Polyimide cross-linked mixed matrix gas separation membrane and preparation method thereof

Abstract

The invention provides a polyimide cross-linked mixed matrix gas separation membrane and a preparation method thereof. The polyimide cross-linked mixed matrix gas separation membrane is prepared from a spinning solution prepared from raw materials including a cross-linking agent and a polyimide solution, the cross-linking agent comprises an amino-functionalized molecular sieve and a dispersing agent; the amino-functionalized molecular sieve is at least one of an amino-functionalized MWW type molecular sieve, an amino-functionalized MFI type molecular sieve, an amino-functionalized CHA type molecular sieve, an amino-functionalized MOR type molecular sieve, an amino-functionalized AEI type molecular sieve and an amino-functionalized AFX type molecular sieve. The preparation method comprises the step of mixing the cross-linking agent with a polyimide solution to prepare a spinning solution. The prepared polyimide cross-linked mixed matrix gas separation membrane is high in CO2 / N2 selectivity and good in CO2 plasticization resistance.

Description

Technical Field

[0001] This invention relates to the field of gas separation membrane technology, and more specifically, to a polyimide cross-linked mixed matrix gas separation membrane and its preparation method. Background Technology

[0002] Gas separation membrane technology has advanced rapidly since the 1950s, driven by advancements in materials science. Gas separation membranes are based on the differences in solubility and diffusivity of gas molecules within the membrane material. Generally, smaller molecules or more soluble gases pass through the membrane faster, while larger molecules or less soluble gases pass through more slowly. Furthermore, some membranes utilize molecular sieving mechanisms, allowing only molecules of specific sizes or shapes to pass through.

[0003] Gas separation membranes are made from a wide range of materials, including but not limited to polymers (such as polyimide, polysulfone, polyethersulfone, etc.), inorganic materials (such as ceramics, metals, carbon materials), and composite materials. Different material and structural designs can be optimized for specific separation tasks.

[0004] Polyimide (PI) gas separation membranes are high-performance polymer membranes widely used in gas separation. Due to their excellent thermal stability, chemical stability, mechanical properties, and good gas separation performance, polyimide is widely used in the separation and purification of industrial gases. Examples include: air separation for producing high-purity nitrogen or oxygen; natural gas processing for removing impurities such as carbon dioxide and hydrogen sulfide from natural gas and increasing methane content; hydrogen recovery for recycling in oil refining and chemical processes; and carbon dioxide capture for capturing carbon dioxide generated in power plants and industrial processes, helping to reduce greenhouse gas emissions.

[0005] Polyimide (PI) gas separation membranes encounter a significant problem when used for carbon dioxide (CO2) separation: CO2 plasticization. This phenomenon can lead to a decline in membrane performance under certain conditions, particularly when handling high CO2 concentrations or in high-pressure environments. Understanding the impact of CO2 plasticization on polyimide membranes is crucial for designing and optimizing highly efficient and stable gas separation membranes.

[0006] Plasticization increases the free volume of the membrane, thereby increasing its permeability. At first glance, this seems like a positive effect, but this increase lacks selectivity, meaning the membrane's permeability to gases other than CO2, such as nitrogen or methane, will also increase, thus reducing the membrane's separation selectivity. Decreased Selectivity: One of the main performance indicators of gas separation membranes is their selectivity for separating different gases. The loose structure and increased free volume caused by CO2 plasticization typically lead to a decrease in the membrane's selectivity for separating CO2 from other gases (such as N2, CH4, etc.). Decreased Mechanical Properties: Long-term exposure to high CO2 concentrations can also cause a decrease in the membrane's mechanical properties, such as reduced strength and toughness, affecting the membrane's durability and stability.

[0007] To meet the industrial demand for efficient and stable gas separation membranes that combine good gas separation performance with good anti-plasticization properties, it is necessary to develop a polyimide gas separation membrane with better performance. Summary of the Invention

[0008] To address the technical problems existing in the prior art, the present invention provides a polyimide crosslinked mixed matrix gas separation membrane and its preparation method.

[0009] This invention significantly improves the anti-plasticization properties of polyimide membranes and enhances their performance in CO2 separation applications by incorporating amino-functionalized molecular sieves into polyimide materials, while also considering crosslinking and filling methods.

[0010] One objective of this invention is to provide a polyimide crosslinked mixed matrix gas separation membrane, which is prepared from a spinning solution containing raw materials including a crosslinking agent and a polyimide solution; the crosslinking agent includes an amino-functionalized molecular sieve and a dispersant; the amino-functionalized molecular sieve is at least one of amino-functionalized MWW type molecular sieve, amino-functionalized MFI type molecular sieve, amino-functionalized CHA type molecular sieve, amino-functionalized MOR type molecular sieve, amino-functionalized AEI type molecular sieve, and amino-functionalized AFX type molecular sieve.

[0011] In a preferred embodiment of the present invention,

[0012] The amino-functionalized molecular sieve is obtained by amino-functionalizing a molecular sieve with an aminosilane coupling agent; preferably, the aminosilane coupling agent is 3-aminopropyltriethoxysilane; the molecular sieve is at least one of MWW-type molecular sieve, MFI-type molecular sieve, CHA-type molecular sieve, MOR-type molecular sieve, AEI-type molecular sieve, and AFX-type molecular sieve; the amino-functionalization treatment is carried out in a solvent, and the solvent is at least one of toluene and ethanol; more preferably, the molecular sieve is dispersed in a solvent, the aminosilane coupling agent is added, the mixture is filtered, and then washed with a solvent to obtain the amino-functionalized molecular sieve.

[0013] For example, an aqueous dispersion of a molecular sieve sample was heated under reflux for 6 hours at 100°C, filtered, and then activated by vacuum drying at 120°C for 12 hours. The resulting sample was dispersed in a dry toluene medium, and 3-aminopropyltriethoxysilane (APTES) was added dropwise at a ratio of molecular sieve sample mass to APTES mass of 1:10. After stirring for 24 hours, the sample was filtered and repeatedly washed with toluene and ethanol to obtain an amino-functionalized molecular sieve.

[0014] The crosslinking agent is obtained by dispersing amino-functionalized molecular sieves in a dispersant; in the crosslinking agent, the solid content of the amino-functionalized molecular sieves is 0.1% to 30%, preferably 10% to 30%;

[0015] The dispersant is at least one of methanol, ethanol, propanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and deionized water.

[0016] The second objective of this invention is to provide a method for preparing a polyimide crosslinked mixed matrix gas separation membrane, comprising the step of mixing the crosslinking agent with a polyimide solution to obtain a spinning solution.

[0017] In a preferred embodiment of the present invention,

[0018] The preparation method includes the following steps:

[0019] (1) Polymerize diamine and dianhydride monomers into polyamic acid, then imidize it to obtain polyimide slurry, and then perform post-treatment to obtain polyimide resin;

[0020] (2) Dissolve the polyimide resin obtained in step (1) in a solvent to obtain a polyimide solution;

[0021] (3) The crosslinking agent is added to the polyimide solution obtained in step (2), and the spinning solution is obtained after post-treatment.

[0022] (4) The spinning solution obtained in step (3) is spun with the core solution to obtain nascent hollow fiber membrane filaments, which are then transformed into hollow fiber membranes through phase inversion.

[0023] (5) The hollow fiber membrane obtained in step (4) is heated and post-treated to obtain the polyimide cross-linked mixed matrix gas separation membrane.

[0024] In a preferred embodiment of the present invention,

[0025] Step (1),

[0026] The diamine is at least one of 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA), 4,4-diaminodiphenylmethane (MDA), 4,4-diaminodiphenyl ether (ODA), 4,4′-methylenebis(2,6-dimethylaniline) (MDX), 4,4′-diaminotriphenylamine (DATPA), 5-amino-1,3,3-trimethylcyclohexylmethylamine (IPDA), and tetramethyl-p-phenylenediamine (pTeMPD);

[0027] The dianhydride is at least one selected from the following: pyromellitic dianhydride (PMDA), 1,4,5,8-naphthalenetetracarboxylic anhydride (NTCDA), 4,4'-hexafluoroisopropylphthalic anhydride (6FDA), 4,4'-oxobisphthalic anhydride (ODPA), 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) (BPDADA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), and 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA).

[0028] The method for polymerizing the diamine and dianhydride monomers into polyamic acid and imidizing them can be a general method in the art. For example, imidization can be chemical imidization or thermal imidization. Chemical imidization is prepared by using acid anhydride as a dehydrating agent and tertiary amines as catalysts at a temperature of 150-200°C.

[0029] The post-processing includes precipitation, washing, and drying; preferably, the precipitation is carried out in a solvent, which can be a commonly used solvent in the prior art, such as methanol; the washing is performed with a solvent, which can be a commonly used solvent in the prior art, such as methanol; the drying can be carried out using general methods in the prior art, such as vacuum drying.

[0030] In a preferred embodiment of the present invention,

[0031] Step (2),

[0032] The solvent is at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and chloroform; preferably a mixture of two or more solvents, such as N-methylpyrrolidone (NMP) or a mixture of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF);

[0033] The solid content of the polyimide solution is 20-35 wt%.

[0034] In a preferred embodiment of the present invention,

[0035] Step (3),

[0036] The mass ratio of the crosslinking agent to the polyimide solution is 1:(1-50), preferably 1:(8-50);

[0037] The second post-processing includes mixing, degassing, and filtration; preferably, the mixing is carried out under stirring; the degassing can be performed using common methods of the prior art, such as ultrasonic degassing; the filtration can be performed using common methods of the prior art.

[0038] In a preferred embodiment of the present invention,

[0039] Step (4),

[0040] The core fluid is at least one selected from deionized water, methanol, ethanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO); preferably, it is a mixture of deionized water and an organic solvent, more preferably, the mass ratio of the organic solvent to the deionized water is (8-20):1, and the organic solvent is more preferably at least one selected from N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP);

[0041] The spinning solution is ejected through the spinning solution nozzle of the spinneret and meets the core solution ejected from the core solution nozzle of the spinneret to form a nascent hollow fiber membrane filament.

[0042] The nascent hollow fiber membrane filaments pass through an air gap and then enter a gel bath, where they undergo phase transformation to form a hollow fiber membrane. The gel bath is at least one of deionized water, methanol, ethanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0043] In a preferred embodiment of the present invention,

[0044] Step (5),

[0045] The heating temperature is 80–250℃; preferably 180–250℃.

[0046] The heating time is 1 to 180 minutes, preferably 3 to 60 minutes; for example, a range with any two points as endpoints, such as 3 to 30 minutes;

[0047] The post-processing step three includes soaking, solvent removal, and drying; preferably, the soaking is soaking in a solvent, which can be a commonly used solvent in the prior art, such as deionized water, ethanol, n-hexane, etc.; the solvent removal and drying can both be carried out using conventional methods in the prior art.

[0048] The third objective of this invention is to provide a polyimide cross-linked mixed matrix gas separation membrane obtained by the above method.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] This invention provides a polyimide crosslinked mixed matrix gas separation membrane and its preparation method, which is simple and easy to implement. In this invention, amino-functionalized molecular sieves are dispersed in a dispersant and added to a polyimide solution for crosslinking. On the one hand, the crosslinking reaction and filler mechanisms jointly improve the CO2 plasticization resistance of the polyimide gas separation membrane; on the other hand, the addition of molecular sieves enhances CO2 adsorption, thereby improving CO2 / N2 selectivity. The dispersant in the crosslinking agent can also act as an additive in the spinning solution, adjusting the composition of the spinning solution and enhancing gas separation performance. Detailed Implementation

[0051] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0052] The raw materials used in the examples and comparative examples were all commercially available.

[0053] Molecular sieves were purchased from Tianjin Nanhua Catalyst Co., Ltd.; other major reagents were purchased from Sinopharm Reagent Co., Ltd.

[0054] Methods for determining CO2 gas flux and selectivity of hollow fiber membranes:

[0055] Ten hollow fiber membranes were encapsulated in epoxy resin within a stainless steel tube to create a performance evaluation element. The effective length of the membrane was 20 mm. This element was inserted into a stainless steel container, fixed, and sealed to form a performance evaluation module. The inlet gas temperature was controlled at 35°C. A mixed gas (20 vol% CO2, 80% N2) was introduced into the performance evaluation module. The upstream gas on the shell side was the feed gas, and the downstream gas was the retentate gas. The gas collected through the hollow fiber membrane was the permeate gas. The retentate gas side pressure regulating valve was controlled to test the module under constant pressure, and the permeate gas flow rate was measured. Gas chromatography was used to determine the content of the two gases in the mixed gas, thus obtaining the CO2 / N2 selectivity in the mixed gas.

[0056] Example 1

[0057] (1) 3-aminopropyltriethoxysilane (APTES) was added to the activated and dried toluene medium of MFI molecular sieve ZSM-5, stirred, filtered, and repeatedly washed with toluene and ethanol to obtain amino-functionalized MFI molecular sieve ZSM-5. After grinding, it was dispersed in methanol to obtain a crosslinking agent with a solid content of 10%.

[0058] (2) Polyamic acid was synthesized from 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA), 4,4-diaminodiphenyl ether (ODA), and 4,4'-hexafluoroisopropylphthalic anhydride (6FDA), wherein 6FDA:6FpDA:ODA = 5:2:3 (molar ratio), the polymerization temperature was 50℃, and the polymerization reaction time was 24h. Acetic anhydride and isoquinoline were added, wherein acetic anhydride:isoquinoline:6FDA = 2:2:1 (molar ratio), to complete chemical imidization at 150℃ for 24h, yielding a polyimide slurry. The slurry was poured into methanol to precipitate a solid product, washed with methanol, and dried under vacuum to obtain the polyimide resin PI-6FDA-6FpDA-ODA. Polyimide resin PI-6FDA-6FpDA-ODA was dissolved in a mixed solvent of NMP and THF (weight ratio NMP:THF = 4:1) to obtain a polyimide solution with a solid content of 30 wt%.

[0059] (3) Add 1 part by weight of crosslinking agent to 9 parts by weight of polyimide solution, stir mechanically for 3 hours, degas by ultrasonication, and filter with a filter with a filtration accuracy of 10 microns to obtain spinning solution.

[0060] (4) Prepare the core solution by mixing NMP and water (weight ratio NMP:deionized water = 9:1); extrude the spinning solution obtained in (3) through the spinning solution nozzle of the spinneret, and eject the core solution through the core solution nozzle of the spinneret. The spinning solution and the core solution meet at the spinneret to form nascent hollow fiber membrane filaments. After passing through an air gap, the nascent hollow fiber membrane filaments enter the gel bath, which contains deionized water. After phase inversion, a hollow fiber membrane is formed.

[0061] (5) The hollow fiber membrane obtained in (4) is placed in an oven and heated at 200°C for 30 minutes. After being soaked in deionized water, ethanol and n-hexane in sequence, the solvent is removed and the membrane is dried to obtain a polyimide cross-linked mixed matrix gas separation membrane.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that no crosslinking agent was added, and the 30wt% polyimide solution obtained in step (2) was used as the spinning solution;

[0064] Except for the differences mentioned above, the other conditions of Comparative Example 1 are the same as those of Example 1, and a polyimide crosslinked mixed matrix gas separation membrane is obtained through steps (4) and (5).

[0065] Example 2

[0066] (1) 3-aminopropyltriethoxysilane (APTES) was added to the activated and dried toluene medium of MFI molecular sieve ZSM-5, stirred, filtered, and repeatedly washed with toluene and ethanol to obtain amino-functionalized MFI molecular sieve ZSM-5. After grinding, it was dispersed in methanol to obtain a crosslinking agent with a solid content of 10%.

[0067] (2) Polyamic acid was synthesized from 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA), 4,4-diaminodiphenyl ether (ODA) and 4,4'-hexafluoroisopropylphthalic anhydride (6FDA), with a molar ratio of 6FDA:6FpDA:ODA = 5:2:3, a polymerization temperature of 50℃, and a polymerization reaction time of 24h; acetic anhydride and isoquinoline were added, with a molar ratio of acetic anhydride:isoquinoline:6FDA = 2:2:1, to complete chemical imidization at a temperature of 150℃ for 24h, thus obtaining a polyimide slurry. The solid product was precipitated by pouring it into methanol, washed with methanol, and dried under vacuum to obtain polyimide resin PI-6FDA-6FpDA-ODA. The polyimide resin PI-6FDA-6FpDA-ODA was dissolved in NMP-THF mixed solvent (NMP:THF = 4:1 by weight) to obtain a polyimide solution with a solid content of 30 wt%.

[0068] (3) Add 1 part by weight of crosslinking agent to 19 parts by weight of polyimide solution, stir mechanically for 3 hours, degas by ultrasonication, and filter with a filter with a filtration accuracy of 10 microns to obtain spinning solution.

[0069] (4) Prepare the core solution by mixing NMP and water (weight ratio NMP:deionized water = 9:1); extrude the spinning solution obtained in (3) through the spinning solution nozzle of the spinneret, and eject the core solution through the core solution nozzle of the spinneret. The spinning solution and the core solution meet at the spinneret to form nascent hollow fiber membrane filaments. After passing through an air gap, the nascent hollow fiber membrane filaments enter the gel bath, which contains deionized water. After phase inversion, a hollow fiber membrane is formed.

[0070] (5) The hollow fiber membrane obtained in (4) is placed in an oven and heated at 250°C for 3 minutes. After being soaked in deionized water, ethanol and n-hexane in sequence, the solvent is removed and the membrane is dried to obtain a polyimide cross-linked mixed matrix gas separation membrane.

[0071] Comparative Example 2

[0072] The difference from Example 2 is that no crosslinking agent was added, and the 30wt% polyimide solution obtained in step (2) was used as the spinning solution;

[0073] Except for the differences mentioned above, the other conditions of Comparative Example 2 are the same as those of Example 2, and a polyimide crosslinked mixed matrix gas separation membrane is obtained through steps (4) and (5).

[0074] Example 3

[0075] (1) 3-aminopropyltriethoxysilane (APTES) was added to the activated and dried toluene medium of MFI molecular sieve ZSM-5, stirred, filtered, and repeatedly washed with toluene and ethanol to obtain amino-functionalized MFI molecular sieve ZSM-5. After grinding, it was dispersed in methanol to obtain a crosslinking agent with a solid content of 20%.

[0076] (2) Polyamic acid was synthesized from 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA), 4,4-diaminodiphenylmethane (MDA) and pyromellitic dianhydride (PMDA), with a molar ratio of PMDA:6FpDA:ODA = 5:2:3, a polymerization temperature of 50℃, and a polymerization reaction time of 24h; acetic anhydride and isoquinoline were added, with a molar ratio of acetic anhydride:isoquinoline:PMDA = 2:2:1, to complete chemical imidization at a temperature of 150℃ for 24h, thus obtaining a polyimide slurry. The solid product was precipitated by pouring it into methanol, washed with methanol, and dried under vacuum to obtain polyimide resin PI-PMDA-6FpDA-MDA. The polyimide resin PI-PMDA-6FpDA-MDA was dissolved in a DMF-THF mixed solvent (weight ratio DMF:THF = 5:1) to obtain a polyimide solution with a solid content of 25 wt%.

[0077] (3) Add 1 part by weight of crosslinking agent to 9 parts by weight of polyimide solution, stir mechanically for 3 hours, degas by ultrasonication, and filter with a filter with a filtration accuracy of 10 microns to obtain spinning solution.

[0078] (4) Prepare the core solution by mixing NMP and water (weight ratio NMP:deionized water = 9:1); extrude the spinning solution obtained in (3) through the spinning solution nozzle of the spinneret, and eject the core solution through the core solution nozzle of the spinneret. The spinning solution and the core solution meet at the spinneret to form nascent hollow fiber membrane filaments. After passing through an air gap, the nascent hollow fiber membrane filaments enter the gel bath, which contains deionized water. After phase inversion, a hollow fiber membrane is formed.

[0079] (5) The hollow fiber membrane obtained in (4) is placed in an oven and heated at 180°C for 30 minutes. After being soaked in deionized water, ethanol and n-hexane in sequence, the solvent is removed and the membrane is dried to obtain a polyimide cross-linked mixed matrix gas separation membrane.

[0080] Comparative Example 3

[0081] The difference from Example 2 is that no crosslinking agent was added, and the 30wt% polyimide solution obtained in step (2) was used as the spinning solution; the core solution NMP:deionized water (weight ratio) = 9:1;

[0082] Except for the differences mentioned above, the other conditions of Comparative Example 2 are the same as those of Example 2, and a polyimide crosslinked mixed matrix gas separation membrane is obtained through steps (4) and (5).

[0083] Example 4

[0084] (1) After activation, SSZ-13 of CHA type molecular sieve was dispersed and dried in toluene medium, 3-aminopropyltriethoxysilane (APTES) was added, stirred, filtered, and repeatedly washed with toluene and ethanol to obtain amino-functionalized CHA type molecular sieve SSZ-13. After grinding, it was dispersed in ethanol to obtain a crosslinking agent with a solid content of 10%.

[0085] (2) Polyamic acid was synthesized from 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA), 4,4-diaminodiphenyl ether (ODA) and 4,4'-hexafluoroisopropylphthalic anhydride (6FDA), with a molar ratio of 6FDA:6FpDA:ODA = 5:2:3, a polymerization temperature of 50℃, and a polymerization reaction time of 24h; acetic anhydride and isoquinoline were added, with a molar ratio of acetic anhydride:isoquinoline:6FDA = 2:2:1, to complete chemical imidization at a temperature of 150℃ for 24h, thus obtaining a polyimide slurry. The solid product was precipitated by pouring it into methanol, washed with methanol, and dried under vacuum to obtain polyimide resin PI-6FDA-6FpDA-ODA. The polyimide resin PI-6FDA-6FpDA-ODA was dissolved in NMP-THF mixed solvent (NMP:THF = 4:1 by weight) to obtain a polyimide solution with a solid content of 30 wt%.

[0086] (3) Add 1 part by weight of crosslinking agent to 9 parts by weight of polyimide solution, stir mechanically for 3 hours, degas by ultrasonication, and filter with a filter with a filtration accuracy of 10 microns to obtain spinning solution.

[0087] (4) Prepare the core solution by mixing NMP and water (weight ratio NMP:deionized water = 19:1); extrude the spinning solution obtained in (3) through the spinning solution nozzle of the spinneret, and eject the core solution through the core solution nozzle of the spinneret. The spinning solution and the core solution meet at the spinneret to form nascent hollow fiber membrane filaments. After passing through an air gap, the nascent hollow fiber membrane filaments enter the gel bath, which contains deionized water. After phase inversion, a hollow fiber membrane is formed.

[0088] (5) The hollow fiber membrane obtained in (4) is placed in an oven and heated at 200°C for 30 minutes. After being soaked in deionized water, ethanol and n-hexane in sequence, the solvent is removed and the membrane is dried to obtain a polyimide cross-linked mixed matrix gas separation membrane.

[0089] Example 5

[0090] (1) 3-aminopropyltriethoxysilane (APTES) was added to the toluene medium after the MWW type molecular sieve SCM-1 was activated and dispersed and dried. The mixture was stirred, filtered, and washed repeatedly with toluene and ethanol to obtain amino-functionalized MWW type molecular sieve SCM-1. After grinding, it was dispersed in methanol to obtain a crosslinking agent with a solid content of 30%.

[0091] (2) Polyamic acid was synthesized from 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA), 4,4-diaminodiphenyl ether (ODA), and 4,4'-hexafluoroisopropylphthalic anhydride (6FDA), with a molar ratio of 6FDA:6FpDA:ODA = 5:2:3. The polymerization temperature was 50℃, and the polymerization reaction time was 24h. Acetic anhydride and isoquinoline were added, with a molar ratio of acetic anhydride:isoquinoline:6FDA = 2:2:1. The chemical reaction was then completed. Amination was performed at 150°C for 24 hours to obtain a polyimide slurry. The slurry was then poured into methanol to precipitate a solid product. After washing with methanol and vacuum drying, polyimide resin PI-6FDA-6FpDA-ODA was obtained. The polyimide resin PI-6FDA-6FpDA-ODA was dissolved in a mixed solvent of NMP and THF (weight ratio NMP:THF = 4:1) to obtain a polyimide solution with a solid content of 30 wt%.

[0092] (3) Add 1 part by weight of crosslinking agent to 49 parts by weight of polyimide solution, stir mechanically for 3 hours, degas by ultrasonication, and filter with a filter with a filtration accuracy of 10 microns to obtain spinning solution.

[0093] (4) Prepare the core solution by mixing NMP and water (weight ratio NMP:deionized water = 19:1); extrude the spinning solution obtained in (3) through the spinning solution nozzle of the spinneret, and eject the core solution through the core solution nozzle of the spinneret. The spinning solution and the core solution meet at the spinneret to form nascent hollow fiber membrane filaments. After passing through an air gap, the nascent hollow fiber membrane filaments enter the gel bath, which contains deionized water. After phase inversion, a hollow fiber membrane is formed.

[0094] (5) The hollow fiber membrane obtained in (4) is placed in an oven and heated at 200°C for 30 minutes. After being soaked in deionized water, ethanol and n-hexane in sequence, the solvent is removed and the membrane is dried to obtain a polyimide cross-linked mixed matrix gas separation membrane.

[0095] Table 1 compares the gas permeability of Examples 1-5 and Comparative Examples 1-2.

[0096] Table 1

[0097]

[0098] 1 GPU = 10 -6 cm 3 (STP) / (cm 2 ·s·cmHg)

[0099] As can be seen from Table 1:

[0100] Compared with Comparative Example 1: Example 1:

[0101] At 0.5 MPa, the selectivity α(CO2 / N2) increased from 30.6 to 32.3, and the CO2 flux increased from 23.3 GPU to 25.7 GPU;

[0102] At 2 MPa, the selectivity α(CO2 / N2) increased from 27.3 to 36.1, and the CO2 flux increased from 27.5 GPU to 29.2 GPU.

[0103] Compared with the pure polyimide gas separation membrane of Comparative Example 1, the polyimide cross-linked mixed matrix gas separation membrane prepared in Example 1 showed improved selectivity α (CO2 / N2) and increased CO2 flux at test pressures of 0.5 MPa and 2 MPa. Furthermore, when the test pressure increased from 0.5 MPa to 2 MPa, the gas selectivity of Comparative Example 1 decreased by 10.8%, indicating plasticization. The polymer membrane swelled after absorbing CO2, accelerating the permeation of other gases such as N2, causing the polymer membrane to lose its selectivity. In contrast, the gas separation membrane of Example 1 not only did not decrease but actually increased by 11.8%, demonstrating that the polyimide gas separation membrane's resistance to CO2 plasticization was improved, and its CO2 / N2 selectivity was enhanced.

[0104] Compared with Comparative Example 2: Example 2:

[0105] At 0.5 MPa, the selectivity α (CO2 / N2) is basically the same, and the CO2 flux increases from 20.2 GPU to 24.5 GPU;

[0106] At 2 MPa, the selectivity α(CO2 / N2) increased from 28.5 to 33.3, and the CO2 flux increased from 27.5 GPU to 29.1 GPU;

[0107] Compared with the pure polyimide gas separation membrane of Comparative Example 2, the polyimide cross-linked mixed matrix gas separation membrane prepared in Example 2 showed improved selectivity α (CO2 / N2) and increased CO2 flux to some extent under test pressures of 0.5 MPa and 2 MPa. Furthermore, when the test pressure increased from 0.5 MPa to 2 MPa, the gas selectivity of Comparative Example 2 decreased by 9.5%, indicating plasticization, while the gas separation membrane of Example 2 not only did not decrease but actually increased by 7.1%, further demonstrating that the polyimide gas separation membrane's resistance to CO2 plasticization was improved and its CO2 / N2 selectivity was enhanced.

[0108] Compared with Comparative Example 3: Example 3:

[0109] At 0.5 MPa, the selectivity α(CO2 / N2) increased from 25.5 to 27.6, and the CO2 flux increased from 13.7 GPU to 18.9 GPU;

[0110] At 2 MPa, the selectivity α(CO2 / N2) increased from 22.2 to 29.4, and the CO2 flux increased from 14.8 GPU to 19.9 GPU;

[0111] Compared with the pure polyimide gas separation membrane of Comparative Example 3, the polyimide cross-linked mixed matrix gas separation membrane prepared in Example 3 showed improved selectivity α (CO2 / N2) and increased CO2 flux to some extent under test pressures of 0.5 MPa and 2 MPa. Furthermore, when the test pressure increased from 0.5 MPa to 2 MPa, the gas selectivity of Comparative Example 3 decreased by 12.9%, indicating plasticization, while the gas separation membrane of Example 3 not only did not decrease but actually increased by 6.5%, further demonstrating that the polyimide gas separation membrane's resistance to CO2 plasticization was improved and its CO2 / N2 selectivity was enhanced.

[0112] The polyimide cross-linked mixed matrix gas separation membranes prepared in Examples 1-5 exhibit high CO2 / N2 selectivity, good resistance to CO2 plasticization, and simple and easy preparation methods, achieving good technical results.

Claims

1. A polyimide crosslinked mixed matrix gas separation membrane, prepared from a spinning solution comprising a crosslinking agent and a polyimide solution; wherein the crosslinking agent comprises an amino-functionalized molecular sieve and a dispersant; wherein the amino-functionalized molecular sieve is at least one of amino-functionalized MWW type molecular sieve, amino-functionalized MFI type molecular sieve, amino-functionalized CHA type molecular sieve, amino-functionalized MOR type molecular sieve, amino-functionalized AEI type molecular sieve, and amino-functionalized AFX type molecular sieve.

2. The polyimide crosslinked mixed matrix gas separation membrane as described in claim 1, characterized in that: The amino-functionalized molecular sieve is obtained by amino-functionalizing a molecular sieve with an aminosilane coupling agent; preferably, the aminosilane coupling agent is 3-aminopropyltriethoxysilane; and / or, the molecular sieve is at least one of MWW-type molecular sieve, MFI-type molecular sieve, CHA-type molecular sieve, MOR-type molecular sieve, AEI-type molecular sieve, and AFX-type molecular sieve; and / or, the amino-functionalization treatment is carried out in a solvent, and the solvent is at least one of toluene and ethanol; more preferably, the molecular sieve is dispersed in a solvent, the aminosilane coupling agent is added, mixed and filtered, and then washed with a solvent to obtain the amino-functionalized molecular sieve; and / or The crosslinking agent is obtained by dispersing an amino-functionalized molecular sieve in a dispersant; and / or, In the crosslinking agent, the solid content of the amino-functionalized molecular sieve is 0.1% to 30%, preferably 10% to 30%; and / or, The dispersant is at least one of methanol, ethanol, propanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, and deionized water.

3. A method for preparing a polyimide crosslinked mixed matrix gas separation membrane as described in claim 1 or 2, comprising the step of mixing the crosslinking agent with a polyimide solution to obtain a spinning solution.

4. The method for preparing the polyimide crosslinked mixed matrix gas separation membrane as described in claim 3, characterized in that... The preparation method includes the following steps: (1) Polymerize diamine and dianhydride monomers into polyamic acid, then imidize it to obtain polyimide slurry, and then perform post-treatment to obtain polyimide resin; (2) Dissolve the polyimide resin obtained in step (1) in a solvent to obtain a polyimide solution; (3) The crosslinking agent is added to the polyimide solution obtained in step (2), and the spinning solution is obtained after post-treatment. (4) The spinning solution obtained in step (3) is spun with the core solution to obtain nascent hollow fiber membrane filaments, which are then transformed into hollow fiber membranes through phase inversion. (5) The hollow fiber membrane obtained in step (4) is heated and post-treated to obtain the polyimide cross-linked mixed matrix gas separation membrane.

5. The method for preparing the polyimide crosslinked mixed matrix gas separation membrane as described in claim 4, characterized in that: Step (1), The diamine is at least one selected from 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether, 4,4′-methylenebis(2,6-dimethylaniline), 4,4′-diaminotriphenylamine, 5-amino-1,3,3-trimethylcyclohexylmethylamine, and tetramethyl-p-phenylenediamine; and / or The dianhydride is at least one selected from the following: pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, 4,4'-hexafluoroisopropylphthalic anhydride, 4,4'-oxobisphthalic anhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), 3,3′,4,4′-biphenyltetracarboxylic anhydride, 1,2,3,4-cyclobutanetetracarboxylic anhydride, 3,3′,4,4′-benzophenone tetracarboxylic anhydride, and 3,3′,4,4′-diphenylsulfone tetracarboxylic anhydride; and / or The post-processing includes precipitation, washing, and drying.

6. The method for preparing the polyimide crosslinked mixed matrix gas separation membrane as described in claim 4, characterized in that: Step (2), The solvent is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, and chloroform; and / or, The solid content of the polyimide solution is 20-35 wt%.

7. The method for preparing the polyimide crosslinked mixed matrix gas separation membrane as described in claim 4, characterized in that: Step (3), The mass ratio of the crosslinking agent to the polyimide solution is 1:(1-50), preferably 1:(8-50); and / or, The second post-processing includes mixing, degassing, and filtration.

8. The method for preparing the polyimide crosslinked mixed matrix gas separation membrane as described in claim 4, characterized in that: Step (4), The core fluid is at least one selected from deionized water, methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; and / or, The spinning solution is ejected through the spinning solution nozzles of the spinneret and meets the core solution ejected from the core solution nozzles of the spinneret to form nascent hollow fiber membrane filaments; and / or, The nascent hollow fiber membrane fibers pass through an air gap and then enter a gel bath, where they undergo phase transformation to form a hollow fiber membrane. The gel bath is at least one of deionized water, methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

9. The method for preparing the polyimide crosslinked mixed matrix gas separation membrane as described in claim 4, characterized in that: Step (5), The heating temperature is 80–250°C; preferably 180–250°C; and / or, The heating time is 1 to 180 minutes, preferably 3 to 60 minutes; and / or, The post-processing includes soaking, solvent removal, and drying.

10. A polyimide crosslinked mixed matrix gas separation membrane obtained by the preparation method according to any one of claims 3 to 9.

Images