A method for preparing a crosslinked self-microporous polymer membrane for gas separation

Abstract

The application belongs to the technical field of membrane preparation and application, and discloses a preparation method of a crosslinked self-microporous polymer membrane for gas separation. A dicyan crosslinking agent is used to crosslink a self-microporous polymer to synthesize a cyan crosslinked self-microporous polymer membrane. The crosslinked self-microporous polymer gas separation membrane prepared by the application can effectively improve the free volume and size sieving effect of the self-microporous polymer membrane due to the formed micropores and crosslinked network structure, and is expected to improve the gas permeability and gas separation selectivity of the self-microporous polymer membrane. The high-performance self-microporous polymer membrane material prepared by the application can be used for separating carbon dioxide, methane, hydrogen and other gases.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of membrane preparation and application, and discloses a preparation method of a crosslinked self-microporous polymer membrane for gas separation. BACKGROUND

[0002] At present, in view of the environmental problems such as greenhouse effect caused by large emission of carbon dioxide, it is necessary to separate and capture carbon dioxide. Traditional carbon dioxide separation methods such as pressure swing adsorption and chemical absorption have the disadvantages of high energy consumption and low separation efficiency, while the membrane separation method is widely used due to its environmental friendliness and low energy consumption. Membrane separation is to realize separation according to the different permeation rates of gases through the membrane, and has the advantages of small occupied area, simple operation and high separation efficiency.

[0003] Membrane materials are the core of membrane separation, which can be divided into organic membrane materials, inorganic membrane materials and mixed matrix membrane materials. Among them, the most widely developed is organic membrane material. 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 material has been widely concerned due to its high free volume and high permeability, but it has 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 self-microporous polymer membrane, the present application carries out cyano crosslinking modification method, crosslinks self-microporous polymer and dicyan crosslinking agent, changes the pore structure of self-microporous polymer, and makes it form crosslinking network, which helps to improve the free volume and size sieving effect, and the chemical bond between polymer molecular chains limits the chain segment fluidity, 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

[0004] In view of the deficiencies of the gas separation performance and plasticization resistance of the self-microporous polymer membrane, the application provides a preparation method of crosslinked self-microporous polymer membrane for gas separation.

[0005] In order to achieve the above purpose, the application provides a preparation method of crosslinked self-microporous polymer membrane for gas separation, which crosslinks the self-microporous polymer membrane material with dicyan crosslinking agent to synthesize a cyano crosslinked self-microporous polymer membrane, which can improve the separation performance and plasticization resistance of carbon dioxide.

[0006] The technical scheme of the application is as follows:

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

[0008] (1) Preparation of a self-microporous polymer membrane

[0009] Dissolve the self-microporous polymer material A in a solvent A to prepare a casting solution, stir for a period of time, and stand for defoaming; pour the casting solution into a glass surface dish, dry under vacuum for several hours to remove the solvent A, and obtain a dense self-microporous polymer membrane;

[0010] (2) Preparation of a dicyan cross-linked self-microporous polymer membrane

[0011] Immerse the self-microporous polymer membrane in a cross-linking agent B solution for a period of time, dry under vacuum to obtain a cyano surface-modified self-microporous polymer membrane; and place the cyano surface-modified self-microporous polymer membrane in a tube furnace, perform cross-linking heat treatment under a protective gas A at a certain cross-linking temperature and cross-linking time to obtain a dicyan cross-linked self-microporous polymer membrane.

[0012] The self-microporous polymer material A is one or a mixture of two or more of self-microporous polymers PIM-1, tetraphenyl ethylene-based ladder polymer TPE-PIM, and spirobifluorene-based 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, trichloromethane, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl pyrrolidone;

[0015] The cross-linking agent B is one or a mixture of two or more of malononitrile, succinonitrile, adiponitrile, terephthalonitrile, o-phthalonitrile, and m-phthalonitrile; 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 2-80 wt%, the stirring time of the casting solution is 12-48 h; the vacuum drying temperature is 50-120°C, and the time is 12-72 h; the thickness of the self-microporous polymer membrane is 50-100 μm;

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

[0020] The present application has the following advantages: the dinitrile crosslinking agent is crosslinked with the PIM-1, and the dinitrile crosslinking agent is crosslinked with the cyano group of the PIM-1 through chemical bonds, so that a microporous and network structure is formed, which helps to improve the size sieving effect and gas permeability, and the chemical bonds generated between the polymer molecular chains further limit the chain segment flowability, so that the swelling effect of high-pressure CO2 is reduced, and the plasticization resistance is increased. DETAILED DESCRIPTION

[0021] The specific embodiments of the present application will be further described below in combination with the technical solutions.

[0022] The preparation method of the PIM-1 used in the present application is as follows: 3.41 g of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisoindane, 3.0 g of tetrafluoroterephthalonitrile and 8.5 g of potassium carbonate are added into a flask, 40 ml of anhydrous DMAC and 20 ml of toluene are added, and stirring and dissolution are performed, then after complete dissolution, the temperature is increased to 150°C, and the reaction is performed under a nitrogen atmosphere for about 50 min. After the reaction is completed, the heating is stopped, and the temperature is naturally cooled to room temperature, then the mixture is poured into methanol to precipitate the precipitate, the precipitate is washed with methanol, and finally the mixture is placed in a vacuum oven at 80°C for drying for 72 h, so that the PIM-1 is obtained and stored for use.

[0023] The gas separation performance test in the present application is performed by using the constant volume pressure swing method. 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 PIM-1 is dissolved in 10 ml of chloroform, stirring is performed for 48 h, and the mixture is left to stand and degassed, then the mixture is cast on a glass surface dish, and the mixture is placed in a vacuum drying oven at 100°C for drying for 24 h, so that the PIM-1 membrane is obtained.

[0026] The PIM-1 membrane is immersed in a 10% terephthalonitrile / methanol solution for 24 h, and the surface is chemically modified, then the mixture is placed in a vacuum oven for drying for 24 h, so that the cyano surface modified PIM membrane is obtained.

[0027] Example 1

[0028] 0.5 g of the PIM-1 is dissolved in 10 ml of chloroform, stirring is performed for 48 h, and the mixture is left to stand and degassed, then the mixture is cast on a glass surface dish, and the mixture is placed in a vacuum drying oven at 100°C for drying for 24 h, so that the PIM-1 membrane is obtained.

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

[0030] The 1 g of terephthalonitrile surface modified membrane was placed in a tube furnace and heat crosslinked under nitrogen atmosphere at a temperature of 250°C for 10 h to obtain the crosslinked membrane of Example 1.

[0031] Example 2

[0032] The 0.5 g of PIM-1 was dissolved in 10 ml of chloroform, stirred for 48 h, and then cast on a glass surface dish and dried in a vacuum oven at 100°C for 24 h to obtain a microporous polymer membrane.

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

[0034] The 1 g of terephthalonitrile surface modified membrane was placed in a tube furnace and heat crosslinked under nitrogen atmosphere at a temperature of 300°C for 10 h to obtain the crosslinked membrane of Example 1.

[0035] Example 3

[0036] The 0.5 g of PIM-1 was dissolved in 10 ml of chloroform, stirred for 48 h, and then cast on a glass surface dish and dried in a vacuum oven at 100°C for 24 h to obtain a microporous polymer membrane.

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

[0038] The 1 g of terephthalonitrile surface modified membrane was placed in a tube furnace and heat crosslinked under nitrogen atmosphere at a temperature of 350°C for 10 h to obtain the crosslinked membrane of Example 2.

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

[0040]

[0041] Compared with Comparative Example 1, the permeability and selectivity of Example 2 are increased, the CO2 permeability is increased from 8284 Barrer to 12005 Barrer, increased by 31%, and the CO2 / CH4 selectivity is increased from 17.8 to 18.1, which shows that the microporous structure and crosslinked network formed by the reaction of terephthalonitrile crosslinking agent and PIM-1 can effectively improve the gas separation performance of the PIM-1 membrane.

Claims

1. A method for preparing a crosslinked self-microporous polymer membrane for gas separation, characterized by, The steps are as follows: (1) Preparation of self-microporous polymer film Dissolve self-microporous polymer material A in solvent A to prepare casting solution, stir for a period of time, and stand for defoaming; pour the casting solution into a glass surface dish, dry under vacuum for several hours to remove solvent A, and obtain a dense self-microporous polymer film. (2) Preparation of dinitrile crosslinked self-microporous polymer film The self-microporous polymer film is immersed in a solution of crosslinking agent B for a period of time, dried under vacuum to obtain a cyano surface-modified self-microporous polymer film; and the cyano surface-modified self-microporous polymer film is placed in a tube furnace, crosslinked and heat-treated in a protective gas A for a heat crosslinking time of 12-72 h and a crosslinking temperature of 200-400 o C to obtain a dicyan crosslinked self-microporous polymer film.

2. The method for preparing a cross-linked self-porous 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 self-microporous polymer PIM-1, tetraphenyl ethylene-based ladder polymer TPE-PIM, and spirobifluorene-based self-microporous polymer PIM-SBF.

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

4. The method for preparing a cross-linked self-porous 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, o-phthalonitrile, and m-phthalonitrile.

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

6. The crosslinked self-microporous polymer film preparation method according to claim 1, wherein In step (1), the concentration of the casting solution is 2-80 wt%, the stirring time of the casting solution is 12-48 h, and the thickness of the self-microporous polymer film is 50-100 μm. Vacuum drying temperature is 50-120 o C, time is 12-72 h; 7. The crosslinked self-microporous polymer film preparation method according to claim 1, wherein In step (2), the concentration of the methanol solution of the crosslinking agent B is 5-60 wt%, and the immersion time is 12-72 h. ​ Vacuum drying temperature is 60-150 o C, drying time is 12-48 h; The heat crosslinking time is 12-72 h, and the crosslinking temperature is 200-400 o C.

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