Porous gelatin cross-linked mof composite gas separation membrane, preparation method and application

Abstract

The application discloses a porous gelatin crosslinked MOF composite gas separation membrane, a preparation method and application, relates to the technical field of gas separation, and the preparation method of the membrane comprises the following steps: gelatin solution is added to a graphene oxide suspension dispersion solution to be dissolved, an oil phase is added, ultrasonic treatment is carried out, and a gelatin microemulsion suspension is obtained; metal organic framework is dissolved, ultrasonic stirring is carried out, and then the metal organic framework is added to aluminum silicate sol, stirring, aging, washing, calcination and ball milling are carried out, and a porous gelatin coated MOF material is prepared; the porous gelatin coated MOF material is added to the gelatin microemulsion suspension to be ultrasonically stirred, then is poured on the surface of a base film to form a film, and after drying, an uncrosslinked composite film is obtained; the uncrosslinked composite film is placed in a glutaraldehyde solution to carry out crosslinking reaction, and the porous gelatin crosslinked MOF composite gas separation membrane is obtained after cleaning and drying; the application obtains a gas separation membrane with high permeation rate and permeation selectivity, and has good application value in gas separation.

Description

Technical Field

[0001] This invention relates to the field of gas separation technology, specifically to a porous gelatin crosslinked MOF composite gas separation membrane, its preparation method, and its application. Background Technology

[0002] Gas separation membranes are a pressure-driven, phase-change-free gas separation technology with advantages such as low energy consumption, small footprint, and simple maintenance, playing an increasingly important role in energy gas separation and environmental protection. Although gas membrane separation, as a "green technology," has been applied in many fields, large-scale industrial application still faces certain difficulties. The main problem is that the permeability and selectivity of gas membranes are affected by the "seesaw effect," resulting in low permeability or selectivity, as well as poor membrane mechanical strength. Organic membranes, due to their low price, good moldability, and adjustable separation performance, have become the mainstay of current large-scale gas separation membrane applications. Currently, almost all traditional commercial gas separation membranes are polymer membranes based on the solution-diffusion mechanism, such as polyimide, cellulose acetate, and organosilicon. Polyimide, due to its nitrogen-containing aromatic heterocyclic structure, has good permeability and excellent permeation selectivity, and also possesses advantages such as strong chemical solvent resistance, strong thermal stability, and good mechanical properties, allowing for the fabrication of high-flux self-supporting membranes. Cellulose acetate and its derivatives have advantages such as easy membrane fabrication and abundant raw material sources. However, most polymer molecular chains have the disadvantages of high rigidity and poor air permeability, resulting in poor gas separation performance.

[0003] Patent document CN202211718697.7 discloses a polyimide gas separation membrane, its preparation method, and its applications. Addressing the problem that existing polyimide gas separation membranes suffer from severe solvent damage to the base membrane during fabrication, making it impossible to obtain a morphologically intact and high-performance polyimide asymmetric membrane through coating, a new preparation method is provided: Polyimide A particles or powder (as the base membrane material) and a polymeric additive are dissolved in an organic solvent to prepare a blended base membrane of polyimide A and the polymeric additive; polyimide B particles or powder (as the separation layer material) are dissolved in an organic solvent to prepare a coating solution; the coating solution is then applied to the base membrane to obtain the polyimide gas separation membrane. The base membrane and separation layer are firmly bonded, exhibiting excellent permeability and selectivity. However, the wide pore size distribution and disordered structure of polyimide gases often affect its gas separation performance.

[0004] Patent application CN202311156009.7 discloses a cross-linked polysulfonamide gas separation membrane, its preparation method, and its application. To address the problem of low stability of polyimide-based separation membranes in handling impurity gases, especially acidic gases, the patent provides a novel method for preparing the membrane. The method involves pretreating a base membrane to obtain a pretreated base membrane. The base membrane includes one or more of the following: polyacrylonitrile membrane, polyvinyl chloride membrane, polypropylene membrane, polyvinylidene fluoride membrane, and cellulose acetate membrane. The pretreated base membrane is sequentially immersed in monomer A solution and monomer C solution to obtain a composite membrane. The composite membrane is then reacted to obtain the cross-linked polysulfonamide gas separation membrane. This patented gas separation membrane has a cross-linked structure, which can suppress the plasticizing effect during use and improve the stability of the cross-linked polysulfonamide gas separation membrane. However, this cross-linked structure still suffers from problems such as excessively large pores, low porosity, and low gas selectivity.

[0005] Therefore, how to prepare separation membranes with good stability, high permeability, and good gas selectivity is an urgent problem to be solved. Summary of the Invention

[0006] This invention aims to solve the technical problem of how to obtain a new gas separation membrane with good stability, high permeability and good gas selectivity. The purpose is to provide a porous gelatin crosslinked MOF composite gas separation membrane, its preparation method and application. The resulting gas separation membrane has high permeability and good permeability selectivity and has good application value in gas separation.

[0007] This invention is achieved through the following technical solution:

[0008] The first objective of this invention is to provide a method for preparing a porous gelatin crosslinked MOF composite gas separation membrane, comprising the following steps:

[0009] (1) Graphene oxide was added to water and dispersed to prepare a graphene oxide suspension.

[0010] (2) Dissolve solid gelatin in water to obtain a gelatin solution, add the gelatin solution to a graphene oxide suspension and dissolve it, add an oil phase, and perform ultrasonic treatment to make the components uniformly dispersed to obtain a gelatin microemulsion suspension; it has a uniform and stable porous structure.

[0011] (3) Dissolve the metal-organic framework in a solvent, stir it with ultrasound to make it dissolve and mix evenly, then add it to the aluminosilicate sol, stir and mix it again to make the components mix evenly, age for 2-3 hours, wash with water, calcine at 480-520℃, and ball mill to prepare a porous gel coating MOF material.

[0012] (4) The porous gel-coated MOF material was added to the gelatin microemulsion suspension and ultrasonically stirred to disperse and mix the components evenly.

[0013] (5) The solution obtained in step (4) is poured onto the surface of the base film to form a film, and after drying, an uncrosslinked composite film is obtained;

[0014] (6) The uncrosslinked composite membrane was placed in glutaraldehyde solution for crosslinking reaction. After crosslinking, it was washed and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

[0015] This invention combines porous gelatin and MOF materials on an organic polymer-based membrane to form a cross-linked porous structure with regular pore size, which has good gas permeability and high selectivity.

[0016] This invention first prepares porous gelatin by forming a stable emulsion using solid nanoparticles adsorbed at the oil / water interface. The use of graphene oxide in the stable emulsion enhances the stability of the porous gelatin, resulting in a uniform porous structure. Secondly, the invention incorporates a metal-organic framework (MOF) into the stable emulsion, further cross-linking and supporting the porous gelatin, ensuring the stability and uniformity of the porous structure during subsequent cross-linking reactions. The composite structure of the MOF and porous gelatin provides richer pores and higher gas selectivity. Finally, the MOF and porous gelatin composite membrane solution is further composited with an organic polymer substrate membrane to form an organic-inorganic mixed matrix membrane. This method improves the interfacial defects between the MOF porous material and the polymer substrate, thereby enhancing the affinity between the MOF porous material and the polymer.

[0017] This invention modifies a metal-organic framework (MOF) by coating it with an aluminosilicate sol. The outer aluminosilicate layer also possesses a large specific surface area and a porous structure. Furthermore, due to the hollow core of the framework, it exhibits strong adsorption capacity and enhances the affinity between the MOF and gelatin, making the cross-linked three-dimensional porous network structure more stable. When applied to the separation of water-containing gases such as natural gas, the aluminosilicate layer absorbs water for a certain period, hydrating the surface of the gel framework to form a gel layer with a degree of expansion. This gradually narrows the channels in the porous network structure, further preventing the passage of large gas molecules. Therefore, with increasing usage time, carbon dioxide separation can be continuously achieved, avoiding the significant decrease in separation efficiency that occurs with conventional separation membranes after a period of use.

[0018] Further, in step (1), the specific preparation method of the graphene oxide suspension is as follows: add graphene oxide suspension to deionized water, and sonicate for 10 to 60 minutes to obtain a graphene oxide suspension with a concentration of 10 to 15 g / L.

[0019] Further, in step (2), the specific preparation method of the gelatin microemulsion suspension is as follows: the gelatin solution is added to the graphene oxide suspension at 25-50℃ to dissolve, the oil phase polyvinyl alcohol solution is added, and the mixture is ultrasonically treated for 5-20 minutes to obtain the gelatin microemulsion suspension.

[0020] Furthermore, the volume ratio of the oil phase to the water phase is 3:(4-6).

[0021] Furthermore, the mass ratio of graphene oxide to gelatin is 1:(15-20).

[0022] Further, in step (3), the metal-organic framework uses a nickel salt solution and an organic ligand 3-methyl-1,2,4-triazole, and the solvent is N-methylpyrrolidone.

[0023] Furthermore, the mass ratio of the metal-organic framework to the aluminum silicate sol is (3-4):6.

[0024] Furthermore, in step (4), the mass ratio of porous gel-coated MOF material to gelatin is (2-3):8.

[0025] Furthermore, the base film is a polyimide film, a polypropylene film, or a polyethersulfone film.

[0026] Furthermore, the base membrane needs to be pretreated before step (5): the base membrane is soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0027] Further, step (5) specifically involves: placing the pretreated base film in a container, pouring the solution obtained in step (4) onto the surface of the pretreated base film in a water bath at 35-65°C to form a film, and then drying it at 40-60°C to obtain an uncrosslinked composite film.

[0028] Further, step (6) specifically involves immersing the uncrosslinked composite membrane in a 2-3 wt% glutaraldehyde solution and maintaining it at 50-65°C for 5-6 hours. After crosslinking, the membrane is washed and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

[0029] Furthermore, ethanol and deionized water were used for cleaning.

[0030] The second objective of this invention is to provide a porous gelatin crosslinked MOF composite gas separation membrane, which is prepared by the aforementioned preparation method.

[0031] The third objective of this invention is to provide the application of the aforementioned porous gelatin crosslinked MOF composite gas separation membrane in natural gas helium extraction, natural gas decarbonization, CO2 separation in oil and gas fields, or CO2 capture in flue gas.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] 1. This invention combines porous gelatin and MOF materials on an organic polymer-based membrane to form a cross-linked porous structure with regular pore size, which has good gas permeability and high selectivity.

[0034] 2. This invention first prepares porous gelatin by forming a stable emulsion using solid nanoparticles adsorbed at the oil / water interface. The use of graphene oxide in the stable emulsion enhances the stability of the porous gelatin, resulting in a uniform porous structure. Secondly, the invention incorporates a metal-organic framework (MOF) into the stable emulsion, further cross-linking and supporting the porous gelatin, ensuring the stability and uniformity of the porous structure during subsequent cross-linking reactions. The composite structure of the MOF and porous gelatin provides richer pores and higher gas selectivity. Finally, the MOF and porous gelatin composite membrane solution is further composited with an organic polymer substrate membrane to form an organic-inorganic mixed matrix membrane. This method improves the interfacial defects between the MOF porous material and the polymer substrate, thereby enhancing the affinity between the MOF porous material and the polymer.

[0035] 3. This invention modifies the metal-organic framework (MOF) by coating it with aluminum silicate sol. The outer aluminum silicate layer also has a large specific surface area and a porous structure. Furthermore, because the core of the framework is hollow, it has strong adsorption capacity and can improve the affinity between the MOF and gelatin, making the three-dimensional porous network structure between them more stable. When applied to the separation of water-containing gases such as natural gas, the aluminum silicate layer hydrates on the surface of the gel framework after absorbing water for a certain period, forming a gel layer with a certain degree of expansion. Therefore, the channels of the porous network structure gradually narrow, further preventing the passage of large gas molecules. Thus, with increasing usage time, carbon dioxide separation can be continuously achieved, avoiding the significant decrease in separation efficiency that occurs with conventional separation membranes after a period of use. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0037] The following details the embodiments of a porous gelatin crosslinked MOF composite gas separation membrane, its preparation method, and its applications according to the present invention. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0038] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0042] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0043] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0044] It should be noted that, unless otherwise specified, the experimental methods used in the embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0045] Example 1

[0046] This invention provides a method for preparing a porous gelatin crosslinked MOF composite gas separation membrane, comprising the following steps:

[0047] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0048] (2) Add graphene oxide (GO) to deionized water and sonicate for 50 min to obtain a GO suspension with a concentration of 10 g / L.

[0049] (3) Dissolve solid gelatin in water to obtain gelatin solution. Add gelatin solution to GO suspension at 45°C and dissolve. Add oil phase polyvinyl alcohol solution. The volume ratio of oil phase to water phase is 3:5. Sonicate for 20 min to obtain gelatin microemulsion suspension. The mass ratio of GO to gelatin is 1:15.

[0050] (4) Metal-organic framework powder was prepared by using nickel salt solution and organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone, ultrasonically stirred, and then added to aluminosilicate sol. The mixture was stirred and mixed for 15 min, aged for 2 h, washed with water, calcined at 480 °C, and ball-milled to obtain a porous gel-coated MOF. The mass ratio of the metal-organic framework to the aluminosilicate sol was 3:6.

[0051] (5) The porous gel-coated MOF was added to the gelatin microemulsion suspension and ultrasonically stirred. The mass ratio of the porous gel-coated MOF to the gelatin was 2:8.

[0052] (6) Place the pretreated polyimide film in a container, place it in a water bath at 55°C, then pour the solution obtained in step (5) onto the surface of the polyimide film to form a film, and then place it at 50°C to dry to obtain an uncrosslinked composite film.

[0053] (7) The uncrosslinked composite membrane was immersed in a 2wt% glutaraldehyde solution and kept at 50°C for 5 hours. After crosslinking, it was washed with ethanol and deionized water and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

[0054] Example 2

[0055] This invention provides a method for preparing a porous gelatin crosslinked MOF composite gas separation membrane, comprising the following steps:

[0056] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0057] (2) GO was added to deionized water and ultrasonically treated for 60 min to obtain a GO suspension dispersion with a concentration of 15 g / L.

[0058] (3) Dissolve solid gelatin in water to obtain gelatin solution. Add gelatin solution to GO suspension at 50°C and dissolve. Add oil phase polyvinyl alcohol solution. The volume ratio of oil phase to water phase is 3:5. Sonicate for 20 min to obtain gelatin microemulsion suspension. The mass ratio of GO to gelatin is 1:20.

[0059] (4) Metal-organic framework powder was prepared by using nickel salt solution and organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone, ultrasonically stirred, and then added to aluminosilicate sol. The mixture was stirred and mixed for 15 min, aged for 3 h, washed with water, calcined at 500 °C, and ball-milled to obtain a porous gel-coated MOF. The mass ratio of the metal-organic framework to the aluminosilicate sol was 3.5:6.

[0060] (5) The porous gel-coated MOF was added to the gelatin microemulsion suspension and ultrasonically stirred. The mass ratio of the porous gel-coated MOF to the gelatin was 2.5:8.

[0061] (6) Place the pretreated imide membrane in a container and place it in a water bath at 60°C. Then pour the solution obtained in step (5) onto the surface of the polyimide membrane to form a film. Then place it at 50°C to dry to obtain an uncrosslinked composite membrane.

[0062] (7) The uncrosslinked composite membrane was immersed in a 3wt% glutaraldehyde solution and kept at 60°C for 6 hours. After crosslinking, it was washed with ethanol and deionized water and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

[0063] Example 3

[0064] This invention provides a method for preparing a porous gelatin crosslinked MOF composite gas separation membrane, comprising the following steps:

[0065] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0066] (2) GO was added to deionized water and ultrasonically treated for 40 min to obtain a GO suspension dispersion with a concentration of 13 g / L.

[0067] (3) Dissolve solid gelatin in water to obtain gelatin solution. Add gelatin solution to GO suspension at 35°C and dissolve. Add oil phase polyvinyl alcohol solution. The volume ratio of oil phase to water phase is 3:5. Sonicate for 20 min to obtain gelatin microemulsion suspension. The mass ratio of GO to gelatin is 1:18.

[0068] (4) Metal-organic framework powder was prepared by using nickel salt solution and organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone, ultrasonically stirred, and then added to aluminosilicate sol. The mixture was stirred and mixed for 15 min, aged for 3 h, washed with water, calcined at 520 °C, and ball-milled to obtain a porous gel-coated MOF. The mass ratio of the metal-organic framework to the aluminosilicate sol was 4:6.

[0069] (5) The porous gel-coated MOF was added to the gelatin microemulsion suspension and ultrasonically stirred. The mass ratio of the porous gel-coated MOF to the gelatin was 3:8.

[0070] (6) Place the pretreated polyimide film in a container, place it in a water bath at 40°C, then pour the solution obtained in step (5) onto the surface of the polyimide film to form a film, and then place it at 50°C to dry to obtain an uncrosslinked composite film.

[0071] (7) The uncrosslinked composite membrane was immersed in a 3wt% glutaraldehyde solution and kept at 55°C for 6 hours. After crosslinking, it was washed with ethanol and deionized water and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

[0072] Example 4

[0073] This invention provides a method for preparing a porous gelatin crosslinked MOF composite gas separation membrane, comprising the following steps:

[0074] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0075] (2) GO was added to deionized water and ultrasonically treated for 50 min to obtain a GO suspension dispersion with a concentration of 12 g / L.

[0076] (3) Dissolve solid gelatin in water to obtain gelatin solution. Add gelatin solution to GO suspension at 45°C and dissolve. Add oil phase polyvinyl alcohol solution. The volume ratio of oil phase to water phase is 3:5. Sonicate for 20 min to obtain gelatin microemulsion suspension. The mass ratio of GO to gelatin is 1:20.

[0077] (4) Metal-organic framework powder was prepared by using nickel salt solution and organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone, ultrasonically stirred, and then added to aluminosilicate sol. The mixture was stirred and mixed for 15 min, aged for 2 h, washed with water, calcined at 480 °C, and ball-milled to obtain a porous gel-coated MOF. The mass ratio of the metal-organic framework to the aluminosilicate sol was 3:6.

[0078] (5) The porous gel-coated MOF was added to the gelatin microemulsion suspension and ultrasonically stirred. The mass ratio of the porous gel-coated MOF to the gelatin was 2.5:8.

[0079] (6) Place the pretreated polyimide film in a container, place it in a water bath at 45°C, then pour the solution obtained in step (5) onto the surface of the polyimide film to form a film, and then place it at 50°C to dry to obtain an uncrosslinked composite film.

[0080] (7) The uncrosslinked composite membrane was immersed in a 2wt% glutaraldehyde solution and kept at 50°C for 5 hours. After crosslinking, it was washed with ethanol and deionized water and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

[0081] Example 5

[0082] This invention provides a method for preparing a porous gelatin crosslinked MOF composite gas separation membrane, comprising the following steps:

[0083] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0084] (2) GO was added to deionized water and ultrasonically treated for 50 min to obtain a GO suspension dispersion with a concentration of 15 g / L.

[0085] (3) Dissolve solid gelatin in water to obtain gelatin solution. Add gelatin solution to GO suspension at 45°C and dissolve. Add oil phase polyvinyl alcohol solution. The volume ratio of oil phase to water phase is 3:5. Sonicate for 20 min to obtain gelatin microemulsion suspension. The mass ratio of GO to gelatin is 1:15.

[0086] (4) Metal-organic framework powder was prepared by using nickel salt solution and organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone, ultrasonically stirred, and then added to aluminosilicate sol. The mixture was stirred and mixed for 15 min, aged for 2 h, washed with water, calcined at 480 °C, and ball-milled to obtain a porous gel-coated MOF. The mass ratio of the metal-organic framework to the aluminosilicate sol was 3.5:6.

[0087] (5) The porous gel-coated MOF was added to the gelatin microemulsion suspension and ultrasonically stirred. The mass ratio of the porous gel-coated MOF to the gelatin was 3:8.

[0088] (6) Place the pretreated polyimide film in a container, place it in a water bath at 50°C, then pour the solution obtained in step (5) onto the surface of the polyimide film to form a film, and then place it at 50°C to dry to obtain an uncrosslinked composite film.

[0089] (7) The uncrosslinked composite membrane was immersed in a 2.5wt% glutaraldehyde solution and kept at 55°C for 5 hours. After crosslinking, it was washed with ethanol and deionized water and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

[0090] Comparative Example 1

[0091] This comparative example provides a method for preparing a composite gas separation membrane, without composite porous gel-coated MOF material, including the following steps:

[0092] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0093] (2) GO was added to deionized water and ultrasonically treated for 40 min to obtain a GO suspension dispersion with a concentration of 13 g / L.

[0094] (3) The gelatin solution was added to the GO suspension at 35°C and dissolved. The oil phase polyvinyl alcohol solution was added, and the volume ratio of the oil phase to the water phase was 3:5. The mixture was ultrasonically treated for 20 min to obtain a gelatin microemulsion suspension. The mass ratio of GO to gelatin was 1:18.

[0095] (4) Place the pretreated polyimide film in a container, place it in a water bath at 40°C, then pour the solution obtained in step (3) onto the surface of the polyimide film to form a film, and then place it at 50°C to dry to obtain an uncrosslinked composite film.

[0096] (5) The uncrosslinked composite membrane was immersed in a 3wt% glutaraldehyde solution and kept at 55°C for 6 hours. After crosslinking, it was washed with ethanol and deionized water and dried to obtain the composite gas separation membrane.

[0097] Comparative Example 2

[0098] This comparative example provides a method for preparing a composite gas separation membrane without composite porous gelatin material, including the following steps:

[0099] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0100] (2) A metal-organic framework powder was prepared using a nickel salt solution and the organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone and ultrasonically stirred.

[0101] (3) Place the pretreated polyimide film in a container, place it in a water bath at 40°C, then pour the solution obtained in step (2) onto the surface of the polyimide film to form a film, and then place it at 50°C to dry to obtain an uncrosslinked composite film.

[0102] (6) The uncrosslinked composite membrane was immersed in a 3wt% glutaraldehyde solution and kept at 55°C for 6 hours. After crosslinking, it was washed with ethanol and deionized water and dried to obtain the composite gas separation membrane.

[0103] Comparative Example 3

[0104] This comparative example provides a method for preparing a composite gas separation membrane, which does not use graphene oxide to prepare the gelatin microemulsion suspension, nor does it coat the metal-organic framework with an aluminum silicate layer. Specifically, it includes the following steps:

[0105] (1) The polyimide membrane was soaked in deionized water and then vacuum degassed to obtain a pretreated base membrane.

[0106] (2) Dissolve solid gelatin in water to obtain gelatin solution, add oil phase polyvinyl alcohol solution, the volume ratio of oil phase to water phase is 3:5, sonicate for 20 min to obtain gelatin microemulsion suspension;

[0107] (3) A metal-organic framework powder was prepared by using a nickel salt solution and the organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone, ultrasonically stirred, and then added to a gelatin microemulsion suspension and ultrasonically stirred again. The mass ratio of the metal-organic framework to gelatin was 3:8.

[0108] (4) Place the pretreated polyimide film in a container, place it in a water bath at 40°C, then pour the solution obtained in step (3) onto the surface of the polyimide film to form a film, and then place it at 50°C to dry to obtain an uncrosslinked composite film.

[0109] (5) The uncrosslinked composite membrane is immersed in a 2-3 wt% glutaraldehyde solution and kept at 55°C for 6 hours. After crosslinking, it is washed with ethanol and deionized water and dried to obtain a composite gas separation membrane.

[0110] Comparative Example 4

[0111] This comparative example provides a method for preparing a composite gas separation membrane without using a base membrane, including the following steps:

[0112] (1) GO was added to deionized water and ultrasonically treated for 40 min to obtain a GO suspension dispersion with a concentration of 13 g / L.

[0113] (2) Dissolve solid gelatin in water to obtain gelatin solution. Add gelatin solution to GO suspension at 35°C and dissolve. Add oil phase polyvinyl alcohol solution. The volume ratio of oil phase to water phase is 3:5. Sonicate for 20 min to obtain gelatin microemulsion suspension. The mass ratio of GO to gelatin is 1:18.

[0114] (3) Metal-organic framework powder was prepared by using nickel salt solution and organic ligand 3-methyl-1,2,4-triazole. The metal-organic framework powder was dissolved in N-methylpyrrolidone, ultrasonically stirred, and then added to aluminosilicate sol. The mixture was stirred for 15 min, aged for 3 h, washed with water, calcined at 520 °C, and ball-milled to obtain a porous gel-coated MOF. The mass ratio of the metal-organic framework to the aluminosilicate sol was 4:6.

[0115] (4) The porous gel-coated MOF was added to the gelatin microemulsion suspension and ultrasonically stirred. The mass ratio of the porous gel-coated MOF to the gelatin was 3:8.

[0116] (5) In a water bath at 40°C, the solution obtained in step (4) is poured into a film and then placed at 50°C to dry to obtain an uncrosslinked film;

[0117] (6) The uncrosslinked membrane is immersed in a 2-3 wt% glutaraldehyde solution and kept at 55°C for 6 hours. After crosslinking, it is washed with ethanol and deionized water and dried to obtain a gas separation membrane.

[0118] Comparative Example 5

[0119] This comparative example provides a gas separation membrane, including a polyimide membrane.

[0120] Performance testing

[0121] The membrane materials prepared in each embodiment and comparative example were subjected to gas permeability and selectivity performance tests. The pure gas permeability coefficient (unit: Barrer, 1 Barrer = 10) was used. -10 cm 3 (STP)cm / (cm 2 The gas permeability coefficient (·s·cmHg) was measured using the isochoric-pressure swing method at 35℃ and 1.0MPa. Before testing, the upstream and downstream sides of the membrane were degassed under high vacuum for 24 hours. During testing, a high-purity gas (He, H2, CO2, O2, N2, and CH4 or a CO2 / CH4 mixture) was introduced upstream. A low-pressure sensor downstream detected the rate of change of gas pressure permeating the membrane over time. The gas permeability coefficient was calculated using the following method:

[0122]

[0123] in:

[0124] V: Device volume

[0125] β: Gas compressibility

[0126] A: Effective area of ​​the membrane

[0127] t: Pressure decay time

[0128] ΔP0: Initial pressure difference

[0129] ΔP(t): Pressure difference at time t

[0130] The test results are shown in Table 1 below.

[0131] Table 1. Permeability and selectivity of membrane materials prepared in each example and comparative example.

[0132]

[0133] As can be seen from the data in Table 1, the porous gelatin crosslinked MOF composite gas separation membranes obtained in Examples 1-5 exhibit very high permeability selectivity and high CO2 / CH4 separation performance, making them particularly suitable for gas separation applications such as natural gas helium extraction, natural gas decarbonization, CO2 separation in oil and gas fields, or CO2 capture in flue gas. Comparative Example 1 did not use composite porous gel coated MOF material, Comparative Example 2 did not use composite porous gelatin material, Comparative Example 3 did not use graphene oxide to prepare gelatin microemulsion suspension and did not coat the metal-organic framework with an aluminum silicate layer, Comparative Example 4 did not use a base membrane, and Comparative Example 5 used only a polyimide membrane as the gas separation membrane. The membrane performance of these comparative examples is significantly lower than that of the embodiments of the present invention, which also proves that only by using the technical solution of the present invention can a gas separation membrane with high permeability and high selectivity be obtained.

[0134] Table 2. CO2 / CH4 separation coefficients after a period of use in each embodiment

[0135] Usage time 12h 24h 36h 48h 60h 72h Example 1 315 310 306 312 303 309 Example 2 325 312 305 310 301 302 Example 3 277 275 264 269 272 265 Example 4 299 288 289 281 279 285 Example 5 281 280 276 278 269 275

[0136] As can be seen from the data in Table 2, the membrane material prepared by the present invention can continuously achieve the separation of carbon dioxide, and maintains a high separation coefficient even after a period of use. The reduction in separation effect is small. Moreover, even after 72 hours of use, the separation effect is still higher than that of the comparative examples.

[0137] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a porous gelatin crosslinked MOF composite gas separation membrane, characterized in that, Includes the following steps: (1) Graphene oxide was added to water and dispersed to prepare a graphene oxide suspension. (2) Dissolve solid gelatin in water to obtain gelatin solution, add the gelatin solution to graphene oxide suspension and dissolve, add oil phase, disperse evenly to obtain gelatin microemulsion suspension; (3) Dissolve the metal-organic framework in a solvent, mix it evenly, then add it to the aluminosilicate sol, mix it evenly again, age it for 2-3 hours, wash it, calcine it at 480-520℃, and ball mill it to prepare a porous gel-coated MOF material. (4) Add the porous gel-coated MOF material to the gelatin microemulsion suspension and disperse it evenly; (5) The solution obtained in step (4) is poured onto the surface of the base film to form a film, thereby obtaining an uncrosslinked composite film; (6) The uncrosslinked composite membrane was placed in glutaraldehyde solution to carry out a crosslinking reaction to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

2. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, In step (1), the specific preparation method of the graphene oxide suspension is as follows: add graphene oxide suspension to deionized water, and sonicate for 10 to 60 minutes to obtain a graphene oxide suspension with a concentration of 10 to 15 g / L.

3. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, In step (2), the specific preparation method of the gelatin microemulsion suspension is as follows: the gelatin solution is added to the graphene oxide suspension at 25-50℃ to dissolve, the oil phase polyvinyl alcohol solution is added, and the mixture is ultrasonically treated for 5-20 minutes to obtain the gelatin microemulsion suspension.

4. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 3, characterized in that, The volume ratio of the oil phase to the water phase is 3:(4-6).

5. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 3, characterized in that, The mass ratio of graphene oxide to gelatin is 1:(15-20).

6. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, In step (3), the metal-organic framework uses a nickel salt solution and an organic ligand 3-methyl-1,2,4-triazole, and the solvent is N-methylpyrrolidone.

7. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, The mass ratio of the metal-organic framework to the aluminum silicate sol is (3-4):

6.

8. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, In step (4), the mass ratio of porous gel-coated MOF material to gelatin is (2-3):

8.

9. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, The base film is a polyimide film, a polypropylene film, or a polyethersulfone film.

10. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, Before step (5), the base membrane needs to be pretreated: the base membrane is soaked in deionized water and then vacuum degassed to obtain the pretreated base membrane.

11. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 10, characterized in that, Step (5) involves placing the pretreated base film in a container and pouring the solution obtained in step (4) onto the surface of the pretreated base film in a water bath at 35-65°C to form a film. Then, the film is dried at 40-60°C to obtain an uncrosslinked composite film.

12. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 1, characterized in that, Step (6) involves immersing the uncrosslinked composite membrane in a 2-3 wt% glutaraldehyde solution and maintaining it at 50-65°C for 5-6 hours. After crosslinking, the membrane is washed and dried to obtain a porous gelatin crosslinked MOF composite gas separation membrane.

13. The method for preparing a porous gelatin crosslinked MOF composite gas separation membrane according to claim 12, characterized in that, Cleaning was performed using ethanol and deionized water.

14. A porous gelatin crosslinked MOF composite gas separation membrane, prepared by the preparation method according to any one of claims 1-13.

15. The application of the porous gelatin crosslinked MOF composite gas separation membrane as described in claim 14 in natural gas helium extraction, natural gas decarbonization, CO2 separation in oil and gas fields, or CO2 capture in flue gas.

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