Gas separation membrane, gas separation method, method for manufacturing gas separation membrane, and gas separation system

Abstract

There is a demand for a gas separation membrane that does not require crosslinking, has improved thermal stability and chemical resistance, has no defects associated with existing materials, and has improved CO2 permeability and selectivity. The present invention relates to a gas separation membrane that is based on siloxane-modified pullulan and / or siloxane-modified norbornene, a method for manufacturing the membrane, and a gas separation method. The gas separation membrane comprises a separation function layer. The separation function layer contains siloxane-modified pullulan and / or siloxane-modified norbornene as a matrix polymer. Incorporating the siloxane-modified polymer improves CO2 permeability, selectivity, and resistance to physical and chemical aging, improves film performance, and is very effective for a variety of gas separation uses.

Description

Gas separation membrane, gas separation method, gas separation membrane manufacturing method, and gas separation system

[0001] The present invention relates to highly stable gas separation membranes based on siloxane-modified polymers, with an emphasis on improved resistance to physical and chemical aging, methods for producing the membranes, and methods for gas separation.

[0002] To reduce energy costs and the environmental impact of atmospheric carbon dioxide, technologies are being developed to capture carbon dioxide (CO2) from industrial gas streams. Major sources of CO2 emissions include power plants, cement kilns, natural gas processing facilities, ammonia plants, and hydrogen plants. The captured CO2 can be used for a variety of applications, including sequestration, enhanced oil recovery, and promoting algae growth. In the case of hydrogen, ammonia, and natural gas, CO2 must be removed to increase the value of the gas stream.

[0003] Existing technologies for capturing CO2 from flue gas streams, such as traditional absorption and adsorption, have high energy consumption and overall costs, posing a major obstacle to industrial implementation. Absorption using monoethanolamine (MEA) is currently the only commercially available option, but its cost remains prohibitive. Furthermore, the chemicals used in amine absorption pose an additional source of pollution to the environment. To address this challenge, membrane-based gas separation methods offer the potential for significant cost reductions.

[0004] While polymeric membrane technology is economically and technically viable, its performance is limited. The balance between permeability and selectivity influences whether a polymeric membrane is used to separate CO2 from waste gas streams, with low permeability making CO2 separation very expensive and requiring very large membrane areas, resulting in high investment costs. Permeability is a measure of the membrane's ability to transport a particular gas and is equivalent to the reciprocal of the membrane resistance to that gas. It is expressed in Gas Permeability Units (GPU): Selectivity is defined as the ratio of the permeabilities of two gases and indicates the ability of a membrane to distinguish between gases. It is calculated using the following formula: A higher selectivity value indicates a better separation performance of the membrane for gas A over gas B.

[0005] Gas separation membranes typically consist of a separation functional layer and a support layer. The separation functional layer plays an important role in determining the gas permeability characteristics of the gas separation membrane. While there are gas separation membranes in the literature and prior art that achieve optimal properties of high permeability and high selectivity, most membranes have a lifespan of approximately three years. If the lifespan is shorter than this, frequent membrane replacement will significantly increase operational costs.

[0006] When the separation functional layer is coated with another type of layer, a selective layer, it is sometimes called a "gutter layer," and is outlined in Non-Patent Document 1. It is disclosed that a gutter layer is interposed between the selective membrane material and the structural support material to facilitate and improve their combination. Patent Document 1 discloses a composite gas separation membrane made by in-situ crosslinking of an aminoorganofunctional polysiloxane and a diisocyanate to form a gutter layer on the surface of a highly porous polymer substrate such as polysulfone or polystyrene. A gas separator such as polyphenylene oxide can then be coated onto the gutter layer.

[0007] Silicone, which has an organosiloxane polymer structure, is a suitable material for the gutter layer. Polydimethylsiloxane (PDMS) is widely used as the gutter layer in gas separation membranes due to its unique properties. PDMS is characterized by high gas permeability (3,000 CO2 Barrer), flexibility, and the ability to form thin, uniform films.

[0008] Gas separation membranes such as PDMS require in situ crosslinking for optimal performance, and crosslinked polymers with intentionally added crosslinking agents have been proposed as the primary constituent of gas separation membranes (Non-Patent Document 2).

[0009] While cross-linked polymers improve selectivity, they also pose challenges such as complex solution preparation, difficulty in coating, and limited pot life of the coating solution, which may affect the production efficiency and scalability of the membranes.

[0010] Alternatively, gas separation membranes may be polymerized directly onto a support membrane by various techniques. In some cases, this involves coating the support with a prepolymer solution. For example, a silicone rubber layer is typically applied to a composite in prepolymer form and then cured to form the finished polymer. In other cases, the agent involved is not a prepolymer of the finished material, and more fundamental chemical changes are involved. For example, reverse osmosis membranes can be produced by interfacial polymerization, as disclosed in U.S. Patent No. 5,629,997 or U.S. Patent No. 5,629,997. U.S. Patent No. 5,629,997 discloses a method for producing gas separation membranes in which an ultrathin selective layer is formed directly on a support by plasma polymerization. U.S. Patent No. 5,629,997 discloses a method for producing polyimide membranes in which a polyamic acid solution is applied to a polyimide support and the coated substrate is treated at high temperatures to convert the polyamic acid to polyimide by imide cyclization.

[0011] Therefore, polydimethylsiloxane (PDMS) is known as a typical rubbery polymer that does not undergo physical aging, but its permeability is significantly lower than that of glassy polymers. Patent Document 6 discloses the use of a composite membrane with a PDMS gutter layer coated on polyetherimide by a dip coating method, resulting in a CO2 permeability of 5,900 GPU.

[0012] On the other hand, glassy polymers such as poly(1-trimethylsilyl-1-propyne) (PTMSP) are high-free-volume materials with very high gas permeability (47,000 GPU), but low selectivity. U.S. Patent No. 6,299,499 discloses that PTMSP gutter layers initially exhibited a maximum CO permeability of 42,100 GPU, which decreased to 850 GPU after 24 hours of aging. Furthermore, the incorporation of PDMS resulted in a 35% decrease in relative CO permeability after approximately 2,800 minutes of aging, whereas PTMSP exhibited an 80% decrease in relative permeability after only 700 minutes of aging. This highlights the susceptibility of PTMSP to physical aging, a gradual, time-dependent process in which polymer chains rearrange into denser configurations. Physical aging reduces the free volume within the polymer, hindering gas permeability and resulting in reduced membrane performance.

[0013] Amorphous perfluoropolymers (Teflon™ AF, Solvay's Hyflon®, and AGC Chemicals' Cytop®) are polymers completely devoid of crystalline regions. Most of their structures are disordered and irregular. They are known for their excellent chemical resistance and stability due to the strength of the carbon-fluorine bond. The bulky fluorine atoms cause steric hindrance to gas diffusion, resulting in low to moderate gas permeability (200 CO2 barrier), ultimately reducing gas selectivity and limiting their use as the separation layer in membranes.

[0014] US Patent No. 5,999,949 describes a composite membrane having a gas separation layer made of a fluorinated ionomer and a gutter layer, in which the gutter layer is prepared by solution casting a fluorinated polymer material, such as Teflon AF2400, pre-dissolved in a fluorinated solvent onto a porous layer support.

[0015] Additionally, the solvents required to process Teflon™ AF can be problematic: solvents such as Fluorinert® 770 are often highly fluorinated and are toxic, expensive, and difficult to handle, posing significant challenges for large-scale membrane production.

[0016] Another important issue is that many membrane materials are unable to absorb NOx present in flue gases and other emissions streams. x , S.O. x , susceptible to degradation by contaminants such as H2S.

[0017] Although there are gas separation membranes in the literature and prior art that offer optimal properties of high permeability and high selectivity, most of the membranes mentioned have a lifespan of about three years or less, below which frequent membrane replacement significantly increases operational costs.

[0018] US Patent No. 4,602,922 US Patent No. 4,277,344 US Patent No. 4,559,139 US Patent No. 4,581,043 US Patent No. 4,440,643 International Publication No. 2020 / 028079 International Publication No. 2022 / 015088 US Patent No. 10,399,044 US Patent No. 4,230,463 US Patent No. 9,403,120 US Patent No. 11,077,405 JP 8-208989 A JP 2011-012114 A JP 2002-232305 A JP 8-134103 A International Publication No. 2014 / 181747 Russian Patent Application Publication No. 2410397

[0019] Kattula, Moon, et al. "Designing ultrathin film composite membranes: the impact of a gutter layer." Scientific reports 5.1 (2015): 15016.O Selyanchyn et al., Critical Role of the Molecular Interface in Double-Layered Pebax-1657 / PDMS Nanomembranes for Highly Efficient CO2 / N2 Gas Separation, ACS Applied Materials & Interfaces, 2020, 12, 29, 33196-33209.Finkelshtein, E. Sh, et al. "Addition-type polynorbornenes with Si (CH3) 3 side groups: synthesis, gas permeability, and free volume." Macromolecules 39.20 (2006): 7022-7029.Chapala, Pavel P., et al. "A novel, highly gas-permeable polymer representing a new class of silicon-containing polynorbornens as efficient membrane materials." Macromolecules 48.22 (2015): 8055-8061.Yu, Shuwen, et al. "High-performance microporous polymer membranes prepared by interfacial polymerization for gas separation." Journal of Membrane Science 573 (2019): 425-438.

[0020] A key problem to be solved is achieving gas separation membranes that combine high CO permeability and high CO / N selectivity while maintaining long-term stability and resistance to physical and chemical aging. Traditional materials such as polydimethylsiloxane (PDMS) are flexible and have relatively high gas permeability, but require crosslinking and have low CO permeability, limiting their performance. In contrast, materials such as poly(1-trimethylsilyl-1-propyne) (PTMSP) have high initial CO permeability but experience a significant degradation in performance with physical aging.

[0021] There is a need for gas separation membranes that do not require crosslinking, have improved thermal stability and chemical resistance, and offer improved CO permeability and selectivity without the drawbacks associated with existing materials. Siloxane-modified polymers, such as siloxane-modified pullulan and siloxane-modified norbornene, offer a promising solution by addressing the limitations of both PDMS and PTMSP due to their unique chemical structure and advantageous properties.

[0022] The core of the present invention is the use of a siloxane-modified polymer as the separation functional layer. Polymers having an organosiloxane skeleton include polyorganosiloxanes and siloxane-modified polymers in which an organosiloxane skeleton has been introduced into the molecular chain by block copolymerization or graft polymerization. Examples of such polymers include the siloxane-modified pullulan polymer described in Patent Document 12, the siloxane-modified cycloolefin polymer described in Patent Document 13, and the siloxane-modified polyimide described in Patent Document 14.

[0023] In the present invention, siloxane-modified polymers such as siloxane-modified pullulan and / or siloxane-modified norbornene are used, for example, trimethylsiloxysilylcarbamoylpullulan, TSPL-30-ID and TSPL-30-D5 (hereinafter referred to as siloxane-modified pullulan) manufactured by Shin-Etsu Chemical Co., Ltd., Japan, and norbornene / tris(trimethylsiloxy)silylnorbornene copolymer, NBN-30-ID (hereinafter referred to as siloxane-modified norbornene) manufactured by Shin-Etsu Chemical Co., Ltd., Japan, and combinations thereof.

[0024] Due to their unique chemical structure, siloxane-modified pullulan and / or siloxane-modified norbornene are particularly promising candidates for gas separation membranes. Without intending to be bound by theory, it is believed that the incorporation of siloxane groups confers several advantageous properties. The siloxane groups increase the hydrophobicity of the polymer, reducing water absorption and improving performance in humid conditions. Furthermore, the presence of siloxane groups improves the thermal stability of the membrane, allowing it to maintain structural integrity and performance even at high temperatures.

[0025] Siloxane modified polymers contain NO x , S.O. x , and exhibits excellent resistance to chemical attack by contaminants such as HS, extending the operational life of the membrane. Without being bound by theory, the siloxane modification addresses all existing challenges, including physical and chemical aging effects, resulting in improved and stable gas separation performance.

[0026] The unique combination of siloxane modification and the inherent properties of pullulan and norbornene significantly enhances CO permeability and CO / N selectivity, making these materials ideal for efficient and effective gas separation. These properties make siloxane-modified pullulan and siloxane-modified norbornene highly suitable for use in gas separation membranes, offering a balance of high permeability, selectivity, and long-term stability in demanding industrial applications.

[0027] Unlike silicone rubber and many other polymers, our materials are applied directly as a polymer solution and do not require curing, heat treatment, or other chemical reactions for polymerization, so fabrication of the composite is a simple, one-step process.

[0028] The present invention has been completed based on the above findings, and is exemplified below.

[0029] [Aspect 1] A gas separation membrane comprising a separation functional layer, the separation functional layer comprising a matrix polymer selected from the group consisting of: (a) siloxane-modified pullulan, (b) siloxane-modified norbornene, and (c) a combination thereof. [Aspect 2] The gas separation membrane of Aspect 1, wherein the matrix polymer comprises (a) siloxane-modified pullulan. [Aspect 3] The gas separation membrane of Aspect 2, wherein the siloxane-modified pullulan comprises a carbamoyl group or a carbamic acid group. [Aspect 4] The gas separation membrane of Aspect 3, wherein the carbamoyl group is a trialkylsiloxysilylcarbamoyl group. [Aspect 5] The gas separation membrane of Aspect 4, wherein the alkyl group of the trialkylsiloxysilylcarbamoyl group is selected from the group consisting of methyl, ethyl, propyl, and butyl. [Aspect 6] The gas separation membrane according to any one of Aspects 1 to 5, wherein the matrix polymer comprises (b) a siloxane-modified norbornene, and the siloxane-modified norbornene comprises a silicon-substituted norbornene structure. [Aspect 7] The gas separation membrane according to Aspect 6, wherein the siloxane-modified norbornene has an exosilicon-substituted norbornene structure. [Aspect 8] The gas separation membrane according to any one of Aspects 1 to 7, wherein the separation functional layer has a thickness of 0.01 to 50 μm. [Aspect 9] The gas separation membrane according to any one of Aspects 1 to 8, wherein the gas separation membrane has a CO2 permeability of 800 GPU or more and a CO2 / N2 selectivity of 5 or more, when measured at 25°C. Aspect 10: The gas separation membrane according to any one of Aspects 1 to 9, wherein the gas separation membrane exhibits a change in CO permeability of less than 70% after 100 hours of exposure to 60°C, when measured at 25°C, and a change in CO / N selectivity of less than 20% after 100 hours of exposure to 60°C. Aspect 11: The gas separation membrane exhibits a change in CO / N selectivity of less than 50 ppm NO at 80°C, when measured at 25°C. x Less than 70% change in CO2 permeability after 32 hours of exposure to 50 ppm NO at 80°C xThe gas separation membrane according to any one of Aspects 1 to 10, wherein the change in CO2 / N2 selectivity after 32 hours of exposure to a gas separation membrane according to any one of Aspects 1 to 11 is less than 20%. [Aspect 12] The gas separation membrane according to any one of Aspects 1 to 11, wherein the separation functional layer is supported on a porous support layer. [Aspect 13] A method for separating a predetermined gas from a mixed gas, comprising selectively passing the predetermined gas in the mixed gas through the gas separation membrane according to any one of Aspects 1 to 12, wherein the predetermined gas is at least one gas selected from the group consisting of hydrocarbons and gases containing at least one of a hydrogen atom, a sulfur atom, an oxygen atom, and a nitrogen atom. [Aspect 14] The method according to Aspect 13, wherein the predetermined gas is at least one gas selected from the group consisting of H2, HS, CO, CO2, an alkane, an alkene, N2, and O2. [Aspect 15] A gas separation system comprising the gas separation membrane according to any one of Aspects 1 to 12. [Aspect 16] The gas separation system of Aspect 15, further comprising a feed gas inlet for receiving the mixed gas, and a permeate gas outlet for discharging the predetermined gas. [Aspect 17] The gas separation system of Aspect 15 or 16, wherein the gas separation membrane has a spirally wound modular configuration. [Aspect 18] The gas separation system of any one of Aspects 15 to 17, wherein the gas separation membrane has a plate and frame modular configuration. [Aspect 19] The gas separation system of any one of Aspects 15 to 17, wherein the gas separation membrane has a hollow fiber modular configuration. [Aspect 20] A method for producing the gas separation membrane of any one of Aspects 1 to 12, comprising the steps of: dissolving a siloxane-modified polymer in a solvent to prepare a coating solution; applying the obtained coating solution to a surface of a support layer; and drying the coated surface at a temperature below the melting point of the support layer to form a separation functional layer on the support layer.[Aspect 21] A method for producing the gas separation membrane according to any one of Aspects 1 to 12, comprising the steps of: dissolving a siloxane-modified polymer in a solvent to prepare a coating solution; immersing the surfaces of hollow fibers in the obtained coating solution; and drying the coated surfaces at a temperature below the melting point of the hollow fibers to form a separation functional layer on the hollow fibers.

[0030] The present inventors have found that the above problems can be solved by using siloxane-modified polymers, i.e., siloxane-modified pullulan, siloxane-modified norbornene, and combinations thereof, as the separation functional layer. More specifically, the following advantages are achieved: - Ease of manufacturing: By using materials that do not require crosslinking during coating, the manufacturing process is simplified, the pot life of the coating solution is extended, and the overall efficiency of membrane manufacturing is improved. - Chemical and thermal stability: Siloxane modification provides the membrane with excellent chemical and thermal stability, especially in the case of NO. x and SO x This ensures durability in harsh operating environments where gases are present. Furthermore, the hydrophobic nature of the siloxane moiety improves the membrane's moisture resistance, further extending its operational life. High permeability: The enhanced structural properties of siloxane-modified pullulan and siloxane-modified norbornene reduce transport resistance, maximize gas permeation flux across the membrane, and improve separation performance. Improved CO2 / N2 selectivity: The CO2 / N2 selectivity of siloxane-modified pullulan and siloxane-modified norbornene is superior to that of PDMS and PTMSP, improving the balance between performance and manufacturability.

[0031] FIG. 1 is a schematic diagram showing the operation of a gas separation membrane (film-like) according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the operation of a gas separation membrane (fibrous) according to one embodiment of the present invention. FIG. 3 shows the evaluation of the relative CO permeability and heat aging resistance of the gas separation membranes obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2. FIG. 4 shows the evaluation of the relative CO / N selectivity and heat aging resistance of the gas separation membranes obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2. FIG. 5 shows the evaluation of the relative CO permeability and NO permeability of the gas separation membranes obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2. x6 shows the evaluation of aging resistance. x 7 shows the thickness dependency of the performance of the gas separation membranes obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2. The results show the evaluation of aging resistance.

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it goes without saying that those skilled in the art can appropriately change or improve the design based on their ordinary knowledge without departing from the spirit of the present invention.

[0033] In one embodiment, the present invention provides a gas separation membrane comprising at least a portion of a separation functional layer, the gas separation membrane being in the form of a film or fiber, and the separation functional layer comprising a siloxane-modified polymer as the primary membrane material. The siloxane-modified polymer functions as a "matrix," which refers to the primary polymer material that constitutes the majority of the separation functional layer and provides the structural framework. It forms a continuous polymer phase or skeleton into which other components, such as fillers and additives, can be incorporated.

[0034] The gas separation membranes of the present invention include a separation functional layer designed to selectively separate a first gas component from at least a second gas component present in a mixed gas feed stream. The present invention also covers free-standing separation functional layers, which means that the gas separation membrane does not necessarily require a support layer, which may be attached to provide mechanical strength.

[0035] In some embodiments, the separation functional layer may be supported by a support layer. The separation functional layer may be bonded to the support layer by any suitable means. The support layer provides mechanical robustness to the gas separation membrane. The support layer may be in either a film or fiber form. The portion of the support layer that does not form the separation functional layer does not have a separation function and may only be capable of controlling the flow of gas.

[0036] The system separates any substance present in a gaseous state, including, but not limited to, components containing oxygen (O), carbon (C), hydrogen (H), nitrogen (N), chlorine (Cl), and fluorine (F) atoms. Examples of first and second gaseous components that may be separated include, but are not limited to: CO (first) and N (second) in flue gas streams; CO (first) and CH (second) in natural gas streams; O (first) and N (second) in air separation; H (first) and CO / CH / N (second) in hydrogen purification; hydrocarbons such as C3H8 (first) and CH / N (second) in olefin / paraffin separation; HO (first) and alcohols (second) in pervaporation processes; and HO, Ar, He, Ne (first) and various other gases (second) in industrial applications.

[0037] When the gas separation membrane having a separation function layer of the present invention is combined with a support layer, the shape thereof is not limited, and it can be in any shape such as a film or fiber.

[0038] Gas separation membranes in film form offer significant advantages due to the simplicity of the manufacturing process. Any method for producing multilayer films can be used. Membranes can be easily cast onto support layers using techniques such as roll-to-roll processing, solution casting, dip coating, spin coating, lamination, phase inversion, and thermal evaporation. These methods enable continuous production, improving efficiency and scalability. As a result, manufacturing and operating costs are reduced, making this approach suitable for industrial applications.

[0039] Furthermore, film-type gas separation membranes have the important advantage that their thin, uniform structure results in a low pressure drop across the membrane, facilitating gas flow.

[0040] During operation, the mixed gas feed contacts the separation functional layer on the feed side of the membrane. The separation functional layer selectively permeates a first gas component, concentrating it on the permeate side. At the same time, a second gas component has low permeability through the separation functional layer and travels along the feed flow direction in a retentate or retentate stream, depleting the first component (see Figure 1).

[0041] U.S. Patent No. 5,929,699 (the entire contents of which are incorporated herein by reference) discloses a membrane gas separation system utilizing a flat plate or film composite membrane. The porous substrate does not provide a separation function, but rather provides mechanical strength, ease of handling, and the ability to function as a support base for an ultra-thin separation layer.

[0042] U.S. Patent No. 6,277,699 (the entire contents of which are incorporated herein by reference) discloses high-performance flat-sheet composite membranes from Membrane Technology Research, Inc. that contain a selectively fluorinated polymer layer useful for desulfurizing natural gas by removing CO and H S, as well as other applications such as enriching O in air.

[0043] When the gas separation membrane is in a fibrous form, it preferably consists of bundles or aggregates of separate continuous fiber filaments that are essentially loosely unbonded to one another. This unbonded fiber configuration differs from the consolidated fibers of nonwoven fabrics formed by bonding methods such as needlepunching, thermal calendering, hydroentangling, etc., and also differs from the highly ordered, intertwined weave patterns created during the weaving process of textiles.

[0044] It has advantages such as being able to increase the membrane area per unit volume compared to a film-like membrane, and also has a greater resistance to forces applied in the cross-sectional direction, making it possible to operate at high pressures, which is preferable because it allows for highly efficient gas membrane separation.

[0045] During operation, a mixed gas feed enters the hollow fiber membrane and flows through the lumen of the hollow fiber. The separating functional layer selectively allows a first gas component to permeate from the lumen side to the shell side. The permeate gas, enriched in the first component, is collected on the shell side.

[0046] At the same time, the second gas component becomes less permeable through the separation functional layer and proceeds along the flow direction in the bore side, depleting the first component. This depleted stream, called the retentate or split-off, exits the opposite end of the fiber (see Figure 2).

[0047] U.S. Patent No. 6,277,629 (the entire contents of which are incorporated herein by reference) discloses hollow fiber gas separation membranes made of polymer gels with hollow fiber supports based on polyethersulfone or polyvinylidene fluoride for gas separation of carbon dioxide and olefins.

[0048] The support layer is a film-like or fibrous component that has gas permeability and provides the gas separation membrane with mechanical strength and structure, such as a porous layer, woven fabric, or nonwoven fabric. The gas permeable support layer may be one layer or two or more layers, and in the case of two or more layers, the layers may be the same or different. The thickness of the gas permeable support layer is preferably 1 to 3,000 μm, more preferably 5 to 1,000 μm, and even more preferably 10 to 500 μm.

[0049] Materials for forming the gas permeable support layer include, but are not limited to, polymer compounds such as thermosetting resins, thermoplastic resins, and inorganic materials.

[0050] Examples of thermoplastic resins used for the support layer include, but are not limited to: polyacrylonitrile (PAN), polyethersulfone (PES), polyphenylene sulfide (PPS), polysulfone (PSf), polystyrene, polyketone, polyetheretherketone, polycarbonate, polystyrene, poly(methyl methacrylate), polyphenylene oxide, polyvinyl alcohol, polylactic acid membranes using woven or nonwoven fabrics; fluoropolymers such as polyvinylidene fluoride (PVDF) membranes and polytetrafluoroethylene (PTFE) membranes using uniaxially stretched films; cellulose polymers such as cellulose acetate membranes using biaxially stretched films; polyolefins such as monolayer polypropylene (PP) membranes produced by uniaxial and biaxial stretching; polyethylene (PE) membranes using three-layer PP / PE / PP porous films produced by wet lamination. Composite membranes consisting of a single layer of PP / PE laminated onto a nonwoven fabric by thermal bonding or adhesive lamination; mixed matrix membranes combining organic and inorganic components.

[0051] Examples of thermosetting resins used in the matrix include, but are not limited to, unsaturated polyester resins, alkyd resins, melamine resins, urea resins, polyimide resins, diallyl phthalate resins, lignin resins, epoxy resins, urethane resins, etc. Examples of thermosetting resins also include copolymers thereof, modified products thereof, and blend resins containing two or more of these.

[0052] Examples of inorganic materials used for the support layer include, but are not limited to, zeolite, silica, alumina, metal materials, carbon materials, etc. For example, ceramic membranes with inorganic coatings, zeolite-based membranes, etc. can be used.

[0053] <Separation Functional Layer> The core of the present invention is the use of a siloxane-modified polymer as the separation functional layer. Polymers having an organosiloxane skeleton include polyorganosiloxanes and siloxane-modified polymers in which an organosiloxane skeleton has been introduced into the molecular chain by block copolymerization or graft polymerization. Examples include the siloxane-modified pullulan polymer described in Patent Document 12, the siloxane-modified cycloolefin polymer described in Patent Document 13, and the siloxane-modified polyimide described in Patent Document 14. As demonstrated in the present invention, siloxane-modified pullulan and siloxane-modified cycloolefin polymers, such as siloxane-modified polynorbornene, are particularly preferred because they have excellent physical and chemical stability and CO2 / N2 selectivity superior to existing materials.

[0054] While the present invention is not bound by any theory, it is believed that the incorporation of siloxane modifications significantly improves material properties by providing superior thermal stability and physical and chemical resistance compared to existing polymers. These improvements enable siloxane-modified polymers to maintain their functional integrity over a wider range of conditions, leading to more reliable and efficient separation processes.

[0055] The siloxane-modified pullulan compound used in the present invention, represented by the following formula (1), can be obtained by reacting a silicone compound containing terminal isocyanate groups, such as organopolysiloxane, with a pullulan compound in a solvent, such as an organic solvent. The reaction between the silicone compound and the pullulan compound can be carried out using a conventional method, such as the method described in Patent Document 15.

[0056] The siloxane-modified pullulan compound according to the present invention can be obtained by a known method as described above, and specifically, is trimethylsiloxysilylcarbamoylpullulan (TSPL). Commercially available products that can be used include TSPL-30-D5 (manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in decamethylcyclopentasiloxane and TSPL-30-ID (manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in isododecane.

[0057] In the formula, PL- represents the glucose residue of pullulan, and each R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably a methyl group, and each R 2 is a monovalent hydrocarbon radical having 1 to 10 carbon atoms, preferably a methyl radical, or a radical of the general formula O—SiR 3 and each R is a triorganosiloxy group represented by 3 is a monovalent hydrocarbon radical having 1 to 8 carbon atoms, preferably a methyl radical; the subscript n is a positive integer not exceeding 10, preferably 3; the subscript a is 0 or 1; and the subscript b is 0, 1, or 2.

[0058] The average number of silicone compounds (degree of substitution) per unit sugar of the pullulan compound is preferably 0.5 to 2.5, and the average molecular weight of the silicone-modified pullulan compound is 50,000 to 10,000,000.

[0059] R 1 ~R 3Specific examples of unsubstituted or substituted monovalent hydrocarbon groups represented by the formula (I) include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, heptyl, and octyl. Furthermore, alkenyl groups such as vinyl and allyl, aryl groups such as phenyl, and aralkyl groups such as benzyl may also be included. Some or all of the hydrogen atoms in these groups may be substituted with halogen atoms such as fluorine, bromine, and chlorine, or with cyano groups. Examples of such substitutions include chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, and cyanoethyl groups. R 1 ~R 3 As the unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I), unsubstituted or halogen-substituted monovalent hydrocarbon groups are preferred, and unsubstituted monovalent hydrocarbon groups are particularly preferred. Of these, alkyl groups or aryl groups, particularly methyl groups, ethyl groups, and phenyl groups, are most preferred because they are easy to synthesize and provide stability to the compound.

[0060] In particular, trimethylsiloxysilyl groups have been found to be particularly advantageous as they enhance the solubility and processability of the modified pullulan, leading to increased flexibility in the film, making it ideal for applications where ease of processing and flexibility are paramount.

[0061] Furthermore, the siloxane-modified pullulan preferably contains carbamoyl or carbamic acid groups. It is advantageous to attach the carbamoyl or carbamic acid groups to trimethylsiloxysilyl groups and then graft them onto the pullulan backbone. These functional groups have been shown to significantly increase CO2 permeability relative to other gases, thereby improving the overall performance of the material in gas separation applications. This increased CO2 selectivity helps to resolve issues related to the physical and chemical aging of the membrane and maintain performance over long periods of use.

[0062] The carbamoyl group may be a trialkylsiloxysilylcarbamoyl group. The alkyl group of the trialkylsiloxysilylcarbamoyl group may be selected from the group consisting of methyl, ethyl, propyl, and butyl, such as a trimethylsiloxysilylcarbamoyl group. Trimethylsiloxysilylcarbamoyl pullulan involves a simpler modification. In this case, the trimethylsiloxy group is directly bonded to the carbamoyl group and then grafted onto the pullulan backbone. This modification is less bulky than tri(trimethylsiloxy)silylpropylcarbamic acid, suggesting easier synthesis and the possibility of more appropriate modification to the polymer's properties. The simpler structure helps maintain high CO2 permeability and selectivity while ensuring long-term stability.

[0063] In other disclosures, such as U.S. Patent No. 5,999,103, the compound is sometimes referred to as tri(trimethylsiloxy)silylpropylcarbamate pullulan. This structure involves a large and complex modification in which tri(trimethylsiloxy)silyl groups are attached to propylcarbamate and then grafted onto the pullulan backbone. The presence of three trimethylsiloxy groups indicates significant increases in bulk and hydrophobicity, potentially resulting in significant changes in the polymer's properties. These changes include improved CO2 permeability and selectivity, and improved resistance to physical and chemical aging, making it highly suitable for long-term gas separation applications.

[0064] In addition to siloxane-modified pullulan, siloxane-modified norbornene is also a promising candidate for gas separation membranes due to its unique chemical structure. Norbornene, a cycloolefin, is known for its rigid ring structure, which contributes to its high mechanical strength and thermal stability.

[0065] Modification with siloxane groups improves flexibility and hydrophobicity, further enhancing the properties of gas separation membranes. This siloxane modification improves resistance to physical and chemical aging, contributing to the membrane's long-term durability. Siloxane-modified norbornene has improved CO2 permeability and CO2 / N2 selectivity, making it highly effective for gas separation applications.

[0066] Siloxane-modified norbornenes, specifically polynorbornenes, incorporate an organosiloxane backbone into their structure. This backbone consists of alternating silicon and oxygen atoms, with organic groups bonded to at least some of the silicon atoms. The organic groups are alkyl, aryl, aralkyl, or alkenyl groups, each containing 1 to 30 carbon atoms, and may be substituted with halogen atoms. Siloxane-modified norbornenes can include silicon-substituted norbornene structures, such as exosilicon-substituted norbornenes.

[0067] Siloxane-modified norbornene compounds are represented by addition polymerization and methods from substituted polynorbornenes or other siloxane-modified cycloolefins.

[0068] These materials can be synthesized by addition polymerization of cycloolefins such as 5-trimethylsilyl-2-norbornene, as disclosed in Non-Patent Document 4.

[0069] Other siloxane-modified cycloolefins can also be synthesized by addition polymerization of 3,3-bis(trimethylsilyl)tricyclonon-7-ene, as disclosed in Non-Patent Document 5 and Patent Document 17.

[0070] The method for preparing siloxane-modified cycloolefin compounds involves several key steps. First, a selected cycloolefin, such as 5-trimethylsilyl-2-norbornene or 3,3-bis(trimethylsilyl)tricyclonon-7-ene, is dissolved in an organic solvent, such as toluene or chloroform. An appropriate catalyst is then used to initiate addition polymerization, producing the desired polymer.

[0071] For copolymers such as norbornene / tris(trimethylsiloxy)silylnorbornene copolymer, synthesis involves a copolymerization process. Both monomers are dissolved in an organic solvent. A suitable catalyst is used to initiate the copolymerization, forming the desired copolymer. The resulting copolymer is purified by precipitation with a non-solvent, such as methanol, followed by filtration and drying under reduced pressure.

[0072] The methods disclosed in U.S. Patent No. 5,629,999 describe the synthesis and application of siloxane-modified norbornene polymers. By improving these processes and optimizing the polymer properties, the present invention provides improved materials suitable for a variety of applications, particularly in the formation of gutter layers in advanced material systems.

[0073] The siloxane-modified norbornene compound according to the present invention can be obtained by a known method as described above, and specifically, it is a norbornene / tris(trimethylsiloxy)silylnorbornene copolymer (NBN). A commercially available product that can be used is NBN-30-ID (manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in isododecane. The average molecular weight of the silicone-modified norbornene is 50,000 to 10,000,000.

[0074] Siloxane-modified polymers are known in the art, as in Patent Documents 12 to 16 cited herein, but their applications have been in the fields of cosmetics, skin care cosmetics, makeup cosmetics, hair cosmetics, quasi-drugs, etc. While the application of such polymers to gas separation has not previously been considered, the inventors have discovered that the properties of siloxane-modified pullulan and siloxane-modified norbornene provide a balance of high permeability, selectivity, and long-term stability in demanding industrial applications, making them highly suitable for use in gas separation membranes.

[0075] Therefore, the present invention has the advantage of solving the above-mentioned problems in the prior art. The present invention provides siloxane-modified pullulan and siloxane-modified norbornene, which can exhibit unique properties such as high CO permeability, high CO / N selectivity, and reduced physical and chemical aging.

[0076] The thickness of the separation functional layer is not limited and can be, for example, 0.01 to 50 μm, preferably 0.05 to 5 μm. Thinner films generally have higher gas permeability, but are more susceptible to defects and pinholes, which can reduce selectivity. Thicker films may have lower permeability than thinner films, but have improved mechanical stability and resistance to defects and pinholes. This is advantageous in applications where high selectivity is important, even at the expense of reduced gas permeability.

[0077] Separation function refers to the ability of a membrane to distinguish between gases and allow them to have different gas permeabilities. This is quantified by selectivity. Selectivity is defined as the ratio of gas permeabilities, with a minimum selectivity value of 1.1 for gas pairs including but not limited to O2 / N2, CO2 / N2, CO2 / CH4, and H2 / CO2. Gases passing through the membrane are analyzed by mass flow rate recorded in standard cubic centimeters per second (Horiba, S-TEC series), and gas permeability is calculated as follows: Permeability = [Flow Rate (cm 3 / s) × 10 -6 ] / [Membrane area (cm 2 ) × pressure (cmHg)] where 1 GPU = 10 -6 cm 3 (STP) / (cm 2 Selectivity is an important parameter and is calculated using the following formula: Selectivity = Gas Permeability (A) / Gas Permeability (B) A higher selectivity value indicates a better separation performance of the membrane for gas (A) than for gas (B). Gases evaluated herein include, but are not limited to, O, N, CO, H, and CH.

[0078] A gas separation membrane according to one embodiment of the present invention has a CO2 permeability of 800 GPU or more and a CO2 / N2 selectivity of 5 or more when measured at 25°C.

[0079] The present invention also relates to a method for separating a predetermined gas from a mixed gas, which method comprises selectively passing the predetermined gas in the mixed gas through a gas separation membrane of the present invention, wherein the predetermined gas is at least one gas selected from the group consisting of hydrocarbons and gases containing at least one of a hydrogen atom, a sulfur atom, an oxygen atom, and a nitrogen atom. The predetermined gas may be at least one gas selected from the group consisting of H, HS, CO, CO, alkanes, alkenes, N, and O.

[0080] In one embodiment of the present invention, the gas separation membrane exhibits reduced physical aging due to the composition of the separation functional layer compared to PDMS and PTMSP. Specifically, as summarized in Table 2, gas separation exhibits less than a 70% change in CO permeability and less than a 20% change in CO / N selectivity after exposure to 60°C for 100 hours.

[0081] In one embodiment of the present invention, the gas separation membrane has high chemical stability in the presence of water vapor, oxygen, and other contaminants such as NOx, compared to PDMS and PTMSP due to the composition of the separation functional layer. Specifically, the gas separation membrane can withstand 50 ppm NOx, as shown in Table 2. x Preferably, after exposure to a simulated gas containing HCl at 80° C. for 32 hours, the change in CO 2 permeability is less than 70% and the change in CO 2 / N 2 selectivity is less than 20%.

[0082] In addition to their water stability, gas separation membranes also have high chemical stability due to the composition of their separation functional layers. They are resistant to acids produced by water reactions, such as hydrochloric acid (HCl), nitric acid (HNO3), and sulfuric acid (H2SO4). They are also resistant to halogenated gases, such as fluorine (F2) and chlorine (Cl2). This enhanced stability allows the membranes to maintain their structural integrity and performance over long periods of time, making them suitable for a variety of industrial gas separation applications.

[0083] In gas separation processes, it is important to provide consistent performance in both throughput (measured by permeability) and purity (measured by selectivity). Gas separation system equipment is designed and sized for a specific range of throughput and purity. With this in mind, it is important that the permeability and selectivity of a gas separation membrane do not increase or decrease over time when exposed to temperature or the presence of contaminants. Therefore, the percent change in permeability and selectivity when exposed to temperature or the presence of contaminants is an important factor in selecting a gas separation membrane. However, percent change can include increases as well as decreases. The percentage change is the absolute difference between the initial CO2 permeability and CO2 / N2 selectivity (considered to be 100%) and the relative CO2 permeability and relative CO2 / N2 selectivity after aging. The percent change is calculated using the following formulas: % Change = |100 - Relative CO2 Permeability| % Change = |100 - Relative CO2 / N2 Selectivity|

[0084] A gas separation membrane according to one embodiment of the present invention exhibits a change in CO permeability of less than 70% after 100 hours of storage (physical aging) at 60°C, and a change in CO / N selectivity of less than 20% after 100 hours of storage (physical aging) at 60°C, as measured at 25°C.

[0085] The gas separation membrane according to one embodiment of the present invention has a NOx content of 50 ppm at 80°C as measured at 25°C. x The change in CO2 permeability before and after 32 hours of exposure (chemical aging) was less than 70%, and the x The change in CO2 / N2 selectivity before and after 32 hours of exposure (chemical aging) is less than 20%.

[0086] <Method for Producing Gas Separation Membrane> Hereinafter, a method for producing a gas separation membrane according to one embodiment of the present invention will be described, but the method is not limited to the following method.

[0087] The gas separation membrane of this embodiment includes at least the following steps: a step of dissolving a siloxane-containing polymer such as siloxane-modified pullulan, siloxane-modified norbornene, or a combination thereof in a solvent to prepare a coating solution (coating solution preparation step); a step of applying the obtained coating solution to the surface of a support layer (coating step); and a step of drying the coated surface at a temperature lower than the melting point of the support layer to form a gas separation functional layer (drying step).

[0088] <Coating Liquid Production Process> The coating liquid of this embodiment can be produced by dissolving a desired gas separating siloxane-modified polymer in an organic solvent.

[0089] The concentration of the siloxane-modified pullulan polymer and / or siloxane-modified norbornene polymer in the coating liquid is preferably 0.05% by mass or more and 50% by mass or less, and more preferably 0.5% by mass or more and 30% by mass or less.

[0090] If the concentration is less than 0.05% by weight, the resulting gas separation membrane will have low selectivity, insufficient mechanical strength, and insufficient viscosity, which may result in poor membrane formation and problems such as pore soaking. Conversely, if the concentration is more than 30% by weight, the solution will have excessively high viscosity, making uniform coating difficult and potentially causing defects in the membrane structure.

[0091] The coating solution may include organic solvents with a low polarity index (non-polar), including, but not limited to, alkanes (pentane, hexane, heptane, isooctane, isododecane, etc.), cycloalkanes (cyclohexane, cyclopentane, etc.), aromatic hydrocarbons (benzene, toluene, xylene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), halogenated solvents (dichloromethane, chloroform, etc.), esters (ethyl acetate, butyl acetate, etc.), ketones (acetone, methyl ethyl ketone, etc.), certain alcohols (isopropanol, butanol, etc.), petroleum ether, n-butyl chloride, etc. These organic solvents may be used alone or in combination of two or more.

[0092] From the viewpoint of coating productivity, solvents with low polarity are preferred because they evaporate quickly. However, solvents with low polarity often have low flash points, which can pose a safety hazard during film production. To increase the flash point of the entire coating solution, it is preferable to add solvents or additives with high flash points.

[0093] The coating solution may contain only the above components, or may further contain optional components such as surfactants, pH adjusters, thickeners, antioxidants, and preservatives.

[0094] <Coating Step> In the coating step for forming a film-like gas separation membrane, the support layer is brought into contact with a coating solution, as described above. Examples of the contacting method include a roll-to-roll method, solution casting, dip coating, spin coating, lamination, phase inversion, and thermal evaporation.

[0095] In another embodiment, the gas separation membrane is fibrous. As a support, a preformed hollow fiber is contacted with the coating solution as described above. Examples of contacting methods include dip coating, spray coating, electrospinning, or any method of depositing the coating solution onto a support layer that produces an acceptable coating.

[0096] The temperature of the coating liquid in contact with the support layer is preferably 0° C. or higher and 100° C. or lower, more preferably 20° C. or higher and 80° C. or lower. If the contact temperature is too low, the coating liquid may not be uniformly applied to the support layer, and conversely, if the contact temperature is too high, the solvent in the coating liquid may evaporate during contact. Furthermore, exposing the support layer to excessively high temperatures above 100° C. may cause thermal degradation, melting, or physical deformation of the support material, risking the loss of its structural integrity and pore morphology.

[0097] <Drying step> After the coating step, a drying step (solvent removal step) is performed. In this drying step, the coated support layer is heated at a temperature lower than the melting point of the polymer that constitutes the support layer. This allows the coated film to be properly dried, and a separation functional layer is formed on the support layer.

[0098] The drying step is preferably carried out in an environment with a temperature between 10°C and 160°C, more preferably between 40°C and 120°C. As an example, for roll-to-roll coated materials, the drying time is defined by the time the sample remains in the oven. If the oven length is 10 meters and the line speed is 15 meters / minute, the drying time is 40 seconds. The drying time is preferably between 10 seconds and 3 hours, more preferably between 30 seconds and 1 hour.

[0099] If the drying temperature is too low, the drying time is too short, or both, problems such as insufficient solvent removal may occur. If the drying temperature is too high, the drying time is too long, or both, there is a risk of thermal degradation, melting, or physical deformation of the support material, compromising its structural integrity and pore morphology. These problems lead to increased production costs and reduced production efficiency.

[0100] Gas Separation Systems Gas separation systems utilizing various types of membranes are well known in the art. U.S. Patent No. 6,275,999 (the entire contents of which are incorporated herein by reference) discloses a membrane gas separation system for removing CO2 from a natural gas stream.

[0101] The present invention also relates to a gas separation system incorporating a membrane for selectively separating a first gas component from at least a second gas component in a mixed gas feed stream. The gas separation system of this embodiment includes a gas separation membrane according to any one of the above embodiments of the present invention. The gas separation system may further include a feed gas inlet for receiving the mixed gas and a permeate outlet for discharging the selected gas.

[0102] In one embodiment, the separation system includes a housing or vessel that encloses a module, the module includes a gas separation membrane, and the separation functional layer includes siloxane-modified pullulan and / or siloxane-modified norbornene.

[0103] The module is integrated into a housing that allows a mixed gas feed to contact the feed side of the membrane, which is selectively permeable to a first gas component, thereby enriching the permeate stream in that component and depleting the retentate stream in that component.

[0104] Gas separation membranes can be configured in spiral-wound, plate-and-frame, or hollow fiber module configurations. Spiral-wound module configurations mean that the gas separation membranes are spirally wrapped around a central perforated tube, forming multiple layers. The feed gas stream enters the module and flows through the gaps between adjacent membrane layers, while the permeate gas passes through the membrane layers toward the central tube. This configuration maximizes surface area for efficient gas separation, making it ideal for large-volume applications such as industrial gas processing and air separation.

[0105] The plate-and-frame module configuration means that the gas separation membrane is sandwiched between flat plates, with alternating feed and permeate channels formed between adjacent plates. Feed gas enters the module through one set of channels, while permeate gas passes through the membrane and is collected in another set of channels. This configuration offers flexibility in modular design and scalability, making it suitable for a variety of gas separation processes, including small-scale applications and pilot plants.

[0106] The hollow fiber modular configuration means that the gas separation membrane is composed of many hollow fibers bundled within a housing. The feed gas is introduced into the lumen of the hollow fibers, and the permeate gas diffuses through the fiber walls and collects on the outside of the fibers. This configuration has a high surface area-to-volume ratio, allowing for a compact modular design, making it suitable for applications where space is limited, such as mobile gas separation units and compact gas purification systems.

[0107] This membrane gas separation system allows for the efficient separation and recovery of target gas components from multi-component gas mixtures. Potential applications include, but are not limited to: CO2 (first) and N2 (second) in flue gas streams; CO2 (first) and CH4 (second) in natural gas streams; O2 (first) and N2 (second) in air separation; H2 (first) and CO2 / CH4 / N2 (second) in hydrogen purification; Hydrocarbons such as C3H8 (first) and CH4 / N2 (second) in olefin / paraffin separation; H2O (first) and alcohols (second) in pervaporation processes; H2O, Ar, He, Ne (first) and various other gases (second) in industrial applications.

[0108] The housing or container of the gas separation system of this embodiment includes at least a gas separation membrane, and the gas separation module is fixed to the housing or container by an adhesive, and the front side (outside) of the gas separation membrane is fixed by an adhesive. As long as it can separate the space to which the back side (inside) of the gas separation membrane belongs, any structure or shape is acceptable, such as a cylindrical shape or a casing shape.

[0109] It is preferable that the housing or container has a flow path for circulating the mixed gas and the separated gas between the space to which the front side of the gas separation membrane belongs and the space to which the back side of the gas separation membrane belongs, which are separated by the adhesive portion.

[0110] The material constituting the housing or container is not particularly limited as long as it has sufficient chemical resistance to the substances to be separated and sufficient durability at the operating temperature and pressure, and examples thereof include metal, synthetic resin, etc. The size of the housing or container can be appropriately set depending on the size, separation processing capacity, etc. of the gas separation module to be incorporated.

[0111] Examples and comparative examples are shown below to help better understand the present invention, but the present invention is not limited to the following examples.

[0112] The siloxane-modified pullulan compound according to the present invention is trimethylsiloxysilylcarbamoylpullulan (TSPL), and examples of commercially available products that can be used include TSPL-30-D5 (manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in decamethylcyclopentasiloxane and TSPL-30-ID (manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in isododecane.

[0113] The siloxane-modified norbornene compound according to the present invention is a norbornene / tris(trimethylsiloxy)silylnorbornene copolymer (NBN), and a commercially available product such as NBN-30-ID (manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in isododecane can be used.

[0114] For each example, the gas permeability and selectivity between CO2 and N2 were measured and evaluated as follows:

[0115] The entire separation membrane including the support was cut into a piece with a diameter of 46 mm, and a cellulose membrane filter (Whatman filter) was placed on the permeation side to prepare a permeation test sample. 2 The separation membrane was placed in a thermostatic chamber set at 60°C, and the gas was allowed to flow through the permeation side without any gas flow. After the contact exposure, the cell was cooled to room temperature and purged. 2 ) was passed through the permeation side under conditions of relative humidity 0%, temperature 25°C, and total pressure 200 kPa (gauge pressure), with CO2 and N2 as test gases flowing alone.

[0116] The gas passing through the membrane is analyzed by mass flow rate recorded in standard cubic centimeters per second (Horiba, S-TEC series), and gas permeation units are calculated as follows: Permeability = [Flow rate (cm 3 / s) × 10 -6 ] / [Membrane area (cm 2 ) × pressure (cmHg)] where 1 GPU = 10 -6 cm 3 (STP) / (cm 2s cmHg) CO2 / N2 selectivity is an important parameter and is calculated using the following formula: Selectivity = CO2 permeability (GPU) / N2 permeability (GPU) A higher selectivity value indicates that the membrane has better CO2 separation performance than N2 separation performance.

[0117] The present invention, which prevents physical and chemical aging, is compared to state-of-the-art materials known in the prior art. The following physical and chemical aging tests were evaluated:

[0118] [Heat Aging Test] Using each of the separation membranes prepared as described above, the carbon dioxide gas separation performance was evaluated as follows.

[0119] The entire separation membrane including the support was cut to a diameter of 46 mm, and a cellulose membrane filter (Whatman filter) was installed on the permeation side to prepare a permeation test sample. The effective gas permeation membrane area was 2.40 cm 2 It was.

[0120] As the test gas, a single gas of CO2 and N2 was supplied under the conditions of relative humidity 0%, temperature 25°C, and total pressure 200 kPa (gauge pressure), and was allowed to flow into the transmission side.

[0121] The gas passing through the membrane is analyzed by mass flow rate recorded in standard cubic centimeters per second (Horiba, S-TEC series), and gas permeation units are calculated as follows: Permeability = [Flow rate (cm 3 / s) × 10 -6 ] / [Membrane area (cm 2 ) × pressure (cmHg)] where 1 GPU = 10 -6 cm 3 (STP) / (cm 2 s cmHg) CO2 / N2 selectivity is an important parameter and is calculated using the following formula: Selectivity = CO2 permeability (GPU) / N2 permeability (GPU) A higher selectivity value indicates that the membrane has better CO2 separation performance than N2 separation performance.

[0122] Each sample was exposed to a temperature of 60°C in a static environment (no gas flow) for up to 100 hours (aging period). To evaluate the effect of physical aging on membrane performance, the relative CO2 permeability was calculated using the following formula: Relative CO2 permeability = 100 x (CO2 permeability (aged) / CO2 permeability (initial)). The percentage change is the absolute difference between the initial CO2 permeability (considered to be 100%) and the relative CO2 permeability after aging. The % change is calculated using the following formula: % change = |100 - relative CO2 permeability|

[0123] If the percent change in CO2 permeability was less than 20%, the stability was rated "excellent." If the percent change was greater than 20 but less than 70%, the stability was rated "good." If the percent change was greater than 70%, the stability was rated "poor."

[0124] The physical aging resistance of the membranes and the resulting relative permeability are shown in FIG.

[0125] To evaluate the effect of physical aging on membrane performance, the relative CO2 / N2 selectivity was calculated using the following formula: Relative CO2 / N2 selectivity = 100 x (CO2 / N2 selectivity (aged) / CO2 / N2 selectivity (initial)). The percentage change is the absolute difference between the initial CO2 / N2 selectivity (considered to be 100%) and the relative CO2 / N2 selectivity after physical aging. The % change is calculated using the following formula: % change = |100 - relative CO2 / N2 selectivity|

[0126] If the percent change in CO2 / N2 selectivity was less than 20%, the stability was rated "excellent." If the percent change was greater than 20 but less than 70%, the stability was rated "good." If the percent change was greater than 70%, the stability was rated "poor."

[0127] The membrane physical aging resistance and the resulting relative CO2 / N2 selectivity are shown in FIG.

[0128] [NO xExposure test and gas separation evaluation] The entire separation membrane including the support was cut into a diameter of 46 mm, and a cellulose membrane filter (Whatman filter) was installed on the permeation side to prepare a permeation test sample. The effective gas permeation membrane area was 2.40 cm 2 It was.

[0129] As the test gas, a single gas of CO2 and N2 was supplied under the conditions of relative humidity 0%, temperature 25°C, and total pressure 200 kPa (gauge pressure), and was allowed to flow into the transmission side.

[0130] The gas passing through the membrane is analyzed by mass flow rate recorded in standard cubic centimeters per second (Horiba, S-TEC series), and gas permeation units are calculated as follows: Permeability = [Flow rate (cm 3 / s) × 10 -6 ] / [Membrane area (cm 2 ) × pressure (cmHg)] where 1 GPU = 10 -6 cm 3 (STP) / (cm 2 s cmHg) CO2 / N2 selectivity is an important parameter and is calculated using the following formula: Selectivity = CO2 permeability (GPU) / N2 permeability (GPU) A higher selectivity value indicates that the membrane has better CO2 separation performance than N2 separation performance.

[0131] If the CO2 / N2 selectivity was greater than 8, the selectivity rating was rated "excellent." If the relative CO2 / N2 selectivity was greater than 5 but less than 8, the selectivity rating was rated "good." If the CO2 / N2 selectivity was less than 5, the selectivity rating was rated "poor."

[0132] Each sample was subjected to a chemical aging period of up to 32 hours under conditions of 90% relative humidity or higher, a flow rate of 500 sccm, a temperature of 80°C, and a total pressure of 200 kPa (gauge pressure). xThe cells were exposed to a simulated gas mixture of CO2 / N2 / O2 = 10 / 80 / 10 (volume ratio) containing 50 ppm or more of CO2 (including 4 ppm or more of NO2). After contact exposure, the cells were cooled to room temperature and purged. To evaluate the effect of chemical aging on membrane performance, the relative CO2 permeability was calculated using the following formula: Relative CO2 permeability = 100 x (CO2 permeability after chemical aging) / CO2 permeability (initial value)). The percentage change is the absolute difference between the initial CO2 permeability (considered to be 100%) and the relative CO2 permeability after chemical aging. The % change is calculated using the following formula: % change = |100 - Relative CO2 permeability|

[0133] If the percent change in CO2 permeability was less than 20%, the stability was rated "excellent." If the percent change was greater than 20 but less than 70%, the stability was rated "good." If the percent change was greater than 70%, the stability was rated "poor."

[0134] Membrane NO x The aging resistance and resulting relative CO2 permeability are shown in Figure 5.

[0135] To evaluate the effect of chemical aging on membrane performance, the relative CO2 / N2 selectivity was calculated using the following formula: Relative CO2 / N2 selectivity = 100 x (CO2 / N2 selectivity (aged) / CO2 / N2 selectivity (initial)). The percentage change is the absolute difference between the initial CO2 / N2 selectivity (considered to be 100%) and the relative CO2 / N2 selectivity after physical aging. The % change is calculated using the following formula: % change = |100 - relative CO2 / N2 selectivity|

[0136] If the percent change in CO2 / N2 selectivity was less than 20%, the stability was rated "excellent." If the percent change was greater than 20 but less than 70%, the stability was rated "good." If the percent change was greater than 70%, the stability was rated "poor."

[0137] Membrane NO x The chemical aging resistance and the resulting relative CO2 / N2 selectivity for .

[0138] The gas separation membranes of the Examples and Comparative Examples were produced according to the following specific structures and conditions. The thickness dependence of the performance of the resulting gas separation membranes of Examples 1, 2, Comparative Examples 1 and 2 is shown in FIG. 7 and Table 1.

[0139] [Example 1] Support layer: The microporous support layer is a polyacrylonitrile (PAN) sheet, specifically PAN #22C manufactured by TOMAC Co., Ltd. (Higashi Osaka) Separation function layer: The separation function layer is formed by applying a solution containing siloxane-modified pullulan to the PAN support layer.

[0140] Preparation of Coating Solutions: Siloxane-modified pullulan (Shin-Etsu Chemical Co., Ltd. TSPL-30-ID, 30 wt. % in isododecane) was directly diluted with cyclohexane by magnetic stirring at a temperature of 50°C for 1 hour. The solids content of siloxane-modified pullulan in the coating solutions was varied between 1.00%, 2.00%, 4.00%, 6.00%, 8.00%, and 10.00% by weight. The solids content was selected to achieve an appropriate viscosity range suitable for the coating process.

[0141] Coating and Drying: The coating solution is applied to a PAN substrate using a coating bar (wire bar) to a wet thickness of 4 μm. The coated membrane is dried at 50°C in an oven with air circulation, a line speed of 1 m / min, and an oven length of 1.5 m.

[0142] The evaluation results are shown in FIG.

[0143] [Example 2] Support layer: The microporous support layer is a polyacrylonitrile (PAN) sheet, specifically PAN #22C manufactured by TOMAC Co., Ltd. (Higashi Osaka) Separation functional layer: The separation functional layer is formed by applying a solution containing siloxane-modified norbornene.

[0144] Preparation of Coating Solutions: Siloxane-modified norbornene (NBN-30-ID, Shin-Etsu Chemical Co., Ltd., 30 wt. % in isododecane) was directly diluted with cyclohexane by magnetic stirring at a temperature of 50°C for 1 hour. The solids content of siloxane-modified norbornene in the coating solutions was varied between 1.00%, 2.00%, 4.00%, 6.00%, 8.00%, and 10.00% by weight. The solids content was selected to achieve an appropriate viscosity range suitable for the coating process.

[0145] Coating and Drying: The coating solution is applied to a PAN substrate using a coating bar (wire bar) to a wet thickness of 4 μm. The coated membrane is dried at 50°C in an oven with air circulation, a line speed of 1 m / min, and an oven length of 1.5 m.

[0146] The evaluation results are shown in FIG.

[0147] Comparative Example 1 Support layer: The microporous support layer is a polyacrylonitrile (PAN) sheet, specifically PAN #22C manufactured by TOMAC Corporation (Higashi Osaka). Separation functional layer: The separation functional layer is formed by coating a solution containing crosslinked amine-terminated polydimethylsiloxane (PDMS) with trimesoyl chloride. Non-Patent Document 5 describes layer formation by interfacial polymerization of amine-terminated PDMS and trimesoyl chloride.

[0148] Preparation of Coating Solutions: Aminopropyl-terminated PDMS (DMS-A35, Gelest, Inc.) was dissolved in cyclohexane to form the organic phase. 1,3,5-Benzenetricarbonyl trichloride (T1262, Tokyo Chemical Industry Co., Ltd., Japan) was dissolved in cyclohexane. The two solutions were brought into contact, allowing the amine groups to react with trimesoyl chloride. The reaction time was set to 10 minutes at room temperature. The solids content of aminopropyl-terminated PDMS and trimesoyl chloride in the coating solutions was varied between 1.00%, 2.00%, 4.00%, 6.00%, 8.00%, and 10.00% by weight. The solids content was selected to achieve an appropriate viscosity range suitable for the coating process.

[0149] Coating and Drying: The coating solution is applied to a PAN substrate using a coating bar to a wet thickness of 4 μm. The coated membrane is dried at 50°C in an oven with air circulation, a line speed of 1 m / min, and an oven length of 1.5 m.

[0150] The evaluation results are shown in FIG.

[0151] [Comparative Example 2] Support layer: The microporous support layer is a polyacrylonitrile (PAN) sheet, specifically PAN #22C manufactured by TOMAC Co., Ltd. (Higashi Osaka) Separation function layer: The separation function layer is formed by applying a solution containing poly(1-trimethylsilyl-1-propyne).

[0152] Preparation of Coating Solutions: Poly(1-trimethylsilyl-1-propyne) (PTMSP, Product No. SSP-070, Gelest, Inc.) was directly diluted in cyclohexane. 2 grams of PTMSP was redissolved in 98 grams of cyclohexane and magnetically stirred at 50°C for 1 hour. 4 grams of PTMSP was redissolved in 96 grams of cyclohexane and magnetically stirred at 50°C for 1 hour. 6 grams of PTMSP was redissolved in 94 grams of cyclohexane and magnetically stirred at 50°C for 1 hour. 8 grams of PTMSP was redissolved in 92 grams of cyclohexane and magnetically stirred at 50°C for 1 hour. 10 grams of PTMSP was coated in 90 grams of cyclohexane by magnetically stirring at 50°C for 1 hour. The solids content of PTMSP in the coating solutions was varied between 1.00%, 2.00%, 4.00%, 6.00%, 8.00%, and 10.00% by weight. The solids content was selected to achieve an appropriate viscosity range suitable for the coating process.

[0153] Coating and Drying: The coating solution is applied to a PAN substrate using a coating bar (wire bar) to a wet thickness of 4 μm. The coated membrane is dried at 50°C in an oven with air circulation, a line speed of 1 m / min, and an oven length of 1.5 m.

[0154] The evaluation results are shown in FIG.

[0155]

[0156]

[0157] As shown in Table 1, the invention exemplified in Examples 1 and 2 demonstrates gas separation membranes with both high permeability to CO and CO / N selectivity, which is especially important for thin coatings (low target dry thickness) that are prone to defect formation, which can lead to reduced CO / N selectivity.

[0158] To fully evaluate membrane performance, it is essential to consider CO permeability and CO / N selectivity simultaneously. High CO permeability alone is insufficient if the membrane does not effectively separate CO and N, and vice versa. By optimizing both parameters in a balanced manner, the membrane can not only efficiently process large amounts of gas, but also achieve precise separation capabilities. This balance is effectively demonstrated by the inventions in Examples 1 and 2.

[0159] As shown in Table 2, the inventions exemplified in Examples 1 and 2 demonstrate that the gas separation membranes of the present invention exhibit stable performance, whereas the conventional comparative examples do not. Simultaneous consideration of CO permeability and CO / N selectivity after aging tests is necessary to fully evaluate the long-term performance of a membrane. High CO permeability alone is insufficient if the membrane does not maintain its CO and N separation function, and vice versa. A balanced optimization of both parameters ensures that the membrane remains effective and efficient throughout its operational life.

Claims

1. A gas separation membrane comprising a separation functional layer, the separation functional layer comprising a matrix polymer selected from the group consisting of: (a) siloxane-modified pullulan, (b) siloxane-modified norbornene, and (c) a combination thereof.

2. The gas separation membrane of claim 1, wherein the matrix polymer comprises (a) siloxane-modified pullulan.

3. The gas separation membrane according to claim 2, wherein the siloxane-modified pullulan contains a carbamoyl group or a carbamic acid group.

4. The gas separation membrane according to claim 3, wherein the carbamoyl group is a trialkylsiloxysilylcarbamoyl group.

5. The gas separation membrane according to claim 4, wherein the alkyl group of the trialkylsiloxysilylcarbamoyl group is selected from the group consisting of methyl, ethyl, propyl, and butyl.

6. The gas separation membrane according to claim 1, wherein the matrix polymer comprises (b) a siloxane-modified norbornene, the siloxane-modified norbornene comprising a silicon-substituted norbornene structure.

7. The gas separation membrane according to claim 6, wherein the structure of the siloxane-modified norbornene is an exosilicon-substituted norbornene.

8. The gas separation membrane according to claim 1, wherein the separation functional layer has a thickness of 0.01 to 50 μm.

9. The gas separation membrane according to claim 1, wherein the gas separation membrane has a CO2 permeability of 800 GPU or more and a CO2 / N2 selectivity of 5 or more, as measured at 25°C.

10. The gas separation membrane according to claim 1, wherein the gas separation membrane exhibits a change in CO2 permeability of less than 70% after 100 hours of storage (physical aging) at 60°C, and a change in CO2 / N2 selectivity of less than 20% after 100 hours of storage (physical aging) at 60°C, as measured at 25°C.

11. The gas separation membrane has a NOx content of 50 ppm at 80°C when measured at 25°C. x The change in CO2 permeability before and after 32 hours of exposure (chemical aging) was less than 70%, and the x 2. The gas separation membrane of claim 1, wherein the change in CO2 / N2 selectivity before and after exposure to (chemical aging) for 32 hours is less than 20%.

12. The gas separation membrane according to claim 1, wherein the separation functional layer is supported on a porous support layer.

13. A method for separating a predetermined gas from a mixed gas, comprising selectively passing the predetermined gas in the mixed gas through a gas separation membrane according to any one of claims 1 to 12, wherein the predetermined gas is at least one gas selected from the group consisting of hydrocarbons and gases containing at least one of a hydrogen atom, a sulfur atom, an oxygen atom, or a nitrogen atom.

14. The method of claim 13, wherein the predetermined gas is at least one gas selected from the group consisting of H2, H2S, CO, CO2, alkanes, alkenes, N2, O2, He, Ne, Ar, Kr, and Xe.

15. A gas separation system comprising the gas separation membrane of any one of claims 1 to 12.

16. The gas separation system of claim 15, further comprising a feed gas inlet for receiving a mixed gas, and a permeate gas outlet for discharging a selected gas.

17. The gas separation system of claim 15, wherein the gas separation membrane is in a spiral wound modular configuration.

18. The gas separation system of claim 15, wherein the gas separation membrane is a plate and frame modular construction.

19. The gas separation system of claim 15, wherein the gas separation membrane is in a hollow fiber modular configuration.

20. A method for producing the gas separation membrane of claim 1, comprising the steps of: dissolving a siloxane-modified polymer in a solvent to prepare a coating solution; applying the obtained coating solution to the surface of a support layer; and drying the coated surface at a temperature below the melting point of the support layer to form a separation functional layer on the support layer.

21. A method for producing the gas separation membrane of claim 1, comprising the steps of: dissolving a siloxane-modified polymer in a solvent to prepare a coating solution; immersing the surface of a hollow fiber in the obtained coating solution; and drying the coated surface at a temperature below the melting point of the hollow fiber to form a separation functional layer on the hollow fiber.

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