High-strength plasticized-resistant gas separation membrane, preparation method and application

Abstract

The application discloses a high-strength plasticization-resistant gas separation membrane, a preparation method and application. By introducing a rigid group BPDA (3,3',4,4'-biphenyl tetracarboxylic dianhydride) with good crystallinity, PMDA (1,2,4,5-benzene tetracarboxylic dianhydride) and a high-crystallinity aromatic diamine into a 6FDA (hexafluoro dianhydride) and DABA (3,5-diamino benzoic acid) system, the flowability of a polymer chain is reduced, and the plasticization resistance and mechanical strength of the polymer are improved. In order to improve the solubility of monomers, a polyimide represented by a general formula (I) is obtained by dissolving a polymerization system by using a phenol as a solvent. The hollow fiber membrane prepared by spinning the obtained polyimide has the advantages of high strength, plasticization resistance and the like in a gas separation process, has good thermal stability, improves the permeation rate, and can maintain good selectivity for CO2 / N2 and CO2 / CH4, and has an important role in the field of flue gas and biogas CO2 removal. n is the polymerization degree of different components of the polymer, n is an integer of 100-200, and x is the mole ratio of the DABA part, x is an integer of 0-100.

Description

Technical Field

[0001] This invention belongs to the field of polymer membrane separation technology, specifically relating to a high-strength, anti-plasticization gas separation membrane, its preparation method, and its application. The gas separation membrane is made of polyimide. This invention relates to the manufacture and use of aromatic polyimide. The gas separation membrane is an asymmetric structure gas separation membrane, which exhibits good permeability, strong resistance to CO2 plasticization, and high mechanical properties. This invention also relates to a CO2 gas separation method using the aforementioned gas separation membrane. Background Technology

[0002] CO2 is produced by the combustion of fossil fuels, and how to purify the CO2 in the flue gas has become the key to controlling CO2 emissions.

[0003] Biogas contains a large amount of methane, as well as a large amount of carbon dioxide impurities. The presence of a large amount of carbon dioxide may reduce the calorific value of biogas and increase compression and transportation costs (International Journal of Hydrogen Energy, 2021, 46(11): 21318-21337), thus limiting the economic viability of biogas for direct power generation at the production site. By removing these impurities, the purified gas is expected to contain high-quality methane and can facilitate its use in a variety of applications (Bioresource Technology Reports, 2018, 1: 79-88).

[0004] In recent years, membrane technology has played an increasingly important role in the field of CO2 separation, especially hollow fiber membranes, which have attracted widespread attention due to their advantages such as simple operation, small footprint, low energy consumption, flexible design, and high separation efficiency.

[0005] CN202210321067.X discloses a method for preparing a high-performance functionalized carbon nanotube / polyimide hybrid matrix membrane and its application. The hybrid matrix membrane of this invention has significant effects in gas separation, effectively separating carbon dioxide and air, and is simple to operate. CN201911306031.9 discloses a method for preparing a hollow fiber composite membrane for separating carbon dioxide in a mixed gas. By adding a functional layer material into the support layer, a local cross-linking reaction is introduced between the support layer and the functional layer during the formation of the functional layer, making the bond between the two layers tighter and significantly improving the long-term stability of the composite membrane.

[0006] Polyimide membranes based on 6FDA exhibit excellent CO2 / CH4 separation performance, along with good thermal and chemical stability. The CO2 / CH4 selectivity of the 6FDA-DABA system reaches 62.2 at 35°C and 100 psi, higher than most commercial polyimide membranes (Polymer, 2013, 54(22):6226-6235). Furthermore, DABA contains carboxyl groups, which can be decarboxylated and crosslinked through heat treatment at certain temperatures, significantly improving its resistance to plasticization. Therefore, the 6FDA-DABA system has attracted increasing attention in fields such as natural gas separation and flue gas purification.

[0007] Le's research team prepared 6FDA-naphthyldiamine (NDA) / 3,5-diaminobenzoic acid (DABA) copolyimide and its sulfonated PI, and obtained good flux and separation coefficient in the ethanol dehydration system (Journal of Membrane Science, 2014, 454(15):62-73); MehtapSafak Boroglu's research team prepared a mixed matrix membrane by doping ZIF-11 into the polyimide membrane of the 6FDA-DAM system, which improved the CO2 / CH4 gas selectivity of the membrane (Separation and Purification Technology, 2017, 173(1):269-279).

[0008] However, compared to other polyimide polymers used for gas separation, the 6FDA-DABA system has a low molecular weight and poor mechanical properties, with molecular weights concentrated around 15,000, making it difficult to use in hollow fiber membrane spinning. The resulting gas separation membranes, especially hollow fiber membranes, have poor performance. Furthermore, the 6FDA-DABA polymer system has a low CO2 flux, making it difficult to achieve efficient gas separation. These problems limit the further application of this system in gas separation.

[0009] To meet the requirements of practical industrial and domestic applications, this invention aims to prepare a gas separation membrane for CO2 separation that possesses excellent properties such as high permeability, high selectivity, resistance to plasticization, and strong mechanical properties. This invention prepares an asymmetric gas separation membrane by introducing an aromatic, highly crystalline diamine and dianhydride monomer into a 6FDA-DABA system. This membrane exhibits high permeability and selectivity while also possessing practical mechanical strength and excellent resistance to plasticization. Summary of the Invention

[0010] This invention provides a high-strength, anti-plasticization gas separation membrane, its preparation method, and its application. The preparation method is a method for preparing a polyimide gas separation membrane with high mechanical strength and high resistance to CO2 plasticization.

[0011] This invention introduces highly crystalline, rigid groups BPDA (3,3',4,4'-biphenyltetracarboxylic dianhydride), PMDA (1,2,4,5-pyromellitic dianhydride), and a series of highly crystalline aromatic diamines, along with DABA (3,5-diaminobenzoic acid), into a 6FDA (hexafluorodianhydride) and DABA (3,5-diaminobenzoic acid) system. This reduces the fluidity of the polymer chain and improves the polymer's resistance to plasticization and its mechanical strength. To improve the solubility of the monomers, phenols such as p-chlorophenol are used as solvents to dissolve the polymerization system, resulting in a polyimide polymer with high mechanical strength and high resistance to CO2 plasticization. Hollow fiber membranes spun from the obtained polyimide exhibit high strength and resistance to plasticization during gas separation, along with good thermal stability. They improve permeability while maintaining good selectivity for CO2 / N2 and CO2 / CH4, playing a crucial role in CO2 removal from flue gas and biogas.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] The present invention discloses a high-strength, plasticizing-resistant gas separation membrane, wherein the gas separation membrane is made of a polyimide polymer having the structure shown in general formula (I):

[0014]

[0015] Where n represents the degree of polymerization of the different components of the polymer, and n is an integer from 100 to 200; x represents the molar ratio of the structural units derived from DABA, and x is an integer from 0 to 100; the weight-average molecular weight of the polymer is between 200,000 and 500,000. For example, n can be 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, or 200. For example, x can be 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100.

[0016] Furthermore, the weight-average molecular weight of the polymer is 200,000-500,000, for example, the weight-average molecular weight of the polymer is 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320 000, 330000, 340000, 350000, 360000, 370000, 380000, 390000, 400000, 410000, 420000, 430000, 440000, 450000, 460000, 470000, 480000, 490000 or 500000.

[0017] The R1 group is one or more of the following groups:

[0018]

[0019] The R2 group comprises any one or more of the following structures:

[0020]

[0021] Furthermore, the gas separation membrane is a polyimide gas separation membrane.

[0022] Furthermore, the polyimide polymer has a high resistance to CO2 plasticization and high mechanical properties.

[0023] The method for preparing the gas separation membrane as described above includes the following steps:

[0024] (1) At room temperature, DABA, 6FDA, aromatic diamine, and aromatic dianhydride were first dissolved in p-chlorophenol. The molar ratio of the monomers was aromatic diamine: aromatic dianhydride = 1-2.2:1-2 (for example, the molar ratio of aromatic diamine: aromatic dianhydride was 1:1-2, 1.1:1-2, 1.2:1-2, 1.3:1-2, 1.4:1-2, 1.5:1-2, 1.6:1-2, 1.7.1:1-2, 1.8:1-2, 1.9:1-2, 2:1-2, 2.1:1-2, 2.2:1-2, 1-2.2:1, 1-2.2:1.1, 1-2.2:1.2 ... The solutions are prepared in the following ratios: 1.2:1.3, 1~2.2:1.4, 1~2.2:1.5, 1~2.2:1.6, 1~2.2:1.7, 1~2.2:1.8:1, 1~2.2:1.9, 1~2.2:2, 1~2:1~1.8, 1~1.8:1~1.6, 1~1.6:1~1.4, 1~1.5:1~1.5, 1~1.2:1~1.3 or 1:1, with a solid content of 15-20 wt%, and then heated to 90-120℃ under a N2 atmosphere; wherein the monomers are composed of DABA, 6FDA, aromatic diamine and aromatic dianhydride, with aromatic diamine being monomer A and aromatic dianhydride being monomer B;

[0025] (2) After the monomer is completely dissolved in p-chlorophenol, an isoquinoline catalyst is added to the solution, and then the temperature is raised to 190-200℃ and stirred to promote the polymerization reaction; polymerization is initiated at 190-200℃ and then reacted at this temperature; after the reaction is completed, the solution is poured into methanol or ethanol to obtain a fibrous polymer. After multiple precipitation and washing, the solvent in the polymer is removed. The obtained polymer is dried in a vacuum drying oven at 120-130℃ for 20-24 hours and then weighed. The dried polymer is polyimide; wherein the molar ratio of aromatic diamine and aromatic dianhydride in the reaction system is maintained at aromatic dianhydride = 1-2.2:1-2.

[0026] (3) Dissolve the dried polymer in a polar solvent, controlling the solid content of the solution at 15-20 wt%, and control the rotational viscosity of the solution at 100-105°C at 280-800 poise. Filter the polyimide solution with a metal mesh, then extrude it through a hollow fiber membrane spinning nozzle, and pass the extruded hollow fiber body through an N2 atmosphere. Subsequently, perform a phase inversion in an ethanol-water solution condensation bath at -10 to -5°C to produce wet fibers. Immerse the wet fibers in ethanol at 50-60°C for 2-3 hours, and then immerse them in isooctane at 65-75°C for 3-5 hours to remove the solvent from the fibers. Dry them thoroughly at 100-120°C, and then heat treat them at 320-350°C for 10-20 hours. Optionally, the treatment time increases with temperature, from 20 hours at 320°C to 1 hour at 350°C to obtain the finished hollow fiber membrane.

[0027] Wherein, monomer A is selected from any one or more of the following compounds:

[0028] 2,2'-Di(trifluoromethyl)diaminobiphenyl, 2,2',5,5'-tetrachlorodiphenylamine, p-diaminobiphenyl, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 2,3,5,6-tetramethyl-1,4-phenylenediamine, 3,6-diaminocarbazole, 3,6-diamino-9-ethylcarbazole;

[0029] The monomer B is selected from any one or more of the following compounds:

[0030]

[0031] Specifically, the method for preparing a gas separation membrane of a copolymer of highly crystalline aromatic diamine and aromatic dianhydride provided by the present invention includes the following steps:

[0032] (1). At room temperature, DABA, 6FDA, aromatic diamine (monomer A) and aromatic dianhydride (monomer B) were first dissolved in p-chlorophenol, with a diamine: dianhydride ratio of 1:1 and a solid content of 15-20 wt%. Then the solution was heated to 120 °C under N2 atmosphere.

[0033] (2) After the monomer is completely dissolved in the solvent, an isoquinoline catalyst is added to the solution, and then the temperature is raised to 190°C and stirred to promote the polymerization reaction. Polymerization is initiated at 190°C and then reacted at this temperature for 20-24 hours. After the reaction is complete, the solution is poured into methanol or ethanol to obtain a fibrous polymer. After multiple precipitation and washing, the solvent in the polymer is removed. The obtained polymer is dried in a vacuum drying oven at 120°C for 24 hours and then weighed. The molar ratio of diamine to dianhydride in the reaction system is maintained at 1:1, and the amount of catalyst is 0.05 wt% of the total monomer mass.

[0034] In the above preparation method, monomer A is selected from any one or more of the following compounds:

[0035] 2,2'-Di(trifluoromethyl)diaminobiphenyl, 2,2',5,5'-tetrachlorodiphenylamine, p-diaminobiphenyl, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 2,3,5,6-tetramethyl-1,4-phenylenediamine, 3,6-diaminocarbazole, 3,6-diamino-9-ethylcarbazole.

[0036] The monomer B is selected from any one or more of the following compounds:

[0037]

[0038] (3) The dried polymer is dissolved in a polar solvent at 100°C, with the solid content of the solution controlled at approximately 15 wt%, and the rotational viscosity of the solution at 100°C controlled at approximately 800 poise. Solutions with excessively high viscosity are difficult to extrude from the nozzle. A polyimide solution is filtered through a 400-mesh metal wire mesh, then extruded through a hollow fiber membrane spinning nozzle, and the extruded hollow fiber body is passed through an N2 atmosphere. Subsequently, it undergoes phase inversion in a condensation bath of a specific concentration (25%) ethanol aqueous solution at -5°C to produce wet fibers. The wet fibers are impregnated in ethanol at 50°C for 2 hours, and then impregnated in isooctane at 70°C for 3 hours to remove the solvent from the fibers. The fibers are thoroughly dried at 100°C, and then heat-treated at a specific temperature (320-350°C), with the treatment time increasing from 20 hours at 320°C to 1 hour at 350°C to obtain the finished hollow fiber membrane.

[0039] Methods for determining CO2 flux and selectivity of hollow fiber membranes in this invention embodiment:

[0040] A permeation performance evaluation element with an effective length of 20 mm was fabricated using approximately 10 hollow fiber membranes, a stainless steel tube, and an epoxy resin-based adhesive. This element was inserted into a stainless steel container to form a pencil-shaped assembly. The temperature was kept constant at 35°C, and pure CO2 gas was introduced at a fixed rate into the exterior of the hollow fibers of the pencil-shaped assembly. The gas preceding the hollow fiber membrane element was considered the upstream gas, and the gas passing through the element was considered the downstream gas. The upstream gas pressure was kept constant, and the change in downstream gas pressure over time was measured. The CO2 permeation flux was calculated using a formula; the CH4 permeation flux was tested in the same manner. The CO2 / CH4 selectivity was obtained by comparing the two.

[0041] The pure gas in the above method was replaced with a CH4 / CO2 mixture containing 50% CH4. The same method was used to test the mixed gas flux, and the ratio of the two gases in the mixture was determined to obtain the CO2 / CH4 selectivity. Based on this testing method, the performance measurement results of the gas separation membranes obtained in various embodiments of the present invention are shown in Table 1.

[0042] The viscosity used in this invention is rotational viscosity.

[0043] Measurement of rotational viscosity (i.e., rotational viscosity):

[0044] The rotational viscosity of the polyamide solution was measured at 100°C using a rotational viscometer (proRheo R180 rotational viscometer, Germany) (rotor shear rate: 1.75 / sec).

[0045] The application of the gas separation membrane prepared from the copolymer of highly crystalline aromatic diamine and aromatic dianhydride of the present invention includes the following steps:

[0046] Gas separation membranes made from copolymers of highly crystalline aromatic diamines and aromatic dianhydrides are applied to CO2 removal from flue gas and biogas.

[0047] Approximately 1000-10000 hollow fiber membranes of suitable length, prepared by the method of this invention, are bundled together. The two sides of the fiber bundle are fixed to a tube sheet with resin, and an opening is made at one end of each fiber to allow air intake. The membrane module is then assembled in this way. The membrane module is then connected to a container containing a mixed gas inlet, a permeate gas outlet, and a non-permeate gas outlet, thus isolating the space connecting the interior of the hollow fiber membrane from the space connecting the exterior of the hollow fiber membrane. In such a gas separation membrane module, the mixed gas is input from the mixed gas inlet into the interior of the hollow fiber membrane or into the space communicating with the exterior, but is not limited to this. When the mixed gas comes into contact with the hollow fiber membrane, specific gas components contained in the mixed gas selectively permeate through the membrane. The permeate gas exits from the permeate gas outlet, and the non-permeate gas that does not permeate the membrane exits from the non-permeate gas outlet. Gas separation is achieved in this way. Elements of a gas separation membrane module are prepared in this manner.

[0048] The components are inserted into a stainless steel container to form a membrane separation assembly. Under a pressure of 300 psi, the flue gas or biogas material to be separated is passed into the outside of the gas separation membrane, and the de-CO2 flue gas or biogas is obtained at the product gas outlet.

[0049] The beneficial results of this invention are:

[0050] (1) This invention discloses a gas separation membrane prepared from a copolymer of a highly crystalline aromatic diamine and an aromatic dianhydride. It is a copolymer with strong polymer chain rigidity, high mechanical properties, and strong resistance to CO2 plasticization;

[0051] (2) The obtained gas separation membrane has good thermal stability and mechanical properties, with a glass transition temperature of about 400℃ and a tensile strength of more than 13MPa.

[0052] (3) This gas separation membrane is applied to CO2 removal from biogas and flue gas, and has excellent gas selectivity and permeation flux;

[0053] (4) When the gas separation membrane is applied to the CO2 separation membrane, under a pressure of 500psi and a mixed feed of 50:50CH4 / CO2, after 200h of treatment, the permeability decreases by about 15% and no plasticization occurs, indicating that the gas separation membrane can operate stably for a long time under high feed pressure. Attached Figure Description

[0054] Figure 1 The graph shows the changes in permeation flux and selectivity of the polymer membrane prepared in Example 1 under pure gas conditions and different feed pressures.

[0055] Figure 2 The thermogravimetric curve of the polymer film prepared in Example 4 is shown.

[0056] Figure 3 The tensile strength curves are for the polymers prepared in Example 4 and the comparative example. Detailed Implementation

[0057] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not to be construed as limiting the scope of the present invention.

[0058] Example 1:

[0059] (1). At room temperature, the monomers DABA, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:2,2'-bis(trifluoromethyl)diaminobiphenyl = 1:1:1:1.5:1.5, and the solid content of the solution was 18wt%. Then, the temperature was raised to 120℃ under N2 atmosphere.

[0060] (2) After the monomers were completely dissolved in the solvent, 0.05% isoquinoline catalyst (based on the total mass of the monomers) was added to the solution. The temperature was then raised to 190°C, and the mixture was stirred to promote the polymerization reaction. Polymerization was initiated at 190°C and then reacted at this temperature for 24 hours. After the reaction was complete, the solution was poured into methanol to obtain a fibrous polymer. After repeated precipitation and washing, the solvent in the polymer was removed. The obtained polymer was dried in a vacuum drying oven at 120°C for 24 hours and then weighed. The molar ratio of diamine to dianhydride in the reaction system was maintained at 1:1, and the amount of catalyst was 0.05 wt% of the total mass of the monomers. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0061] (3) The dried polymer was dissolved in a polar solvent at room temperature, with the solid content of the solution controlled at 15 wt% and the rotational viscosity of the solution controlled at 100 °C at 800 poise. The polyimide solution was filtered through a 400-mesh metal wire mesh and then extruded through a hollow fiber membrane spinning nozzle (1000 μm circular aperture, 300 μm circular slit width, 350 μm central hole diameter). The extruded hollow fiber body was passed through an N2 atmosphere and then subjected to phase inversion in a condensation bath of a specific concentration (25 wt%) ethanol aqueous solution at -5 °C to produce wet fibers. The wet fibers were impregnated in ethanol at 50 °C for 2 hours, and then impregnated in isooctane at 70 °C for 3 hours to remove the solvent from the fibers. The fibers were thoroughly dried at 100 °C and then heat-treated at a specific temperature (330 °C) for 10 hours to obtain a finished hollow fiber membrane with an outer diameter of approximately 500 μm, an inner diameter of approximately 400 μm, and a membrane thickness of approximately 70 μm.

[0062] The obtained highly crystalline aromatic diamines and aromatic dianhydrides were applied to CO2 removal from flue gas and biogas.

[0063] Approximately 105 hollow fiber membranes of suitable length, prepared by the method of this invention, are bundled together. These hollow fibers are tightly packed (fill rate approximately 50%), with both ends of the fiber bundle embedded in thermosetting epoxy resin, and fixed in a tube sheet. An opening is made at one end of each fiber to allow air intake, thus assembling the membrane module. The membrane module is then connected to a container containing a mixed gas inlet, a permeate gas outlet, and a non-permeate gas outlet, thereby isolating the space connecting the interior of the hollow fiber membrane from the space connecting the exterior of the hollow fiber membrane. In such a gas separation membrane module, the mixed gas is input from the mixed gas inlet into the interior of the hollow fiber membrane or into the space communicating with the exterior, but is not limited thereto. When the mixed gas comes into contact with the hollow fiber membrane, specific gas components contained in the mixed gas selectively permeate through the membrane. The permeate gas exits from the permeate gas outlet, and the non-permeate gas that does not permeate the membrane exits from the non-permeate gas outlet. A gas separation element is thus prepared.

[0064] The components are inserted into a stainless steel container to form a membrane separation assembly. Under a pressure of 300 psi, the flue gas or biogas to be separated is passed into the external hole side of the gas separation membrane, and the de-CO2 flue gas or biogas is obtained at the product gas outlet.

[0065] Example 2:

[0066] At room temperature, DABA, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 6FDA, and BPDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:DABA:2,2',5,5'-tetrachlorodiphenylamine = 1:1:0.8:1.2, and the solid content of the solution was 18 wt%. The remaining experimental and application procedures were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0067] Example 3:

[0068] At room temperature, DABA, 2,2',5,5'-tetrachlorodiphenylamine, 6FDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was 6FDA:PMDA:DABA:2,2',5,5'-tetrachlorodiphenylamine = 1:1:1:1, and the solid content of the solution was 18 wt%. The remaining experimental and application procedures were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0069] Example 4:

[0070] At room temperature, DABA, 2,2',5,5'-tetrachlorodiphenylamine, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:2,2',5,5'-tetrachlorodiphenylamine = 1:1:1:1.2:1.8, and the solid content of the solution was 18 wt%. The remaining experimental and application procedures were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0071] Example 5:

[0072] At room temperature, DABA, p-diaminobiphenyl, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:p-diaminobiphenyl = 1:1:1:1.5:1.5, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0073] Example 6:

[0074] At room temperature, DABA, p-diaminobiphenyl, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:p-diaminobiphenyl = 1:1:1:1.2:1.8, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0075] Example 7:

[0076] At room temperature, DABA, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, and 6FDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was 6FDA:DABA:4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl = 3:1.5:1.5, and the solid content of the solution was 18 wt%. The remaining experimental and application procedures were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0077] Example 8:

[0078] At room temperature, DABA, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, and 6FDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was 6FDA:DABA:4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl = 3:1.2:1.8, and the solid content of the solution was 18 wt%. The remaining experimental and application procedures were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0079] Example 9:

[0080] At room temperature, DABA, 4,4'-diamino-3,3'-dimethylbiphenyl, and 6FDA were first dissolved in p-chlorophenol. The molar ratio of monomers was 6FDA:DABA:4,4'-diamino-3,3'-dimethylbiphenyl = 3:1.5:1.5, and the solid content of the solution was 18 wt%. The remaining experimental and application procedures were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0081] Example 10:

[0082] At room temperature, DABA, 4,4'-diamino-3,3'-dimethylbiphenyl, and 6FDA were first dissolved in p-chlorophenol. The molar ratio of monomers was 6FDA:DABA:4,4'-diamino-3,3'-dimethylbiphenyl = 3:1.2:1.8, and the solid content of the solution was 18 wt%. The remaining experimental and application procedures were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0083] Example 11:

[0084] At room temperature, DABA, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol, with a monomer molar ratio of BPDA:6FDA:PMDA:DABA = 1:1:1:3, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different polymer components was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0085] Example 12:

[0086] At room temperature, DABA, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol, with a monomer molar ratio of BPDA:6FDA:PMDA:DABA = 1:1:1:3, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different polymer components was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0087] Example 13:

[0088] At room temperature, DABA, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol, with a monomer molar ratio of BPDA:6FDA:PMDA:DABA = 1:1:1:3, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different polymer components was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0089] Example 14:

[0090] At room temperature, DABA, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol, with a monomer molar ratio of BPDA:6FDA:PMDA:DABA = 1:1:1:3, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different polymer components was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0091] Example 15:

[0092] At room temperature, DABA, 3,6-diamino-9-ethylcarbazole, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:3,6-diamino-9-ethylcarbazole = 1:1:1:1.5:1.5, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0093] Example 16:

[0094] At room temperature, DABA, 3,6-diamino-9-ethylcarbazole, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:3,6-diamino-9-ethylcarbazole = 1:1:1:1.2:1.8, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0095] Example 17:

[0096] At room temperature, DABA, 2,2',5,5'-tetrachlorodiphenylamine, 3,6-diamino-9-ethylcarbazole, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:3,6-diamino-9-ethylcarbazole:2,2',5,5'-tetrachlorodiphenylamine = 1:1:1:1:1:1, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0097] Example 18:

[0098] At room temperature, DABA, 2,2',5,5'-tetrachlorodiphenylamine, 3,6-diamino-9-ethylcarbazole, 6FDA, BPDA, and PMDA were first dissolved in p-chlorophenol. The molar ratio of the monomers was BPDA:6FDA:PMDA:DABA:3,6-diamino-9-ethylcarbazole:2,2',5,5'-tetrachlorodiphenylamine = 1:1:1:0.8:0.8:1.4, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1. The degree of polymerization of the different components of the polymer was approximately 200, and the weight-average molecular weight of the polymer was approximately 250,000.

[0099] Comparative example:

[0100] This example uses the 6FDA-DABA polymer system as a comparative example: at room temperature, DABA and 6FDA were dissolved in p-chlorophenol, with a monomer molar ratio of 6FDA:DABA = 1:1, and the solid content of the solution was 18 wt%. The remaining experimental and application steps were the same as in Example 1.

[0101] Table 1 compares the performance of the polymer membranes prepared in all examples and the comparative examples. Table 1 shows the gas permeation performance of different examples and the comparative examples. It can be seen that, compared with the pure 6FDA-DABA system, the addition of aromatic monomers greatly increases the permeation flux of the gas separation membrane, while maintaining a very high selectivity.

[0102] Figure 1 This is a graph showing the changes in permeation flux and selectivity of the polymer membrane prepared in Example 1 under pure gas conditions and different feed pressures. Figure 1 It can be seen that the gas separation membrane with added aromatic monomers has excellent resistance to plasticization. It does not plasticize even at a feed pressure of 500 psi, proving that the membrane can operate stably for a long time under high feed pressure.

[0103] Figure 2 The thermogravimetric curve of the polymer film prepared in Example 4 is shown. Figure 2 The high-temperature resistance of the membrane of the present invention can be clearly seen from the thermogravimetric curve. The membrane only begins to lose weight gradually above 400°C, indicating that the membrane prepared by the present invention can remain stable at a high temperature of 400°C and can meet almost all harsh application temperatures.

[0104] Figure 3 The tensile strength curves are for the polymers prepared in Example 4 and the comparative example. Figure 3 This indicates that the mechanical properties of the gas separation membrane after adding aromatic monomers are significantly higher than those of the membrane prepared using the pure 6FDA-DABA system. This ensures that no fiber breakage occurs during spinning, and the membrane is more robust and durable, greatly expanding the application fields of polyimide gas separation membranes. The tensile strength test method used in the experiment followed the national standard GB / T1040.2-2006. The testing instrument used was a CMT4502 dual-column floor-standing electronic universal testing machine, manufactured by Shanghai Jiehu Instrument Co., Ltd. The test procedure involved tensile testing of a single hollow fiber membrane at a tensile speed of 50 mm / min.

[0105] Table 1

[0106]

[0107] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A high-strength, anti-plasticization gas separation membrane, characterized in that, The gas separation membrane is made of a polyimide polymer, which has the structure shown in the following general formula (I): （Ⅰ） Where n represents the degree of polymerization of different components of the polymer, and n is an integer from 100 to 200; x represents the molar ratio of structural units derived from DABA, and x is an integer greater than 0 and less than or equal to 100; the weight-average molecular weight of the polymer is 200,000 to 500,000. The R1 group is one or more of the following groups: The R2 group comprises any one or more of the following structures: 。 2. The gas separation membrane as described in claim 1, characterized in that, The gas separation membrane is a gas separation membrane composed of a copolymer of crystalline aromatic diamine and aromatic dianhydride. The copolymer is prepared by crystalline aromatic diamine and aromatic dianhydride, and phenols are used as solvents in the preparation of the copolymer.

3. The gas separation membrane as described in claim 1, characterized in that, Polyimide polymers were obtained directly using a one-step method.

4. The method for preparing the gas separation membrane according to claim 1, characterized in that, The method includes the following steps: (1). At room temperature, DABA, 6FDA, aromatic diamine and aromatic dianhydride were first dissolved in p-chlorophenol. The molar ratio of the monomers was aromatic diamine: aromatic dianhydride = 1~2.2: 1~2, and the solid content of the solution was 15-20wt%. Then, the temperature was raised to 90~120℃ under N2 atmosphere. The monomers consisted of DABA, 6FDA, aromatic diamine and aromatic dianhydride. Aromatic diamine was monomer A and aromatic dianhydride was monomer B. (2) After the monomer is completely dissolved in p-chlorophenol, an isoquinoline catalyst is added to the solution, and then the temperature is raised to 190-200℃ and stirred to promote the polymerization reaction; polymerization is initiated at 190-200℃ and then reacted at this temperature; after the reaction is completed, the solution is poured into methanol or ethanol to obtain a fibrous polymer. After multiple precipitation and washing, the solvent in the polymer is removed. The obtained polymer is dried in a vacuum drying oven at 120-130℃ for 20-24 h and then weighed. The dried polymer is polyimide; wherein the molar ratio of aromatic diamine and aromatic dianhydride in the reaction system is maintained at 1-2.2:1-2; (3) Dissolve the dried polymer in a polar solvent, controlling the solid content of the solution to be 15-20 wt%, and control the rotational viscosity of the solution at 100-105 °C to be 280-800 poise. Filter the polyimide solution with a metal mesh, then extrude it through a hollow fiber membrane spinning nozzle, and pass the extruded hollow fiber body through an N2 atmosphere. Subsequently, it undergoes phase inversion in an ethanol-water solution condensation bath at -10 to -5 °C to produce wet fibers. Immerse the wet fibers in ethanol at 50-60 °C for 2-3 hours, and then in isooctane at 65-75 °C for 3-5 hours to remove the solvent from the fibers. Dry them thoroughly at 100-120 °C, and then heat treat them at 320-350 °C for 10-20 hours to obtain the finished hollow fiber membrane. Wherein, monomer A is selected from any one or more of the following compounds: 2,2'-Di(trifluoromethyl)diaminobiphenyl, 2,2',5,5'-tetrachlorodiphenylamine, p-diaminobiphenyl, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 2,3,5,6-tetramethyl-1,4-phenylenediamine, 3,6-diaminocarbazole, 3,6-diamino-9-ethylcarbazole; The monomer B is selected from any one or more of the following compounds: 。 5. The method for preparing the gas separation membrane as described in claim 4, characterized in that, The method includes the following steps: (1). At room temperature, DABA, 6FDA, aromatic diamine (monomer A) and aromatic dianhydride (monomer B) were first dissolved in p-chlorophenol. The molar ratio of the monomers was diamine: dianhydride = 1:1, and the solid content of the solution was 15-20 wt%. Then, the temperature was raised to 120℃ under N2 atmosphere. (2) After the monomer is completely dissolved in the solvent, add the isoquinoline catalyst to the solution, then heat to 190℃ and stir to promote the polymerization reaction; initiate polymerization at 190℃ and react at this temperature for 20-24 h; after the reaction is complete, pour the solution into methanol or ethanol to obtain fibrous polymer. After multiple precipitation and washing, remove the solvent from the polymer, and dry the obtained polymer in a vacuum drying oven at 120℃ for 24 h and weigh it; wherein the molar ratio of diamine to dianhydride in the reaction system is maintained at 1:1, and the mass of the catalyst is 0.05% of the total mass of the monomer; (3) Dissolve the dried polymer in a polar solvent at 100°C, control the solid content of the solution at 15wt%, and control the rotational viscosity of the solution at 100°C at 800 poise; filter the polyimide solution with a 400-mesh metal wire mesh, then extrude it through a hollow fiber membrane spinning nozzle, and pass the extruded hollow fiber body through a N2 atmosphere, and then carry out phase inversion in a condensation bath of 25wt% ethanol aqueous solution at -5°C to produce wet fibers; The wet fibers were immersed in ethanol at 50°C for 2 hours, and then immersed in isooctane at 70°C for 3 hours to remove the solvent from the fibers; they were then thoroughly dried at 100°C, and then heat-treated at 320-350°C to obtain the finished hollow fiber membrane.

6. The preparation method according to claim 4, characterized in that, In step (2), the mass of the catalyst is 0.05% of the total mass of the monomers.

7. The preparation method according to claim 4, characterized in that, In step (2), the polymerization reaction is carried out at 190°C.

8. The preparation method according to claim 4, characterized in that, In step (2), the polymerization reaction time is 20-24 hours.

9. The application of the gas separation membrane according to any one of claims 1-3 or the gas separation membrane prepared by the method according to any one of claims 4-8, characterized in that: (1) Use gas separation membranes for CO2 removal from flue gas and biogas; and / or (2) Use gas separation membranes for N2 to CO2 removal.

10. The application as described in claim 9, characterized in that, The application scope includes flue gas removal in thermal power plants, steelmaking plants, aluminum electrolysis, and natural gas extraction, or biogas purification in biogas generating devices.

Images