Anti-aging polyimide gas separation membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of gas separation membranes, and provides an anti-aging polyimide gas separation membrane as well as a preparation method and application thereof. The preparation method comprises the following step: carrying out bromination reaction on a polyimide membrane in the presence of a brominating agent and a first catalyst to obtain the anti-aging polyimide gas separation membrane. The preparation method of the anti-aging polyimide gas separation membrane provided by the invention is mild in reaction condition, the integrity of a polymer main chain can be ensured, and meanwhile, the microstructure of the gas separation membrane is not damaged. The polyimide gas separation membrane is brominated by adopting the preparation method provided by the invention, so that the mutual stacking and free volume fraction reduction of polymer chains of the polyimide gas separation membrane can be effectively inhibited, the anti-aging performance of the polyimide gas separation membrane can be enhanced, the service life of the polyimide gas separation membrane is prolonged, and the production cost is reduced. And the polyimide film can maintain better mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of gas separation membrane technology, and more specifically, to an anti-aging polyimide gas separation membrane, its preparation method, and its application. Background Technology

[0002] Membrane gas separation is a membrane process used to separate components in gas mixtures. It has the technical characteristics of being "economical, convenient, efficient, and clean" and is widely used in the petroleum, natural gas, chemical, metallurgical, and pharmaceutical industries for the separation and concentration of mixed gases such as N2 / H2, O2 / N2, CO2 / CH4, and CO2 / N2. It has played a positive role in promoting energy conservation, emission reduction, and technological progress in industrial enterprises.

[0003] Compared to existing polymeric membrane materials used in gas membrane separation, such as cellulose acetate (CA), polydimethylsiloxane (PDMS), polysulfone (PS), and polycarbonate (PC), polyimide (PI) possesses both high permeability and high selectivity, making it an ideal material for gas membrane separation. Polyimide is synthesized by the condensation polymerization of dianhydride and diamine monomers. Polyimides containing benzene rings exhibit excellent thermal stability and mechanical strength due to the presence of aromatic ring structures in their molecular backbone. They also possess good chemical stability and are soluble in many common solvents (such as NMP, DMAc, and DMF), making them easy to process. However, during long-term use, polyimide gas separation membranes exhibit significant aging, which cannot be ignored. Gas separation membrane aging refers to the process where, under high pressure and certain temperatures, the polymer macromolecular chains stack together, reducing the free volume fraction and thus decreasing the gas permeation rate of the gas separation membrane, significantly reducing its service life.

[0004] Existing technologies disclose some gas separation membranes that improve anti-aging performance, but the process of improving anti-aging performance can easily lead to a significant deterioration in the mechanical properties of the gas separation membrane.

[0005] Therefore, it is very meaningful to develop a polyimide gas separation membrane with both ideal anti-aging properties and mechanical properties. Summary of the Invention

[0006] The purpose of this invention is to provide an anti-aging polyimide gas separation membrane and its preparation method, so as to solve the technical problem that polyimide gas separation membranes in the prior art cannot simultaneously possess good anti-aging properties and mechanical properties.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing an anti-aging polyimide gas separation membrane, comprising: subjecting a polyimide membrane to a bromination reaction in the presence of a brominating agent and a first catalyst to obtain the anti-aging polyimide gas separation membrane.

[0009] In this invention, the brominating agent substitutes bromine at the β-position of the aromatic hydrocarbon in the polyimide backbone on the surface of the separation membrane through a bromination reaction, thereby improving the anti-aging properties of the polyimide membrane.

[0010] The preparation method provided by this invention involves substituting bromine on the surface of a polyimide membrane using a brominating agent and a first catalyst. Compared to methods that introduce halogen-containing monomers into the polyimide backbone, this method not only eliminates the need for special raw materials but also allows for the preparation of polyimide membranes using conventional raw materials and methods. This method is simple to operate and has lower costs. Furthermore, since bromine substitution is performed only on the membrane surface, it does not damage the physical structure of the separation membrane itself, allowing the brominated polyimide membrane to maintain good mechanical properties.

[0011] According to some embodiments of the present invention, the brominating agent includes at least one of N-bromosuccinimide (NBS), dibromohydantoin (DBH), and N-bromophthalimide (NBP).

[0012] According to some embodiments of the present invention, the first catalyst includes at least one of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), and lauroyl peroxide (LPO).

[0013] According to some embodiments of the present invention, the polyimide film includes at least one of a homogeneous film, a composite film, and hollow fibers.

[0014] According to some embodiments of the present invention, the mass ratio of the polyimide film to the brominating agent is 1:(0.05~0.5), for example, it can be 0.05, 0.07, 0.09, 0.1, 0.15, 0.18, 0.2, 0.25, 0.3, 0.33, 0.35, 0.38, 0.4, 0.45, 0.5, etc.

[0015] In this invention, excessive use of brominating agent will cause excessive substitution of bromine on the polyimide backbone, thus adversely affecting the gas separation performance and mechanical properties of the gas separation membrane; insufficient use of brominating agent will not effectively improve the anti-aging performance of the gas separation membrane.

[0016] According to some embodiments of the present invention, the mass ratio of the polyimide film to the first catalyst is 1:(0.004~0.2), for example, it can be 0.004, 0.005, 0.006, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.08, 0.09, 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, etc.

[0017] In this invention, excessive use of catalyst will cause the reaction rate to be too fast, resulting in severe exothermic reaction, damage to the membrane structure, and loss of performance.

[0018] According to some embodiments of the present invention, the temperature of the bromination reaction is 20–40°C.

[0019] In this invention, the temperature of the bromination reaction affects the reaction rate. An excessively high reaction temperature will cause the reaction rate to be too fast, which is not conducive to maintaining the good separation performance of the gas separation membrane.

[0020] According to some embodiments of the present invention, the bromination reaction takes 6 to 18 hours.

[0021] According to some embodiments of the present invention, the bromination reaction is carried out in a first solvent.

[0022] According to some embodiments of the present invention, the first solvent includes at least one of cyclohexane, n-hexane, n-heptane, and toluene.

[0023] In this invention, by selecting cyclohexane, n-hexane, n-heptane, and toluene as the first solvent, it is ensured that the bromination reaction does not occur in the solvent molecules, and the integrity of the polymer backbone is maintained during the bromination reaction, so as not to cause damage to the microstructure of the polyimide film, thereby enabling the bromination-treated polyimide film to maintain better mechanical properties.

[0024] According to some embodiments of the present invention, after the bromination reaction is completed, the brominated polyimide membrane is washed.

[0025] According to some embodiments of the present invention, the preparation method includes: placing a polyimide membrane in a first solvent, adding a brominating agent and a first catalyst, reacting at 20-40°C for 6-18 hours, and washing after the reaction to obtain the anti-aging polyimide gas separation membrane.

[0026] In this invention, the polyimide film can be a commercially available polyimide film, or it can be prepared by various existing preparation methods.

[0027] According to some embodiments of the present invention, the preparation process of the polyimide membrane includes: adding dianhydride monomer and diamine monomer to a second solvent to undergo a polymerization reaction; then adding a second catalyst and a dehydrating agent to perform imidization treatment; then performing post-treatment to obtain polyimide; dissolving the polyimide in a third solvent to obtain a casting solution, and using the casting solution to form a membrane to obtain the polyimide membrane.

[0028] According to some embodiments of the present invention, the dianhydride monomer is selected from compounds with the structural formula O(O=C)2-R1-(C=O)2O, wherein R1 comprises at least one of the following structural units:

[0029]

[0030]

[0031] According to some embodiments of the present invention, the diamine monomer is selected from compounds with the structural formula NH2-R2-NH2, wherein R2 comprises at least one of the following structural units:

[0032]

[0033]

[0034] According to some embodiments of the present invention, the molar ratio of the dianhydride monomer to the diamine monomer is 0.95 to 1.

[0035] According to some embodiments of the present invention, the total mass fraction of the dianhydride monomer and the diamine monomer in the reaction system comprising the dianhydride monomer, the diamine monomer, and the second solvent is 5 to 40 wt%.

[0036] According to some embodiments of the present invention, the second solvent includes at least one of dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), or N-methylpyrrolidone (NMP).

[0037] According to some embodiments of the present invention, the second catalyst comprises at least one of pyridine compounds, alkylamine compounds, and quinoline compounds, preferably at least one of 4-dimethylaminopyridine, 3-methylpyridine, 2,4-dimethylpyridine, triethylamine, pyridine, diethylamine, quinoline, and isoquinoline.

[0038] According to some embodiments of the present invention, the molar ratio of the second catalyst to the diamine monomer is (0.025 to 0.25):1.

[0039] According to some embodiments of the present invention, the dehydrating agent includes at least one of acid anhydrides; preferably, the dehydrating agent includes at least one of acetic anhydride, propionic anhydride, n-butyric anhydride, n-valeric anhydride, trifluoroacetic anhydride, and benzoic anhydride.

[0040] According to some embodiments of the present invention, the molar ratio of the dehydrating agent to the diamine monomer is (2.2-5):1.

[0041] According to some embodiments of the present invention, the third solvent includes at least one of dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), or N-methylpyrrolidone (NMP).

[0042] According to some embodiments of the present invention, the concentration of the casting solution is 5 to 40 wt%.

[0043] According to some embodiments of the present invention, the conditions for the polymerization reaction include: a reaction temperature of 20–40°C and a reaction time of 4–18 h.

[0044] According to some embodiments of the present invention, the polymerization reaction is carried out under a nitrogen atmosphere.

[0045] According to some embodiments of the present invention, the conditions for the imidization treatment include: a temperature of 60–90°C and a time of 4–12 h.

[0046] According to some embodiments of the present invention, the post-processing includes precipitating the imidized solution in water, washing, and first drying to obtain polyimide.

[0047] According to some embodiments of the present invention, the conditions for the first drying include: a drying temperature of 80 to 120°C and a drying time of 12 to 24 hours.

[0048] According to some embodiments of the present invention, a second drying process is performed after the film formation.

[0049] According to some embodiments of the present invention, the conditions for the second drying include: a drying temperature of 100–200°C and a drying time of 6–24 h.

[0050] According to some embodiments of the present invention, the polyimide membrane undergoes solvent exchange before the bromination reaction to fully remove any residual first solvent and / or second solvent in the polyimide membrane, thereby preventing the residual first solvent and / or second solvent from undergoing bromination substitution reaction.

[0051] Preferably, the solvent exchange includes: immersing the polyimide membrane in a fourth solvent, stirring for 12-24 hours, draining, and washing.

[0052] According to some embodiments of the present invention, the fourth solvent includes at least one of ethanol, methanol, and acetone.

[0053] Secondly, the present invention provides an anti-aging polyimide gas separation membrane, which is prepared by the preparation method described in the first aspect.

[0054] Thirdly, the present invention provides the application of the anti-aging polyimide gas separation membrane described in the second aspect in gas separation and gas concentration.

[0055] The beneficial effects of this invention are at least as follows:

[0056] The preparation method of the anti-aging polyimide gas separation membrane provided by this invention has mild reaction conditions, which can ensure the integrity of the polymer backbone and prevent damage to the microstructure of the gas separation membrane. By using the preparation method provided by this invention to bromine the polyimide gas separation membrane, the mutual stacking of polymer chains and the reduction of free volume fraction of the polyimide gas separation membrane can be effectively inhibited, thereby enhancing the anti-aging performance of the polyimide gas separation membrane, increasing its service life, and maintaining better mechanical properties. Detailed Implementation

[0057] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0058] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0059] Example 1

[0060] At room temperature, 13.5 g of 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindene was weighed and placed in a dry three-necked flask. 144.2 g of N-methylpyrrolidone (NMP) was added, and the mixture was stirred at 250 rpm under a nitrogen atmosphere until completely dissolved. Then, 22.5 g of hexafluorodianhydride was added in batches. After mechanical stirring until the dianhydride dissolved, the reaction was continued for 12 h to obtain a polyamic acid solution. 15 g of acetic anhydride and 1 g of 3-methylpyridine were slowly added dropwise to the polyamic acid solution, and the mixture was stirred at 90 °C for 4 h to obtain a fully imidized polyimide (PI) solution. After the reaction was complete, the highly viscous polyimide solution was poured into water to precipitate, filtered, and washed with water to remove residual solvent. The resulting polyimide particles were then dried in a vacuum oven at 120 °C for 24 h.

[0061] The dried polymer particles were dissolved in NMP and stirred until completely dissolved to obtain a casting solution (concentration 30 wt%). The casting solution was filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. The filtered casting solution was then uniformly coated onto the surface of a glass plate and transferred to a nitrogen oven at 180–200 °C for 6 h to remove residual solvent. The resulting polyimide membrane had a thickness of 20 μm. The polyimide membrane was then peeled off in methanol, soaked for 24 h, and the solvent was drained.

[0062] 7g of polyimide membrane was placed in cyclohexane, and 1.6g of N-bromosuccinimide and 0.15g of azobisisobutyronitrile were added. After stirring and reacting at 20℃ for 12h, the membrane was washed twice in cyclohexane and dried to obtain a homogeneous polyimide gas separation membrane.

[0063] Example 2

[0064] At room temperature, 9.72 g of 2,3,4,6-tetramethyl-1,4-phenylenediamine was weighed and placed in a dry three-necked flask. Then, 144.0 g of N-methylpyrrolidone (NMP) was added, and the mixture was stirred at 250 rpm under a nitrogen atmosphere until completely dissolved. Next, 25.8 g of hexafluorodianhydride was added in batches; the mixture was mechanically stirred until the dianhydride dissolved, and the reaction continued for 12 h to obtain a polyamic acid solution. 16 g of acetic anhydride and 1.5 g of isoquinoline were slowly added dropwise to the polyamic acid solution, and the mixture was stirred at 90 °C for 4 h to obtain a fully imidized polyimide (PI) solution. After the reaction was complete, the highly viscous polyimide solution was poured into water to precipitate, filtered, and washed with water to remove residual solvent. The resulting polyimide particles were then dried in a vacuum oven at 120 °C for 24 h.

[0065] The dried polymer particles were dissolved in NMP and stirred until completely dissolved to obtain a casting solution (concentration 30 wt%). The casting solution was filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. The filtered casting solution was then uniformly coated onto the surface of a glass plate and transferred to a nitrogen oven at 180–200 °C for 6 h to remove residual solvent. The resulting polyimide membrane had a thickness of 20 μm. The polyimide membrane was then peeled off in methanol, soaked for 24 h, and the solvent was drained.

[0066] 7g of polyimide membrane was placed in cyclohexane, and 0.5g of N-bromophthalimide and 0.5g of azobisisobutyronitrile were added. After stirring and reacting at 25°C for 12h, the membrane was washed twice in cyclohexane and dried to obtain a polyimide homogeneous gas separation membrane.

[0067] Example 3

[0068] At room temperature, 13.5 g of 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindene was weighed and placed in a dry three-necked flask. 144.2 g of N-methylpyrrolidone (NMP) was added, and the mixture was stirred at 250 rpm under a nitrogen atmosphere until completely dissolved. Then, 22.5 g of hexafluorodianhydride was added in batches. After mechanical stirring until the dianhydride dissolved, the reaction was continued for 12 h to obtain a polyamic acid solution. 15 g of acetic anhydride and 1 g of 3-methylpyridine were slowly added dropwise to the polyamic acid solution, and the mixture was stirred at 90 °C for 4 h to obtain a fully imidized polyimide (PI) solution. After the reaction was complete, the highly viscous polyimide solution was poured into water to precipitate, filtered, and washed with water to remove residual solvent. The resulting polyimide particles were then dried in a vacuum oven at 120 °C for 24 h.

[0069] The dried polymer particles were dissolved in NMP and stirred until completely dissolved to obtain a casting solution (concentration 30 wt%). The casting solution was filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. The filtered casting solution was then uniformly coated onto the surface of a glass plate and transferred to a nitrogen oven at 180–200 °C for 6 h to remove residual solvent. The resulting polyimide membrane had a thickness of 20 μm. The polyimide membrane was then peeled off in methanol, soaked for 24 h, and the solvent was drained.

[0070] 10g of polyimide membrane was placed in cyclohexane, and 4g of N-bromosuccinimide and 0.05g of benzoyl peroxide were added. After stirring and reacting at 20°C for 12h, the membrane was washed twice in cyclohexane and dried to obtain a polyimide homogeneous gas separation membrane.

[0071] Example 4

[0072] The preparation method of the polyimide homogeneous gas separation membrane is the same as in Example 1, except that the amount of N-bromosuccinimide used is 0.2g.

[0073] Example 5

[0074] The preparation method of the polyimide homogeneous gas separation membrane is the same as in Example 1, except that the amount of N-bromosuccinimide used is 5g.

[0075] Example 6

[0076] The preparation method of the polyimide homogeneous gas separation membrane is the same as in Example 1, except that azobisisobutyronitrile is not added.

[0077] Example 7

[0078] The preparation method of the polyimide homogeneous gas separation membrane is the same as in Example 1, except that the amount of azobisisobutyronitrile used is 2g.

[0079] Example 8

[0080] The preparation method of the polyimide homogeneous gas separation membrane is the same as in Example 1, except that the bromination reaction temperature is different, as detailed below:

[0081] 7g of polyimide membrane was placed in cyclohexane, and 1.6g of N-bromosuccinimide and 0.15g of azobisisobutyronitrile were added. After stirring and reacting at 30℃ for 12h, the membrane was washed twice in cyclohexane and dried to obtain a homogeneous polyimide gas separation membrane.

[0082] Comparative Example 1

[0083] The preparation method of the polyimide homogeneous gas separation membrane is the same as in Example 1, except that the polyimide membrane is peeled off in methanol, soaked for 24 hours and then drained of solvent, without bromination treatment.

[0084] Comparative Example 2

[0085] The preparation method of the polyimide homogeneous gas separation membrane is the same as in Example 1, except that the polyimide is first brominated before film formation.

[0086] The specific method is as follows:

[0087] Take 7g of the prepared dried polyimide particles and dissolve them in 200mL of chloroform with stirring. Add 1.6g of N-bromosuccinimide and 0.15g of azobisisobutyronitrile and heat at 50℃ for 12h. After the reaction is completed, pour the polyimide solution into methanol to precipitate it. After filtration, wash with methanol to remove residual solvent. Then dry the obtained polyimide particles in a vacuum oven at 80℃ for 24h.

[0088] The dried brominated polymer particles were dissolved in NMP to prepare a polyimide film. The polyimide film was then peeled off in methanol, soaked for 24 hours, and the solvent was drained to obtain a homogeneous polyimide gas separation membrane.

[0089] Performance Evaluation

[0090] (1) Evaluation of anti-aging performance

[0091] The gas permeability coefficient and selectivity of the polyimide homogeneous gas separation membranes of each embodiment and comparative example were tested; then they were placed in a constant temperature and humidity chamber (relative humidity 50%, temperature 50℃) for 90 days, and the gas permeability coefficient and selectivity were tested again. The results are shown in Table 1.

[0092] The test method for gas permeability coefficient refers to GB / T1038.1-2022; the selectivity is to use a pressure difference gas permeability tester under the conditions of 25℃ and 101325pa pressure difference.

[0093] Table 1

[0094]

[0095] As can be seen from the test results in Table 1, after the aging test, the gas permeation coefficient of the unbroken polyimide membrane in Comparative Example 1 decreased significantly, indicating that the gas separation membrane material underwent aging. In contrast, the gas permeation coefficient of the homogeneous polyimide gas separation membranes in each embodiment decreased less compared to the unbroken polyimide membrane in Comparative Example 1, indicating that the cross-linked gas separation membrane material maintains high throughput while exhibiting good anti-aging properties. Adding excessive brominating agents or excessive catalysts can lead to excessively rapid reaction rates (as in Examples 5 and 7). Vigorous reactions result in poor separation performance of the gas separation membrane, or even complete loss of separation performance (significantly reduced gas selectivity).

[0096] (2) Evaluation of mechanical properties

[0097] The mechanical properties of the polyimide homogeneous gas separation membranes of Example 1 and Comparative Examples 1-2 were tested using an electronic tensile testing machine. The results are shown in Table 2.

[0098] Table 2

[0099] Group Strength (MPa) Modulus (GPa) Elongation (%) Comparative Example 1 160 3.73 12 Comparative Example 2 126 3.58 9 Example 1 145 3.62 11

[0100] As can be seen from the test results in Table 2, compared with the separation membrane prepared by the method in Comparative Example 2 where polyimide was first brominated before membrane fabrication, the polyimide gas separation membrane prepared by the method provided by this invention exhibits significantly better mechanical properties. This is because the preparation method provided by this invention only brominates the surface of the polyimide membrane, without damaging the core structure of the membrane material. Therefore, the mechanical properties of the prepared polyimide gas separation membrane decrease significantly less compared to the unbrominated polyimide membrane.

[0101] Furthermore, the preparation method of Comparative Example 2 is more complicated and generates more organic waste liquid.

[0102] Therefore, the preparation method provided by the present invention is simple to operate and environmentally friendly, and the polyimide gas separation membrane prepared therefrom can maintain good mechanical properties while improving its aging performance.

[0103] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing an anti-aging polyimide gas separation membrane, characterized in that, include: The polyimide membrane is subjected to a bromination reaction in the presence of a brominating agent and a first catalyst to obtain the anti-aging polyimide gas separation membrane.

2. The preparation method according to claim 1, characterized in that, The brominating agent includes at least one of N-bromosuccinimide, dibromohydantoin and N-bromophthalimide; And / or, the first catalyst comprises at least one of azobisisobutyronitrile, benzoyl peroxide, and dilauryl peroxide; And / or, the polyimide film includes at least one of a homogeneous film, a composite film, and hollow fibers.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the polyimide film to the brominating agent is 1:(0.05~0.5); And / or, the mass ratio of the polyimide film to the first catalyst is 1:(0.004 to 0.2).

4. The preparation method according to any one of claims 1-3, characterized in that, The bromination reaction is carried out at a temperature of 20–40°C. And / or, the bromination reaction takes 6 to 18 hours.

5. The preparation method according to any one of claims 1-4, characterized in that, The bromination reaction is carried out in a first solvent; preferably, the first solvent includes at least one of cyclohexane, n-hexane, n-heptane, and toluene. And / or, after the bromination reaction is completed, the brominated polyimide membrane is washed.

6. The preparation method according to any one of claims 1-5, characterized in that, The preparation process of the polyimide membrane includes: adding dianhydride monomer and diamine monomer to a second solvent to undergo a polymerization reaction; then adding a second catalyst and a dehydrating agent to perform imidization treatment; then performing post-treatment to obtain polyimide; dissolving the polyimide in a third solvent to obtain a casting solution, and using the casting solution to form a membrane to obtain the polyimide membrane.

7. The preparation method according to claim 6, characterized in that, The dianhydride monomer is selected from compounds with the structural formula O(O=C)2-R1-(C=O)2O, wherein R1 includes at least one of the following structural units: And / or, the diamine monomer is selected from compounds with the structural formula NH2-R2-NH2, wherein R2 comprises at least one of the following structural units: And / or, the molar ratio of the dianhydride monomer to the diamine monomer is 0.95 to 1; And / or, the second solvent includes at least one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone; And / or, the second catalyst comprises at least one of pyridine compounds, alkylamine compounds, and quinoline compounds, preferably at least one of 4-dimethylaminopyridine, 3-methylpyridine, 2,4-dimethylpyridine, triethylamine, pyridine, diethylamine, quinoline, and isoquinoline; And / or, the molar ratio of the second catalyst to the diamine monomer is (0.025–0.25):1; And / or, the dehydrating agent includes at least one of acid anhydrides; preferably, the dehydrating agent includes at least one of acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, trifluoroacetic anhydride, and benzoic anhydride; And / or, the molar ratio of the dehydrating agent to the diamine monomer is (2.2–5):1; And / or, the third solvent includes at least one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone; And / or, the concentration of the casting solution is 5 to 40 wt%.

8. The preparation method according to claim 6 or 7, characterized in that, The polyimide membrane undergoes solvent exchange before the bromination reaction; Preferably, the solvent exchange includes: immersing the polyimide membrane in a fourth solvent, stirring for 12-24 hours, draining, and washing; More preferably, the fourth solvent includes at least one of ethanol, methanol, and acetone.

9. An anti-aging polyimide gas separation membrane, prepared by the preparation method described in any one of claims 1-8.

10. The application of the anti-aging polyimide gas separation membrane according to claim 9 in gas separation and gas concentration.

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