Gas separation polymer composite membrane with high pressure resistance as well as preparation method and application thereof

Abstract

The invention relates to a gas separation polymer composite membrane with high pressure resistance as well as a preparation method and application thereof. The method comprises the following steps: dissolving a crystalline polymer in a good solvent, uniformly coating the polymer solution on the surface of a flat substrate, immersing the flat substrate in an ionic liquid with weak interaction with the polymer, and carrying out solvent exchange treatment at a constant temperature. The polymer / ionic liquid composite membrane prepared by the method is used for gas separation. According to the gas separation polymer composite membrane, the high ionic liquid content is maintained, and meanwhile the high mechanical performance of the composite membrane is maintained. The ionic liquid can stably exist in a polymer matrix to improve the continuity of a gas transmission path, and meanwhile, the ionic liquid which weakly interacts with a macromolecular chain can effectively promote a polymer molecular chain to form a microcrystalline structure in the exchange process, so that the mechanical property of the composite membrane in the gas separation process is greatly improved, and the gas separation efficiency is improved. And during gas separation, high pressure resistance, high permeability and high selectivity are shown. The method is simple in process, convenient to operate and mild in condition.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane technology, specifically relating to a gas separation polymer composite membrane with high pressure resistance, its preparation method, and its application. Background Technology

[0002] Currently, the massive emission of carbon dioxide has led to the greenhouse effect, causing serious environmental problems. At the same time, carbon dioxide is also an important carbon resource, which can be used to synthesize organic compounds. Therefore, how to achieve efficient capture and separation of carbon dioxide is one of the most pressing issues facing sustainable development, and developing efficient carbon dioxide capture materials is also an effective method to achieve "carbon peaking and carbon neutrality."

[0003] Carbon dioxide capture methods mainly include absorption, adsorption, and cryogenic distillation. However, due to their high energy consumption, high cost, and low economic efficiency, these methods require further optimization. Membrane separation, a novel separation technology that has emerged in the last decade or so, has attracted considerable attention due to its advantages such as high energy efficiency, simple operation, low maintenance costs, and environmental friendliness.

[0004] Among materials used for gas separation using membranes, polymer membranes are widely used due to their advantages such as abundant raw material sources, low cost, and good overall performance. Ionic liquids generally refer to organic salts that are liquid at room temperature, and their structure is usually composed of large-volume organic cations and organic or inorganic anions. Ionic liquids have strong dissolving power and extremely low vapor pressure, making them commonly used green liquid materials for dissolving and absorbing carbon dioxide. Therefore, by combining ionic liquids with polymer matrices to construct composite membranes that combine high carbon dioxide permeability, high selectivity, and excellent mechanical stability, efficient and stable carbon dioxide separation and resource recovery can be achieved.

[0005] Polymer / ionic liquid composite membranes combine the excellent processability and stable mechanical properties of polymer materials with the strong carbon dioxide solubility of ionic liquids, making them ideal materials for carbon dioxide separation and capture technologies. These composite membrane materials utilize specific anions and cations of the ionic liquid (such as [BMIM]). + [Tf2N] -There are strong physical and chemical interactions between ionic liquids and carbon dioxide (such as Lewis acid-base interactions, hydrogen bonds, and van der Waals forces), leading to preferential dissolution and transport of carbon dioxide, thus forming permeation channels for carbon dioxide transport. Polymers can effectively coat ionic liquids, preventing their loss under high pressure differential operating conditions, while the crystallization behavior of polymers endows the materials with strong mechanical properties. Regulating the microcrystalline structure of the polymer matrix and the continuous pathways of carbon dioxide within the matrix is ​​key to improving the mechanical properties, carbon dioxide permeability, and selectivity of these composite membrane materials. Increasing the carbon dioxide content in the composite membrane promotes the construction of carbon dioxide pathways, thereby improving carbon dioxide permeability and selectivity. However, increasing the carbon dioxide content will reduce the mechanical stability of the composite membrane, consequently decreasing the gas pressure resistance.

[0006] Patent CN120623686A discloses a method for preparing a strong and tough polyvinyl alcohol-based ionic gel. This gel employs two solvent exchanges to construct a triple dynamic network structure containing "dynamic covalent bonds + ionic bonds + hydrogen bonds," achieving excellent properties such as high toughness and high strength. Patent CN120399271A discloses a method for preparing a high-strength and tough physical hydrogel. It also involves solvent exchange by immersing the flocculated hydrogel in a poor solvent to regulate its mechanical properties, preparing a novel gel material with both high strength and high toughness. However, the weak mechanical properties and leakage of the gel material significantly reduce its high pressure resistance and long-term operational stability.

[0007] This invention utilizes a solvent exchange strategy to prepare a composite membrane with high pressure resistance and long-term operational stability, featuring a microcrystalline distribution and a polymer / ionic liquid bicontinuous phase structure. After dissolving the polymer in a good solvent, solvent exchange is performed using an ionic liquid with weak polymer-solvent interaction. This results in stronger polymer-polymer interactions than polymer-solvent interactions, enhancing polymer-polymer interactions. The crystallizable portions of the polymer form microcrystalline regions, while the amorphous regions have denser polymer chain segments. The microcrystalline and dense amorphous regions endow the composite membrane with strong mechanical properties, achieving a tensile stress of up to 3 MPa and a gas breakdown pressure of 6 bar, overcoming the limitations of traditional carbon dioxide separation membranes with weak mechanical properties. Simultaneously, the enhanced interactions between ionic liquids allow the ionic liquid to form a continuous structure within the polymer matrix, constructing a continuous ionic liquid pathway conducive to carbon dioxide permeation, thus enhancing carbon dioxide permeability and selectivity. The carbon dioxide permeation flux reaches 857 barrer, a three-fold increase compared to composite membranes prepared by traditional solvent casting methods. This study provides a new approach for preparing separation membrane materials with high pressure resistance, high gas permeability, and high selectivity. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a gas separation polymer composite membrane with high pressure resistance, its preparation method, and its application.

[0009] To achieve the above objectives, the present invention employs the following technical solutions.

[0010] Firstly, this invention provides a method for preparing a gas separation polymer composite membrane with high pressure resistance. Based on the competitive interaction mechanism among polymer-polymer, polymer-solvent, and ionic liquid-ionic liquid interactions, a method for preparing a gas separation polymer composite membrane with high pressure resistance using a solvent exchange strategy is proposed. When the polymer combines with a good solvent, the self-interaction of the polymer is broken, forming a loose polymer network. When switching to a relatively weaker solvent (i.e., an ionic liquid), the interactions between polymers are restored, the interactions between polymer chains are enhanced, and they assemble into a densely packed network structure, with microcrystals generated. Simultaneously, the polymer chain segments in the amorphous regions become more densely packed. The microcrystals and the denser amorphous regions endow the composite membrane with strong mechanical properties, thereby achieving good gas stability. The ionic liquids aggregate with each other, forming ionic liquid pathways for transporting carbon dioxide, improving the permeability and selectivity of carbon dioxide.

[0011] Specifically, this method involves dissolving a crystalline polymer in a good solvent, followed by solvent exchange using an ionic liquid with weaker interactions to the crystalline polymer. This results in polymer-to-polymer interactions being stronger than polymer-solvent interactions, prompting the stacking of crystalline polymer chains to induce crystallization and form numerous microcrystalline structures. Simultaneously, the polymer chain segments in the amorphous regions become more densely packed, ultimately forming a solid polymer composite film along with the construction of the polymer crystalline framework. Furthermore, the enhanced interactions between the ionic liquids confine them within the tight spaces of the crystalline polymer framework, ensuring their stable existence within the polymer matrix and further creating continuous gas transport channels.

[0012] Furthermore, the method specifically includes the following steps:

[0013] Step (1): Dissolve the crystalline polymer in a good solvent to prepare a polymer solution with a mass fraction of 30-35 wt%, i.e., casting solution;

[0014] Step (2): Use a scraper to evenly coat the casting solution onto the surface of the flat substrate;

[0015] Step (3): Immerse the flat substrate of the casting liquid in step (2) into the ionic liquid and perform solvent exchange treatment at a constant temperature to obtain the polymer / ionic liquid composite membrane.

[0016] Preferably, the crystalline polymer is one or more of polyvinylidene fluoride, poly(styrene-ethylene oxide-styrene), polyacrylonitrile, poly(vinylidene fluoride-hexafluoropropylene), polyvinylidene fluoride copolymer, polyethylene glycol-polystyrene, or poly(vinylidene fluoride-trifluoroethylene-trifluorochloroethylene).

[0017] Preferably, the good solvent is one or more of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, ethyl acetate, and N,N-dimethylacetamide.

[0018] Preferably, the ionic liquid includes, but is not limited to, imidazole ionic liquids, pyridine ionic liquids, and quaternary ammonium ionic liquids, and further, its anions include halogens (such as Cl). - ,Br - ), tetrafluoroborate ([BF4]) - ), hexafluorophosphate ([PF6]) - ), bis(trifluoromethanesulfonyl)imine salt ([NTf2) - And alkyl sulfuric acid / sulfonic acid derivatives (such as [CH3SO3]). - [C2H5SO4] - One or more of the following. More preferably, the ionic liquid is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, or 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0019] Preferably, the solvent exchange process in step (3) takes 1 h to 24 h and is carried out at a constant temperature of 25°C.

[0020] Preferably, in step (1), the polymer solution has a mass fraction of 30 wt%, that is, the polymer mass is 3 g and the good solvent is 7.3 ml.

[0021] Preferably, in step (3), the amount of ionic liquid used is approximately 120 mL. To ensure complete solvent exchange, the amount of ionic liquid used should be increased as much as possible.

[0022] Secondly, the present invention provides a polymer composite membrane with high pressure resistance and a thickness of 35~40 µm.

[0023] Thirdly, the present invention provides an application of a polymer composite membrane in gas separation, wherein the gas separation is the separation of carbon dioxide / nitrogen and other gases, preferably carbon dioxide gas separation.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention utilizes a solvent exchange strategy to prepare a gas separation polymer composite membrane with high pressure resistance, based on the competitive mechanism between polymer-polymer interactions and ionic liquid-ionic liquid interactions. This method is simple, convenient, and operates under mild conditions.

[0026] 2. The composite membrane obtained by the present invention maintains a high ionic liquid loading while ensuring the microcrystalline structure of the polymer, without sacrificing the mechanical stability of the composite membrane, thus giving it excellent pressure resistance.

[0027] 3. Based on the competition of interaction forces between ionic liquids, a continuous and stable ionic liquid channel is constructed within the membrane, which effectively promotes the dissolution and diffusion of carbon dioxide, achieving high permeability and high selectivity of carbon dioxide. Attached Figure Description

[0028] Figure 1 The graph shows the ionic liquid content in the polymer composite membranes prepared in Examples 1-6.

[0029] Figure 2 Differential scanning calorimetry (DSC) graphs of the polymer composite membranes prepared in Examples 3, 7, 8, and 9.

[0030] Figure 3 The mechanical properties of the polymer composite films prepared in Examples 3, 7, 8, and 9 are shown in the test diagrams.

[0031] Figure 4 The breakdown pressure test results are shown for the polymer composite membranes prepared in Examples 3, 7, and 8.

[0032] Figure 5 The graphs show the gas performance test results of the polymer composite membranes prepared in Examples 3, 7, and 8. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0034] This invention provides a method for preparing a polymer / ionic liquid composite membrane, comprising the following steps:

[0035] Step (1): Dissolve the crystalline polymer in a good solvent at 60 °C to prepare a polymer solution with a mass fraction of 30-35 wt%, which is the casting solution.

[0036] The crystalline polymer is one or more of polyvinylidene fluoride, poly(styrene-ethylene oxide-styrene), polyacrylonitrile, poly(vinylidene fluoride-hexafluoropropylene), polyvinylidene fluoride copolymer, polyethylene glycol-polystyrene, or poly(vinylidene fluoride-trifluoroethylene-trifluorochloroethylene), preferably polyvinylidene fluoride.

[0037] The good solvent is a good solvent for the above-mentioned crystalline polymer, such as one or more of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, ethyl acetate, and N,N-dimethylacetamide, preferably N,N-dimethylformamide.

[0038] Ionic liquids are poor solvents for the aforementioned crystalline polymers, such as imidazole, pyridine, and quaternary ammonium ionic liquids, whose anions include halogens (such as Cl-). - ,Br - ), tetrafluoroborate ([BF4]) - ), hexafluorophosphate ([PF6]) - ), bis(trifluoromethanesulfonyl)imine salt ([NTf2) - And alkyl sulfuric acid / sulfonic acid derivatives (such as [CH3SO3]). - [C2H5SO4] - One or more of the following, preferably imidazole bis(trifluoromethanesulfonyl)imide salts. For example, the ionic liquid is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide or 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0039] The mass fraction of the polymer solution directly affects the formability and structural integrity of the composite membrane. When the mass fraction is below 30 wt%, the polymer / ionic liquid composite membrane prepared in the subsequent solution exchange process is easily damaged due to insufficient structural strength, making it difficult to use for gas separation testing; while when the mass fraction is above 35 wt%, the polymer is difficult to fully dissolve in a good solvent.

[0040] Step (2): Apply the casting solution evenly to the surface of the plate.

[0041] In one embodiment, the flat plate can be a glass plate with a smooth and flat surface.

[0042] Step (3): Immerse the flat plate of the casting solution from step (2) into the poor solvent ionic liquid and soak it at a constant temperature for a certain period of time to obtain the polymer / ionic liquid composite membrane.

[0043] In one embodiment, the solvent exchange treatment time is 1 h to 24 h, and the solvent exchange is carried out at a constant temperature of 25 ℃.

[0044] Furthermore, in step (3), the amount of ionic liquid used is approximately 120 mL. To ensure complete solvent exchange, the amount of ionic liquid used should be increased as much as possible.

[0045] In this invention, when a plate coated with a casting solution is immersed in an ionic liquid, a concentration gradient exists in the system, causing the good solvent to diffuse into the ionic liquid phase. Simultaneously, the ionic liquid diffuses back into the polymer solution, gradually replacing the original solvent (i.e., the good solvent). The ionic liquid, acting as a poor solvent for the polymer, induces stacking and crystallization of the polymer molecular chains, forming numerous microcrystalline structures. As solvent exchange proceeds, the composite membrane continuously absorbs the ionic liquid, accompanied by the construction of the polymer crystalline framework, ultimately forming a solid polymer composite membrane. The polymer microcrystals endow the composite membrane with mechanical properties, enabling it to maintain excellent mechanical strength while retaining a high ionic liquid content. In this structure, the ionic liquid is confined within the tight space of the polymer chains, allowing it to exist stably within the polymer matrix and further forming continuous gas transport channels. This structural feature endows the composite membrane with high pressure resistance, high carbon dioxide permeability, and high selectivity during gas separation.

[0046] The technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Example 1

[0048] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 10 min to obtain a polymer / ionic liquid composite membrane.

[0049] Example 2

[0050] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 30 min to obtain a polymer / ionic liquid composite membrane.

[0051] Example 3

[0052] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 1 h to obtain a polymer / ionic liquid composite membrane.

[0053] Example 4

[0054] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 6 h to obtain a polymer / ionic liquid composite membrane.

[0055] Example 5

[0056] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 12 h to obtain a polymer / ionic liquid composite membrane.

[0057] Example 6

[0058] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 24 h to obtain a polymer / ionic liquid composite membrane.

[0059] Example 7

[0060] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 1 h to obtain a polymer / ionic liquid composite membrane.

[0061] Example 8

[0062] 3 g of polyvinylidene fluoride was dissolved in 7.3 ml of N,N-dimethylformamide at 60 °C to prepare a polymer solution with a mass fraction of 30 wt%. The polymer solution was used to form a membrane, which was then immersed in an excess of 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt for solvent exchange for 1 h to obtain a polymer / ionic liquid composite membrane.

[0063] Example 9 (also known as the comparative example)

[0064] 3 g of polyvinylidene fluoride was dissolved in an appropriate amount of N,N-dimethylformamide at 60 °C, followed by the addition of 4.14 g of ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt), with the ionic liquid concentration based on the polymer mass of 58 wt%. The polymer solution was cast into a polytetrafluoroethylene mold and dried in an oven to remove residual solvent, yielding a polymer / ionic liquid blend membrane.

[0065] Performance testing

[0066] Test Example 1: Thermogravimetric Analysis Test

[0067] Thermogravimetric analysis (TGA) was performed on the polymer composite membranes prepared in Examples 1-6, and the content of ionic liquid in the composite membranes was confirmed by fitting the DTG peaks. Figure 1 As shown, after the solvent exchange time reaches 1 h, the ionic liquid content in the composite membrane tends to stabilize, and the ionic liquid content is about 58%.

[0068] This indicates that the ionic liquid content in the composite membrane did not change significantly with increasing solvent exchange time. To optimize the experimental procedure, subsequent studies used 1 hour as the standard solvent exchange time.

[0069] Test Example 2: Differential Scanning Calorimetry Test

[0070] Differential scanning calorimetry (DSC) analysis was performed on the polymer composite films prepared in Examples 3, 7, 8, and 9. Figure 2 As shown, with the increase of the carbon chain length of the cationic imidazole group in the ionic liquid, the melting point and crystallization temperature of α and β crystals in the composite membrane gradually increase, but both remain lower than the melting point and crystallization temperature of polyvinylidene fluoride. Meanwhile, the melting and crystallization temperatures of the solvent exchange composite membrane are higher than those of the blend membrane (∆T = 4 °C). The crystallinity of the composite membranes prepared in Examples 3, 7, 8, and 9 are 23.5%, 26.9%, 27.9%, and 17.2%, respectively. With the increase of the cationic imidazole carbon chain length, the crystallinity of the composite membrane gradually increases, while the crystallinity of the solvent exchange composite membrane is higher than that of the blend membrane.

[0071] Test Example 3: Mechanical Property Test

[0072] The mechanical properties of the polymer composite films prepared in Examples 3, 7, 8, and 9 were tested, and the results are shown in the appendix. Figure 3The tensile strength of Example 3 was 1.43 MPa, the elongation at break was 146%, and the Young's modulus was 6.1 MPa; the tensile strength of Example 7 was 1.84 MPa, the elongation at break was 194%, and the Young's modulus was 8 MPa; the tensile strength of Example 8 was 2.9 MPa, the elongation at break was 249%, and the Young's modulus was 13.3 MPa; the tensile strength of Example 9 was 0.77 MPa, the elongation at break was 143%, and the Young's modulus was 3.4 MPa. With the increase of the carbon chain length of the IL-cation imidazole group, the tensile strength, elongation at break, and Young's modulus of the composite membrane gradually increased. The composite membranes prepared in Examples 3, 8, and 9 exhibited good mechanical properties. The tensile strength, elongation at break, and Young's modulus of the solvent exchange composite membrane were all higher than those of the blend membrane.

[0073] Test Example 4: Breakdown Pressure Test

[0074] Breakdown pressure refers to the critical pressure at which the prepared polymer composite membrane is broken down by gas, i.e., the membrane is destroyed. Breakdown pressure can reflect the membrane's pressure resistance and stability.

[0075] The prepared composite membrane is fixed in the membrane tank of the gas separation device. A soap membrane flow meter is connected to one side of the membrane tank, and the end of the flow meter is connected to the atmosphere. A positive pressure is applied to the other side, and the pressure increases gradually over time. The critical pressure at which bubbles appear in the flow meter is measured. This pressure is the membrane breakdown pressure.

[0076] The breakdown pressures of Examples 3, 7, and 8 were tested. The test gas was N2. The test method was to increase the pressure by 0.02 MPa on the upper side of the membrane every five minutes until the membrane was punctured, and the breakdown pressure at this time was recorded.

[0077] like Figure 4 As shown, when the PVDF concentration in the casting solution is 30 wt%, the breakdown pressure of the composite membrane gradually increases with the increase of the length of the cationic imidazole carbon chain, and it can withstand a maximum gas pressure of 6 bar. The polymer composite membranes prepared in Examples 3, 7, and 8 have good gas pressure resistance.

[0078] Test Example 5: Gas Separation Performance Test

[0079] Gas separation performance refers to the ability of a membrane to selectively separate a specific gas component under ideal gas conditions. The separation performance of a specific gas component is calculated by measuring the different permeation rates of different gas components through the membrane.

[0080] The polymer composite membranes prepared in Examples 3, 7, and 8 were subjected to gas performance tests. The permeability of different gas components was calculated by using a constant volume change pressure gas separation performance testing device and pressure gauge readings.

[0081] like Figure 5 As shown, when the casting solution concentration is 30 wt%, the carbon dioxide flux gradually increases with the increase of the cationic imidazole carbon chain length, while the carbon dioxide selectivity slowly decreases. The highest carbon dioxide flux reaches 857 barrer, and the highest resolution reaches 33.7. The composite membranes prepared in Examples 3, 7, and 8 exhibit high permeability and selectivity.

[0082] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a gas separation polymer composite membrane with high pressure resistance, characterized in that, The preparation method involves dissolving a crystalline polymer in a good solvent, followed by solvent exchange using an ionic liquid with weak interaction with the crystalline polymer. This results in a stronger interaction between crystalline polymers than between the polymer and the solvent, promoting the stacking of polymer chains to induce crystallization and form numerous microcrystalline structures. Simultaneously, the polymer chain segments in the amorphous regions become more densely packed, ultimately forming a solid polymer composite film along with the construction of the polymer crystalline framework. Furthermore, the enhanced interaction between ionic liquids confines the ionic liquids within the tight space of the crystalline polymer framework, ensuring their stable existence within the polymer matrix and further forming continuous gas transport channels.

2. The method according to claim 1, characterized in that, The method specifically includes the following steps: Crystalline polymers are dissolved in a good solvent to prepare a polymer solution with a mass fraction of 30-35 wt%. The polymer solution is uniformly coated onto the surface of the flat substrate; A flat substrate with a polymer solution is immersed in an ionic liquid that has a weak interaction with the polymer, and solvent exchange is performed at a constant temperature to obtain a polymer / ionic liquid composite membrane.

3. The method according to claim 2, characterized in that, The crystalline polymer is one or more of polyvinylidene fluoride, poly(styrene-ethylene oxide-styrene), polyacrylonitrile, poly(vinylidene fluoride-hexafluoropropylene), polyvinylidene fluoride copolymer, polyethylene glycol-polystyrene, or poly(vinylidene fluoride-trifluoroethylene-trifluorochloroethylene).

4. The method according to claim 1, characterized in that, The good solvent is one or more of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, ethyl acetate, and N,N-dimethylacetamide.

5. The method according to claim 1, characterized in that, The ionic liquids include, but are not limited to, imidazole ionic liquids, pyridine ionic liquids, and quaternary ammonium ionic liquids.

6. The method according to claim 1, characterized in that, The solvent exchange treatment time is 1 h to 24 h.

7. The method according to claim 1, characterized in that, The solvent exchange treatment temperature is 25°C.

8. The method according to claim 1, characterized in that, The polymer solution has a mass fraction of 30 wt%.

9. A gas separation polymer composite membrane with high pressure resistance, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. The application of the polymer composite membrane of claim 9 in gas separation.

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