate such that 85% to 95% by weight of said solvent is removed in a period of 15 minutes to 24 hours; d) heating the dried film obtained in step c) at a temperature below the glass transition temperature of the polymer, said heating being maintained for a period of between 5 minutes and 24 hours and / or carried out at a temperature between 30° C. and 300° C., provided that said temperature is below the transition temperature of the polymer; A method comprising:

15. 15. The method of claim 14, wherein the solution of the polymer and the dispersion of the zeolite are prepared separately and subsequently mixed.

16. 16. The method according to claim 14 or 15, wherein the drying in step c) is carried out at a rate such that 85% to 95% by weight of the solvent is removed in a period of 5 minutes to 24 hours.

17. 16. The method according to claim 14 or 15, wherein the drying in step c) is carried out at a rate such that 85% to 95% by weight of the solvent is removed in a period of 3 hours to 24 hours.

18. The method according to any one of claims 14 to 17, wherein in step d, the membrane is heated to a temperature of from 30°C to the glass transition temperature of the polymer.

19. 18. The method according to any one of claims 14 to 17, wherein in step d, the membrane is heated to a temperature of from 120°C or 150°C to the glass transition temperature of the polymer.

20. 20. The method according to any one of claims 14 to 19, wherein the heating in step d) is maintained for a period of between 4 hours and 24 hours.

21. 20. The method according to any one of claims 14 to 19, wherein the heating in step d) is maintained for a period of between 8 hours and 24 hours.

22. 20. The method according to any one of claims 14 to 19, wherein the heating in step d) is maintained for a period of between 8 hours and 24 hours and / or step d) is carried out at a temperature between 150°C and 300°C.

23. The method of any one of claims 14 to 22, followed by a step of determining that no voids are present.

24. 24. The method of claim 23, wherein the absence of voids is determined by microscopic examination.

25. 24. The method of claim 23, wherein the absence of voids is determined by measuring the flow rate of gas over the membrane.

26. The method according to any one of claims 14 to 25, wherein the zeolite is in the form of platelets.

27. 27. The method according to any one of claims 14 to 26, wherein the zeolite is of the AEI type.

28. The method of any one of claims 14 to 27, wherein the polymer is a polyimide.

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