A polyimide hollow fiber membrane for oxygen-enriched combustion scenarios and a method of making the same

Abstract

The present application relates to a kind of polyimide hollow fiber membrane for oxygen-enriched combustion scene and its preparation method, belong to separation membrane technical field, specifically including the membrane material of the hollow fiber membrane is by naphthalene diamine, dianhydride and terephthaloyl chloride polymerization;The molar ratio of terephthaloyl chloride and dianhydride is 100:1-70:30, the fiber membrane is applied in the gas separation of temperature 80-150 DEG C, oxygen-enriched combustion environment, can be enriched to 30%-35% from 21% oxygen concentration, the present application has high O2 / N2 selectivity, high gas permeability, also has excellent thermal stability and moisture resistance.

Description

Technical Field

[0001] This invention relates to a polyimide hollow fiber membrane for oxygen-rich combustion scenarios and its preparation method, belonging to the field of separation membrane technology. Background Technology

[0002] Oxygen-enriched combustion technology significantly improves fuel combustion efficiency (energy savings of 10%-30%) by increasing the oxygen concentration in the air from 21% to 25%-35%, while simultaneously reducing nitrogen oxides (NOx). X Oxygen-enriched combustion systems, which reduce emissions by over 60% and facilitate carbon dioxide capture and storage (CCS) in flue gas, are key technologies for achieving the "dual carbon" target. In oxygen-enriched combustion systems, the energy consumption and stability of the oxygen enrichment process directly determine the techno-economic viability; therefore, developing efficient oxygen separation materials that can withstand harsh environments is of great significance.

[0003] Currently, there are three main types of mainstream oxygen enrichment technologies: cryogenic separation, which achieves oxygen-nitrogen separation through low-temperature distillation, achieving oxygen purity of over 99.5%, but requires large equipment investment, consumes a lot of energy, and is only suitable for large-scale centralized scenarios. Pressure swing adsorption (PSA) utilizes the adsorption differences of molecular sieves to separate oxygen and nitrogen, offering fast response speeds, but has a short adsorbent lifespan, moderate energy consumption, and its pure oxygen production is limited by adsorption capacity. In contrast, membrane separation is based on the permeation differences of polymer membranes to separate oxygen and nitrogen, offering advantages such as low energy consumption, compact equipment, and simple operation. However, traditional membrane materials have significant drawbacks: poor temperature resistance (long-term operating temperature <80 ℃), low O2 / N2 selectivity (separation factor <7), and susceptibility to aging in the high-temperature and high-humidity environment (80-150 ℃, humidity >80%) of oxygen-enriched combustion scenarios, making it difficult to meet the requirements for long-term stable operation.

[0004] Polyimide has become a core material for membrane separation due to its excellent thermal stability and mechanical properties. However, traditional polyimide has two major bottlenecks: first, the molecular chains are tightly packed, resulting in a low oxygen permeability coefficient and a large membrane module size; second, the chain segments are not flexible enough and are prone to rigid collapse at high temperatures, causing the O2 / N2 selectivity to drop sharply with increasing temperature, with the separation factor dropping below 5 at 100 °C. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a polyimide hollow fiber membrane for oxygen-rich combustion scenarios and its preparation method, which combines high O2 / N2 selectivity, high air permeability, and excellent thermal stability and moisture resistance.

[0006] To achieve the above objectives, the technical solution adopted in this invention is a polyimide hollow fiber membrane for oxygen-enriched combustion scenarios. The membrane material of this hollow fiber membrane is polymerized from naphthalenediamine, dianhydride, and terephthaloyl chloride. The molar ratio of terephthaloyl chloride to dianhydride is 100:1-70:30. When this fiber membrane is applied to gas separation in an oxygen-enriched combustion environment at a temperature of 80-150℃, it can enrich the oxygen concentration from 21% to 30%-35%.

[0007] Preferably, the naphthalenediamine is one of 1,5-naphthalenediamine and 1,7-naphthalenediamine; the dianhydride is one of hexafluorodianhydride, bisphenol A type diether dianhydride, and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

[0008] A method for preparing a polyimide hollow fiber membrane for oxygen-rich combustion scenarios includes the following steps:

[0009] S1. Prepare a polyamic acid solution by controlling the ratio of the total moles of naphthalenediamine to the total moles of dianhydride and terephthaloyl chloride to be 1:1, and the solid content of the reaction system to be 15%-30%. Dissolve naphthalenediamine in N-methylpyrrolidone under nitrogen protection, and add dianhydride and terephthaloyl chloride in batches at a low temperature of 0-10℃, stir and react to form a polyamic acid solution.

[0010] S2. Polyimide powder is prepared by chemical imidization of polyamic acid solution with acetic anhydride and 3-methylpyridine, followed by precipitation purification and drying to obtain polyimide powder;

[0011] S3. Hollow fiber membrane is prepared by using a dry-wet spinning process.

[0012] Preferably, in step S3, the wet-dry spinning process is as follows: polyimide powder is dissolved in N-methylpyrrolidone solvent to prepare a casting solution of 15wt%-20wt%. After vacuum degassing, a DMAc / water mixture with a volume ratio of 30% is used as the core liquid. The air section length is controlled to be 5-10cm. The mixture is solidified in a deionized water coagulation bath at 25℃. After washing with water for 24h to remove residual solvent, it is vacuum dried at 60℃ for 12h and then heat-treated at 150-200℃ for 2h to finally obtain a hollow fiber membrane with an asymmetric structure.

[0013] Compared with existing technologies, this invention has the following technical advantages: This invention uses naphthalenediamine, specific dianhydrides, and terephthaloyl chloride to copolymerize polyimide, which has significant advantages over traditional systems. The rigid naphthalene ring of naphthalenediamine enhances the rigidity of the molecular chain through a conjugated π system, improving the thermal stability of the membrane, with a glass transition temperature (Tg) > 300 ℃, while simultaneously reducing chain segment movement at high temperatures and maintaining O2 / N2 selectivity. The dianhydride is selected from hexafluorodianhydride, bisphenol A type diether dianhydride, and 3,3',4,4'-benzophenone tetracarboxylic dianhydride. The hexafluoroisopropyl group in 6FDA imparts hydrophobicity and free volume to the molecular chain, improving oxygen permeability; the ether bond in BPADA increases chain segment flexibility to balance air permeability and mechanical properties; the ketone group in BTDA enhances intermolecular forces to improve aging resistance. Terephthaloyl chloride, as the third monomer, has a rigid benzene ring that optimizes the molecular chain packing density. While ensuring high oxygen permeability, it improves O2 / N2 selectivity through size sieving. The "rigid framework-flexible connection-polarity regulation" structure formed by ternary copolymerization balances high permeability and high selectivity, improving film uniformity and mechanical strength. It can maintain long-term operation in high-humidity, oxygen-enriched combustion scenarios (80-150℃), exhibiting superior aging resistance and anti-plasticization properties compared to traditional materials. The gas separation membrane prepared by this invention can enrich the oxygen concentration from 21% to 30%-35% in high-humidity, oxygen-enriched combustion scenarios (80-150℃), providing an efficient solution for energy saving, carbon reduction, and CO2 capture in industrial oxygen-enriched combustion. Detailed Implementation

[0014] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0015] Example 1

[0016] (1) 15.82 g of 1,5-naphthyldiamine was added to a pre-dried three-necked flask, and 391.2 mL of NMP (15% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 0 °C and stabilized for 30 min. 44.44 g of 6FDA was added in portions, and after stirring for 30 min, 0.18 g of TPC (6FDA:TPC=100:1) was added. The mixture was stirred continuously at 0 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0017] (2) Dissolve 15g of polyimide powder in 97.09mL of NMP to prepare a 15wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 5cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 150℃ for 2h to obtain the finished film.

[0018] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. Its O2 permeability coefficient was 42 Barrer and its O2 / N2 separation factor was 9.2.

[0019] Example 2

[0020] (1) 15.82 g of 1,7-naphthyldiamine was added to a pre-dried three-necked flask, and 242 mL of NMP (22.5% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 5 °C and stabilized for 30 min. 37.52 g of BPADA was added in portions, and after stirring for 30 min, 2.75 g of TPC (6FDA:TPC=85:15) was added. The mixture was stirred continuously at 5 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0021] (2) Dissolve 17g of polyimide powder in 97.09mL of NMP to prepare a 17wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 7cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 180℃ for 2h to obtain the finished film.

[0022] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. Its O2 permeability coefficient was 35 Barrer and its O2 / N2 separation factor was 10.5.

[0023] Example 3

[0024] (1) 15.82 g of 1,7-naphthyldiamine was added to a pre-dried three-necked flask, and 242 mL of NMP (30% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 10 °C and stabilized for 30 min. 22.57 g of BTDA was added in portions, and after stirring for 30 min, 5.5 g of TPC (6FDA:TPC=70:30) was added. The mixture was stirred continuously at 10 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0025] (2) Dissolve 20g of polyimide powder in 97.09mL of NMP to prepare a 20wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 8cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 200℃ for 2h to obtain the finished film.

[0026] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. Its O2 permeability coefficient was 28 Barrer and its O2 / N2 separation factor was 11.8.

[0027] Comparative Example 1 (compared to Example 1)

[0028] (1) 15.82 g of 1,5-naphthyldiamine was added to a pre-dried three-necked flask, and 322.3 mL of NMP (15% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 0 °C and stabilized for 30 min. 26.66 g of 6FDA was added in portions, and after stirring for 30 min, 7.32 g of TPC (6FDA:TPC=60:40) was added. The mixture was stirred continuously at 0 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0029] (2) Dissolve 15g of polyimide powder in 97.09mL of NMP to prepare a 15wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 5cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 150℃ for 2h to obtain the finished film.

[0030] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. Excessive TPC caused excessive cross-linking of molecular chains and severe densification of membrane structure. The O2 permeability coefficient of the product was only 18 Barrer), and the O2 / N2 separation factor was 8.2.

[0031] Comparative Example 2 (compared to Example 1)

[0032] (1) 15.82 g of 1,5-naphthyldiamine was added to a pre-dried three-necked flask, and 392.9 mL of NMP (15% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 0 °C and stabilized for 30 min. 44.89 g of 6FDA was added in portions, without the addition of TPC (6FDA:TPC=100:0). The mixture was stirred continuously at 0 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0033] (2) Dissolve 15g of polyimide powder in 97.09mL of NMP to prepare a 15wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 5cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 150℃ for 2h to obtain the finished film.

[0034] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. Due to the lack of TPC size sieving control, the molecular chain stacking uniformity was insufficient, the O2 / N2 separation factor was only 7.5, and the O2 permeability coefficient was 38 Barrer.

[0035] Comparative Example 3 (compared to Example 2)

[0036] (1) 15.82 g of 1,7-naphthyldiamine was added to a pre-dried three-necked flask, and 544.6 mL of NMP (10% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 5 °C and stabilized for 30 min. 37.52 g of BPADA was added in portions, and after stirring for 30 min, 2.75 g of TPC (6FDA:TPC=85:15) was added. The mixture was stirred continuously at 5 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0037] (2) Dissolve 17g of polyimide powder in 97.09mL of NMP to prepare a 17wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 7cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 180℃ for 2h to obtain the finished film.

[0038] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. The reaction system was too dilute, the molecular chain growth was hindered, the viscosity of polyamic acid decreased, the O2 permeability coefficient of the product was 29 Barrer, and the O2 / N2 separation factor was 8.7.

[0039] Comparative Example 4 (compared to Example 3)

[0040] (1) 15.82 g of 1,7-naphthyldiamine was added to a pre-dried three-necked flask, and 121.7 mL of NMP (35% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 10 °C and stabilized for 30 min. 22.57 g of BTDA was added in portions, and after stirring for 30 min, 5.5 g of TPC (6FDA:TPC=70:30) was added. The mixture was stirred continuously at 10 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0041] (2) Dissolve 20g of polyimide powder in 97.09mL of NMP to prepare a 20wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 8cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 200℃ for 2h to obtain the finished film.

[0042] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. The system viscosity was too high, the dianhydride and TPC were not dispersed evenly, the reaction was incomplete, and unreacted monomers remained in the polyimide powder. The O2 permeability coefficient of the product was 23 Barrer, and the O2 / N2 separation factor was 8.5.

[0043] Comparative Example 5 (compared to Example 1)

[0044] (1) 15.82 g of 1,5-naphthyldiamine was added to a pre-dried three-necked flask, and 391.2 mL of NMP (15% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to -5℃ and stabilized for 30 min. 44.44 g of 6FDA was added in portions, and after stirring for 30 min, 0.18 g of TPC (6FDA:TPC=100:1) was added. The mixture was stirred continuously at -5℃ for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80℃ for 24 h to obtain polyimide.

[0045] (2) Dissolve 15g of polyimide powder in 97.09mL of NMP to prepare a 15wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 5cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 150℃ for 2h to obtain the finished film.

[0046] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. The low temperature during polymerization caused the reaction rate to be too slow, the monomer reaction was incomplete, and the molecular weight of polyimide was low. The O2 permeability coefficient of the product was 22 Barrer, and the O2 / N2 separation factor was 8.1.

[0047] Comparative Example 6 (compared to Example 2)

[0048] (1) 10.81 g of 4,4'-diaminodiphenyl ether (ODA, replacing naphthyldiamine) was added to a pre-dried three-necked flask. 242 mL of NMP (22.5% solid content) was added under a high-purity nitrogen atmosphere and stirred until completely dissolved. Subsequently, the reaction system temperature was lowered to 5 °C and stabilized for 30 min. 37.52 g of BPADA was added in batches, and after stirring for 30 min, 2.75 g of TPC (6FDA:TPC=85:15) was added. The mixture was stirred continuously at 5 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the reaction was carried out for 24 h to complete the chemical imidization. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0049] (2) Dissolve 17g of polyimide powder in 97.09mL of NMP to prepare a 17wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 7cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 180℃ for 2h to obtain the finished film.

[0050] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N2 separation test on a gas separation tester. After ODA was used to replace naphthalene diamine, the product lacked the rigid skeleton of naphthalene ring, and the glass transition temperature (Tg) dropped to 265℃ (<300℃); the O2 permeability coefficient was 32 Barrer, and the O2 / N2 separation factor was 7.8.

[0051] Comparative Example 7 (compared to Example 3)

[0052] (1) 15.82 g of 1,7-naphthyldiamine was added to a pre-dried three-necked flask, and 242 mL of NMP (30% solid content) was added under a high-purity nitrogen atmosphere. The mixture was stirred until completely dissolved. Subsequently, the temperature of the reaction system was lowered to 10 °C and stabilized for 30 min. 22.57 g of BTDA was added in portions, and after stirring for 30 min, 5.5 g of TPC (6FDA:TPC=70:30) was added. The mixture was stirred continuously at 10 °C for 24 h to form a viscous polyamic acid solution. 90 mL of acetic anhydride and 10 mL of 3-methylpyridine (volume ratio 9:1) were added dropwise to the solution, and the chemical imidization was completed after 24 h of reaction. The reaction solution was poured into deionized water to precipitate the precipitate. After filtration, the precipitate was washed four times with deionized water and dried under vacuum at 80 °C for 24 h to obtain polyimide.

[0053] (2) Dissolve 20g of polyimide powder in 97.09mL of NMP to prepare a 20wt% casting solution. Stir at 60℃ for 48h and degas under vacuum for 2h. Use wet-dry spinning method, with the core solution being a 30% DMAc / water mixture (volume ratio), an air section length of 8cm, and deionized water at 25℃ in the coagulation bath. After curing, wash the fiber with water for 24h to remove residual solvent, vacuum dry at 60℃ for 12h, and then heat treat at 120℃ for 2h to obtain the finished film.

[0054] (3) The polyimide hollow fiber membrane prepared above was subjected to O2 / N separation test on a gas separation tester. Due to the decrease in heat treatment temperature, the membrane structure was not completely stable and the molecular chain arrangement was loose. The O2 / N separation factor of the product was 9.1.

[0055] 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 polyimide hollow fiber membrane for oxygen-enriched combustion scenarios, characterized in that: The hollow fiber membrane is made of naphthalenediamine, dianhydride and terephthaloyl chloride polymerized together; the molar ratio of terephthaloyl chloride to dianhydride is 100:1-70:

30. This fiber membrane is used in gas separation in an oxygen-rich combustion environment at a temperature of 80-150℃, and can enrich the oxygen concentration from 21% to 30%-35%. Includes the following steps, S1. Prepare a polyamic acid solution by controlling the ratio of the total moles of naphthalenediamine to the total moles of dianhydride and terephthaloyl chloride to be 1:1, and the solid content of the reaction system to be 15%-30%. Dissolve naphthalenediamine in N-methylpyrrolidone under nitrogen protection, and add dianhydride and terephthaloyl chloride in batches at a low temperature of 0-10℃, stir and react to form a polyamic acid solution. S2. Polyimide powder is prepared by chemical imidization of polyamic acid solution with acetic anhydride and 3-methylpyridine, followed by precipitation purification and drying to obtain polyimide powder; S3. Hollow fiber membrane is prepared by using a dry-wet spinning process.

2. The method for preparing a polyimide hollow fiber membrane for oxygen-rich combustion scenarios according to claim 1, characterized in that: The naphthalenediamine is one of 1,5-naphthalenediamine and 1,7-naphthalenediamine; the dianhydride is one of hexafluorodianhydride, bisphenol A type diether dianhydride, and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

3. The method for preparing a polyimide hollow fiber membrane for oxygen-rich combustion scenarios according to claim 1, characterized in that: In step S3, the wet-dry spinning process is as follows: polyimide powder is dissolved in N-methylpyrrolidone solvent to prepare a casting solution of 15wt%-20wt%. After vacuum degassing, a DMAc / water mixture with a volume ratio of 30% is used as the core liquid. The length of the air section is controlled to be 5-10cm. The mixture is solidified in a deionized water coagulation bath at 25℃. After washing with water for 24h to remove residual solvent, it is vacuum dried at 60℃ for 12h and then heat-treated at 150-200℃ for 2h to finally obtain a hollow fiber membrane with an asymmetric structure.