A polyimide desulfurization and decarbonization membrane and its preparation method

Abstract

The present invention discloses a polyimide desulfurization and decarbonization membrane and a preparation method thereof, belonging to the technical field of gas separation. The key points of the technical solution include the following preparation steps: S1. Place diamine in a solvent and stir under a nitrogen atmosphere until completely dissolved; S2. Add dianhydride to step S1 and continue stirring until the dianhydride is dissolved; S3. Add a dehydrating agent and a catalyst to S2 for imidization to obtain a polyimide solution, and then filter, wash, and dry to obtain a polyimide solid; S4. Add the metal-organic framework material MOF-808 to ethanol dissolved with imidazole-based ionic liquid, stir and react, and then centrifuge the product to obtain a composite filler; S5. Add the composite filler to a solvent and disperse it evenly, then add the polyimide solid and stir evenly to obtain a casting solution. Pour the casting solution on a glass plate and heat it at 50-60°C, and then dry the film to obtain a polyimide desulfurization and decarbonization membrane, achieving the technical effect of improving the permeability coefficients of sulfur dioxide and carbon dioxide.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and in particular to a polyimide desulfurization and decarburization membrane and a preparation method thereof. Background Art

[0002] Due to the outstanding advantages of low energy consumption, convenient operation, and no environmental pollution, gas separation membrane technology has been widely used in air separation and purification, recovery of carbon dioxide in combustion waste gas, and natural gas purification. Gases are separated by a polymer membrane due to different permeation rates. The separation performance is related to factors such as gas molecules, the structural properties of the membrane, and the interaction between the gas and the membrane. Different gases have different dissolution and diffusion abilities in the separation membrane, thus realizing gas separation.

[0003] Among the currently commonly used membrane materials, polyvinylidene fluoride materials have excellent chemical stability, thermal stability, and acid and alkali resistance. When prepared into a dense gas separation membrane, they have a wide application space in the gas separation field. However, for the separation membrane made of polyvinylidene fluoride materials, the solubility and permeability coefficient of sulfur dioxide in the membrane are relatively low, and it is difficult to achieve rapid separation. Summary of the Invention

[0004] In order to improve the permeability of sulfur dioxide, the present invention provides a polyimide desulfurization and decarburization membrane and a preparation method thereof.

[0005] The polyimide desulfurization and decarburization membrane and the preparation method thereof provided by the present invention adopt the following technical solutions:

[0006] A preparation method of a polyimide desulfurization and decarburization membrane includes the following preparation steps:

[0007] S1. Place diamine in an aprotic solvent, stir under a nitrogen atmosphere until completely dissolved, and then cool to below 10°C; the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of (5-8):1;

[0008] S2. Add dianhydride to step S1 and continue to stir until the dianhydride is dissolved to obtain an amic acid solution;

[0009] S3. Add a dehydrating agent and a catalyst to the amic acid solution for imidization to obtain a polyimide solution. After filtering and washing the polyimide solution, vacuum dry it to obtain a polyimide solid;

[0010] S4. Add metal-organic framework material MOF-808 to ethanol dissolved with imidazole-based ionic liquid, stir and react at 50-60°C for 10-15 h, and then centrifuge the product to obtain a composite filler;

[0011] S5. Add the composite filler to the aprotic solvent and disperse it evenly. Then add the polyimide solid obtained in step S3 and stir evenly to obtain a casting solution. Pour the casting solution onto a glass plate and heat it at 50 - 60 °C to evaporate the solvent to obtain a film. Then dry the film to obtain a polyimide desulfurization and decarbonization membrane. The addition amount of the composite filler is 5 - 10% of the mass of the polyimide solid.

[0012] Preferably, the metal-organic framework material MOF-808 is the metal-organic framework material MOF-808 modified by an amino acid. The modification method is as follows: Add the metal-organic framework material MOF-808 and the amino acid to water, stir and react at 60 - 70 °C for 15 - 20 h, filter to obtain a precipitate, wash the precipitate with water multiple times and then dry to obtain the amino acid-modified metal-organic framework material MOF-808.

[0013] Preferably, the mass ratio of the metal-organic framework material MOF-808 to the amino acid is 1:(5 - 10).

[0014] Preferably, the weight ratio of the metal-organic framework material MOF-808 to the imidazole-based ionic liquid in step S4 is (1 - 3):1.

[0015] Preferably, the weight ratio of the diamine to the dianhydride is 1:(3.2 - 3.5).

[0016] Preferably, the imidazole-based ionic liquid uses 1-ethyl-3-methylimidazolium chloride.

[0017] Preferably, the aprotic solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, and N,N-dimethylacetamide.

[0018] Preferably, the dianhydride uses 4,4'-(hexafluoroisopropylidene)diphthalic anhydride.

[0019] Preferably, the dehydrating agent is one of acetic anhydride and phthalic anhydride, and the catalyst is one of triethylamine and pyridine.

[0020] The second object of the present invention is to provide a polyimide desulfurization and decarbonization membrane obtained by the preparation method of the polyimide desulfurization and decarbonization membrane as described above.

[0021] In summary, the present invention has the following beneficial effects:

[0022] In the present application, after the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, the entanglement of polymer chains in the polyimide film can be changed, the segmental motion can be altered, enabling the polyimide film to have a more compact segmental packing, enhancing the selectivity for carbon dioxide and sulfur dioxide. Moreover, after adding the metal-organic framework material MOF-808 modified by an imidazole-based ionic liquid to the polyimide, the free volume in the polyimide film can be increased and an additional gas diffusion path can be provided, leading to an increase in the permeability coefficients of sulfur dioxide and carbon dioxide, thereby improving the separation performance of the polyimide film for carbon dioxide and sulfur dioxide.

[0023] After the metal-organic framework material MOF-808 is modified by amino acids, the amino acids can be chemically fixed in the pores of the highly stable metal-organic framework material, successfully constructing pores of appropriate size and high-density basic sites, thereby enhancing the separation selectivity of the polyimide film for carbon dioxide and sulfur dioxide, enabling carbon dioxide and sulfur dioxide to preferentially permeate. Detailed implementation mode

[0024] The present invention will be further described in detail below in conjunction with embodiments.

[0025] The raw materials used in the examples and comparative examples of the present application are all commercially available. Example 1

[0026] A preparation method of a polyimide desulfurization and decarbonization membrane includes the following preparation steps:

[0027] S1. Place 300 g of diamine in 6.5 L of anhydrous N,N-dimethylformamide, stir under a nitrogen atmosphere until completely dissolved, and then cool to 5 °C; the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of 5:1, that is, the content of m-phenylenediamine is 250 g and the content of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is 50 g;

[0028] S2. Add 960 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to step S1 and continue stirring until 4,4'-(hexafluoroisopropylidene)diphthalic anhydride is dissolved to obtain an amic acid solution, that is, the weight ratio of diamine to dianhydride is 1:3.2;

[0029] S3. Add 2.4 L of acetic anhydride and 0.8 L of pyridine to the amic acid solution, react for 24 h under a nitrogen atmosphere for imidization to obtain a polyimide solution, slowly pour the polyimide solution into an excessive ethanol-water (volume ratio of ethanol to water is 1:1) for precipitation, filter to collect the fibrous polymer, wash the polymer with ethanol, and then vacuum dry at 180 °C to obtain a polyimide solid;

[0030] S4. Add 10 g of metal-organic framework material MOF-808 to ethanol dissolving 10 g of 1-ethyl-3-methylimidazolium chloride, stir and react at 50 °C for 10 h, and then centrifuge the product to obtain the composite filler;

[0031] S5. Take 5 g of the composite filler obtained in step S4 and disperse it evenly in 3 L of anhydrous N,N-dimethylformamide, then add 100 g of the polyimide solid obtained in step S3 and stir evenly to obtain the casting solution. Pour the casting solution on a glass plate and heat it at 60 °C to evaporate the solvent to obtain a film, and then vacuum dry the film to obtain the polyimide desulfurization and decarbonization membrane, that is, the addition amount of the composite filler is 5% of the mass of the polyimide solid. Example 2

[0032] A preparation method of a polyimide desulfurization and decarbonization membrane includes the following preparation steps:

[0033] S1. Place 300 g of diamine in 6.5 L of anhydrous N,N-dimethylformamide, stir under a nitrogen atmosphere until completely dissolved, and then cool to below 0 °C; the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of 7:1, that is, the content of m-phenylenediamine is 262.5 g and the content of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is 37.5 g;

[0034] S2. Add 1020 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to step S1 and continue to stir until 4,4'-(hexafluoroisopropylidene)diphthalic anhydride is dissolved to obtain an amic acid solution, that is, the weight ratio of diamine to dianhydride is 1:3.4;

[0035] S3. Add 2.45 L of acetic anhydride and 0.9 L of pyridine to the amic acid solution and react for 24 h under a nitrogen atmosphere for imidization to obtain a polyimide solution. Slowly pour the polyimide solution into an excessive ethanol-water (volume ratio of ethanol to water is 1:1) for precipitation. After filtration, collect the fibrous polymer, wash the polymer with ethanol, and then vacuum dry it at 180 °C to obtain the polyimide solid;

[0036] S4. Add 20 g of metal-organic framework material MOF-808 to ethanol dissolving 10 g of 1-ethyl-3-methylimidazolium chloride, stir and react at 50 °C for 10 h, and then centrifuge the product to obtain the composite filler; that is, the weight ratio of the metal-organic framework material MOF-808 to 1-ethyl-3-methylimidazolium chloride is 2:1;

[0037] S5. Take 6 g of the composite filler obtained in step S4 and disperse it evenly in 3 L of anhydrous N,N-dimethylformamide. Then add 100 g of the polyimide solid obtained in step S3 and stir evenly to obtain a casting solution. Pour the casting solution onto a glass plate and heat it at 60 °C to evaporate the solvent to obtain a film. Then vacuum-dry the film to obtain a polyimide desulfurization and decarbonization membrane, that is, the addition amount of the composite filler is 6% of the mass of the polyimide solid. Example 3

[0038] A preparation method of a polyimide desulfurization and decarbonization membrane includes the following preparation steps:

[0039] S1. Place 300 g of diamine in 6.5 L of anhydrous N,N-dimethylformamide, stir under a nitrogen atmosphere until completely dissolved, and then cool to below 10 °C; the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of 8:1, that is, the content of m-phenylenediamine is 266.7 g and the content of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is 33.3 g;

[0040] S2. Add 1050 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to step S1 and continue stirring until 4,4'-(hexafluoroisopropylidene)diphthalic anhydride is dissolved to obtain an amic acid solution, that is, the weight ratio of diamine to dianhydride is 1:3.5;

[0041] S3. Add 2.45 L of acetic anhydride and 0.9 L of pyridine to the amic acid solution and react for 24 h under a nitrogen atmosphere for imidization to obtain a polyimide solution. Slowly pour the polyimide solution into an excessive ethanol-water (the volume ratio of ethanol to water is 1:1) for precipitation. After filtration, collect the fibrous polymer. Wash the polymer with ethanol and then vacuum-dry it at 180 °C to obtain a polyimide solid;

[0042] S4. Add 30 g of metal-organic framework material MOF-808 to ethanol dissolving 10 g of 1-ethyl-3-methylimidazolium chloride, stir and react at 50 °C for 10 h, and then centrifuge the product to obtain a composite filler; that is, the weight ratio of the metal-organic framework material MOF-808 to 1-ethyl-3-methylimidazolium chloride is 3:1

[0043] S5. Take 8 g of the composite filler obtained in step S4 and disperse it evenly in 3 L of anhydrous N,N-dimethylformamide. Then add 100 g of the polyimide solid obtained in step S3 and stir evenly to obtain a casting solution. Pour the casting solution onto a glass plate and heat it at 60 °C to evaporate the solvent to obtain a film. Then vacuum-dry the film to obtain a polyimide desulfurization and decarbonization membrane, that is, the addition amount of the composite filler is 8% of the mass of the polyimide solid. Example 4

[0044] A preparation method of a polyimide desulfurization and decarbonization membrane, comprising the following preparation steps:

[0045] S1. Place 300 g of diamine in 6.5 L of anhydrous N,N-dimethylformamide, stir in a nitrogen atmosphere until completely dissolved, and then cool to below 0 °C; the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of 7:1, that is, the content of m-phenylenediamine is 262.5 g and the content of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is 37.5 g;

[0046] S2. Add 1020 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to step S1 and continue to stir until the 4,4'-(hexafluoroisopropylidene)diphthalic anhydride is dissolved to obtain an amic acid solution, that is, the weight ratio of diamine to dianhydride is 1:3.4;

[0047] S3. Add 2.45 L of acetic anhydride and 0.9 L of pyridine to the amic acid solution and react for 24 h in a nitrogen atmosphere for imidization to obtain a polyimide solution. Slowly pour the polyimide solution into an excessive ethanol-water (volume ratio of ethanol to water is 1:1) for precipitation. After filtration, collect the fibrous polymer. Wash the polymer with ethanol and then vacuum dry it at 180 °C to obtain a polyimide solid;

[0048] S4. Add 20 g of metal-organic framework material MOF-808 and 100 g of amino acid to 500 g of water, stir and react at 60 °C for 15 h, filter to obtain a precipitate, wash the precipitate with water multiple times and then dry it to obtain an amino acid-modified metal-organic framework material MOF-808;

[0049] S5. Add 20 g of metal-organic framework material MOF-808 to ethanol dissolved with 10 g of 1-ethyl-3-methylimidazolium chloride, stir and react at 50 °C for 10 h, and then centrifuge the product to obtain a composite filler; that is, the weight ratio of the metal-organic framework material MOF-808 to 1-ethyl-3-methylimidazolium chloride is 2:1;

[0050] S6. Take 6 g of the composite filler obtained in step S4 and disperse it evenly in 3 L of anhydrous N,N-dimethylformamide, then add 100 g of the polyimide solid obtained in step S3 and stir evenly to obtain a casting solution. Pour the casting solution on a glass plate and heat it at 60 °C to evaporate the solvent to obtain a film, and then vacuum dry the film to obtain a polyimide desulfurization and decarbonization membrane, that is, the addition amount of the composite filler is 6% of the mass of the polyimide solid. Example 5

[0051] A preparation method of a polyimide desulfurization and decarbonization membrane, comprising the following preparation steps:

[0052] S1. Place 300 g of diamine in 6.5 L of anhydrous N,N-dimethylformamide, stir under a nitrogen atmosphere until completely dissolved, and then cool to below 0 °C. The diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of 7:1, that is, the content of m-phenylenediamine is 262.5 g and the content of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is 37.5 g;

[0053] S2. Add 1020 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to Step S1 and continue stirring until the 4,4'-(hexafluoroisopropylidene)diphthalic anhydride is dissolved to obtain an amic acid solution, that is, the weight ratio of diamine to dianhydride is 1:3.4;

[0054] S3. Add 2.45 L of acetic anhydride and 0.9 L of pyridine to the amic acid solution and react for 24 h under a nitrogen atmosphere for imidization to obtain a polyimide solution. Slowly pour the polyimide solution into an excessive ethanol-water (volume ratio of ethanol to water is 1:1) for precipitation. After filtration, collect the fibrous polymer. Wash the polymer with ethanol and then vacuum dry it at 180 °C to obtain a polyimide solid;

[0055] S4. Add 20 g of metal-organic framework material MOF-808 and 160 g of amino acid to 500 g of water, stir and react at 65 °C for 17 h, filter to obtain a precipitate, wash the precipitate with water multiple times and then dry it to obtain an amino acid-modified metal-organic framework material MOF-808;

[0056] S5. Add 20 g of metal-organic framework material MOF-808 to ethanol dissolved with 10 g of 1-ethyl-3-methylimidazolium chloride, stir and react at 50 °C for 10 h, and then centrifuge the product to obtain a composite filler; that is, the weight ratio of metal-organic framework material MOF-808 to 1-ethyl-3-methylimidazolium chloride is 2:1;

[0057] S6. Take 6 g of the composite filler obtained in Step S4 and disperse it evenly in 3 L of anhydrous N,N-dimethylformamide, then add 100 g of the polyimide solid obtained in Step S3 and stir evenly to obtain a casting solution. Pour the casting solution on a glass plate and heat it at 60 °C to evaporate the solvent to obtain a film, and then vacuum dry the film to obtain a polyimide desulfurization and decarbonization membrane, that is, the addition amount of the composite filler is 6% of the mass of the polyimide solid. Example 6

[0058] A preparation method of a polyimide desulfurization and decarbonization membrane, comprising the following preparation steps:

[0059] S1. Place 300 g of diamine in 6.5 L of anhydrous N,N-dimethylformamide, stir under a nitrogen atmosphere until completely dissolved, and then cool to below 0 °C. The diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of 7:1, that is, the content of m-phenylenediamine is 262.5 g and the content of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is 37.5 g;

[0060] S2. Add 1020 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to Step S1 and continue stirring until 4,4'-(hexafluoroisopropylidene)diphthalic anhydride is dissolved to obtain an amic acid solution, that is, the weight ratio of diamine to dianhydride is 1:3.4;

[0061] S3. Add 2.45 L of acetic anhydride and 0.9 L of pyridine to the amic acid solution and react for 24 h under a nitrogen atmosphere for imidization to obtain a polyimide solution. Slowly pour the polyimide solution into an excessive ethanol-water (volume ratio of ethanol to water is 1:1) for precipitation. After filtration, collect the fibrous polymer. Wash the polymer with ethanol and then vacuum dry it at 180 °C to obtain a polyimide solid;

[0062] S4. Add 20 g of metal-organic framework material MOF-808 and 200 g of amino acid to 500 g of water, stir and react at 70 °C for 20 h, filter to obtain a precipitate, wash the precipitate with water multiple times and then dry it to obtain an amino acid-modified metal-organic framework material MOF-808;

[0063] S5. Add 20 g of metal-organic framework material MOF-808 to ethanol dissolved with 10 g of 1-ethyl-3-methylimidazolium chloride, stir and react at 50 °C for 10 h, and then centrifuge the product to obtain a composite filler; that is, the weight ratio of metal-organic framework material MOF-808 to 1-ethyl-3-methylimidazolium chloride is 2:1;

[0064] S6. Take 6 g of the composite filler obtained in Step S4 and disperse it evenly in 3 L of anhydrous N,N-dimethylformamide, then add 100 g of the polyimide solid obtained in Step S3 and stir evenly to obtain a casting solution. Pour the casting solution on a glass plate and heat it at 60 °C to evaporate the solvent to obtain a film, and then vacuum dry the film to obtain a polyimide desulfurization and decarbonization membrane, that is, the addition amount of the composite filler is 6% of the mass of the polyimide solid. Example 7

[0065] A method for preparing a polyimide desulfurization and decarbonization membrane, which is different from Example 2 in that an equal amount of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate is used instead of 1-ethyl-3-methylimidazolium chloride, and the others are the same as in Example 2. Example 8

[0066] A preparation method of a polyimide desulfurization and decarbonization membrane, which is different from that of Example 2 in that 1-butyl-3-methylimidazolium tetrafluoroborate of equal amount is used to replace 1-ethyl-3-methylimidazolium chloride, and the others are the same as those in Example 2. Comparative Example 1

[0067] A preparation method of a polyimide desulfurization and decarbonization membrane, which is different from that of Example 2 in that in step S1, the diamine only uses 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and the others are the same as those in Example 2. Comparative Example 2

[0068] A preparation method of a polyimide desulfurization and decarbonization membrane, which is different from that of Example 2 in that in step S1, the diamine only uses m-phenylenediamine, and the others are the same as those in Example 2. Comparative Example 3

[0069] A preparation method of a polyimide desulfurization and decarbonization membrane, which is different from that of Example 2 in that in step S1, an equal amount of 2,5-dimethyl-1,4-phenylenediamine is used to replace m-phenylenediamine, and the others are the same as those in Example 2. Comparative Example 4

[0070] A preparation method of a polyimide desulfurization and decarbonization membrane, which is different from that of Example 2 in that in step S1, an equal amount of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl is used to replace 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and the others are the same as those in Example 2. Comparative Example 5

[0071] A preparation method of a polyimide desulfurization and decarbonization membrane, which is different from that of Example 2 in that the metal-organic framework material MOF-808 is not modified by imidazole-based ionic liquid, specifically:

[0072] S1. Place 300 g of diamine in 6.5 L of anhydrous N,N-dimethylformamide, stir under a nitrogen atmosphere until completely dissolved, and then cool to below 0 °C; the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of 7:1, that is, the content of m-phenylenediamine is 262.5 g and the content of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is 37.5 g;

[0073] S2. Add 1020 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to step S1 and continue to stir until 4,4'-(hexafluoroisopropylidene)diphthalic anhydride is dissolved to obtain an amic acid solution, that is, the weight ratio of diamine to dianhydride is 1:3.4;

[0074] S3. Add 2.45 L of acetic anhydride and 0.9 L of pyridine to the amic acid solution and react for 24 h under a nitrogen atmosphere for imidization to obtain a polyimide solution. Slowly pour the polyimide solution into an excessive amount of ethanol-water (the volume ratio of ethanol to water is 1:1) for precipitation. After filtration, collect the fibrous polymer. Wash the polymer with ethanol and then vacuum dry it at 180 °C to obtain polyimide solid;

[0075] S4. Disperse 6 g of the organic framework material MOF-808 evenly in 3 L of anhydrous N,N-dimethylformamide, then add 100 g of the polyimide solid obtained in step S3 and stir evenly to obtain a casting solution. Pour the casting solution onto a glass plate and heat it at 60 °C to evaporate the solvent to obtain a film. Then vacuum dry the film to obtain a polyimide desulfurization and decarbonization membrane, that is, the addition amount of the composite filler is 6% of the mass of the polyimide solid.

[0076] Performance test

[0077] Make the polyimide films obtained in the above examples and comparative examples into hollow fiber membranes for detecting the permeability coefficients and selectivities of carbon dioxide and sulfur dioxide. The detection is based on the standard GB / T 40260-2021 "Test Method for Gas Permeability of Polymer Membrane Materials". The detection results are shown in Table 1.

[0078] Table 1 Detection results of the permeation performance of the polyimide membrane

[0079] Project <![CDATA[SO 2 Permeability Coefficient / Barrer]]> <![CDATA[CO 2 Permeability coefficient / Barrer]]> <![CDATA[N 2 Permeability Coefficient / Barrer]]> <![CDATA[O 2 Permeability Coefficient / Barrer]]> Example 1 5715 4065 864 362 Example 2 5815 4306 915 365 Example 3 5759 4248 893 360 Example 4 6492 4762 958 372 Example 5 6668 4835 972 379 Example 6 6551 4796 965 375 Example 7 5462 3952 850 345 Example 8 5526 3891 842 351 Comparative Example 1 5131 3621 628 165 Comparative Example 2 5268 3654 589 197 Comparative Example 3 5362 3721 695 226 Comparative Example 4 5398 3765 654 206 Comparative Example 5 5426 3754 721 254

[0080] It can be seen from Table 1 that:

[0081] For the polyimide membranes obtained in Examples 1-3 of this application, the permeability coefficients of sulfur dioxide are all greater than 5700 Barrer, the permeability coefficients of carbon dioxide are all greater than 4000 Barrer, while the permeability coefficients of nitrogen and oxygen are much smaller than those of sulfur dioxide and carbon dioxide, indicating that the polyimide membranes obtained in this application have higher selectivity for sulfur dioxide and carbon dioxide and better permeation effect.

[0082] When comparing Examples 4-6 of this application with Example 2, after the metal-organic framework material MOF-808 is modified with amino acids, the permeability coefficients of sulfur dioxide and carbon dioxide of the polyimide membranes obtained in Examples 4-6 are much higher than those of sulfur dioxide and carbon dioxide in Example 2. The permeability coefficients of nitrogen and oxygen have little difference compared with those in Example 2, indicating that after the metal-organic framework material MOF-808 is modified with amino acids, the permeation performance of sulfur dioxide and carbon dioxide of the polyimide membrane can be effectively improved.

[0083] Compared with Example 2, in Examples 7 - 8, when 1 - ethyl - 3 - methylimidazolium trifluoromethanesulfonate or 1 - butyl - 3 - methylimidazolium tetrafluoroborate replaces 1 - ethyl - 3 - methylimidazolium chloride in this application, the sulfur dioxide permeability coefficient and carbon dioxide permeability coefficient of the polyimide film obtained in Examples 7 - 8 are both lower than those in Example 2. It can be seen that when the imidazole - based ionic liquid uses 1 - ethyl - 3 - methylimidazolium chloride, its combined use with the metal - organic framework material MOF - 808 can effectively improve the gas permeability of the polyimide film to sulfur dioxide and carbon dioxide.

[0084] Compared with Example 2, in Comparative Examples 1 - 2, when the diamine only uses 2,2 - bis(3 - amino - 4 - hydroxyphenyl)hexafluoropropane or m - phenylenediamine, the sulfur dioxide permeability coefficient and carbon dioxide permeability coefficient of the polyimide film obtained are both reduced. Moreover, it can be seen from Comparative Examples 3 - 4 that when the diamine is not composed of m - phenylenediamine and 2,2 - bis(3 - amino - 4 - hydroxyphenyl)hexafluoropropane, the sulfur dioxide and carbon dioxide permeability coefficients of the polyimide film obtained in Comparative Examples 3 - 4 are both reduced. Thus, it can be seen that when the diamine is composed of m - phenylenediamine and 2,2 - bis(3 - amino - 4 - hydroxyphenyl)hexafluoropropane, it can effectively improve the gas permeability of the polyimide film to sulfur dioxide and carbon dioxide.

[0085] Compared with Example 2, in Comparative Example 5, after the metal - organic framework material MOF - 808 is not modified with the imidazole - based ionic liquid, the sulfur dioxide and carbon dioxide permeability coefficients of the polyimide film obtained in Comparative Example 5 are both greatly reduced. From this, it can be explained that the preparation steps of this application and the mutual cooperation between the components can effectively improve the gas permeability of the polyimide film to carbon dioxide and sulfur dioxide.

[0086] The examples of this specific embodiment are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a polyimide desulfurization and decarbonization film, characterized in that: The method comprises the following preparation steps: S1. placing a diamine in an aprotic solvent, stirring under a nitrogen atmosphere until completely dissolved, and then cooling to below 10° C.; the diamine is composed of m-phenylenediamine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a weight ratio of (5-8):1; S2, adding dianhydride to step S1 and continuing stirring until the dianhydride is dissolved to obtain an amic acid solution; S3, adding a dehydrating agent and a catalyst to the amic acid solution for imidization to obtain a polyimide solution, filtering and washing the polyimide solution, and then vacuum drying to obtain a polyimide solid; S4, adding the metal organic framework material MOF-808 to ethanol dissolved with imidazole ionic liquid, stirring the reaction at 50-60°C for 10-15h, and then centrifuging the product to obtain a composite filler; the metal organic framework material MOF-808 is a metal organic framework material MOF-808 modified with amino acids, and the modification method is as follows: adding the metal organic framework material MOF-808 and amino acids to water, stirring the reaction at 60-70°C for 15-20h, filtering to obtain a precipitate, washing the precipitate with water for multiple times and then drying to obtain the amino acid-modified metal organic framework material MOF-808; the imidazole ionic liquid is 1-ethyl-3-methylimidazolium chloride; S5. Add the composite filler into the aprotic solvent and disperse it evenly, then add the polyimide solid obtained in step S3 and stir evenly to obtain a casting solution, pour the casting solution onto a glass plate and heat it at 50-60° C. to evaporate the solvent to obtain a film, and then dry the film to obtain a polyimide desulfurization and decarbonization film, wherein the addition amount of the composite filler is 5-10% of the mass of the polyimide solid.

2. The method for preparing a polyimide desulfurization and decarbonization film according to claim 1, characterized in that: The mass ratio of the metal organic framework material MOF-808 to the amino acid is 1:(5-10).

3. The method for preparing a polyimide desulfurization and decarbonization film according to claim 1, characterized in that: In the step S4, the weight ratio of the metal organic framework material MOF-808 to 1-ethyl-3-methylimidazolium chloride is (1-3):

1.

4. The method for preparing a polyimide desulfurization and decarbonization film according to claim 1, characterized in that: The weight ratio of the diamine to the dianhydride is 1:(3.2-3.5).

5. The method for preparing a polyimide desulfurization and decarbonization film according to claim 1, characterized in that: The aprotic solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide and N,N-dimethylacetamide.

6. The method for preparing a polyimide desulfurization and decarbonization film according to claim 1, characterized in that: The dianhydride is 4,4'-(hexafluoroisopropylene) diphthalic anhydride.

7. The method for preparing a polyimide desulfurization and decarbonization film according to claim 1, characterized in that: The dehydrating agent is one of acetic anhydride and phthalic anhydride, and the catalyst is one of triethylamine and pyridine.

8. A polyimide desulfurization and decarbonization film obtained by the method for preparing a polyimide desulfurization and decarbonization film according to any one of claims 1 to 7.