Preparation method and application of economical and efficient MOF gas separation membrane

Abstract

The invention discloses an efficient and economical MOF (Metal Organic Framework) membrane preparation method and application, a spraying gel crystallization method is adopted, firstly, MOF precursor solutions are mixed to obtain a colloidal solution containing MOF nano-particles, sol is coated on a porous membrane carrier by using a spraying tool, the MOF particles are enriched on the surface of the carrier and form a gel layer, and the MOF membrane is prepared through heat treatment. And the amorphous MOF particles in the gel layer are crystallized and are connected with the adjacent particles to grow and synthesize the continuous and compact MOF film layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of porous membrane preparation and gas separation application, and specifically relates to an economical and efficient MOF gas separation membrane preparation method and application. Background Art

[0002] Hydrogen fuel cell vehicles have received attention as a leading field of hydrogen energy application. With the increase in demonstration projects and vehicles, hydrogen supply faces challenges. The "Medium- and Long-Term Plan for the Development of the Hydrogen Energy Industry (2021-2035)" proposes to establish a supply system based on industrial by-product hydrogen and renewable energy hydrogen production, giving priority to the use of industrial by-product hydrogen to reduce costs.

[0003] At present, hydrogen purification technology is widely used, among which pressure swing adsorption, cryogenic separation and membrane separation technologies are the most mature. However, the hydrogen recovery rate of pressure swing adsorption technology is only about 75%, and the hydrogen purity of cryogenic separation technology still needs to be improved. In contrast, membrane separation technology has received more and more attention due to its advantages such as high efficiency and energy saving, simple operation and modularity. Metal-organic frameworks (MOFs) membranes have high porosity (50-90%) and highly adjustable pore size. The characteristics of rich and adjustable active sites can achieve high-throughput precise molecular screening.

[0004] In recent years, researchers have developed a variety of MOF membrane preparation methods based on the characteristics of MOFs materials. The earliest proposed method is the water / solvothermal in situ growth method. However, in the water / solvothermal synthesis process, homogeneous crystallization of the bulk solution is inevitable, which will cause waste of raw materials and often involves modification of the carrier, etc. The operation is complicated and difficult to use for industrial production of MOF membranes. Therefore, many efficient MOF membrane synthesis strategies suitable for industrial production have been proposed, such as direct crystallization, interfacial synthesis, reverse diffusion growth, layer-by-layer assembly, microfluidic processing, and restricted conversion. However, for many methods of synthesizing MOF membranes in solution, the migration of reactants and the process of fluid dynamics changes are very complicated, and it is difficult to avoid homogeneous reactions in the bulk phase of the solution, resulting in waste of reagents. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an efficient and economical method for preparing MOF membranes and their applications. The present invention adopts a spray gel crystallization method. First, MOF precursor solutions are mixed to obtain a colloidal solution containing MOF nanoparticles. The sol is coated on a porous membrane carrier using a spray tool. The MOF particles will be enriched on the carrier surface and form a gel layer. After heat treatment, the amorphous MOF particles in the gel layer will crystallize and connect with adjacent particles to grow and synthesize a continuous and dense MOF membrane layer (such asFigure 1 shown).

[0006] The specific technical solution adopted by the present invention is:

[0007] An economical and efficient method for preparing a MOF gas separation membrane comprises the following steps:

[0008] (1) Preparation of MOF precursor sol:

[0009] The metal source reagent and the solvent are mixed evenly and dissolved completely to prepare solution A; the ligand reagent and the solvent are mixed evenly and dissolved completely to prepare solution B; solution B and solution A are mixed and stirred to obtain precursor sol C;

[0010] (2) Spraying preparation of MOF membrane

[0011] The precursor sol C is loaded into a spraying tool, sprayed directly on the surface of the porous membrane, and subjected to heat treatment, soaking, and drying to obtain a MOF gas separation membrane.

[0012] Furthermore, the metal source reagent and the solvent are evenly mixed, and a metal complexing agent is added and dissolved completely to prepare a solution A.

[0013] Furthermore, the molar ratio of the metal source reagent to the metal complexing agent is 1:0-10.

[0014] Furthermore, the metal source reagent preferably contains zinc or cobalt compounds.

[0015] Furthermore, the metal complexing agent is preferably ethanolamine.

[0016] Furthermore, the ligand reagent is preferably dimethylimidazole, benzimidazole, or the like.

[0017] Furthermore, the solvent is preferably anhydrous methanol, anhydrous ethanol, etc.

[0018] Furthermore, the molar concentration of the metal source reagent in the solution A is 0.01-2 mol / L.

[0019] Furthermore, the molar ratio of the metal source reagent to the ligand reagent is 1:0.1-10.

[0020] Furthermore, the molar concentration of the ligand reagent in the solution B is 0.001-20 mol / L.

[0021] Furthermore, in step (2), the spraying pressure is 0.001-20 bar; the heat treatment heating temperature is 0-200°C, and the time is 0-7 days; the methanol solution is soaked for 0-5 days, and the drying temperature is 40-100°C.

[0022] Correspondingly, the present invention also provides an economical and efficient MOF gas separation membrane prepared by the above-mentioned preparation method.

[0023] The present invention also provides applications of the economical and efficient MOF gas separation membrane, specifically applications in separation of mixed gases.

[0024] Furthermore, it is applied in separation of H2 / CO2, H2 / N2 and H2 / CH4 mixed gases.

[0025] The beneficial effects of the present invention are as follows: the present invention realizes the coating of MOF precursor by spraying, and the operation is simple and efficient. In the subsequent gel crystallization process, it is almost completely converted into a MOF film layer. The participation of solvents in the synthesis process of MOF film in the traditional method is avoided, the homogeneous reaction involving solvents is greatly reduced, the utilization rate of reagents is increased, and the cost of raw materials is reduced. It has the advantages of being green and environmentally friendly, simple to operate, and easy to form films on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of preparing continuous and dense MOF membrane by spray gel crystallization method. DETAILED DESCRIPTION

[0027] The technical solution of the present application is further described below in conjunction with specific examples. The raw materials used in the following examples, unless otherwise specified, can all be obtained from conventional commercial sources; the processes used, unless otherwise specified, all adopt conventional processes in the art.

[0028] Embodiment 1:

[0029] An economical and efficient method for preparing a MOF gas separation membrane comprises the following steps:

[0030] First, 1.0976 g of zinc acetate dihydrate was mixed with 25 ml of anhydrous methanol to ensure that it was completely dissolved to obtain solution A. 1.642 g of dimethylimidazole was dissolved in 25 ml of anhydrous methanol to form solution B. Finally, solution B was poured into solution A and stirred for 72 hours to obtain sol C.

[0031] Add the prepared sol C to the spray gun and pressurize it with an air compressor. The air pressure is set to 2 bar, the spray height is 20 cm, and the spray time is 20 seconds. After spraying, put it in an oven at 40°C for 12 hours. Soak it in methanol solution for 8 hours and dry it for later use.

[0032] The prepared MOF gas separation membrane was installed into the membrane assembly, and then the pipeline was connected and placed in the gas separation device to test the ideal separation factor of the MOF membrane for mixed gases such as H2 / CO2, H2 / N2 and H2 / CH4: the "dead end method" was used to test, and a pressure of 0.01-0.5MPa was applied on the inlet side. The flow rate J of the permeate side was tested using a flow meter. The gas separation efficiency of the mixed gas is N i / j =J i / J j , where i is hydrogen and j is other gases in the mixed gas. The H2 / CO2, H2 / N2 and H2 / CH4 gas separation efficiencies of the MOF gas separation membrane are 3.20, 10.10 and 11.24 respectively.

[0033] Embodiment 2:

[0034] An economical and efficient method for preparing a MOF gas separation membrane comprises the following steps:

[0035] First, 14.56 g of zinc acetate dihydrate and 70 ml of anhydrous ethanol were mixed evenly, and 4.2 ml of ethanolamine was added dropwise to obtain solution A. 15.56 g of dimethylimidazole was dissolved in 70 ml of anhydrous ethanol to form solution B. Finally, solution B was poured into solution A and stirred for 1 hour to obtain sol C.

[0036] Add the prepared sol C to the spray gun and pressurize it with an air compressor. The air pressure is set to 2 bar, the spray height is 20 cm, and the spray time is 15 seconds. After spraying, put it in an oven at 50°C for 120 hours. Soak it in methanol solution for 80 hours and dry it for later use.

[0037] The prepared MOF gas separation membrane was installed into the membrane assembly, and then the pipeline was connected and placed in the gas separation device to test the ideal separation factor of the MOF membrane for mixed gases such as H2 / CO2, H2 / N2 and H2 / CH4: the "dead end method" was used to test, and a pressure of 0.01-0.5MPa was applied on the inlet side. The flow rate J of the permeate side was tested using a flow meter. The gas separation efficiency of the mixed gas is N i / j =J i / J j , where i is hydrogen and j is other gases in the mixed gas. The H2 / CO2, H2 / N2 and H2 / CH4 gas separation efficiencies of the MOF gas separation membrane are 3.64, 11.03 and 12.32 respectively.

[0038] Embodiment 3:

[0039] An economical and efficient method for preparing a MOF gas separation membrane comprises the following steps:

[0040] First, 1.0976 g of zinc acetate dihydrate was mixed with 25 ml of anhydrous methanol to ensure that it was completely dissolved to obtain solution A. 1.1814 g of dimethylimidazole was dissolved in 25 ml of anhydrous methanol to form solution B. Finally, solution B was poured into solution A and stirred for 12 hours to obtain sol C.

[0041] Add the prepared sol C to the spray gun and pressurize it with an air compressor. The air pressure is set to 2 bar, the spray height is 30 cm, and the spray time is 40 seconds. After spraying, put it in an oven at 70°C for 24 hours. Soak it in methanol solution for 4 hours and dry it for later use.

[0042] The prepared MOF gas separation membrane was installed into the membrane assembly, and then the pipeline was connected and placed in the gas separation device to test the ideal separation factor of the MOF membrane for mixed gases such as H2 / CO2, H2 / N2 and H2 / CH4: the "dead end method" was used to test, and a pressure of 0.01-0.5MPa was applied on the inlet side. The flow rate J of the permeate side was tested using a flow meter. The gas separation efficiency of the mixed gas is N i / j =J i / J j , where i is hydrogen and j is other gases in the mixed gas. The H2 / CO2, H2 / N2 and H2 / CH4 gas separation efficiencies of MOF gas separation membranes are 3.12, 9.54 and 11.41 respectively.

[0043] Embodiment 4:

[0044] An economical and efficient method for preparing a MOF gas separation membrane comprises the following steps:

[0045] First, 1.2455 g of zinc acetate dihydrate was mixed with 25 ml of anhydrous methanol to ensure that it was completely dissolved to obtain solution A. 1.6422 g of benzimidazole was dissolved in 25 ml of anhydrous methanol to form solution B. Finally, solution B was poured into solution A and stirred for 24 hours to obtain sol C.

[0046] Add the prepared sol C to the spray gun and pressurize it with an air compressor. The air pressure is set to 2 bar, the spray height is 15 cm, and the spray time is 60 seconds. After spraying, put it in an oven at 40°C for 140 hours. Soak it in methanol solution for 4 hours and dry it for later use.

[0047] The prepared MOF gas separation membrane was installed into the membrane assembly, and then the pipeline was connected and placed in the gas separation device to test the ideal separation factor of the MOF membrane for mixed gases such as H2 / CO2, H2 / N2 and H2 / CH4: the "dead end method" was used to test, and a pressure of 0.01-0.5MPa was applied on the inlet side. The flow rate J of the permeate side was tested using a flow meter. The gas separation efficiency of the mixed gas is N i / j =Ji / J j , where i is hydrogen and j is other gases in the mixed gas. The H2 / CO2, H2 / N2 and H2 / CH4 gas separation efficiencies of the MOF gas separation membrane are 4.12, 10.21 and 12.03 respectively.

[0048] Embodiment 5:

[0049] An economical and efficient method for preparing a MOF gas separation membrane comprises the following steps:

[0050] First, 1.2455 g of zinc acetate dihydrate was mixed with 25 ml of anhydrous ethanol, and 8.4 ml of ethanolamine was added dropwise to ensure that it was completely dissolved to obtain solution A. 0.8211 g of benzimidazole was dissolved in 25 ml of anhydrous ethanol to form solution B. Finally, solution B was poured into solution A and stirred for 2 hours to obtain sol C.

[0051] Add the prepared sol C to the spray gun and pressurize it with an air compressor. The air pressure is set to 2 bar, the spraying height is 20 cm, and the spraying time is 40 seconds. After spraying, put it in an oven at 40°C for 120 hours. Soak it in methanol solution for 72 hours and dry it for later use.

[0052] The prepared MOF gas separation membrane was installed into the membrane assembly, and then the pipeline was connected and placed in the gas separation device to test the ideal separation factor of the MOF membrane for mixed gases such as H2 / CO2, H2 / N2 and H2 / CH4: the "dead end method" was used to test, and a pressure of 0.01-0.5MPa was applied on the inlet side. The flow rate J of the permeate side was tested using a flow meter. The gas separation efficiency of the mixed gas is N i / j =J i / J j , where i is hydrogen and j is other gases in the mixed gas. The H2 / CO2, H2 / N2 and H2 / CH4 gas separation efficiencies of the MOF gas separation membrane are 3.97, 10.34 and 12.16 respectively.

[0053] Although the above embodiments have been described, once those skilled in the art know the basic creative concepts, they can make additional changes and modifications to these embodiments. Therefore, the above description is only an embodiment of the present invention and does not limit the patent protection scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An economical and efficient method for preparing a MOF gas separation membrane, characterized in that: The steps include: (1) Preparation of MOF precursor sol: The metal source reagent and the solvent are mixed evenly and dissolved completely to prepare solution A; the ligand reagent and the solvent are mixed evenly and dissolved completely to prepare solution B; solution B and solution A are mixed and stirred to obtain precursor sol C; (2) Preparation of MOF membrane by spraying The precursor sol C is loaded into a spraying tool, sprayed directly on the surface of the porous membrane, and subjected to heat treatment, soaking, and drying to obtain a MOF gas separation membrane.

2. The preparation method according to claim 1, characterized in that: The metal source reagent and the solvent are mixed evenly, and a metal complexing agent is added and dissolved completely to prepare a solution A.

3. The preparation method according to claim 2, characterized in that: The molar ratio of the metal source reagent to the metal complexing agent is 1:0-10.

4. The preparation method according to any one of claims 1 to 3, characterized in that The metal source reagent preferably contains a zinc or cobalt compound; and / or, The metal complexing agent is preferably ethanolamine; and / or, The ligand reagent is preferably dimethylimidazole or benzimidazole; and / or, The solvent is preferably anhydrous methanol or anhydrous ethanol; and / or, The molar concentration of the metal source reagent in the solution A is 0.01-2 mol / L; and / or, The molar ratio of the metal source reagent to the ligand reagent is 1:0.1-10; and / or, The molar concentration of the ligand reagent in the solution B is 0.001-20 mol / L.

5. The preparation method according to claim 4, characterized in that: In step (2), the spraying pressure is 0.001-20 bar; the heat treatment heating temperature is 0-200° C., and the time is 0-7 days; the methanol solution is soaked for 0-5 days, and the drying temperature is 40-100° C.

6. An economical and efficient MOF gas separation membrane, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the MOF gas separation membrane according to claim 6 in separating mixed gases.

8. The use according to claim 7, characterized in that: The mixed gas is H2 / CO2, H2 / N2 and H2 / CH4 mixed gas.

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