Gas separation membrane element and preparation method thereof

Abstract

The invention belongs to the technical field of gas separation membranes, and provides a gas separation membrane element and a preparation method thereof. The gas separation membrane element is prepared from a composite membrane comprising a modified polysulfone microporous base layer, a transition layer and a metal organic framework material loaded high-molecular functional layer which are sequentially arranged from bottom to top. The preparation method comprises the following steps: cutting a composite membrane into a preset size, assembling the composite membrane with a flow guide net and a sealing element, and packaging into a hollow fiber type or flat plate type membrane element to finish the preparation. The gas separation membrane element has the advantages of high separation efficiency, strong pollution resistance, tight interlayer combination and the like, can greatly improve the separation coefficient of methane / nitrogen, and is long in service life. The method can be widely applied to petrochemical engineering unconventional natural gas purification, industrial waste gas methane recovery in the environmental protection field and other scenes, and has remarkable industrial application value and economic benefits. The preparation method is simple to operate and high in repeatability, and large-scale industrial production can be realized.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane technology, specifically, it relates to a gas separation membrane element and its preparation method. Background Technology

[0002] Gas separation membrane technology, with its advantages of low energy consumption, compact equipment, simple operation and environmental friendliness, has become one of the core technologies for methane / nitrogen separation and purification in scenarios such as unconventional natural gas purification in petrochemical industry and methane recovery from industrial waste gas in environmental protection.

[0003] However, existing gas separation membrane elements still face two major technical challenges that urgently need to be addressed in practical applications, severely restricting their industrial application effectiveness. On the one hand, their separation efficiency is relatively low. Due to the similar kinetic diameters and small differences in polarizability between methane and nitrogen, traditional single polymer membranes or simple composite membrane materials have limited gas recognition and selective separation capabilities, making it difficult to achieve efficient separation of the two and failing to meet the purification precision requirements of industrial scenarios. On the other hand, their resistance to contamination is weak. Pollutants such as oily aerosols, ultrafine dust, and organic impurities contained in industrial gases are easily adsorbed on the membrane surface or penetrate into the membrane pores, causing blockage and resulting in rapid decline in membrane flux. This, in turn, shortens the service life of the membrane element and increases industrial operating costs. To improve the gas separation selectivity of membrane elements, metal-organic frameworks (MOFs) are widely used in the preparation of functional layers for modified gas separation membranes due to their tunable pore structure, large specific surface area, and excellent gas adsorption selectivity.

[0004] However, in practical applications of membrane materials, MOFs often encounter problems when combined with polymer matrices and membrane layers, such as easy aggregation of MOF particles, poor compatibility between MOFs and polymer matrices, and loose bonding between the base layer and functional layers. This not only fails to fully leverage the selectivity advantages of MOFs, but may also further reduce the antifouling ability due to defects in the membrane structure, resulting in the overall performance of the membrane element falling short of expectations. Summary of the Invention To address the aforementioned shortcomings of existing technologies, the primary objective of this invention is to provide a gas separation membrane element that possesses advantages such as high separation efficiency, strong anti-fouling properties, and tight interlayer bonding. This significantly improves the methane / nitrogen separation coefficient and extends its service life. It can be widely applied in fields such as unconventional natural gas purification in the petrochemical industry and methane recovery from industrial waste gas, demonstrating significant industrial application value and economic benefits.

[0005] In view of the above-mentioned shortcomings in the prior art, the second objective of the present invention is to provide a method for preparing a gas separation membrane element. This method is simple to operate, highly repeatable, and can be used for large-scale industrial production.

[0006] To achieve the above objectives, the solution adopted by the present invention is as follows: A gas separation membrane element is made of a composite membrane consisting of a modified polysulfone microporous substrate, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0007] Furthermore, in a preferred embodiment of the present invention, the thickness of the modified polysulfone microporous base layer is 80-120 μm, and the modified polysulfone is end-capped with hydroxyl-terminated hyperbranched polyester at an addition amount of 0.3%-0.5% of the polysulfone mass, and the end-capping rate of the hydroxyl-terminated hyperbranched polyester is 40%-50%.

[0008] Further, in a preferred embodiment of the present invention, the preparation method of the modified polysulfone microporous base layer includes: mixing polysulfone, hydroxyl-terminated hyperbranched polyester, N,N-dimethylacetamide and polyethylene glycol 400 in a mass ratio of 15:0.06:70:15, stirring at 80-90°C until completely dissolved to form a casting solution; casting the casting solution on a clean glass plate, controlling the wet film thickness to be 200-250 μm, keeping it at 60°C for 10 min, and then immersing it in deionized water at 25°C to solidify and form a base layer; after washing and drying, the modified polysulfone microporous base layer is obtained.

[0009] Furthermore, in a preferred embodiment of the present invention, the thickness of the transition layer is 1-3 μm, and it is formed by interfacial polymerization of piperazine and pyromellitic trimethylol chloride.

[0010] Further, in a preferred embodiment of the present invention, the method for preparing the transition layer includes: immersing the substrate in a 2% (w / w) piperazine aqueous solution for 3-5 minutes, removing it and drying the surface with nitrogen; then immersing the substrate in a 0.1% (w / w) trimesoyl chloride hexane solution and reacting it at 25°C for 1-2 minutes; after the reaction, washing the unreacted monomers on the surface of the substrate with hexane and drying it at 60°C for 30 minutes to form the transition layer.

[0011] Furthermore, in a preferred embodiment of the present invention, the thickness of the polymer functional layer loaded with the metal-organic framework material is 3-5 μm, the metal-organic framework material is loaded with polyimide as the polymer matrix, and the loading amount of the metal-organic framework material is 15%-20% of the mass of the polymer matrix.

[0012] Further, in a preferred embodiment of the present invention, the method for preparing the metal-organic framework material loaded with polymer functional layer includes: firstly, ultrasonically dispersing the metal-organic framework material at a power of 300 W for 20 min, dispersing it in N-methylpyrrolidone, then adding polyimide, stirring at 70°C for 2 h to form a metal-organic framework-polymer mixed solution, coating the mixed solution on the surface of the transition layer and then vacuum drying to obtain the metal-organic framework material loaded with polymer functional layer, and simultaneously obtaining a composite film.

[0013] Furthermore, in a preferred embodiment of the present invention, when coating the mixed solution onto the surface of the transition layer, the spin coating rate is controlled at 3000-4000 rpm and the spin coating time is 30s.

[0014] Furthermore, in a preferred embodiment of the present invention, the vacuum drying conditions are vacuum drying at 120°C for 2 hours.

[0015] A method for preparing the above-mentioned gas separation membrane element includes: cutting the composite membrane to a preset size, assembling it with a flow guide net and a sealing element, and encapsulating it into a hollow fiber or flat sheet membrane element to complete the preparation.

[0016] The beneficial effects of the gas separation membrane element and its preparation method provided by this invention are: (1) The gas separation membrane element provided by this invention, by adopting a modified polysulfone microporous substrate, can effectively improve the hydrophilicity of the substrate and significantly reduce the water contact angle, thereby significantly reducing the adsorption tendency of pollutants such as oily aerosols and ultrafine dust in industrial gases, reducing the risk of membrane pore blockage. Compared with the use of pure polysulfone membrane, the modified polysulfone microporous substrate can significantly improve the membrane flux recovery rate and significantly improve the antifouling performance. At the same time, after modification, the mechanical strength of the modified polysulfone substrate is optimized, and the tensile strength, tensile elastic modulus and elongation at break are significantly improved. It can withstand pressure fluctuations and backflushing cleaning operations in industrial scenarios, avoid damage to the membrane element during use, adapt to the complex working conditions in the fields of petrochemicals and environmental protection, and broaden the application range of membrane elements. (2) The gas separation membrane element provided by the present invention uses an interfacial polymerization process under specific technical conditions to construct a transition layer, which enables the base layer and the functional layer to form a strong chemical bond, thereby overcoming the problems of poor bonding between metal-organic framework materials and base layer and easy detachment of membrane layer in the prior art. Its service life is extended to more than 3 times that of traditional membrane elements, which greatly reduces the replacement frequency of membrane elements and industrial operation and maintenance costs. (3) The gas separation membrane element provided by the present invention has significant separation efficiency. Among them, MOFs and polyimide polymer form a stable composite system, which, combined with the high permeability of the modified polysulfone substrate, can significantly improve the methane / nitrogen separation coefficient compared with traditional polysulfone membranes, thus achieving a balance between high separation selectivity and permeability. (4) The preparation method of the gas separation membrane element provided by the present invention has strong industrial feasibility, takes into account both performance and production cost, and is easy to promote on a large scale. The core raw materials are all commercially available, and many of the processes used in the preparation process are also mature industrial technologies. The equipment is highly versatile and does not require special customized equipment. It can be directly adapted to existing membrane element production lines to achieve large-scale mass production. In summary, through the modification and synergistic design of the interlayer structure, this invention can simultaneously improve separation efficiency, enhance anti-fouling capabilities, and extend service life. Compared with traditional gas separation membrane elements, it has significant improvements in performance, cost, and stability, and can be widely used in gas separation and purification scenarios in petrochemical, environmental protection, and other fields, with extremely high industrial application value and economic benefits. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0018] The following is a detailed description of a gas separation membrane element and its preparation method provided by an embodiment of the present invention.

[0019] The present invention provides a gas separation membrane element comprising a composite membrane consisting of a modified polysulfone microporous substrate, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0020] The modified polysulfone microporous base layer has a thickness of 80-120 μm. It uses 0.3%-0.5% by weight of hydroxyl-terminated hyperbranched polyester to cap the modified polysulfone, with a capping rate of 40%-50%. It should be noted that in this application, commercially available polysulfone resin (model PSF-UDEL P-1700, viscosity range 0.55-0.65 dL / g) can be used.

[0021] The transition layer has a thickness of 1-3 μm and is formed by interfacial polymerization of piperazine and pyromellitic trimethylol chloride. It should be noted that in this application, the purity of piperazine is ≥99%, and the purity of pyromellitic trimethylol chloride is ≥98%.

[0022] The thickness of the polymer functional layer loaded with the metal-organic framework (MOF) is 3-5 μm. The MOF is loaded with polyimide as the polymer matrix, and the loading amount of the MOF is 15%-20% of the polymer matrix mass. It should be noted that in this application, the polyimide is designated as 6FDA-DAM, with a molecular weight of 50,000-80,000. ZIF-8 (particle size 50-200 nm, purity ≥98%) is selected as the MOF.

[0023] The present invention provides a method for preparing a gas separation membrane element, comprising: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester, N,N-dimethylacetamide and polyethylene glycol 400 are mixed in a mass ratio of 15:0.06:70:15 and stirred at 80-90℃ until completely dissolved to form a casting solution; the casting solution is cast on a clean glass plate, the wet film thickness is controlled to be 200-250μm, and kept at 60℃ for 10 min. Then it is immersed in 25℃ deionized water to solidify and form a mold. After washing and drying, the modified polysulfone microporous base layer is obtained.

[0024] It should be noted that, in this application, the modified polysulfone microporous substrate obtained by modifying the material under the above-mentioned specific technical conditions can reduce the adsorption of pollutants such as oily aerosols and dust, reduce the risk of membrane pore blockage, and at the same time greatly improve mechanical strength.

[0025] (2) The preparation method of the transition layer includes: immersing the base layer in a 2% (w / w) piperazine aqueous solution for 3-5 min, removing it and drying the excess moisture on the surface with nitrogen gas; then immersing the base layer in a 0.1% (w / w) trimesoyl chloride n-hexane solution and reacting at 25°C for 1-2 min; after the reaction is completed, washing the unreacted monomers on the surface of the base layer with n-hexane and drying at 60°C for 30 min to form the transition layer.

[0026] It should be noted that, in this application, the transition layer prepared under the specific conditions described above can ensure gas permeability and achieve a tight bond between the base layer and the functional layer through chemical bonding, thereby preventing the membrane from falling off and improving structural stability.

[0027] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material is ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide is added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate is controlled at 3000-4000 rpm and the spin coating time is 30s. After coating the mixed solution on the surface of the transition layer, it is vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0028] In this application, under the specific technical conditions described above, MOFs and polyimide polymers form a stable composite system. Combined with the high permeability of the modified polysulfone substrate, the methane / nitrogen separation coefficient can be significantly improved, meeting the separation requirements for industrial methane purification.

[0029] The composite membrane is cut to a preset size, assembled with a flow guide and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

[0030] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0031] Example 1 This embodiment provides a gas separation membrane element, which is made of a composite membrane consisting of a modified polysulfone microporous base layer, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0032] The present invention provides a method for preparing a gas separation membrane element, comprising: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester with a capping rate of 45%, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:0.06:70:15 and stirred at 85°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 220 μm, and the film was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a base layer. After washing and drying, the modified polysulfone microporous base layer was obtained.

[0033] (2) The preparation method of the transition layer includes: immersing the base layer in a 2% (w / w) piperazine aqueous solution for 4 min, removing it and blowing off the excess moisture on the surface with nitrogen; then immersing the base layer in a 0.1% (w / w) trimesoyl chloride n-hexane solution and reacting at 25°C for 2 min; after the reaction is completed, washing the unreacted monomers on the surface of the base layer with n-hexane and drying at 60°C for 30 min to form the transition layer.

[0034] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material was ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide was added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate was controlled at 3500 rpm and the spin coating time was 30 s. After coating the mixed solution on the surface of the transition layer, it was vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0035] The composite membrane is cut to a preset size, assembled with a flow guide and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

[0036] Example 2 This embodiment provides a gas separation membrane element, which is made of a composite membrane consisting of a modified polysulfone microporous base layer, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0037] The present invention provides a method for preparing a gas separation membrane element, comprising: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester with a capping rate of 40%, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:0.06:70:15 and stirred at 80°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 200 μm, and it was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a base layer. After washing and drying, the modified polysulfone microporous base layer was obtained.

[0038] (2) The preparation method of the transition layer includes: immersing the base layer in a 2% piperazine aqueous solution for 5 min, removing it and drying the excess moisture on the surface with nitrogen gas; then immersing the base layer in a 0.1% hexane solution of trimesoyl chloride and reacting it at 25°C for 1 min; after the reaction is completed, washing the unreacted monomers on the surface of the base layer with hexane and drying it at 60°C for 30 min to form the transition layer.

[0039] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material is ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide is added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate is controlled at 3000 rpm and the spin coating time is 30 s. After coating the mixed solution on the surface of the transition layer, it is vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0040] The composite membrane is cut to a preset size, assembled with a flow guide and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

[0041] Example 3 This embodiment provides a gas separation membrane element, which is made of a composite membrane consisting of a modified polysulfone microporous base layer, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0042] The present invention provides a method for preparing a gas separation membrane element, comprising: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester with a capping rate of 50%, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:0.06:70:15 and stirred at 90°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 250 μm, and it was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a base layer. After washing and drying, the modified polysulfone microporous base layer was obtained.

[0043] (2) The preparation method of the transition layer includes: immersing the base layer in a 2% piperazine aqueous solution for 3 min, removing it and blowing off the excess moisture on the surface with nitrogen; then immersing the base layer in a 0.1% hexane solution of trimesoyl chloride and reacting at 25°C for 2 min; after the reaction, washing the unreacted monomers on the surface of the base layer with hexane and drying it at 60°C for 30 min to form the transition layer.

[0044] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material was ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide was added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate was controlled at 4000 rpm and the spin coating time was 30 s. After coating the mixed solution on the surface of the transition layer, it was vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0045] The composite membrane is cut to a preset size, assembled with a flow guide and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

[0046] Comparative Example 1 The gas separation membrane element provided in this comparative example is made of a composite membrane consisting of a polysulfone microporous substrate, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0047] The comparative example provides a method for preparing a gas separation membrane element, which includes: (1) Preparation of polysulfone microporous substrate: Polysulfone, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:70:15 and stirred at 85°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 220 μm, and the film was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a substrate. After washing and drying, polysulfone microporous substrate was obtained.

[0048] (2) The preparation method of the transition layer includes: immersing the base layer in a 2% piperazine aqueous solution for 4 min, removing it and drying the excess moisture on the surface with nitrogen gas; then immersing the base layer in a 0.1% hexane solution of trimesoyl chloride and reacting at 25°C for 2 min; after the reaction is completed, washing the unreacted monomers on the surface of the base layer with hexane and drying at 60°C for 30 min to form the transition layer.

[0049] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material was ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide was added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate was controlled at 3500 rpm and the spin coating time was 30 s. After coating the mixed solution on the surface of the transition layer, it was vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0050] The composite membrane is cut to a preset size, assembled with a flow guide and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

[0051] Comparative Example 2 The gas separation membrane element provided in this comparative example is made of a composite membrane consisting of a polysulfone microporous substrate and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0052] The comparative example provides a method for preparing a gas separation membrane element, which includes: (1) Preparation of polysulfone microporous substrate: Polysulfone, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:70:15 and stirred at 85°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 220 μm, and the film was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a substrate. After washing and drying, polysulfone microporous substrate was obtained.

[0053] (2) Preparation of polymer functional layer loaded with metal-organic framework material: First, the metal-organic framework material was ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide was added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate was controlled at 3500 rpm and the spin coating time was 30 s. After coating the mixed solution on the surface of the substrate, it was vacuum dried at 120℃ for 2 h to form a polymer functional layer loaded with metal-organic framework material and obtain a composite film.

[0054] The composite membrane is cut to a preset size, assembled with a flow guide and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

[0055] Comparative Example 3 The gas separation membrane element provided in this comparative example is made of a composite membrane consisting of a polysulfone microporous substrate and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0056] The comparative example provides a method for preparing a gas separation membrane element, which includes: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester with a capping rate of 45%, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:0.06:70:15 and stirred at 85°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 220 μm, and the film was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a base layer. After washing and drying, the modified polysulfone microporous base layer was obtained.

[0057] (2) Preparation of polymer functional layer loaded with metal-organic framework material: First, the metal-organic framework material was ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide was added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate was controlled at 3500 rpm and the spin coating time was 30 s. After coating the mixed solution on the surface of the substrate, it was vacuum dried at 120℃ for 2 h to form a polymer functional layer loaded with metal-organic framework material and obtain a composite film.

[0058] The composite membrane is cut to a preset size, assembled with a flow guide and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

[0059] Comparative Example 4 This embodiment provides a gas separation membrane element, which is made of a composite membrane consisting of a modified polysulfone microporous base layer, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0060] The present invention provides a method for preparing a gas separation membrane element, comprising: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester with a capping rate of 30%, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 12:0.08:60:12 and stirred at 100°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 180 μm, and the film was kept at 70°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a base layer. After washing and drying, the modified polysulfone microporous base layer was obtained.

[0061] (2) The preparation method of the transition layer includes: immersing the base layer in a 2% (w / w) piperazine aqueous solution for 4 min, removing it and blowing off the excess moisture on the surface with nitrogen; then immersing the base layer in a 0.1% (w / w) trimesoyl chloride n-hexane solution and reacting at 25°C for 2 min; after the reaction is completed, washing the unreacted monomers on the surface of the base layer with n-hexane and drying at 60°C for 30 min to form the transition layer.

[0062] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material was ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide was added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate was controlled at 3500 rpm and the spin coating time was 30 s. After coating the mixed solution on the surface of the transition layer, it was vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0063] Comparative Example 5 This embodiment provides a gas separation membrane element, which is made of a composite membrane consisting of a modified polysulfone microporous base layer, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0064] The present invention provides a method for preparing a gas separation membrane element, comprising: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester with a capping rate of 45%, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:0.06:70:15 and stirred at 85°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 220 μm, and the film was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a base layer. After washing and drying, the modified polysulfone microporous base layer was obtained.

[0065] (2) The preparation method of the transition layer includes: immersing the base layer in a 5% piperazine aqueous solution for 2 min, removing it and drying the excess moisture on the surface with nitrogen gas; then immersing the base layer in a 0.3% hexane solution of trimesoyl chloride and reacting it at 22°C for 5 min; after the reaction is completed, washing the unreacted monomers on the surface of the base layer with hexane and drying it at 60°C for 30 min to form the transition layer.

[0066] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material was ultrasonically dispersed at 300 W for 20 min and dispersed in N-methylpyrrolidone. Then, polyimide was added and stirred at 70℃ for 2 h to form a metal-organic framework-polymer mixed solution. The spin coating rate was controlled at 3500 rpm and the spin coating time was 30 s. After coating the mixed solution on the surface of the transition layer, it was vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0067] Comparative Example 6 This embodiment provides a gas separation membrane element, which is made of a composite membrane consisting of a modified polysulfone microporous base layer, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

[0068] The present invention provides a method for preparing a gas separation membrane element, comprising: (1) Preparation of modified polysulfone microporous base layer: Polysulfone, hydroxyl-terminated hyperbranched polyester with a capping rate of 45%, N,N-dimethylacetamide and polyethylene glycol 400 were mixed in a mass ratio of 15:0.06:70:15 and stirred at 85°C until completely dissolved to form a casting solution; the casting solution was cast on a clean glass plate, the wet film thickness was controlled to be 220 μm, and the film was kept at 60°C for 10 min. Then it was immersed in deionized water at 25°C to solidify and form a base layer. After washing and drying, the modified polysulfone microporous base layer was obtained.

[0069] (2) The preparation method of the transition layer includes: immersing the base layer in a 2% (w / w) piperazine aqueous solution for 4 min, removing it and blowing off the excess moisture on the surface with nitrogen; then immersing the base layer in a 0.1% (w / w) trimesoyl chloride n-hexane solution and reacting at 25°C for 2 min; after the reaction is completed, washing the unreacted monomers on the surface of the base layer with n-hexane and drying at 60°C for 30 min to form the transition layer.

[0070] (3) Preparation of the functional layer of polymer loaded on metal-organic framework material: First, the metal-organic framework material is ultrasonically dispersed at 500 W for 10 min and dispersed in N-methylpyrrolidone. Then, polyimide is added and stirred at 60℃ for 3 h to form a metal-organic framework-polymer mixed solution. The spin coating rate is controlled at 5000 rpm and the spin coating time is 20 s. After coating the mixed solution on the surface of the transition layer, it is vacuum dried at 120℃ for 2 h to form a functional layer of polymer loaded on metal-organic framework material and obtain a composite film.

[0071] Experimental Example 1 The water contact angle, membrane flux recovery rate, tensile strength and elongation at break of the polysulfone microporous substrates prepared in Examples 1-3 and Comparative Examples 1-6 were tested respectively. The test results are shown in Table 1.

[0072] (1) Water contact angle (°): The measurement was performed in accordance with the relevant standard GB / T 30693-2014 "Measurement of the contact angle between plastic film and water"; (2) Membrane flux recovery rate (%): Pretreatment: The modified polysulfone microporous substrate sample was cut into a circle with a diameter of 50 mm, installed in the membrane performance testing device, and rinsed with 25℃ deionized water for 1 h to remove surface impurities. Initial flux test: Under controlled operating pressure of 0.1 MPa and 25℃, the initial flux J0 of deionized water through the base layer was measured; Pollution treatment: Prepare a simulated industrial pollutant solution (containing 0.1% oily aerosol and 0.05% ultrafine dust), filter continuously for 3 hours under the same operating conditions, and measure the flux J1 after pollution. Cleaning and Restoration Test: The substrate was backflushed with 25℃ deionized water for 30 minutes, and the flux J2 was measured again. Calculation: Membrane flux recovery rate = (J2 / J0) × 100%.

[0073] (3) Tensile strength (MPa) and elongation at break (%): The tensile strength (MPa) and elongation at break (%) were determined in accordance with the relevant standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets"; Table 1 As shown in Table 1, the substrate of this application has a water contact angle ≤64°, membrane flux recovery rate ≥88%, tensile strength ≥48MPa, and elongation at break ≥21%, exhibiting stable and excellent performance. Compared with Examples 1-3, Comparative Examples 1-2 use ordinary polysulfone substrates, and the substrate process parameters of Comparative Example 4 are not within the scope of protection of this application. Its substrate hydrophilicity, antifouling properties, and mechanical properties are significantly reduced, indicating that the modified polysulfone microporous substrate and substrate process used in this application are the key to ensuring substrate performance.

[0074] Experiment Example 2 The methane / nitrogen (50 / 50, vol) separation coefficient and flux decay rate after 3000 h of continuous operation were tested at 298 K and 0.1 MPa for the composite membranes prepared in Examples 1-3 and Comparative Examples 1-6, respectively. The test results are shown in Table 2.

[0075] (1) Separation coefficient of methane / nitrogen (50 / 50, vol) at 298 K and 0.1 MPa: Under conditions of 298 K and 0.1 MPa, the membrane was purged with high-purity nitrogen (purity ≥99.99%) for 30 min to remove air and impurities from the inside of the membrane and the test pipeline. Test gas preparation: Prepare a methane / nitrogen mixture (volume ratio 50 / 50) with a purity ≥99.9%, and stabilize the gas composition and pressure in advance; Flux and composition testing: The mixed gas was introduced into the testing device, and the operating pressure was controlled at 0.1 MPa and the test temperature at 298 K. After the flow rate stabilized, the volume fractions of methane and nitrogen in the feed gas (inlet end) and permeate gas (permeate end) were determined by gas chromatograph (detection accuracy ≥0.01%). Calculate the separation coefficient: Separation coefficient α(CH4 / N2)=[y(CH4) / y(N2)] / [x(CH4) / x(N2)], where y(CH4) and y(N2) are the volume fractions of methane and nitrogen in the permeate gas, respectively, and x(CH4) and x(N2) are the volume fractions of methane and nitrogen in the feed gas, respectively; each sample is tested 3 times, and the average value is taken as the final result.

[0076] (2) Flux decay rate (%) after 3000 h of continuous operation: Sample installation and pretreatment: The composite membrane element was assembled into a standard test assembly and installed in the continuous operation test device. Under the conditions of 298 K and 0.1 MPa, it was purged with a methane / nitrogen mixed gas (50 / 50, vol) for 1 h to stabilize the initial state. Initial flux test: Record the methane permeation flux J0 (unit: GPU) at the start of the test (0 h), test continuously for 30 min, and take the average value as the initial flux; Continuous operation test: Maintain test conditions (298 K, 0.1 MPa, constant gas mixture composition) and run continuously for 3000 h, recording the methane permeation flux J every 24 h during this period. t To ensure the stability of the pressure, temperature, and gas flow of the testing device and to avoid external interference; Calculate flux decay rate: Flux decay rate = [(J0 - J] 3000 ) / J0]×100%, where J3000 The methane permeation flux is measured after 3000 hours of continuous operation. After the test, the membrane element was checked and found to be undamaged and the membrane layer was not detached.

[0077] Table 2 As shown in Table 2, the composite membrane provided in this application has a separation coefficient ≥7.8 and a flux decay rate ≤10% after 3000 hours of continuous operation, demonstrating excellent separation performance and stability. Compared to the examples, the composite membranes provided in Comparative Examples 1-6 all have separation coefficients below 7.0 and flux decay rates above 15%, indicating that the three-layer composite membrane used in this application—comprised of a modified polysulfone microporous base layer, a transition layer, and a metal-organic framework material-loaded polymer functional layer—and the synergistic effect of the process parameters of each layer are key to ensuring efficient separation and long-term stable operation of the composite membrane.

[0078] In summary, the gas separation membrane element and its preparation method provided by this invention offer advantages such as high separation efficiency, strong anti-fouling properties, and tight interlayer bonding, significantly improving the methane / nitrogen separation coefficient and providing a long service life. It can be widely applied in fields such as unconventional natural gas purification in petrochemical industries and methane recovery from industrial waste gas, demonstrating significant industrial application value and economic benefits.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gas separation membrane element, characterized in that: The gas separation membrane element is made of a composite membrane consisting of a modified polysulfone microporous base layer, a transition layer, and a polymer functional layer supported on a metal-organic framework material arranged sequentially from bottom to top.

2. The gas separation membrane element according to claim 1, characterized in that: The modified polysulfone microporous base layer has a thickness of 80-120 μm. The polysulfone is modified by end-capping with 0.3%-0.5% of the polysulfone mass of hydroxyl-terminated hyperbranched polyester, and the end-capping rate of the hydroxyl-terminated hyperbranched polyester is 40%-50%.

3. The gas separation membrane element according to claim 2, characterized in that: The method for preparing the modified polysulfone microporous substrate includes: mixing the polysulfone, the hydroxyl-terminated hyperbranched polyester, N,N-dimethylacetamide, and polyethylene glycol 400 in a mass ratio of 15:0.06:70:15, stirring at 80-90°C until completely dissolved to form a casting solution; casting the casting solution onto a clean glass plate, controlling the wet film thickness to be 200-250 μm, holding at 60°C for 10 min, then immersing in 25°C deionized water to solidify and form the substrate; and after washing and drying, obtaining the modified polysulfone microporous substrate.

4. The gas separation membrane element according to claim 1, characterized in that: The thickness of the transition layer is 1-3 μm, and it is formed by interfacial polymerization of piperazine and pyromellitic trimethylol chloride.

5. The gas separation membrane element according to claim 4, characterized in that: The method for preparing the transition layer includes: immersing the base layer in a 2% (w / w) piperazine aqueous solution for 3-5 minutes, removing it and drying the surface with nitrogen; then immersing the base layer in a 0.1% (w / w) trimesoyl chloride hexane solution and reacting at 25°C for 1-2 minutes; after the reaction, washing the unreacted monomers on the surface of the base layer with hexane and drying it at 60°C for 30 minutes to form the transition layer.

6. The gas separation membrane element according to claim 1, characterized in that: The thickness of the polymer functional layer loaded on the metal-organic framework material is 3-5 μm. The metal-organic framework material is loaded with polyimide as the polymer matrix, and the loading amount of the metal-organic framework material is 15%-20% of the mass of the polymer matrix.

7. The gas separation membrane element according to claim 6, characterized in that: The preparation method of the metal-organic framework material loaded with polymer functional layer includes: firstly, ultrasonically dispersing the metal-organic framework material at a power of 300 W for 20 min, dispersing it in N-methylpyrrolidone, then adding the polyimide, stirring at 70°C for 2 h to form a metal-organic framework-polymer mixed solution, coating the mixed solution on the surface of the transition layer and then vacuum drying to obtain the metal-organic framework material loaded with polymer functional layer, and simultaneously obtaining the composite film.

8. The gas separation membrane element according to claim 7, characterized in that: When the mixed solution is coated onto the surface of the transition layer, the spin coating rate is controlled at 3000-4000 rpm and the spin coating time is 30s.

9. The gas separation membrane element according to claim 7, characterized in that: The vacuum drying conditions were 120℃ for 2 hours.

10. A method for preparing a gas separation membrane element according to any one of claims 1-9, characterized in that: include: The composite membrane is cut to a preset size, assembled with a flow guide net and sealing components, and encapsulated into a hollow fiber or flat sheet membrane element to complete the preparation.

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