A method for preparing a co-polyamide-imide CO2 separation membrane containing a sulfone group

Abstract

The application relates to a preparation method of a sulfone group-containing copolymer polyamide-imide CO2 separation membrane and belongs to the technical field of gas separation membranes. The method comprises the following steps: a sulfone group-containing diamine, a diacyl chloride and a plurality of dianhydrides are copolymerized to synthesize a polyamide-imide copolymer structure with rigid and flexible alternating structural units; a compact selection layer formed by rigid sulfone group segments can effectively hinder the diffusion of CH4 with a kinetic diameter of 0.38 nm, while CO2 with a kinetic diameter of 0.33 nm can preferentially penetrate through; and flexible segments increase the free volume of the polymer, significantly improving the permeation flux of CO2, so that the effects of removing CO2 in natural gas and enriching methane are achieved.

Description

Technical Field

[0001] This invention relates to a method for preparing a sulfone-containing copolyamide-imide CO2 separation membrane, belonging to the field of gas separation membrane technology. Background Technology

[0002] Natural gas, as a high-quality, low-carbon, and clean energy source, occupies an increasingly important position in the global energy structure. However, its composition is complex, containing impurities such as carbon dioxide (CO2), nitrogen (N2), and hydrogen sulfide (H2S) in addition to its core component, methane (CH4). CO2 not only directly reduces the calorific value of natural gas (approximately 0.5% decrease for every 1% increase in volume fraction), but also forms carbonic acid in humid environments, accelerating pipeline and equipment corrosion. The toxicity and corrosiveness of H2S further threaten safe production. The presence of N2 dilutes the methane concentration, increasing transportation costs. According to my country's "Natural Gas" (GB17820–2018) standard, the volume fraction of CO2 in pipeline-transported natural gas must be ≤3%. Therefore, removing acidic gases and enriching methane are core prerequisites for the commercial utilization of natural gas.

[0003] Traditional purification technologies (such as amine absorption and cryogenic distillation) have significant limitations: amine absorption requires high-temperature regeneration, and energy consumption accounts for 30%-50% of the natural gas processing cost; cryogenic distillation relies on a cryogenic environment, involves large equipment investment, and has a long start-up period, making it difficult to meet the flexible processing needs of dispersed gas sources such as shale gas and coalbed methane. In contrast, membrane separation technology can separate, purify, and concentrate different components based on differences in gas permeation rates. It has advantages such as continuous operation, low energy consumption, small investment, small footprint, and high operational flexibility, making it a highly promising and challenging separation technology for natural gas purification. Among many membrane materials, polyimide, due to the high-temperature resistance, chemical corrosion resistance, and excellent mechanical properties imparted by the imide ring (-CO-NR-CO-), is the preferred membrane separation material. However, single-structure polyimide membranes often suffer from the problem of balancing permeability and selectivity.

[0004] The introduction of the special functional group sulfone (-SO2-) is an important technical approach to solve the above problems. From the perspective of molecular interaction mechanism, the strong polarity of the sulfone group can enhance the solubility selectivity of polar gases (such as CO2), making its solubility in the membrane much higher than that of non-polar CH4. The conjugated system formed by the sulfur atom in the sulfone group and the two oxygen atoms can not only enhance the interaction between molecular chains and improve the heat resistance and mechanical strength of the material, but also regulate the flexibility of the molecular chain through the steric hindrance effect of the sulfone group. In addition, the stable +6 valence electron structure of the sulfur atom in the sulfone group endows the material with excellent oxidation resistance and extends the service life of the membrane. By using the strategy of copolymerizing sulfone-containing diamines (such as 3,3'-diaminodiphenyl sulfone m-DDS and 4,4'-bis(4-aminophenoxy)diphenyl sulfone 4,4'-bis(4-aminophenoxy)diphenyl sulfone) with various dianhydrides and diacid chlorides, the molecular configuration of polyimide can be precisely controlled. By adjusting the proportions of each monomer, this gas separation membrane can effectively concentrate methane while removing CO2, and also maintain the methane on the high-pressure side, simplifying the re-compression process after separation. Furthermore, the unique functional group structure endows this gas separation membrane with excellent gas permeability, significantly reducing energy consumption. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a method for preparing a sulfone-containing copolyamide-imide CO2 separation membrane. This method utilizes a sulfone-containing diamine polymerized with various dianhydrides and diacyl chloride units to form a rigid-flexible polymer structure. By adjusting the polarity of the polymer, CO2 and CH4 with different polarizabilities exhibit high selective permeability in the membrane, thereby achieving the effects of CO2 removal and methane enrichment from natural gas.

[0006] To achieve the above objectives, the technical solution adopted in this invention is a method for preparing a sulfone-containing copolyamide-imide CO2 separation membrane, which is operated according to the following steps:

[0007] S1. Under an argon protective atmosphere, N,N-dimethylacetamide is added to a sulfone-containing diamine monomer, and the solid content of the system is controlled within the range of 10%-40%.

[0008] S2. After the diamine monomer is fully dissolved, maintain the reaction temperature at -15℃ to 20℃, add 4,4'-(hexafluoroisopropene) phthalic anhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride and diacyl chloride, and continue the reaction at this temperature for 24 h.

[0009] S3, followed by the addition of acetic anhydride and 3-methylpyridine to carry out a chemical cyclization reaction;

[0010] S4. After reacting for 24 hours, the polymer solution was placed in methanol for precipitation and washed three times.

[0011] S5. After washing, the product is placed in a 60℃ oven and dried for 24 h to finally obtain the copolymer polyamide imide;

[0012] S6. Dissolve the copolymerized polyamide-imide in N,N-dimethylacetamide to obtain a casting solution, wherein the concentration of polyamide-imide in the casting solution is 15%;

[0013] S7. After stirring and degassing the casting solution, slowly pour the casting solution into a petri dish and dry it in an 80°C oven for 24 hours to finally obtain a polyamide-imide separation membrane copolymerized with sulfone diamine, various dianhydrides and diacyl chlorides.

[0014] Preferably, the diamine monomer is 4,4'-bis(4-aminophenoxy)diphenyl sulfone or 3,3'-diaminodiphenyl sulfone.

[0015] Preferably, the 3,3',4,4'-benzophenone tetracarboxylic dianhydride can be replaced with 3,3',4,4'-biphenyltetracarboxylic dianhydride or...

[0016] Preferably, the diacyl chloride is terephthaloyl chloride or isophthaloyl chloride.

[0017] Compared with existing technologies, this invention has the following technical advantages: This invention prepares a copolymeric polyamide-imide gas separation membrane with a unique molecular structure by rationally selecting sulfone-containing diamines and various dianhydrides and diacid chlorides as comonomers and precisely controlling their ratios. The strong polarity of the sulfone group in the diamine monomer allows CO2 in the feed gas to permeate preferentially. The synergistic copolymerization of various dianhydrides and diamines not only optimizes the thermal stability of the membrane material but also improves the uniformity of membrane formation, enabling the membrane to maintain stable separation performance under high pressure and high humidity environments. Its resistance to plasticization is significantly improved compared to traditional polyimide materials. The polyamide-imide membrane material prepared by this method combines high permeability and selectivity. In practical applications, it can achieve efficient CO2 removal and high-concentration CH4 enrichment within a single-stage membrane module, providing an efficient, energy-saving, and sustainable solution for natural gas purification. Attached Figure Description

[0018] Figure 1 This is a physical image of the sulfone-based copolyamide-imide CO2 separation membrane used in this invention. Detailed Implementation

[0019] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. Example 1

[0020] 17.30 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone and 14.90 g of 3,3'-diaminodiphenyl sulfone were added to a pre-dried three-necked flask. 948.1 mL of N,N-dimethylacetamide was added under an argon atmosphere, resulting in a solid content of 10%. After the 4,4'-bis(4-aminophenoxy)diphenyl sulfone was fully dissolved, the reaction temperature was maintained at -15°C. 22.22 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 16.12 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 18.3 g of terephthaloyl chloride were added sequentially, and the reaction was continued at this temperature for 24 h.

[0021] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0022] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0023] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25°C, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. Its CO2 permeability coefficient was 256 Barrer and its CO2 / CH4 separation factor was 65. Example 2

[0024] 43.25 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone was added to a pre-dried three-necked flask, followed by 420.4 mL of N,N-dimethylacetamide under an argon atmosphere, resulting in a solid content of 25%. After the 4,4'-bis(4-aminophenoxy)diphenyl sulfone was fully dissolved, the reaction temperature was maintained at 8 °C. Then, 22.22 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 14.71 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 18.3 g of isophthaloyl chloride were added sequentially, and the reaction was continued at this temperature for 24 h.

[0025] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0026] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0027] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25°C, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. Its CO2 permeability coefficient was 312 Barrer and its CO2 / CH4 separation factor was 61. Example 3

[0028] 24.83 g of 3,3'-diaminodiphenyl sulfone was added to a pre-dried three-necked flask, followed by 232.5 mL of N,N-dimethylacetamide under an argon atmosphere, resulting in a solid content of 35%. After the 3,3'-diaminodiphenyl sulfone was fully dissolved, the reaction temperature was maintained at 15 °C. Then, 22.22 g of 4,4'-(hexafluoroisopropene) phthalic anhydride, 10.91 g of pyromellitic dianhydride, and 18.3 g of terephthaloyl chloride were added sequentially, and the reaction was continued at this temperature for 24 h.

[0029] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0030] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0031] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25°C, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. Its CO2 permeability coefficient was 298 Barrer and its CO2 / CH4 separation factor was 63. Example 4

[0032] 21.63 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone and 12.41 g of 3,3'-diaminodiphenyl sulfone were added to a pre-dried three-necked flask. Under an argon atmosphere, 241.9 mL of N,N-dimethylacetamide was added, resulting in a solid content of 40%. After the 4,4'-bis(4-aminophenoxy)diphenyl sulfone was fully dissolved, the reaction temperature was maintained at 20 °C. Then, 22.22 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 16.12 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 18.3 g of isophthaloyl chloride were added sequentially, and the reaction was continued at this temperature for 24 h.

[0033] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0034] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0035] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25°C, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. Its CO2 permeability coefficient was 328 Barrer and its CO2 / CH4 separation factor was 59.

[0036] Comparative Example 1: Compared with Example 1

[0037] 17.30 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone and 14.90 g of 3,3'-diaminodiphenyl sulfone were added to a pre-dried three-necked flask. 948.1 mL of N,N-dimethylacetamide was added under an argon atmosphere, resulting in a solid content of 10%. After the diamine monomer was fully dissolved, the reaction temperature was maintained at -25°C. 22.22 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 16.12 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 18.3 g of terephthaloyl chloride were added sequentially, and the reaction was continued at this temperature for 24 h.

[0038] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0039] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0040] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25℃, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. Due to the excessively low preparation temperature, the dissolution rates of dianhydride and diacid chloride decreased significantly, local agglomeration occurred in the reaction system, and the stirring resistance increased. Obvious defects were observed on the membrane surface after formation. The measured CO2 permeability coefficient was 142 Barrer, and the CO2 / CH4 separation factor was 40. The low temperature resulted in incomplete reaction, insufficient molecular chain cross-linking, a loose membrane structure, and a significant decrease in selectivity.

[0041] Comparative Example 2: Compared with Example 4

[0042] In a pre-dried three-necked flask, 21.63 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone and 12.41 g of 3,3'-diaminodiphenyl sulfone were added. Under an argon atmosphere, 241.9 mL of N,N-dimethylacetamide was added, resulting in a solid content of 40%. After the diamine monomer was fully dissolved, the reaction temperature was maintained at 25 °C. Then, 22.22 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 16.12 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 18.3 g of isophthaloyl chloride were added sequentially, and the reaction was continued at this temperature for 24 h.

[0043] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0044] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0045] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25℃, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. Due to the high preparation temperature, the reaction rate was too fast, resulting in localized gelation and a sharp increase in the viscosity of the polymer solution. The membrane thickness was uneven, and the measured CO2 permeability coefficient was 185 Barrer, while the CO2 / CH4 separation factor was 43. The high temperature led to uneven monomer reaction, disordered molecular chain arrangement, and a decrease in both permeability and selectivity.

[0046] Comparative Example 3: Compared with Example 2

[0047] 43.25 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone was added to a pre-dried three-necked flask, followed by 2102 mL of N,N-dimethylacetamide under an argon atmosphere, resulting in a solid content of 5%. After the diamine monomer was fully dissolved, the reaction temperature was maintained at 8 °C, and 22.22 g of 4,4'-(hexafluoroisopropene)phthalic anhydride, 14.71 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 18.3 g of isophthaloyl chloride were added sequentially. The reaction was continued at this temperature for 24 h.

[0048] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0049] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0050] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25°C, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. Due to excessive solvent and low polymer concentration, the solvent evaporated slowly during casting, making the membrane prone to pinholes. Its CO2 permeability coefficient was 198 Barrer, and the CO2 / CH4 separation factor was 37. The low solids content resulted in a non-dense membrane structure, increased CH4 permeation, and deteriorated selectivity.

[0051] Comparative Example 4: Compared with Example 3

[0052] 24.83 g of 3,3'-diaminodiphenyl sulfone was added to a pre-dried three-necked flask, followed by 180.9 mL of N,N-dimethylacetamide under an argon atmosphere, resulting in a solid content of 45%. After the diamine monomer was fully dissolved, the reaction temperature was maintained at 15 °C, and 22.22 g of 4,4'-(hexafluoroisopropene) phthalic anhydride, 10.91 g of pyromellitic dianhydride, and 18.3 g of terephthaloyl chloride were added sequentially. The reaction was continued at this temperature for 24 h.

[0053] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0054] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0055] The polyamide-imide membrane prepared above was tested on a gas separation tester (temperature 25℃, feed pressure 0.4MPa, exhaust gas pressure 0.1MPa). The system had extremely high viscosity, making stirring difficult, and the dianhydride and diacid chloride could not be uniformly dispersed. Unreacted monomer residues were present inside the membrane layer. The measured CO2 permeability coefficient was 163 Barrer, and the CO2 / CH4 separation factor was 42. The high solids content led to uneven reaction, increased defects in the membrane, and decreased performance.

[0056] Comparative Example 5: Compared with Example 2

[0057] 6.01 g of ethylenediamine (sulfonyl diamine) was added to a pre-dried three-necked flask, followed by 261.4 mL of N,N-dimethylacetamide (25% solids content) under an argon atmosphere. After the diamine monomer was fully dissolved, the reaction temperature was maintained at 8 °C, and 22.22 g of 4,4'-(hexafluoroisopropene) phthalic anhydride, 14.71 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 18.3 g of isophthaloyl chloride were added sequentially. The reaction was continued at this temperature for 24 h.

[0058] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0059] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0060] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25°C, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. The polymer solution was light yellow, significantly different from the color of the membrane in Example 2. The heat resistance of the membrane material decreased. The tested CO2 permeability coefficient was 118 Barrer, the CO2 / CH4 separation factor was 31, and the strong polar effect of the lack of sulfone groups resulted in loss of CO2 solubility selectivity and failure of core performance.

[0061] Comparative Example 6: Compared with Example 1

[0062] 17.30 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone and 14.90 g of 3,3'-diaminodiphenyl sulfone were added to a pre-dried three-necked flask. 1013.2 mL of N,N-dimethylacetamide was added under an argon atmosphere, resulting in a solid content of 10%. After the diamine monomer was fully dissolved, the reaction temperature was maintained at -15°C. 44.44 g of 4,4'-(hexafluoroisopropene) phthalic anhydride (a single dianhydride, without other dianhydrides) and 18.3 g of terephthaloyl chloride were added sequentially, and the reaction was continued at this temperature for 24 h.

[0063] 94.53 mL of acetic anhydride and 9.70 mL of 3-methylpyridine were added to initiate a chemical cyclization reaction. After 24 h of reaction, the polymer solution was precipitated in methanol and washed three times. The washed product was then dried in a 60 °C oven for 24 h to finally obtain the sulfone-co-polymerized polyamide-imide.

[0064] The polymer powder was prepared into a 15wt% casting solution using N,N-dimethylacetamide. After stirring for 48 hours, the mixture was ultrasonically degassed for 30 minutes. The casting solution was then uniformly coated onto a clean glass substrate and dried in an 80℃ oven for 24 hours to form a film.

[0065] The polyamide-imide membrane prepared above was tested on a gas separation tester at a temperature of 25°C, a feed pressure of 0.4 MPa, and a tail gas pressure of 0.1 MPa. The polymer molecular chains were too rigid, making the membrane prone to brittleness during formation. The measured CO2 permeability coefficient was 156 Barrer, and the CO2 / CH4 separation factor was 45. The single rigid chain segment resulted in insufficient free volume of the membrane, decreased permeability, poor flexibility, and low practicality.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A method for preparing a sulfone-containing copolyamide-imide CO2 separation membrane, characterized in that: Follow these steps: S1. Under an argon protective atmosphere, N,N-dimethylacetamide is added to a sulfone-containing diamine monomer, and the solid content of the system is controlled within the range of 10%-40%. S2. After the diamine monomer is fully dissolved, maintain the reaction temperature at -15℃ to 20℃, add 4,4'-(hexafluoroisopropene) phthalic anhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride and diacyl chloride, and continue the reaction at this temperature for 24 h. S3, followed by the addition of acetic anhydride and 3-methylpyridine to carry out a chemical cyclization reaction; S4. After reacting for 24 hours, the polymer solution was placed in methanol for precipitation and washed three times. S5. After washing, the product is placed in a 60℃ oven and dried for 24 h to finally obtain the copolymer polyamide imide; S6. Dissolve the copolymerized polyamide-imide in N,N-dimethylacetamide to obtain a casting solution, wherein the concentration of polyamide-imide in the casting solution is 15%; S7. After stirring and degassing the casting solution, slowly pour the casting solution into a petri dish and dry it in an 80°C oven for 24 hours to finally obtain a polyamide-imide separation membrane copolymerized with sulfone diamine and various dianhydrides and diacyl chlorides. The diamine monomer is 4,4'-bis(4-aminophenoxy)diphenyl sulfone or 3,3'-diaminodiphenyl sulfone and mixtures thereof; The 3,3',4,4'-benzophenone tetracarboxylic dianhydride can be replaced with 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride or pyromellitic dianhydride. The diacyl chloride is terephthaloyl chloride or isophthaloyl chloride.

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