MOF-808-CA-Me mixed matrix gas separation membrane as well as preparation method and application thereof

Abstract

The invention discloses an MOF-808-CA-Me mixed matrix gas separation membrane as well as a preparation method and application of the MOF-808-CA-Me mixed matrix gas separation membrane. The preparation method comprises the following steps: preparing MOF-808 (Zr) by utilizing a solvothermal method, reacting with citric acid to graft carboxyl to obtain MOF-808-CA, reacting with melamine to obtain MOF-808-CA-Me, uniformly mixing with a Pebax1657 membrane casting solution, pouring on a base membrane, and obtaining a target membrane material by utilizing a solvent evaporation method. According to the method, an amido bond is formed through a reaction between-COOH of citric acid and-NH2 of melamine, and MOF-808-CA-Me is stabilized in the adsorption and desorption processes of carbon dioxide; the preparation process is simple, convenient and efficient, the cost is low, and the prepared MOF-808-CA-Me mixed matrix gas separation membrane has good selectivity to CO2 / CH4.

Description

Technical Field

[0001] The present invention relates to a highly efficient, simple and excellent-performance MOF-808-CA-Me mixed matrix gas separation membrane, a preparation method thereof and an application thereof, belonging to the technical field of gas separation. Background Art

[0002] As a new, environmentally friendly and attractive separation process, membrane separation technology has broad application prospects in gas, water treatment, solvent purification and other aspects. There is a trade-off between permeability and selectivity in the separation performance of polymer gas membranes. At present, several strategies are adopted to improve the effectiveness of polymer membranes in gas separation applications, including synthesizing mixed matrix membranes, blending polymers, and functionalizing polymers. Mixed matrix membranes (MMMs) can effectively combine the best performance of polymer organic materials with the excellent transport performance of certain filler materials to create membranes with superior permeability and selectivity for gas separation applications, exceeding the so-called Robeson upper limit.

[0003] Generally speaking, incorporating inorganic nanofillers into the polymer structure can change the permeability of polymer chains by achieving molecular sieving, changing solubility, or generating a barrier effect or disorder. However, the fabrication of MMMs faces significant challenges in achieving proper dispersion of inorganic nanofillers in the polymer structure, and the presence of high-concentration fillers reduces gas separation performance and the mechanical stability of the membrane.

[0004] As a new type of porous crystalline material, metal-organic frameworks exhibit unique charm and broad application prospects. Such materials are formed by self-assembly of metal ions or metal clusters with organic ligands, and their structural characteristics lie in a highly ordered pore structure and flexible chemical properties that can be regulated. The selection range of ligands and metal nodes of MOF is quite wide, which makes it possible to construct a rich variety of structures. The diversity of coordination modes enables MOF to form various unique topological structures to meet different application requirements.

[0005] Compared with traditional materials, MOF membranes have a more highly ordered pore structure, which makes them perform excellently in molecular adsorption and separation. By precisely regulating the pore size and chemical functional groups, MOF membranes can achieve highly selective adsorption and separation of molecules. The intercrystalline symbiosis of MOF enables them to form a continuous and dense membrane layer, which not only has excellent mechanical properties but also can maintain a high porosity and chemical stability. Therefore, the mixed matrix membrane prepared by incorporating MOF into a polymer can have good selectivity and permeability, breaking through the Robeson upper limit. In addition, the selectivity of the gas separation membrane can be improved by introducing amino groups with good adsorption for CO 2 onto the MOF material. Summary of the Invention

[0006] The object of the present invention is to provide a MOF-808-CA-Me mixed matrix gas separation membrane, a preparation method thereof and an application thereof.

[0007] In the present invention, a MOF-808(Zr) material is prepared by a solvothermal method. After grafting carboxyl groups by reacting with citric acid, a MOF-808-CA material is obtained. Then, the MOF-808-CA is reacted with melamine to obtain a MOF-808-CA-Me material. After being uniformly mixed with a prepared Pebax 1657 casting solution, it is cast on a substrate membrane, and a MOF-808-CA-Me mixed matrix membrane is obtained by a solvent evaporation method. This method forms amide bonds through the reaction between the -COOH of citric acid and the -NH 2 between them, and the MOF-808-CA-Me is stabilized during the adsorption and desorption processes of carbon dioxide.

[0008] The preparation process of the present invention is simple, efficient and cost-saving. Amino groups are successfully grafted onto MOF-808, increasing the adsorption of carbon dioxide. Moreover, the interaction between Pebax and MOF creates more paths for carbon dioxide to pass through the membrane. Therefore, the prepared MOF-808-CA-Me mixed matrix gas separation membrane has good selectivity for CO 2 / CH 4 .

[0009] The technical solution of the present invention is as follows:

[0010] A preparation method of a MOF-808-CA-Me mixed matrix gas separation membrane, comprising:

[0011] (1) Preparation of acidified MOF-808(Zr)

[0012] Trimellitic acid and zirconium oxychloride are mixed, and a mixed solution of DMF and formic acid is added for dissolution. Stirring reaction is carried out for 1 to 3 days under nitrogen protection at 100 to 150 °C, and then centrifugation, washing and vacuum drying are carried out to obtain MOF-808(Zr); the obtained MOF-808(Zr) is added to a hydrochloric acid solution, and stirring reaction is carried out at 60 to 120 °C for 6 to 24 h, and then centrifugation, washing and vacuum drying are carried out to obtain acidified MOF-808(Zr);

[0013] The mass ratio of trimellitic acid to zirconium oxychloride is 1:3.5 to 8;

[0014] In the mixed solution of DMF and formic acid, the volume ratio of DMF to formic acid is 1:1 to 10;

[0015] The volume-mass ratio of the mixed solution of DMF and formic acid to zirconium oxychloride is 25 to 150:1, mL / g;

[0016] The concentration of the hydrochloric acid solution is 1 - 5 mol / L;

[0017] The volume - mass ratio of the hydrochloric acid solution to MOF - 808(Zr) is 25 - 125:1, mL / g;

[0018] (2) Preparation of MOF - 808 - CA - Me

[0019] Add the acidified MOF - 808(Zr) obtained in step (1) to the ethanol solution of citric acid, stir and react at 30 - 120 °C for 6 - 24 h, wash and dry to obtain MOF - 808 - CA; add MOF - 808 - CA to the ethanol solution of melamine, stir and react at 30 - 120 °C for 12 - 24 h, wash and dry to obtain MOF - 808 - CA - Me;

[0020] The concentration of the ethanol solution of citric acid is 0.02 - 0.05 g / mL;

[0021] The concentration of the ethanol solution of melamine is 2.5 - 12.5 mmol / L;

[0022] (3) Preparation of MOF - 808 - CA - Me mixed - matrix gas separation membrane

[0023] Add Pebax1657 to the mixed solution of ethanol and water, stir at 60 - 80 °C for 2 - 4 h, then add the MOF - 808 - CA - Me obtained in step (2), stir at room temperature for 6 - 24 h to obtain a casting solution; cast the casting solution on a PVDF substrate membrane, let it stand at room temperature for 12 - 24 h to form a membrane, and finally place it at 60 - 80 °C for thermal cross - linking for 6 - 24 h to obtain the MOF - 808 - CA - Me mixed - matrix gas separation membrane;

[0024] In the mixed solution of ethanol and water, the volume ratio of ethanol to water is 2 - 3:1;

[0025] The mass ratio of Pebax1657 to the mixed solution of ethanol and water is 1:15 - 65;

[0026] The mass ratio of Pebax1657 to MOF - 808 - CA - Me is 5 - 30:1.

[0027] The present invention relates to the MOF - 808 - CA - Me mixed - matrix gas separation membrane prepared by the above - mentioned preparation method.

[0028] The MOF - 808 - CA - Me mixed - matrix gas separation membrane of the present invention can be used for the efficient separation of mixed gases, especially for the separation of CO 2 / CH 4 separation.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] Citric acid is used as an intermediate chain to achieve the successful grafting of melamine onto MOF-808, thereby successfully grafting amino groups onto MOF-808. The addition of amino groups effectively enhances the gas separation selectivity. The active functional groups in the MOF-808 ligand, especially the zirconium-based carboxylic acid groups, make the MOF particles have a stronger attraction to carbon dioxide and have good compatibility with the Pebax polymer. The interaction between the polymer and the filler creates more paths for carbon dioxide to pass through the membrane, ultimately achieving better selectivity for separating carbon dioxide from other gases. The PA chain in the Pebax polymer can provide film-forming ability and mechanical strength, making the membrane material have good mechanical stability under higher pressures. Detailed implementation manners

[0031] The present invention will be further described below through specific embodiments, but the protection scope of the present invention is not limited thereto.

[0032] In the following embodiments,

[0033] Pebax 1657 is purchased from Arkema.

[0034] The PVDF bottom membrane is purchased from Delv New Materials Technology Co., Ltd., with a diameter of 50 mm and a pore size of 0.22 μm.

[0035] Example 1

[0036] I. Weigh 1 g of trimesic acid and 3.5 g of zirconium oxychloride and add them to a single-necked flask. Then add a mixed solution of 200 ml of DMF and 200 ml of formic acid to dissolve. Under the protection of nitrogen, place it in an oil bath at 130 °C and stir for 2 days. Centrifuge, wash with DMF and ethanol, and then dry in vacuum to obtain MOF-808(Zr). Weigh 1 g of the obtained MOF-808(Zr) and add it to 100 ml of 1 mol / L hydrochloric acid solution. Stir and react in an oil bath at 100 °C for 8 h. Centrifuge with deionized water, DMF, and ethanol, and then dry in vacuum to obtain acidified MOF-808(Zr).

[0037] II. Weigh 1.86 g of citric acid and dissolve it in 50 ml of ethanol. Weigh 0.1 g of the acidified MOF-808 obtained in step I and add it to the citric acid solution. Stir and react the mixture in an oil bath at 60 °C for 24 h. Wash with ethanol multiple times and dry to finally obtain MOF-808-CA. Weigh 0.3 mmol of melamine and dissolve it in 40 ml of ethanol. Take 0.1 g of the dried MOF-808-CA, stir and react the mixture in an oil bath at 60 °C for 24 h, wash with ethanol multiple times, and dry to finally obtain MOF-808-CA-Me.

[0038] III. Weigh 0.928 g of Pebax 1657 and add it to a mixed solution of 27 ml of ethanol and 9 ml of water. Stir and react in an 80 °C oil bath for 3 h. After the reaction is complete, add 0.047 g of MOF-808-CA-Me from Step II, and mix and stir at room temperature for 6 h. Take 1 ml of the obtained casting solution and cast it on a PVDF substrate film. Let it stand at room temperature for 24 h to form a film. Finally, place it in a 60 °C oven for thermal cross-linking for 12 h to obtain a MOF-808-CA-Me mixed matrix gas separation membrane.

[0039] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was used to test and analyze the membrane separation performance of the mixed gas CO 2 / CH 4 (30 / 70 vol%). The MOF-808-CA-Me mixed matrix gas separation membrane was tested under the conditions of 25 °C and a feed pressure of 1 bar. The Wicke-Kallenbach technique was used for the test, and a gas chromatograph (GC 1690) was used to detect the concentration. According to the results, the CO 2 permeation flux of the membrane was 4.7×10 -7 mol m -2 s -1 Pa -1 , and the CO 2 / CH 4 selectivity was 104.5.

[0040] Example 2

[0041] Step 1 of this example is the same as Step 1 in Example 1.

[0042] In Step 2, weigh 1.86 g of citric acid and dissolve it in 50 ml of ethanol. Weigh 0.1 g of the acidified MOF-808 obtained in Step 1 and add it to the citric acid solution. Stir and react the mixture in a 75 °C oil bath for 24 h. Wash it with ethanol multiple times and dry it to finally obtain MOF-808-CA. Weigh 0.1 mmol of melamine and dissolve it in 40 ml of ethanol. Take 0.1 g of the dried MOF-808-CA, stir and react the mixture in a 75 °C oil bath for 24 h, wash it with ethanol multiple times, and dry it to finally obtain MOF-808-CA-Me.

[0043] III. Weigh 0.928 g of Pebax 1657 and add it to a mixed solution of 27 ml of ethanol and 9 ml of water. Stir and react in an 80 °C oil bath for 3 h. After the reaction is complete, add 0.047 g of MOF-808-CA-Me from Step II, and mix and stir at room temperature for 6 h. Take 1 ml of the obtained casting solution and cast it on a PVDF substrate film. Let it stand at room temperature for 24 h to form a film. Finally, place it in a 60 °C oven for thermal cross-linking for 12 h to obtain a MOF-808-CA-Me mixed matrix gas separation membrane.

[0044] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was used to test and analyze the membrane separation performance of the mixed gas CO 2 / CH 4 (30 / 70 vol%). The MOF-808-CA-Me mixed matrix gas separation membrane was tested under the conditions of 25 °C and a feed pressure of 1 bar. The Wicke-Kallenbach technique was used for the test, and a gas chromatograph (GC 1690) was used to detect the concentration. According to the results, the CO 2 permeation flux of the membrane was 2.4×10 -7 mol m -2 s -1 Pa -1 , and the CO 2 / CH 4 selectivity was 83.6.

[0045] Example 3

[0046] The first step of this example is the same as the first step in Example 1.

[0047] Weigh 1.86 g of citric acid and dissolve it in 50 ml of ethanol. Weigh 0.1 g of the acidified MOF-808 obtained in the first step and add it to the citric acid solution. Stir and react the mixture in an 80 °C oil bath for 24 h. Wash it with ethanol multiple times and dry it to finally obtain MOF-808-CA. Weigh 0.5 mmol of melamine and dissolve it in 40 ml of ethanol. Take 0.1 g of the dried MOF-808-CA, and stir and react the mixture in an 80 °C oil bath for 24 h. Wash it with ethanol multiple times and dry it to finally obtain MOF-808-CA-Me.

[0048] III. Weigh 0.928 g of Pebax 1657 and add it to a mixed solution of 27 ml of ethanol and 9 ml of water. Stir and react in an oil bath at 80 °C for 3 h. After the reaction is complete, add 0.047 g of MOF-808-CA-Me from Step II, and mix and stir at room temperature for 6 h. Take 1 ml of the obtained casting solution and cast it on a PVDF substrate film. Let it stand at room temperature for 24 h to form a film. Finally, place it in an oven at 60 °C for thermal cross-linking for 12 h to obtain a MOF-808-CA-Me mixed matrix gas separation membrane.

[0049] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was used for membrane separation performance test and analysis of the mixed gas CO 2 / CH 4 (30 / 70 vol%). The MOF-808-CA-Me mixed matrix gas separation membrane was tested under the conditions of 25 °C and a feed pressure of 1 bar. The Wicke-Kallenbach technique was used for the test, and the concentration was detected by gas chromatography (GC 1690). According to the results, the CO 2 permeation flux of the membrane was 5.1×10 -7 mol m -2 s -1 Pa -1 , and the CO 2 / CH 4 selectivity was 116.3.

[0050] Example 4

[0051] I. Weigh 0.35 g of trimesic acid and 1.7 g of zirconium oxychloride and add them to a single-necked flask. Then add a mixed solution of 75 ml of DMF and 75 ml of formic acid to dissolve. Under the protection of nitrogen, place it in an oil bath at 120 °C and stir and react for 3 days. Centrifuge, wash with DMF and ethanol, and then dry in vacuum to obtain MOF-808(Zr). Weigh 1 g of the obtained MOF-808(Zr) and add it to 100 ml of 1 mol / L hydrochloric acid solution. Stir and react in an oil bath at 90 °C for 12 h. Centrifuge with deionized water, DMF, and ethanol, and then dry in vacuum to obtain acidified MOF-808(Zr).

[0052] II. Weigh 1.86 g of citric acid and dissolve it in 50 ml of ethanol. Weigh 0.1 g of the acidified MOF-808 obtained in Step I and add it to the citric acid solution. Stir and react the mixture in an oil bath at 70 °C for 24 h. Wash with ethanol multiple times and dry to finally obtain MOF-808-CA. Weigh 0.3 mmol of melamine and dissolve it in 40 ml of ethanol. Take 0.1 g of the dried MOF-808-CA, and stir and react the mixture in an oil bath at 70 °C for 24 h. Wash with ethanol multiple times and dry to finally obtain MOF-808-CA-Me.

[0053] III. Weigh 0.769 g of Pebax 1657 and add it to a mixed solution of 27 ml of ethanol and 9 ml of water. Stir and react in an oil bath at 80 °C for 3 h. After the reaction is complete, add 0.028 g of MOF-808-CA-Me from Step II, and mix and stir at room temperature for 6 h. Take 1 ml of the obtained casting solution and cast it on a PVDF substrate film. Let it stand at room temperature for 24 h to form a film. Finally, place it in an oven at 60 °C for thermal crosslinking for 12 h to obtain a MOF-808-CA-Me mixed matrix gas separation membrane.

[0054] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was used for the membrane separation performance test and analysis of the mixed gas CO 2 / CH 4 (30 / 70 vol%). The MOF-808-CA-Me mixed matrix gas separation membrane was tested under the conditions of 25 °C and a feed pressure of 1 bar. The Wicke-Kallenbach technique was used for the test, and a gas chromatograph (GC 1690) was used to detect the concentration. According to the results, the CO 2 permeation flux of the membrane was 3.3×10 -7 mol m -2 s -1 Pa -1 , and the CO 2 / CH 4 selectivity was 95.3.

[0055] Example 5

[0056] I. Weigh 0.7 g of trimesic acid and 3.3 g of zirconium oxychloride and add them to a single-neck flask. Add 150 ml of a mixed solution of DMF and 150 ml of formic acid to dissolve. Under the protection of nitrogen, place it in an oil bath at 140 °C and stir and react for 3 days. Centrifuge, wash with DMF and ethanol, and then dry in vacuo to obtain MOF-808(Zr). Weigh 1 g of the obtained MOF-808(Zr) and add it to 100 ml of 1 mol / L hydrochloric acid solution. Stir and react in an oil bath at 90 °C for 12 h. Centrifuge with deionized water, DMF, and ethanol, and then dry in vacuo to obtain acidified MOF-808(Zr).

[0057] II. Weigh 1.86 g of citric acid and dissolve it in 50 ml of ethanol. Weigh 0.1 g of the acidified MOF-808 obtained in Step I and add it to the citric acid solution. Stir and react the mixture in an oil bath at 100 °C for 24 h. Wash it with ethanol multiple times and dry it to finally obtain MOF-808-CA. Weigh 0.5 mmol of melamine and dissolve it in 40 ml of ethanol. Take 0.1 g of the dried MOF-808-CA and stir and react the mixture in an oil bath at 100 °C for 24 h. Wash it with ethanol multiple times and dry it to finally obtain MOF-808-CA-Me.

[0058] III. Weigh 0.769 g of Pebax1657 and add it to a mixed solution of 27 ml of ethanol and 9 ml of water. Stir and react it in an oil bath at 80 °C for 3 h. After the reaction is complete, add 0.093 g of the MOF-808-CA-Me obtained in Step II and mix and stir it at room temperature for 6 h. Take 1 ml of the obtained casting solution and cast it on a PVDF substrate film. Let it stand at room temperature for 24 h to form a film, and finally put it in an oven at 60 °C for thermal crosslinking for 12 h to finally obtain a MOF-808-CA-Me mixed matrix gas separation membrane.

[0059] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was used to perform membrane separation performance test and analysis on the mixed gas CO 2 / CH 4 (30 / 70 vol%). The MOF-808-CA-Me mixed matrix gas separation membrane was tested under the conditions of 25 °C and a feed pressure of 1 bar. The Wicke-Kallenbach technique was used for the test, and a gas chromatograph (GC 1690) was used to detect the concentration. According to the results, the CO 2 / CH 4 permeation flux of the membrane was 5.9×10 -7 mol m -2 s -1 Pa -1 ,and the CO 2 / CH 4 selectivity was 122.8.

Claims

1. A method for preparing a MOF-808-CA-Me mixed matrix gas separation membrane, characterized in that: The preparation method comprises: (1) Preparation of acidified MOF-808(Zr) The trimesic acid and zirconium oxychloride are mixed, and a mixed solution of DMF and formic acid is added to dissolve, and the mixture is stirred and reacted at 100-150° C. under nitrogen protection for 1-3 days, and then centrifuged, washed, and vacuum dried to obtain MOF-808 (Zr); the obtained MOF-808 (Zr) is added to a hydrochloric acid solution, stirred and reacted at 60-120° C. for 6-24 hours, and then centrifuged, washed, and vacuum dried to obtain an acidified MOF-808 (Zr); (2) Preparation of MOF-808-CA-Me The acidified MOF-808(Zr) obtained in step (1) is added to an ethanol solution of citric acid, stirred at 30 to 120° C. for 6 to 24 hours, washed and dried to obtain MOF-808-CA; MOF-808-CA is added to an ethanol solution of melamine, stirred at 30 to 120° C. for 12 to 24 hours, washed and dried to obtain MOF-808-CA-Me; (3) Preparation of MOF-808-CA-Me mixed matrix gas separation membrane Pebax1657 is added to a mixed solution of ethanol and water, and stirred at 60-80°C for 2-4 hours. The MOF-808-CA-Me obtained in step (2) is then added, and stirred at room temperature for 6-24 hours to obtain a casting solution. The casting solution is cast on a PVDF substrate, and allowed to stand at room temperature for 12-24 hours to form a membrane. Finally, the mixture is placed at 60-80°C for thermal crosslinking for 6-24 hours to obtain a MOF-808-CA-Me mixed matrix gas separation membrane.

2. The method for preparing the MOF-808-CA-Me mixed matrix gas separation membrane according to claim 1, characterized in that: In step (1), the mass ratio of trimesic acid to zirconium oxychloride is 1:3.5-8.

3. The method for preparing the MOF-808-CA-Me mixed matrix gas separation membrane according to claim 1, characterized in that: In step (1), in the mixed solution of DMF and formic acid, the volume ratio of DMF to formic acid is 1:1-10; the volume mass ratio of the mixed solution of DMF and formic acid to zirconium oxychloride is 25-150:1, mL / g.

4. The method for preparing the MOF-808-CA-Me mixed matrix gas separation membrane according to claim 1, characterized in that: In step (1), the concentration of the hydrochloric acid solution is 1-5 mol / L; the volume mass ratio of the hydrochloric acid solution to MOF-808 (Zr) is 25-125:1, mL / g.

5. The method for preparing the MOF-808-CA-Me mixed matrix gas separation membrane according to claim 1, characterized in that: In step (2), the concentration of the ethanol solution of citric acid is 0.02-0.05 g / mL; the concentration of the ethanol solution of melamine is 2.5-12.5 mmol / L.

6. The method for preparing the MOF-808-CA-Me mixed matrix gas separation membrane according to claim 1, characterized in that: In step (3), in the mixed solution of ethanol and water, the volume ratio of ethanol to water is 2-3:1; and the mass ratio of Pebax1657 to ethanol and water is 1:15-65.

7. The method for preparing the MOF-808-CA-Me mixed matrix gas separation membrane according to claim 1, characterized in that: In step (3), the mass ratio of Pebax1657 and MOF-808-CA-Me is 5 to 30:

1.

8. The MOF-808-CA-Me mixed matrix gas separation membrane prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the MOF-808-CA-Me mixed matrix gas separation membrane as claimed in claim 8 in mixed gas separation.

10. The use according to claim 9, characterized in that The mixed gas is CO2 / CH4.