Polyimide-polyoxyethylene blended hollow fiber membrane and preparation method thereof
Hollow fiber membranes prepared by blending polyimide and polyethylene oxide solve the problems of poor air permeability of traditional polyimide membranes and weak mechanical properties of polyethylene oxide membranes, achieving high selectivity, high air permeability and long-term stability, and are suitable for decarbonization of industrial flue gas.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-24
AI Technical Summary
Traditional polyimide membranes have poor permeability and are easily plasticized in high CO2 partial pressure flue gas environments, while polyoxyethylene membranes have weak mechanical properties, making it difficult to meet industrial requirements when formed alone.
Hollow fiber membranes were prepared by blending polyimide and polyethylene oxide using a dry-wet spinning process with a blending ratio of 80:20-90:10, which improved the CO2 permeability and selectivity of the membrane and enhanced its long-term stability.
It achieves a CO2 penetration rate increase of over 30%, maintains a CO2/N2 selectivity of over 50%, adapts to complex industrial flue gas conditions, reduces equipment investment costs, and possesses good mechanical strength and structural stability.
Abstract
Description
Technical Field
[0001] This invention relates to a polyimide-polyoxyethylene blended hollow fiber membrane and its preparation method, belonging to the field of separation membrane technology. Background Technology
[0002] With the advancement of global carbon neutrality goals, CO2 capture and storage in flue gas has become a key technological direction for addressing climate change. my country has a high proportion of fossil fuels, resulting in massive CO2 emissions from industrial flue gas. If not treated promptly, this will exacerbate the greenhouse effect and waste carbon resources. Therefore, developing efficient and low-cost flue gas decarbonization technologies has significant environmental and economic value.
[0003] Currently, mainstream flue gas decarbonization methods include absorption, adsorption, distillation, and membrane separation. Chemical absorption, using amine solutions as absorbents, boasts high removal efficiency but suffers from high energy consumption, severe equipment corrosion, and easy degradation of the absorbent. Physical adsorption utilizes the selective adsorption of CO2 by the adsorbent, but its regeneration energy consumption is high, the adsorbent capacity is limited, and it is prone to deactivation, making it unsuitable for large-scale applications. Low-temperature distillation separates CO2 from other gases based on their boiling point differences, but this method requires high pressure and low temperature conditions, resulting in extremely high equipment investment and operating costs. In contrast, membrane separation, with its low energy consumption, simple operation, small footprint, and lack of secondary pollution, has become one of the most promising decarbonization technologies.
[0004] In membrane separation decarbonization processes, the membrane material is the core of the entire technology. Among numerous membrane materials, polyimide has become a popular substrate for gas separation membranes due to its excellent thermal stability, mechanical strength, and CO2 / N2 selectivity. However, traditional polyimide membranes suffer from drawbacks such as poor permeability, susceptibility to plasticization under high CO2 partial pressure environments in flue gas, and insufficient long-term operational stability, which limit their industrial application. Polyoxyethylene (PEO) exhibits excellent CO2 permeability due to the specific interaction between the ether oxygen bonds in its molecular chain and CO2, but PEO has weak mechanical properties and is prone to crystallization, making it difficult to meet the requirements of actual operating conditions when used alone as a membrane. Summary of the Invention
[0005] To address the technical problems existing in the prior art, this invention provides a polyimide-polyoxyethylene blended hollow fiber membrane and its preparation method. The method involves blending and modifying polyimide and polyoxyethylene to prepare a hollow fiber membrane that combines high selectivity, high air permeability, and good stability.
[0006] To achieve the above objectives, the technical solution adopted in this invention is a polyimide-polyoxyethylene blended hollow fiber membrane. The membrane material of this hollow fiber membrane is composed of a blend of polyimide and polyoxyethylene, and the mass ratio of polyimide to polyoxyethylene is 80:20-90:10. When this membrane material is applied in flue gas decarbonization, it can operate stably for a long time under flue gas conditions, and the CO2 permeability is increased by more than 30% compared with pure polyimide membranes, while the CO2 / N2 selectivity is maintained above 50.
[0007] A method for preparing a polyimide-polyoxyethylene blend hollow fiber membrane includes the following steps: S1. Synthesis of polyimide: Under nitrogen protection, the diamine monomer is dissolved in N,N-dimethylacetamide solvent and stirred until completely dissolved. Bisphenol A type diether dianhydride is added to the above solution, with a molar ratio of dianhydride to diamine of 1:1. The reaction is carried out at -5 to 10℃ for 24 h to form a polyamic acid solution. Acetic anhydride and 3-methylpyridine are added to the polyamic acid solution and reacted for 24 h to chemically imide the polyimide. After cooling, the reaction solution is poured into deionized water to precipitate the polyimide. After filtration, washing, and vacuum drying, polyimide is obtained. S2. Prepare the blend solution by adding the above polyimide and polyoxyethylene to N,N-dimethylacetamide solvent in a mass ratio of 80:20-90:10, stirring at 60°C for 8 hours until completely dissolved, and then degassing under vacuum for 2 hours to obtain a uniform blend casting solution. S3. Hollow fiber membrane preparation: A polyimide-polyoxyethylene blended hollow fiber membrane was prepared by using a dry-wet spinning process.
[0008] Preferably, the diamine monomer is one of 4,4'-diamino-diphenyl ether, 1,4-bis(4-aminophenoxy)benzene, and 1,3-bis(4'-aminophenoxy)benzene.
[0009] Preferably, in step S3, the blended casting solution is extruded through a hollow fiber spinneret, and N2 is introduced into the inner core of the spinneret as an internal coagulant; the extruded fiber is cured in a deionized water coagulation bath at 25°C after passing through a 5-10cm air section; the cured fiber is soaked in deionized water for 24 hours to remove residual solvent, then vacuum dried at 60°C for 12 hours, and finally heat-treated at 120°C for 2 hours to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0010] Compared with existing technologies, this invention has the following technical advantages: This invention achieves multiple performance improvements through synergistic material effects: First, the rigid framework of polyimide provides the membrane with good mechanical strength and structural stability, while the high CO2 affinity of polyethylene oxide significantly improves the membrane's permeability, achieving an optimized balance between high selectivity and high permeability. The CO2 permeability is increased by more than 30% compared to pure polyimide membranes, and the CO2 / N2 selectivity remains above 50. Second, the presence of polyimide inhibits the crystallization behavior of polyethylene oxide, reducing membrane swelling and plasticization under high CO2 partial pressure, and improving long-term operational stability under flue gas conditions. Third, the preparation process uses mature dry and wet spinning, which is simple to operate and can be mass-produced. The hollow fiber structure increases the specific surface area of the membrane, improving separation efficiency while reducing equipment investment costs. Fourth, the membrane material has strong temperature resistance and resistance to impurity interference, making it suitable for complex industrial flue gas conditions. This provides a feasible solution for achieving low-cost, high-efficiency decarbonization, with significant environmental and economic benefits. Detailed Implementation
[0011] 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. Example 1
[0012] 1) Add 20.02 g of ODA to a pre-dried three-necked flask, and add 342.4 mL of DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool to -5°C and stabilize for 30 min. Add 44.14 g of BPADA in batches of 11.03 g each time, with 30 min intervals, to avoid local overheating of the reaction. Maintain the reaction at -5°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0013] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After reacting at -5°C for 24 h, the polymer solution was placed in deionized water for precipitation. After standing for 2 h, it was washed repeatedly with deionized water four times. The product obtained after washing was dried in an oven at 80°C for 24 h to finally obtain BPADA-ODA type polyimide.
[0014] 3) Dissolve 24g of BPADA-ODA type polyimide and 6g of polyoxyethylene (mass ratio 80:20) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0015] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 5 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0016] The blend membrane prepared above was tested on a gas separation tester, and its CO2 permeability coefficient was 896 GPU and its CO2 / N2 separation factor was 58. Example 2
[0017] 1) Add 28.24 g of TPEQ to a pre-dried three-necked flask, and then add 386.2 mL of DMAc under a high-purity nitrogen atmosphere and stir. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool it to 2°C and stabilize it for 30 min. Add 44.14 g of BPADA in batches, with each addition 30 min apart, to avoid local overheating of the reaction. Maintain the reaction at 2°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0018] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After 24 hours of reaction, the polymer solution was placed in deionized water for precipitation. After standing for 2 hours, it was washed four times repeatedly with deionized water. The product obtained after washing was dried in an 80°C oven for 24 hours to finally obtain BPADA-TPEQ type polyimide.
[0019] 3) Dissolve 25.5g of BPADA-TPEQ type polyimide and 4.5g of polyethylene oxide (mass ratio 85:15) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0020] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 7 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0021] The blend membrane prepared above was tested on a gas separation tester, and its CO2 permeability coefficient was 823 GPU and its CO2 / N2 separation factor was 62. Example 3
[0022] 1) Add 28.24 g of TPER to a pre-dried three-necked flask, and add 386.2 mL of DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool it to 10°C and stabilize it for 30 min. Add 44.14 g of BPADA in batches, with each addition 30 min apart, to avoid local overheating of the reaction. Maintain the reaction at 10°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0023] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After 24 hours of reaction, the polymer solution was placed in deionized water for precipitation. After standing for 2 hours, it was washed four times repeatedly with deionized water. The product obtained after washing was dried in an 80°C oven for 24 hours to finally obtain BPADA-TPER type polyimide.
[0024] 3) Dissolve 27g of BPADA-TPER type polyimide and 3g of polyoxyethylene (mass ratio 90:10) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0025] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 10 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0026] The blend membrane prepared above was tested on a gas separation tester, and its CO2 permeability coefficient was 765 GPU and its CO2 / N2 separation factor was 65. Example 4
[0027] 1) Add 10g ODA and 14.12g TPEQ to a pre-dried three-necked flask, and add 364.2mL DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool to 5℃ and stabilize for 30min. Add 44.14g BPADA in batches, with each addition 30min apart, to avoid local overheating of the reaction. Maintain the reaction at 5℃ with stirring for 24h. During this period, the solution viscosity gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0028] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After 24 hours of reaction, the polymer solution was placed in deionized water for precipitation. After standing for 2 hours, it was washed four times repeatedly with deionized water. The product obtained after washing was dried in an 80°C oven for 24 hours to finally obtain BPADA-ODA-TPEQ type polyimide.
[0029] 3) Dissolve 25.5g of BPADA-ODA-TPEQ type polyimide and 4.5g of polyethylene oxide (mass ratio 85:15) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0030] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through an 8 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0031] The blend membrane prepared above was tested on a gas separation tester, and its CO2 permeability coefficient was 857 GPU and its CO2 / N2 separation factor was 60.
[0032] Comparative Example 1 (compared to Example 1) 1) Add 20.02 g of ODA to a pre-dried three-necked flask, and add 342.4 mL of DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool to -5°C and stabilize for 30 min. Add 44.14 g of BPADA in batches of 11.03 g each time, with 30 min intervals, to avoid local overheating of the reaction. Maintain the reaction at -5°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0033] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After reacting at -5°C for 24 h, the polymer solution was placed in deionized water for precipitation. After standing for 2 h, it was washed repeatedly with deionized water four times. The product obtained after washing was dried in an oven at 80°C for 24 h to finally obtain BPADA-ODA type polyimide.
[0034] 3) Dissolve 22.5g of BPADA-ODA type polyimide and 7.5g of polyethylene oxide (mass ratio 75:25) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0035] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 5 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0036] The blended membrane prepared above was tested on a gas separation tester. Excess PEO led to intensified crystallization and a loose membrane structure. The CO2 permeability coefficient was 912 GPU, but the CO2 / N2 separation factor was only 38.
[0037] Comparative Example 2 (compared to Example 1) 1) Add 20.02 g of ODA to a pre-dried three-necked flask, and add 342.4 mL of DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool to -5°C and stabilize for 30 min. Add 44.14 g of BPADA in batches of 11.03 g each time, with 30 min intervals, to avoid local overheating of the reaction. Maintain the reaction at -5°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0038] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After reacting at -5°C for 24 h, the polymer solution was placed in deionized water for precipitation. After standing for 2 h, it was washed repeatedly with deionized water four times. The product obtained after washing was dried in an oven at 80°C for 24 h to finally obtain BPADA-ODA type polyimide.
[0039] 3) Dissolve 28.5g of BPADA-ODA type polyimide and 1.5g of polyethylene oxide (mass ratio 95:5) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0040] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 5 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0041] The blend membrane prepared above was tested on a gas separation tester. The insufficient PEO content resulted in limited improvement in product permeability; the CO2 permeability coefficient was only 612 GPU, but the CO2 / N2 separation factor was 63.
[0042] Comparative Example 3 (compared to Example 1) 1) Add 20.02 g of ODA to a pre-dried three-necked flask, and add 342.4 mL of DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool to -20°C and stabilize for 30 min. Add 44.14 g of BPADA in batches of 11.03 g each time, with 30 min intervals, to avoid local overheating of the reaction. Maintain the reaction at -20°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0043] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After reacting at -5°C for 24 h, the polymer solution was placed in deionized water for precipitation. After standing for 2 h, it was washed repeatedly with deionized water four times. The product obtained after washing was dried in an oven at 80°C for 24 h to finally obtain BPADA-ODA type polyimide.
[0044] 3) Dissolve 22.5g of BPADA-ODA type polyimide and 7.5g of polyethylene oxide (mass ratio 75:25) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0045] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 5 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0046] The blended membrane prepared above was tested on a gas separation tester. The low temperature during the preparation process caused incomplete polymerization. The CO2 permeation coefficient of the blended membrane was 658 GPU and the CO2 / N2 separation factor was 45.
[0047] Comparative Example 4 (compared to Example 1) 1) Add 20.02 g of ODA to a pre-dried three-necked flask, and add 342.4 mL of DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool to 25°C and stabilize for 30 min. Add 44.14 g of BPADA in batches of 11.03 g each time, with 30 min intervals, to avoid local overheating of the reaction. Maintain the reaction at 25°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0048] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After reacting at -5°C for 24 h, the polymer solution was placed in deionized water for precipitation. After standing for 2 h, it was washed repeatedly with deionized water four times. The product obtained after washing was dried in an oven at 80°C for 24 h to finally obtain BPADA-ODA type polyimide.
[0049] 3) Dissolve 22.5g of BPADA-ODA type polyimide and 7.5g of polyethylene oxide (mass ratio 75:25) in 213.4mL of DMAc solvent, and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0050] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 5 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0051] The blend membrane prepared above was tested on a gas separation tester. The results showed that excessively high temperature during the preparation process could easily trigger side reactions, leading to molecular chain breakage. The CO2 permeation coefficient of the blend membrane was 683 GPU, and the CO2 / N2 separation factor was 42.
[0052] Comparative Example 5 (compared to Example 1) 1) Add 20.02 g of ODA to a pre-dried three-necked flask, and add 342.4 mL of DMAc under a high-purity nitrogen atmosphere with stirring. After the diamine monomer is fully dissolved, place the flask in a low-temperature constant-temperature water bath, cool to 25°C and stabilize for 30 min. Add 44.14 g of BPADA in batches of 11.03 g each time, with 30 min intervals, to avoid local overheating of the reaction. Maintain the reaction at 25°C with stirring for 24 h. During this period, the viscosity of the solution gradually increases, eventually forming a viscous, particle-free polyamic acid solution.
[0053] 2) 90 mL of acetic anhydride and 10 mL of 3-methylpyridine were slowly added dropwise to the above polyamic acid solution as a dehydrating agent and catalyst, respectively, to initiate a chemical ring-closure reaction. After reacting at -5°C for 24 h, the polymer solution was placed in deionized water for precipitation. After standing for 2 h, it was washed repeatedly with deionized water four times. The product obtained after washing was dried in an oven at 80°C for 24 h to finally obtain BPADA-ODA type polyimide.
[0054] 3) Dissolve 27g of BPADA-ODA type polyimide in 192.1mL of DMAc solvent (single polyimide film, without PEO blending), and place in a 60℃ constant temperature water bath and stir for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0055] 4) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the spinneret core as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 5 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0056] The separation membrane prepared above was tested on a gas separation tester. The product's CO2 permeability coefficient was 652 GPU and the CO2 / N2 separation factor was 52.
[0057] Comparative Example 6 (compared to Example 1) 1) Dissolve 30g of PEO in 213.4mL of DMAc solvent (single PEO membrane, without polyimide blend), and stir in a 60℃ constant temperature water bath for 8h until completely dissolved. Then, perform vacuum degassing for 2h to obtain a uniform, bubble-free 15wt% blend casting solution.
[0058] 2) Using a wet-dry spinning equipment, the casting solution is injected into the spinning kettle, and 0.1 MPa of N2 is introduced into the inner core of the spinneret as an internal coagulant. The casting solution is extruded through the spinneret (inner diameter 0.6 mm, outer diameter 1.2 mm), passes through a 5 cm air section, and then enters a 25°C deionized water coagulation bath for curing. The cured fiber is soaked in deionized water for 24 h to remove residual DMAc. It is then vacuum dried at 60°C for 12 h, and finally heat-treated in a 120°C forced-air oven for 2 h to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.
[0059] The separation membrane prepared above was tested on a gas separation tester. The product's CO2 permeability coefficient was 1120 GPU, but the CO2 / N2 separation factor was only 23.
[0060] 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 polyimide-polyoxyethylene blend hollow fiber membrane, characterized in that: The hollow fiber membrane is made of polyimide and polyethylene oxide blend, with a mass ratio of 80:20-90:
10. When applied to flue gas decarbonization, this membrane can operate stably for a long time under flue gas conditions, and its CO2 permeability is increased by more than 30% compared to pure polyimide membranes, while the CO2 / N2 selectivity is maintained above 50.
2. The method for preparing a polyimide-polyoxyethylene blend hollow fiber membrane according to claim 1, characterized in that: Includes the following steps, S1. Synthesis of polyimide: Under nitrogen protection, the diamine monomer is dissolved in N,N-dimethylacetamide solvent and stirred until completely dissolved. Bisphenol A type diether dianhydride is added to the above solution, with a molar ratio of dianhydride to diamine of 1:
1. The reaction is carried out at -5 to 10℃ for 24 h to form a polyamic acid solution. Acetic anhydride and 3-methylpyridine are added to the polyamic acid solution and reacted for 24 h to chemically imide the polyimide. After cooling, the reaction solution is poured into deionized water to precipitate the polyimide. After filtration, washing, and vacuum drying, polyimide is obtained. S2. Prepare the blend solution by adding the above polyimide and polyoxyethylene to N,N-dimethylacetamide solvent in a mass ratio of 80:20-90:10, stirring at 60°C for 8 hours until completely dissolved, and then degassing under vacuum for 2 hours to obtain a uniform blend casting solution. S3. Hollow fiber membrane preparation: A polyimide-polyoxyethylene blended hollow fiber membrane was prepared by using a dry-wet spinning process.
3. The method for preparing a polyimide-polyoxyethylene blend hollow fiber membrane according to claim 2, characterized in that: The diamine monomer is one of 4,4'-diamino-diphenyl ether, 1,4-bis(4-aminophenoxy)benzene, and 1,3-bis(4'-aminophenoxy)benzene.
4. The method for preparing a polyimide-polyoxyethylene blend hollow fiber membrane according to claim 2, characterized in that: In step S3, the blended casting solution is extruded through a hollow fiber spinneret, and N2 is introduced into the inner core of the spinneret as an internal coagulant. The extruded fibers are then cured in a 25°C deionized water coagulation bath after passing through a 5-10cm air section. The cured fibers are then soaked in deionized water for 24 hours to remove residual solvent, followed by vacuum drying at 60°C for 12 hours, and finally heat-treated at 120°C for 2 hours to obtain a polyimide-polyoxyethylene blended hollow fiber membrane.