A MOF-808-CA-Me mixed matrix gas separation membrane and a preparation method and application thereof

Abstract

The application discloses a MOF-808-CA-Me mixed matrix gas separation membrane and a preparation method and application thereof; the MOF-808 (Zr) is prepared by using a solvothermal method, carboxyl is grafted after reaction with citric acid to obtain MOF-808-CA, and then reaction with melamine to obtain MOF-808-CA-Me; after being uniformly mixed with a Pebax1657 casting solution, the MOF-808-CA-Me is poured on a base film to obtain a target membrane material by a solvent evaporation method; the method forms an amide bond between -COOH of citric acid and -NH2 of melamine, and the MOF-808-CA-Me is stable in the adsorption and desorption process of carbon dioxide; the preparation process is simple, efficient and low in cost, and the prepared MOF-808-CA-Me mixed matrix gas separation membrane has good selectivity for CO2 / CH4.

Description

TECHNICAL FIELD

[0001] The application relates to a high-efficiency simple and excellent-performance MOF-808-CA-Me mixed matrix gas separation membrane and a preparation method and application thereof, and belongs to the technical field of gas separation. BACKGROUND

[0002] Membrane separation technology, as a new, environmentally friendly and attractive separation process, has a wide application prospect in gas, water treatment, solvent purification and other aspects. The separation performance of polymer gas membranes is a trade-off between permeability and selectivity. At present, several strategies are used to improve the effectiveness of polymer membranes in gas separation applications, including the synthesis of mixed matrix membranes, the blending of polymers, and the functionalization of polymers. Mixed matrix membranes (MMMs) can effectively combine the best performance of organic polymer materials with the excellent transport performance of certain filler materials, creating membranes with superior permeability and selectivity for gas separation applications, exceeding the so-called Robseon upper limit.

[0003] Generally, the incorporation of inorganic nanofillers into polymer structures can change the permeability of polymer chains by achieving molecular sieving, changing solubility, or creating a barrier effect or disorder. However, the manufacture of MMMs faces major challenges in achieving proper dispersibility of inorganic nanofillers in polymer structures, and the presence of high concentrations of fillers reduces the gas separation performance and mechanical stability of the membranes.

[0004] Metal-organic frameworks (MOFs) are a new type of porous crystalline material that exhibits unique charm and broad application prospects. This type of material is formed by self-assembly of metal ions or metal clusters with organic ligands, and its structural characteristics lie in highly ordered pore structure and flexible controllable chemical properties. The selection range of MOF ligands and metal nodes is quite extensive, which provides the possibility for building a wide variety of structures. The diversity of coordination modes enables MOFs 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 excellent in molecular adsorption and separation. By precisely controlling the pore size and chemical functional groups, MOF membranes can achieve highly selective adsorption and separation of molecules. The intercrystalline symbiosis of MOFs enables them to form continuous and dense membrane layers, which not only have excellent mechanical properties but also maintain high porosity and chemical stability. Therefore, mixed matrix membranes prepared by incorporating MOFs into polymers can have good selectivity and permeability, breaking through the Robseon upper limit. In addition, amino groups with good CO2 adsorption can be introduced into MOF materials to improve the selectivity of gas separation membranes. SUMMARY

[0006] The application aims to provide a MOF-808-CA-Me mixed matrix gas separation membrane and a preparation method and application thereof.

[0007] The application utilizes a solvothermal method to prepare MOF-808(Zr) material, grafts carboxyl groups after reaction with citric acid to obtain MOF-808-CA material, and then reacts the MOF-808-CA with melamine to obtain MOF-808-CA-Me material, uniformly mixes the MOF-808-CA-Me material with prepared Pebax 1657 casting solution, pours on a bottom film, and obtains the MOF-808-CA-Me mixed matrix membrane through a solvent evaporation method. The method forms an amide bond between -COOH of citric acid and -NH2 of melamine, and the MOF-808-CA-Me is stable in the adsorption and desorption process of carbon dioxide.

[0008] The application has the advantages of simple and efficient preparation process, saving production cost, successful grafting of amino groups on MOF-808, increased adsorption of carbon dioxide, and more paths for carbon dioxide to pass through the membrane due to the interaction between Pebax and MOF, so that the prepared MOF-808-CA-Me mixed matrix gas separation membrane has good selectivity for CO2 / CH4.

[0009] The technical scheme of the application is as follows:

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

[0011] (1) preparing acidized MOF-808(Zr)

[0012] Mixing trimesic acid and zirconium oxychloride, dissolving in a mixed solution of DMF and formic acid, stirring and reacting under nitrogen protection at 100-150 DEG C for 1-3 days, then centrifuging, washing, and vacuum drying to obtain MOF-808(Zr); adding the obtained MOF-808(Zr) into a hydrochloric acid solution, stirring and reacting at 60-120 DEG C for 6-24 h, then centrifuging, washing, and vacuum drying to obtain acidized MOF-808(Zr);

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

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

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

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

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

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

[0019] The acidified MOF-808(Zr) obtained in step (1) is added to an ethanol solution of citric acid, stirred at 30-120℃ for 6-24h, washed, dried, and MOF-808-CA is obtained; the MOF-808-CA is added to an ethanol solution of melamine, stirred at 30-120℃ for 12-24h, washed, dried, and MOF-808-CA-Me is obtained;

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

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

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

[0023] Pebax1657 is added to a mixed solution of ethanol and water, stirred at 60-80℃ for 2-4h, then the MOF-808-CA-Me obtained in step (2) is added, stirred at room temperature for 6-24h, and a casting solution is obtained; the casting solution is cast on a PVDF base film, left at room temperature for 12-24h to form a film, and finally heated at 60-80℃ for 6-24h to perform thermal crosslinking, and a MOF-808-CA-Me mixed matrix gas separation membrane is obtained;

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

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

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

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

[0028] The MOF-808-CA-Me mixed matrix gas separation membrane can be used for efficient separation of mixed gas, especially for separation of CO2 / CH4.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] The successful grafting of melamine on MOF-808 was achieved using citric acid as the intermediate chain, thus successfully grafting amino groups on 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 carboxylate groups, make the MOF particles more attractive to carbon dioxide and have good fitting with the Pebax polymer. The interaction between the polymer and the filler material creates more paths for carbon dioxide to pass through the membrane, ultimately achieving better selectivity for separating carbon dioxide from other gases. The PA chains in the Pebax polymer can provide film-forming ability and mechanical strength, so that the membrane material has good mechanical stability at higher pressures. DETAILED DESCRIPTION

[0031] The application will be further described by specific examples, but the scope of protection of the application is not limited to this.

[0032] In the following examples,

[0033] Pebax 1657 was purchased from Arkema.

[0034] The PVDF base membrane was purchased from Deheng New Material Technology Co., Ltd., with a diameter of 50 mm and a pore size of 0.22 um.

[0035] Example 1

[0036] I. 1 g of trimesic acid and 3.5 g of zirconium oxychloride were weighed into a single-necked flask and dissolved in a mixed solution of 200 ml of DMF and 200 ml of formic acid. Under the protection of nitrogen, it was placed in a 130°C oil bath and stirred for 2 days. After centrifugation, washing with DMF and ethanol, and vacuum drying, MOF-808(Zr) was obtained. 1 g of the obtained MOF-808(Zr) was weighed into 100 ml of 1 mol / L hydrochloric acid solution and stirred in a 100°C oil bath for 8 h. After centrifugation with deionized water, DMF, and ethanol, the acidified MOF-808(Zr) was vacuum dried.

[0037] II. 1.86 g of citric acid was dissolved in 50 ml of ethanol, and 0.1 g of the acidified MOF-808 obtained in step I was added to the citric acid solution. The mixture was stirred in a 60°C oil bath for 24 h. After washing with ethanol several times, drying, and finally obtaining MOF-808-CA. 0.3 mmol of melamine was dissolved in 40 ml of ethanol, and 0.1 g of dried MOF-808-CA was taken. The mixture was stirred in a 60°C oil bath for 24 h. After washing with ethanol several times, drying, and finally obtaining MOF-808-CA-Me.

[0038] Step 3: 0.928 g of Pebax1657 was added into 27 ml of ethanol and 9 ml of water mixed solution, stirred in 80 °C oil bath for 3 h, after the reaction was completed, 0.047 g of MOF-808-CA-Me of step 2 was added, mixed and stirred at room temperature for 6 h, 1 ml of the obtained casting solution was cast on the PVDF bottom film, and placed at room temperature for 24 h to form a film, and finally placed in a 60 °C oven for heat crosslinking for 12 h, and finally a MOF-808-CA-Me mixed matrix gas separation membrane was obtained.

[0039] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was tested for membrane separation performance analysis on mixed gas CO2 / CH4(30 / 70 vol%). The test was carried out at 25 °C and a feed pressure of 1 bar using Wicke-Kallenbach technology, and the concentration was detected by gas chromatography (GC 1690). According to the results, the CO2permeation flux of the membrane was 4.7*10 -7 mol m -2 s -1 Pa -1 , and the CO2 / CH4selectivity was 104.5.

[0040] Example 2

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

[0042] In step 2, 1.86 g of citric acid was dissolved in 50 ml of ethanol, and 0.1 g of the acidified MOF-808 obtained in step 1 was added to the citric acid solution. The mixture was stirred and reacted in a 75 °C oil bath for 24 h. After washing with ethanol for several times, drying was finally obtained. MOF-808-CA was obtained. 0.1 mmol of melamine was dissolved in 40 ml of ethanol, and 0.1 g of dried MOF-808-CA was taken. The mixture was stirred and reacted in a 75 °C oil bath for 24 h, washed with ethanol for several times, and dried to finally obtain MOF-808-CA-Me.

[0043] Step 3: 0.928 g of Pebax1657 was added into 27 ml of ethanol and 9 ml of water mixed solution, stirred in 80 °C oil bath for 3 h, after the reaction was completed, 0.047 g of MOF-808-CA-Me of step 2 was added, mixed and stirred at room temperature for 6 h, 1 ml of the obtained casting solution was cast on the PVDF bottom film, and placed at room temperature for 24 h to form a film, and finally placed in a 60 °C oven for heat crosslinking for 12 h, and finally a MOF-808-CA-Me mixed matrix gas separation membrane was obtained.

[0044] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was subjected to membrane separation performance test analysis on mixed gas CO2 / CH4(30 / 70 vol%). The MOF-808-CA-Me mixed matrix gas separation membrane was tested under the condition of 25°C and 1 bar of feed pressure by using Wicke-Kallenbach technology, and the concentration was detected by gas chromatography (GC 1690). According to the results, the CO2 permeation flux of the membrane was 2.4*10 -7 mol m -2 s -1 Pa -1 , and the CO2 / CH4 selectivity was 83.6.

[0045] Example 3

[0046] Step one of this example is the same as step one in example 1.

[0047] 1.86 g of citric acid was weighed and dissolved in 50 ml of ethanol, 0.1 g of the acidified MOF-808 obtained in step one was added to the citric acid solution, and the mixture was stirred in an 80°C oil bath for 24 h. After washing with ethanol for several times, MOF-808-CA was obtained after drying. 0.5 mmol of melamine was weighed and dissolved in 40 ml of ethanol, 0.1 g of dried MOF-808-CA was taken, and the mixture was stirred in an 80°C oil bath for 24 h. After washing with ethanol for several times, MOF-808-CA-Me was obtained after drying.

[0048] III. 0.928 g of Pebax1657 was weighed and added to a mixture of 27 ml of ethanol and 9 ml of water, and the mixture was stirred in an 80°C oil bath for 3 h. After the reaction was completed, 0.047 g of MOF-808-CA-Me of step two was added, and the mixture was stirred at room temperature for 6 h. 1 ml of the obtained casting solution was cast on a PVDF base film, and the film was formed after standing at room temperature for 24 h. Finally, the film was placed in a 60°C oven for heat crosslinking for 12 h, and finally a MOF-808-CA-Me mixed matrix gas separation membrane was obtained.

[0049] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was subjected to membrane separation performance test analysis on mixed gas CO2 / CH4(30 / 70 vol%). The MOF-808-CA-Me mixed matrix gas separation membrane was tested under the condition of 25°C and 1 bar of feed pressure by using Wicke-Kallenbach technology, and the concentration was detected by gas chromatography (GC 1690). According to the results, the CO2 permeation flux of the membrane was 2.4*10 -7 mol m -2 s -1 Pa -1, CO2 / CH4 selectivity is 95.3.

[0050] Example 4

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

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

[0053] III. Take 0.769 g of Pebax1657 into a mixed solution of 27 ml of ethanol and 9 ml of water, and stir in an oil bath at 80°C for 3 h. After the reaction is completed, add 0.028 g of MOF-808-CA-Me of step II, and stir at room temperature for 6 h. Take 1 ml of the obtained casting solution and cast on a PVDF base film, and stand at room temperature for 24 h to form a film. Finally, put into an oven at 60°C for thermal crosslinking for 12 h to finally obtain a MOF-808-CA-Me mixed matrix gas separation membrane.

[0054] The prepared MOF-808-CA-Me mixed matrix gas separation membrane was subjected to membrane separation performance test analysis on a mixed gas CO2 / CH4(30 / 70 vol%). The test was carried out at 25°C and a feed pressure of 1 bar using Wicke-Kallenbach technology, and the concentration was detected by gas chromatography (GC 1690). According to the results, the CO2 permeation flux of the membrane is 3.3*10 -7 mol m -2 s -1 Pa -1 , and the CO2 / CH4 selectivity is 95.3.

[0055] Example 5

[0056] I. Take 0.7 of trimesic acid and 3.3 g of zirconium oxychloride into a single-necked flask, and add 150 ml of DMF and 150 ml of formic acid mixed solution to dissolve, and put into the oil bath at 140°C under the protection of nitrogen, stir for 3 days, centrifugal, washed with DMF and ethanol, and vacuum dried to obtain MOF-808(Zr). Take 1 g of the obtained MOF-808(Zr) into 100 ml of 1 mol / L hydrochloric acid solution, and stir for 12 h in the oil bath at 90°C, and then centrifugal with deionized water, DMF and ethanol, and vacuum dried to obtain acidified MOF-808(Zr).

[0057] II. Take 1.86 g of citric acid dissolved in 50 ml of ethanol, and take 0.1 g of the acidified MOF-808 obtained in step I into the citric acid solution, and stir the mixture in the oil bath at 100°C for 24 h. Wash with ethanol for several times, and dry to finally obtain MOF-808-CA. Take 0.5 mmol of melamine dissolved in 40 ml of ethanol, and take 0.1 g of the dried MOF-808-CA, and stir the mixture in the oil bath at 100°C for 24 h. Wash with ethanol for several times, and dry to finally obtain MOF-808-CA-Me.

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

[0059] The prepared MOF-808-CA-Me mixed matrix gas separation membrane is subjected to membrane separation performance test analysis on mixed gas CO2 / CH4(30 / 70 vol%). The test is carried out at 25°C and the feed pressure is 1 bar, and the Wicke-Kallenbach technique is used, and the concentration is detected by gas chromatography (GC 1690). According to the results, the permeation flux of the membrane is 5.9*10 -7 mol m -2 s -1 Pa -1 , and the CO2 / CH4 selectivity is 122.8.

Claims

1. A method for preparing a MOF-808-CA-Me mixed matrix gas separation membrane, characterized in that, The preparation method includes: (1) Preparation of acidified MOF-808(Zr) Tristyric acid and zirconium oxychloride were mixed and dissolved in a mixed solution of DMF and formic acid. The mixture was stirred and reacted at 100-150°C for 1-3 days under nitrogen protection. After centrifugation, washing, and vacuum drying, MOF-808(Zr) was obtained. The obtained MOF-808(Zr) was added to hydrochloric acid solution and stirred and reacted at 60-120°C for 6-24 hours. After centrifugation, washing, and vacuum drying, acidified MOF-808(Zr) was obtained. (2) Preparation of MOF-808-CA-Me The acidified MOF-808(Zr) obtained in step (1) was added to an ethanol solution of citric acid and stirred at 30~120℃ for 6~24h. After washing and drying, MOF-808-CA was obtained. MOF-808-CA was added to an ethanol solution of melamine and stirred at 30~120℃ for 12~24h. After washing and drying, MOF-808-CA-Me was obtained. (3) Preparation of MOF-808-CA-Me mixed matrix gas separation membrane Pebax1657 was added to a mixed solution of ethanol and water and stirred at 60-80°C for 2-4 hours. Then MOF-808-CA-Me obtained in step (2) was added and stirred at room temperature for 6-24 hours to obtain a casting solution. The casting solution was cast onto a PVDF substrate and allowed to stand at room temperature for 12-24 hours to form a film. Finally, it was 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 as described in claim 1, characterized in that, In step (1), the mass ratio of pyromellitic acid to zirconium oxychloride is 1: (3.5-8).

3. The method for preparing the MOF-808-CA-Me mixed matrix gas separation membrane as described in claim 1, characterized in that, In step (1), the volume ratio of DMF to formic acid in the mixed solution is 1:(1-10); the volume-to-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 as described in claim 1, characterized in that, In step (1), the concentration of hydrochloric acid solution is 1~5 mol / L; the volume-to-mass ratio of 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 as described in claim 1, characterized in that, In step (2), the concentration of the ethanol solution of citric acid is 0.02 to 0.05 g / mL; the concentration of the ethanol solution of melamine is 2.5 to 12.5 mmol / L.

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

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

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. The application of the MOF-808-CA-Me mixed matrix gas separation membrane as described in claim 8 in mixed gas separation.

10. The application as described in claim 9, characterized in that, The gas mixture is CO2 / CH4.