Preparation method of crosslinked intrinsic microporous polymer membrane for gas separation

Abstract

The invention belongs to the technical field of membrane preparation and application, and discloses a preparation method of a crosslinked intrinsic microporous polymer membrane for gas separation. The preparation method comprises the following steps: carrying out cyano crosslinking on a dinitrile crosslinking agent and an intrinsic microporous polymer to synthesize the cyano-crosslinked intrinsic microporous polymer membrane. According to the cross-linked polymer gas separation membrane with the intrinsic micropores, due to the formed micropore and cross-linked network structure, the free volume and size screening effect of the polymer membrane with the intrinsic micropores can be effectively improved, the gas permeability of the polymer membrane with the intrinsic micropores is expected to be improved, and meanwhile the gas separation selectivity is improved. The prepared high-performance self-microporous polymer membrane material can be used for separating gases such as carbon dioxide, methane, hydrogen and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane preparation and application, and discloses a method for preparing a cross-linked self-microporous polymer membrane for gas separation. Background Art

[0002] At present, in order to address environmental issues such as the greenhouse effect caused by large-scale carbon dioxide emissions, it is necessary to separate and capture carbon dioxide. Traditional carbon dioxide separation methods such as pressure swing adsorption and chemical absorption have disadvantages such as high energy consumption and low separation efficiency, while membrane separation methods are widely used due to their environmental friendliness and low energy consumption. Membrane separation achieves separation based on the different permeabilities of gases passing through the membrane. It has the advantages of small footprint, simple operation, and high separation efficiency.

[0003] Membrane materials are the core of membrane separation and can be divided into organic membrane materials, inorganic membrane materials, and mixed matrix membrane materials. Among them, organic membrane materials are the most widely developed. Traditional organic membrane materials such as polyimide have the disadvantage of low gas permeability (Robeson, Lloyd M. "The upper bound revisited." Journal of membrane science 320.1-2 (2008): 390-400.). As a new type of organic microporous polymer material, self-microporous polymer materials have received widespread attention due to their high free volume and high permeability, but they have the disadvantages of plasticization effect and low selectivity (Tiwari, Rajkiran R., et al. "Physical aging, CO2 sorption and plasticization in thin films of polymer with intrinsic microporosity (PIM-1)." Journal of Membrane Science 537 (2017): 362-371.). In order to further improve the gas separation performance and plasticization resistance of intrinsic microporous polymer membranes, the present invention carries out a cyano cross-linking modification method to cross-link the intrinsic microporous polymer and the dinitrile cross-linking agent, thereby changing the pore structure of the intrinsic microporous polymer and forming a cross-linked network, which helps to improve the free volume and size screening effect. The chemical bonds between the polymer molecular chains limit the fluidity of the chain segments, which can effectively improve the gas separation performance and plasticization resistance of the membrane (He, Shanshan, et al. "Intermediate thermal manipulation of polymers of intrinsic microporous (PIMs) membranes for gas separations." AIChE Journal 66.10(2020):e16543.). Summary of the invention

[0004] Aiming at the inadequacies of gas separation performance and anti-plasticization ability of self-microporous polymer membranes, the present invention provides a method for preparing a cross-linked self-microporous polymer membrane for gas separation.

[0005] To achieve the above-mentioned purpose, the present invention provides a method for preparing a cross-linked self-microporous polymer membrane for gas separation, wherein the self-microporous polymer membrane material is cyano cross-linked with a dinitrile cross-linking agent to synthesize a cyano cross-linked self-microporous polymer membrane, which can improve its separation performance for carbon dioxide and its anti-plasticization ability.

[0006] The technical solution of the present invention:

[0007] A method for preparing a cross-linked self-microporous polymer membrane for gas separation, comprising the following steps:

[0008] (1) Preparation of self-contained microporous polymer membranes

[0009] The self-microporous polymer material A is dissolved in the solvent A to prepare a casting solution, stirred for a period of time, and allowed to stand for degassing; the casting solution is cast in a glass watch glass, dried under vacuum conditions for several hours, and the solvent A is removed to obtain a dense self-microporous polymer membrane;

[0010] (2) Preparation of dinitrile cross-linked microporous polymer membranes

[0011] The self-microporous polymer membrane is immersed in a crosslinking agent B solution for a period of time and dried under vacuum conditions to obtain a cyano surface modified self-microporous polymer membrane; and the cyano surface modified self-microporous polymer membrane is placed in a tubular furnace and subjected to crosslinking heat treatment in a protective gas A at a certain crosslinking temperature and crosslinking time to obtain a dinitrile crosslinked self-microporous polymer membrane.

[0012] The self-microporous polymer material A is a mixture of one or more of a self-microporous polymer PIM-1, a tetraphenylethylene ladder polymer TPE-PIM, and a spirobifluorene self-microporous polymer PIM-SBF; the structural formula is as follows:

[0013]

[0014] The solvent A is one or a mixture of two or more of dichloromethane, chloroform, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone;

[0015] The crosslinking agent B is one or a mixture of two or more of malononitrile, succinonitrile, adiponitrile, terephthalonitrile, phthalonitrile, and isophthalonitrile; the structural formula is as follows:

[0016]

[0017] The protective gas A is argon or nitrogen;

[0018] In step (1), the concentration of the casting solution is 2-80wt%, the stirring time of the casting solution is 12-48h; the vacuum drying temperature is 50-120°C, and the time is 12-72h; the thickness of the self-microporous polymer membrane is 50-100μm;

[0019] In step (2), the concentration of the methanol solution of the crosslinking agent B is 5-60wt%; the immersion time is 12-72h; the vacuum drying temperature is 60-150°C, and the drying time is 12-48h; the thermal crosslinking time is 12-72h, and the crosslinking temperature is 200-400°C.

[0020] The beneficial effects of the present invention are as follows: the present invention cross-links the dinitrile cross-linking agent with the self-microporous polymer, and due to the cross-linking effect of the cyanide chemical bond between the dinitrile cross-linking agent and PIM-1, micropores and a network structure are formed, which helps to improve the size screening effect and gas permeability, and due to the chemical bonds generated between the polymer molecular chains, the fluidity of the chain segments is further limited, the swelling effect of high-pressure CO2 is reduced, and the anti-plasticization ability is increased. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described below in conjunction with the technical solution.

[0022] The preparation method of the self-microporous polymer (PIM-1) used in the present invention is as follows: 3.41g 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, 3.0g tetrafluoroterephthalonitrile and 8.5g potassium carbonate are added to 40ml anhydrous DMAC and 20ml toluene in a flask, stirred and dissolved, and after complete dissolution, the temperature is raised to 150°C, and the reaction is carried out for about 50min in a nitrogen atmosphere. After the reaction is completed, the heating is stopped, the mixture is naturally cooled to room temperature, methanol is poured into the mixture to precipitate, the mixture is washed with methanol, and finally dried in a vacuum oven at 80°C for 72h to obtain the self-microporous polymer, which is stored for later use.

[0023] Gas separation performance test: In the present invention, the constant volume variable pressure method is used to test the gas separation performance. The gas separation performance test temperature is 35° C. and the test pressure is 2 bar.

[0024] Comparative Example 1

[0025] 0.5 g of the self-microporous polymer PIM-1 was dissolved in 10 ml of chloroform, stirred for 48 h, allowed to stand for degassing, cast in a glass watch dish, and dried in a vacuum drying oven at 100° C. for 24 h to obtain a self-microporous polymer membrane.

[0026] The PIM-1 membrane was immersed in a 10% terephthalonitrile / methanol solution for 24 hours for surface chemical modification, and then placed in a vacuum oven for drying for 24 hours to obtain a cyano surface modified PIM membrane.

[0027] Example 1

[0028] 0.5 g of the self-microporous polymer PIM-1 was dissolved in 10 ml of chloroform, stirred for 48 h, allowed to stand for degassing, cast in a glass watch dish, and dried in a vacuum drying oven at 100° C. for 24 h to obtain a self-microporous polymer membrane.

[0029] The PIM-1 membrane was immersed in a 10% terephthalonitrile / methanol solution for 24 hours for surface chemical modification, and then placed in a vacuum oven for drying for 24 hours to obtain a cyano surface modified PIM membrane.

[0030] 1 g of the surface-modified terephthalonitrile film was placed in a tubular furnace and subjected to thermal crosslinking treatment in a nitrogen protective atmosphere at a crosslinking temperature of 250° C. for 10 h to obtain the crosslinked film of Example 1.

[0031] Example 2

[0032] 0.5 g of the self-microporous polymer PIM-1 was dissolved in 10 ml of chloroform, stirred for 48 h, allowed to stand for degassing, cast in a glass watch dish, and dried in a vacuum drying oven at 100° C. for 24 h to obtain a self-microporous polymer membrane.

[0033] The PIM-1 membrane was immersed in a 10% terephthalonitrile / methanol solution for 24 hours for surface chemical modification, and then placed in a vacuum oven for drying for 24 hours to obtain a cyano surface modified PIM membrane.

[0034] 1 g of the surface-modified terephthalonitrile film was placed in a tubular furnace and subjected to thermal crosslinking treatment in a nitrogen protective atmosphere at a crosslinking temperature of 300° C. for 10 h to obtain the crosslinked film of Example 1.

[0035] Example 3

[0036] 0.5 g of the self-microporous polymer PIM-1 was dissolved in 10 ml of chloroform, stirred for 48 h, allowed to stand for degassing, cast in a glass watch dish, and dried in a vacuum drying oven at 100° C. for 24 h to obtain a self-microporous polymer membrane.

[0037] The PIM-1 membrane was immersed in a 10% terephthalonitrile / methanol solution for 24 hours for surface chemical modification, and then placed in a vacuum oven for drying for 24 hours to obtain a cyano surface modified PIM membrane.

[0038] 1 g of the surface-modified terephthalonitrile film was placed in a tubular furnace and subjected to thermal crosslinking treatment in a nitrogen protective atmosphere at a crosslinking temperature of 350° C. for 10 h to obtain the crosslinked film of Example 2.

[0039] Table 1 Permeability and selectivity of gas separation membranes prepared in Examples and Comparative Examples

[0040]

[0041] Compared with the control example 1, the permeability and selectivity of the embodiment 2 are increased, the CO2 permeability increases from 8284 Barrer to 12005 Barrer, an increase of 31%, and the CO2 / CH4 selectivity increases from 17.8 to 18.1. It can be seen that the microporous structure and cross-linked network formed by the action of the terephthalonitrile cross-linking agent and PIM-1 can effectively improve the gas separation performance of the PIM-1 membrane.

Claims

1. A method for preparing a cross-linked self-microporous polymer membrane for gas separation, characterized in that: Here are the steps: (1) Preparation of self-contained microporous polymer membranes The self-microporous polymer material A is dissolved in the solvent A to prepare a casting solution, stirred for a period of time, and allowed to stand for degassing; the casting solution is cast in a glass watch glass, dried under vacuum conditions for several hours, and the solvent A is removed to obtain a dense self-microporous polymer membrane; (2) Preparation of dinitrile cross-linked microporous polymer membranes The self-microporous polymer membrane is immersed in a crosslinking agent B solution for a period of time and dried under vacuum conditions to obtain a cyano surface modified self-microporous polymer membrane; and the cyano surface modified self-microporous polymer membrane is placed in a tubular furnace and subjected to crosslinking heat treatment in a protective gas A at a certain crosslinking temperature and crosslinking time to obtain a dinitrile crosslinked self-microporous polymer membrane.

2. The method for preparing a cross-linked self-microporous polymer membrane according to claim 1, characterized in that: The self-microporous polymer material A is one or a mixture of two or more of a self-microporous polymer PIM-1, a tetraphenylethylene ladder polymer TPE-PIM, and a spirobifluorene self-microporous polymer PIM-SBF.

3. The method for preparing a cross-linked self-microporous polymer membrane according to claim 1, characterized in that: The solvent A is one or a mixture of two or more of dichloromethane, chloroform, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

4. The method for preparing a cross-linked self-microporous polymer membrane according to claim 1, characterized in that: The crosslinking agent B is one or a mixture of two or more of malononitrile, succinonitrile, adiponitrile, terephthalonitrile, phthalonitrile and isophthalonitrile.

5. The method for preparing a cross-linked self-microporous polymer membrane according to claim 1, characterized in that: The protective gas A is argon and / or nitrogen.

6. The method for preparing a cross-linked self-microporous polymer membrane according to claim 1, characterized in that: In step (1), The concentration of the casting solution is 2-80wt%, and the stirring time of the casting solution is 12-48h; The vacuum drying temperature is 50-120°C and the time is 12-72h; The thickness of the microporous polymer membrane is 50-100 μm.

7. The method for preparing a cross-linked self-microporous polymer membrane according to claim 1, characterized in that: In step (2), The concentration of the methanol solution of the crosslinking agent B is 5-60wt%, and the immersion time is 12-72h; The vacuum drying temperature is 60-150°C and the drying time is 12-48h; The thermal cross-linking time is 12-72h, and the cross-linking temperature is 200-400°C.

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