Method for separating ch4 / n2 by high vacuum calcination of multi-mof mixed matrix membranes

Abstract

The present application relates to a kind of high vacuum calcination multi MOF mixed matrix membrane separation CH4 / N2 method, to realize the effective separation of methane and nitrogen, and include its preparation method, belong to membrane separation technical field.The method uses vacuum resistance calcination technology, significantly improves the separation performance of CH4 / N2.This patent invented the uniform mixing of basic high molecular polyvinylamine and SCH-M / SCH-Z and SCH-M / SCH-U, and uses the preparation of multi-metal organic framework mixed matrix membrane of blade coating method.The beneficial effects of the present application: the mixed matrix membrane of high vacuum calcination multi MOF separation methane / nitrogen prepared in the present application makes full use of high vacuum resistance calcination to make MOF carbonization, solves the influence of uneven carbonization and the compatibility of polymer matrix poor MMMs gas separation performance.Operating simply, mild, suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of membrane separation, and particularly relates to a method for separating CH4 / N2 by high-vacuum calcination of a multi-MOF mixed matrix membrane. BACKGROUND

[0002] With the increasing demand for energy, it is crucial to seek new clean energy that is environmentally friendly and has high calorific value. The proportion of natural gas in the global energy structure is increasing. Coalbed methane is a kind of unconventional natural gas, which has the characteristics of green transformation and energy saving. However, methane and nitrogen have very similar kinetic diameters and boiling points, making the separation process difficult. Therefore, the presence of nitrogen significantly affects the purification of methane and hinders the exploitation of non-natural gas.

[0003] At present, low-temperature distillation, pressure swing adsorption, temperature swing adsorption and chemical adsorption technology are the main technologies for industrial gas separation. However, these technologies are energy-intensive, require specific operating conditions, and have high operating costs. Compared with these conventional coalbed methane separation processes, membrane separation technology has the advantages of low energy consumption, mild separation conditions, simple operation, compact structure, small land occupation, low running cost and environmental sustainability. The permeability and selectivity of the membrane are the key factors affecting the performance of membrane separation. Mixed matrix membranes are a combination of porous materials and polymer substrates, which exhibit excellent polymer processing performance, as well as adjustable pore size, high porosity and diverse structure of fillers.

[0004] For mixed matrix membranes, the inherent properties of porous materials play a key role in membrane performance. Among them, metal-organic framework materials with rich pore structure, adjustable structure and high specific surface area exhibit excellent gas separation performance compared with other porous materials. SUMMARY

[0005] The purpose of the application is to solve the technical problems of uneven carbonization of metal-organic framework materials during vacuum resistance calcination, poor compatibility with polymer matrix, and limitation of the separation performance of metal-organic framework material mixed matrix membranes for CH4 / N2, and to provide a method for separating CH4 / N2 by high-vacuum calcination of a multi-MOF mixed matrix membrane.

[0006] The technical scheme adopted by the application is as follows: a method for separating CH4 / N2 by high-vacuum calcination of a multi-MOF mixed matrix membrane, uniform mixing of basic high-molecular polyvinylamine with SCH-M / SCH-Z and SCH-M / SCH-U, and preparation of a multi-metal organic framework mixed matrix membrane by a blade coating method to realize efficient separation of CH4 / N2; the steps are as follows:

[0007] S1, dissolve hexahydrate nitric acid and 2-methyl imidazole in equal amounts of methanol respectively, then mix and react to obtain white ZIF-8 nanoparticles;

[0008] Step S2, the nickel nitrate hexahydrate and 2,5-dihydroxyterephthalic acid are added to the mixed solution of N,N-dimethylformamide, ethanol and water for reaction; the zirconium chloride and amino terephthalic acid are dissolved in concentrated hydrochloric acid and N,N-dimethylformamide, and a solvent thermal method is used to obtain yellow-green MOF-74-Ni, white UiO-66-NH2 nanoparticles;

[0009] Step S3, the synthesized ZIF-8, MOF-74-Ni, UiO-66-NH2 nanoparticles are vacuum resistance calcined by using a vacuum resistance evaporation coating instrument to form SCH-Z, SCH-M, SCH-U with surface carbonized hardening;

[0010] Step S4, a hydrophilic modified MPSf membrane surface is prepared by immersing polyvinyl alcohol in the surface of a polysulfone membrane with polydimethylsiloxane;

[0011] Step S5, the basic polymer polyvinylamine is mixed with SCH-MOF (SCH-Z, SCH-M, SCH-U), and is scraped on the surface of the modified MPSf membrane to form a PVAm / 48% (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf mixed matrix membrane and a PVAm / 45% (SCH-M) 0.67 (SCH-U) 0.33 / MPSf mixed matrix membrane.

[0012] Further, in step S1, the mass ratio of zinc nitrate hexahydrate and 2-methylimidazole is 9:10, and the reacted ZIF-8 nanoparticles are washed with anhydrous methanol solution for three days and placed in a 60°C vacuum oven for drying for 12h.

[0013] Further, in step S2, after the nickel nitrate hexahydrate and 2,5-dihydroxyterephthalic acid are completely dissolved by ultrasonic treatment, they are transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, heated to 125°C in a blast oven for 20h, washed with N,N-dimethylformamide three times after the reaction is completed, replaced with methanol, and then centrifuged in the same step and placed in a vacuum oven for drying for 24h.

[0014] Further, in step S2, 0.932g of amino terephthalic acid and zirconium chloride are weighed out, the amino terephthalic acid and zirconium chloride are dissolved in 24mL of N,N-dimethylformamide and 0.665mL of concentrated hydrochloric acid, and immediately stirred uniformly by using a magnetic stirrer; then, the reaction is carried out at 220°C for 24 hours, after which the mixture is washed with N,N-dimethylformamide and methanol three times in succession, and then dried to obtain UiO-66-NH2 nanoparticles.

[0015] Further, in step S3, about 15 mg-20 mg of the nanoparticle material is uniformly placed in the grooves of the tubular tungsten boat, and vacuum evaporation is performed in a vacuum resistance evaporator. When the pressure in the vacuum chamber reaches 4.7 x 10 -3 Pa, the evaporation power is turned on, and current passes through the tubular tungsten boat.

[0016] Further, in step S3, the calcination current of MOF-74-Ni and UiO-66-NH2, ZIF-8 is 75 A (249°C), 110 A (407°C), and 100 A (362°C), respectively, and the calcination time is 5 min, 5 min, and 15 min, respectively. The entire process is cooled by circulating water. After the circulating water cooling process, SCH-MOF (SCH-M, SCH-U, SCH-Z) is obtained, which retains the original microporous characteristics of the metal organic framework and introduces additional mesoporous structures and unsaturated metal sites. The rich metal site active sites and exposed surface atoms can improve the chemical activity and increase the contact efficiency with gas molecules.

[0017] Further, in step S4, 0.025 wt% polyvinyl alcohol is used to soak the surface of the polysulfone membrane with polydimethylsiloxane, and the polysulfone membrane is dried at 30°C and 40% RH. The MPSf membrane has a hydrophilic surface.

[0018] Further, in step S5, SCH-Z and SCH-M, SCH-M and SCH-U are mixed with 0.1 wt% PVAm aqueous solution to produce a uniform PVAm-MOF mixture.

[0019] Further, in step S5, the uniformly dispersed casting solution is uniformly coated on the MPSf membrane with a preset thickness of 400 μm using a doctor blade. The amount of SCH-MOF added is adjusted to prepare casting solutions with different contents (such as Eq. (1)). MOF content (wt%) = (m(MOFs) / (m(MOFs)+m(PVAm))) x 100% (1). PVAm is a polar polymer, and CH4 is a non-polar molecule with a polar bond. According to the principle of similarity, the two can be fused to prepare MMMs, which can promote the adsorption efficiency of CH4, thereby achieving the effect of separation.

[0020] Further, the high-vacuum calcined multi-MOF mixed matrix membrane is used for gas separation.

[0021] Further, the high-vacuum calcined multi-MOF mixed matrix membrane is used for CH4 / N2 gas separation.

[0022] The advantages of the present application are: (1) The present application optimizes the heating area of the vacuum device and mixes two carbonized MOF nanoparticles, thereby adding more metal sites and functional groups to improve CH4 performance and increase CH4 / N2 selectivity. MMMs prepared by blending PVAm with different SCH-M / SCH-Z and SCH-M / SCH-U ratios have good CH4 permeability and excellent CH4 / N2 selectivity, and have wide application prospects.

[0023] (2) The high-vacuum calcined multi-MOF separation methane / nitrogen mixed matrix membrane prepared in the present application fully utilizes high-vacuum resistance calcination to carbonize MOF, solving the problem of uneven carbonization and poor compatibility of MMMs with polymer matrix affecting gas separation performance. The operation is simple, the conditions are mild, and it is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 SEM images of the surface and cross-section of the PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf and PVAm / (SCH-M) 0.67 (SCH-Z) 0.33 / MPSf MMMs film samples.

[0025] Figure 2 Adsorption-desorption isotherms of ZIF-8 and SCH-Z, MOF-74-Ni and SCH-M, UiO-66-NH2 and SCH-U at 77K (Fig. (a), Fig. (b), Fig. (c)) for Example 2.

[0026] Figure 3 EDS images of MMMs with 48% ((SCH-M) 0.5 (SCH-Z) 0.5 ) loading for Example 3 (a) and MMMs with 45% ((SCH-M) 0.5 (SCH-U) 0.5 ) loading (b).

[0027] Figure 4 CH4 and N2 adsorption isotherms of ZIF-8 and SCH-Z, MOF-74-Ni and SCH-M, UiO-66-NH2 and SCH-U at 298K (Fig. (a), Fig. (b), Fig. (c)) for Example 4. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be clearly and completely described below in combination with the drawings and examples, obviously, the described examples are only some of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0029] A method for separating CH4 / N2 by high-vacuum calcination of a multi-MOF mixed matrix membrane, aiming to realize effective separation of methane and nitrogen, belongs to the technical field of membrane separation.

[0030] The method adopted by the present application is vacuum resistance calcination technology, which significantly improves the separation performance of CH4 / N2. Specifically, the materials used include ZIF-8 (SCH-Z) with surface carbonization and hardening, MOF-74-Ni (SCH-M) and UiO-66-NH2 (SCH-U). The nanoparticles treated by vacuum resistance calcination retain the microporous characteristics of MOF, while introducing additional mesoporous structures and unsaturated metal sites.

[0031] The present application adopts uniform mixing of basic high-molecular polyvinylamine with SCH-M / SCH-Z and SCH-M / SCH-U, and prepares a multi-metal organic framework mixed matrix membrane by using the blade coating method. In the experiment, when the pressure is 0.1 MPa and the filler filling amount is 48%, the PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf MMM shows excellent CH4 / N2 separation performance, with CH4 permeability reaching 2888.48 GPU and selectivity being 4.38. On the other hand, when the filling amount is 45%, the ideal CH4 / N2 selectivity and CH4 permeability of the PVAm / (SCH-M) 0.67 (SCH-U) 0.33 / MPSf MMM are 5.57 and 2263.94 GPU, respectively. The present application provides a brand-new idea for introducing multi-radical nanoparticles into metal matrix composites to optimize the gas separation performance.

[0032] The innovation of the present application lies in that the MOF material has poor compatibility with polymers. The multi-MOF blending after vacuum resistance calcination introduces additional mesoporous structures and unsaturated metal sites, and the edge effect and state can improve the chemical activity and increase the contact efficiency with gas molecules. PVAm is a polar polymer, and CH4 is a nonpolar molecule with a polar bond, according to the similar compatibility principle, the two can be fused. The uniform mixing of basic high-molecular polyvinylamine with SCH-M / SCH-Z and SCH-M / SCH-U, and the preparation of a multi-metal organic framework mixed matrix membrane by using the blade coating method can promote the adsorption rate of CH4, thereby obtaining good CH4 / N2 separation effect.

[0033] Example 1:

[0034] (1) SCH-Z (100A (362 °C)), SCH-M (75A (249 °C)), SCH-U (110A (407 °C)) were prepared by vacuum resistance calcination of ZIF-8, MOF-74-Ni, UiO-66-NH2, respectively, with a calcination time of 2 h, and the whole process was cooled by circulating water.

[0035] (2) Hydrophilic modified MPSf membrane surface was prepared by coating 0.025 wt% polyvinyl alcohol on the PDMS-coated polysulfone surface with an average pore size of 20-50 nm.

[0036] (3) 0.1 wt% basic polymer polyvinylamine was prepared with ((SCH-M) 0.7 (SCH-Z) 0.3 ), ((SCH-M) 0.67 (SCH-U) 0.33 ) to form a uniform casting solution

[0037] (4) The prepared uniform casting solution was coated on the hydrophilic modified MPSf membrane surface using a doctor blade to form PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf and PVAm / (SCH-M) 0.67 (SCH-Z) 0.33 / MPSf MMMs.

[0038] Figure 1 The PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf membrane surface and the PVAm / (SCH-M) 0.67 (SCH-Z) 0.33 / MPSf MMMs membrane surface were shown to confirm the successful doping and uniform dispersion of nanoparticles in PVAm, and the membrane surface of MMMS was dense and uniform. Atomic force microscopy further proved that MOF promoted the interface contact with the polymer. In addition, Figure 1 It was shown that the cross-sectional thickness of the MMMs was ~ 602.8 nm and ~ 580.6 nm, respectively, indicating that there was no gap between the MMMS and the support layer, and the interface was well combined.

[0039] Example 2:

[0040] (1) SCH-Z (100A (362 °C), SCH-M (75A (249 °C)), SCH-U (110 (407 °C)) were prepared by vacuum resistance calcination of ZIF-8, MOF-74-Ni, UiO-66-NH2, respectively, with a calcination time of 3 h, and the whole process was cooled by circulating water.

[0041] (2) Hydrophilic modified MPSf membrane surface was prepared by coating 0.75 wt% polyvinyl alcohol on the PDMS-coated polysulfone surface with an average pore size of 20-50 nm.

[0042] (3) 0.5 wt% basic polymer polyvinylamine was prepared with ((SCH-M) 0.7 (SCH-Z) 0.3 ), ((SCH-M) 0.67 (SCH-U) 0.33 ) to form a uniform casting solution

[0043] (4) The prepared uniform casting solution was coated on the hydrophilic modified MPSf membrane surface using a doctor blade to form PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf and PVAm / (SCH-M) 0.67 (SCH-Z) 0.33 / MPSf MMMs.

[0044] Figure 2 The N2adsorption-desorption isotherms of the nanoparticles at 77 K are shown. Vacuum calcination treatment of ZIF-8, MOF 74-Ni and UiO-66-NH2 resulted in a decrease in specific surface area and specific volume, indicating that vacuum treatment led to the collapse of the surface of SCH-Z, SCH-M and SCH-U and the formation of micro defects. Hysteresis loops were observed in the isotherms, and the mesopore volume of the treated nanoparticles increased accordingly, and combined with the analysis of the pore size distribution, it was shown that etching had occurred and mesoporous structures had been produced in the framework. PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf and PVAm / (SCH-M) 0.67 (SCH-Z) 0.33 / MPSf MMMs after vacuum calcination have a hierarchical pore structure and abundant metal sites, which are beneficial to enhancing the compatibility with the PVAm matrix and film-forming performance.

[0045] Figure 2It shows that the nanoparticle FTIR spectrum is used for the characterization of the components of the nanoparticles, and the functional groups involved are determined. As can be seen from the figure, the peak position of SCH-Z, SCH-M, SCH-U spectrum does not change significantly, and the peak intensity of the nanoparticles after vacuum calcination treatment decreases. It shows that part of the Zn-N bond, Ni-O and Zr-O bond is broken, and unsaturated sites and surface atoms are generated. It is beneficial to improve the chemical activity and increase the contact rate with the gas, so as to achieve the separation effect.

[0046] Example 3:

[0047] (1) ZIF-8, MOF-74-Ni, UiO-66-NH2 were prepared by vacuum resistance calcination to prepare SCH-Z (100A (362℃)), SCH-M (75A (249℃)), SCH-U (110A (407℃)), and the calcination time was 2h, and the whole process was cooled by circulating water.

[0048] (2) The hydrophilic modified MPSf membrane surface was prepared by coating 0.025wt% polyvinyl alcohol on the PDMS-coated polysulfone surface with an average pore size of 20-50nm.

[0049] (3) 1.5wt% basic polymer polyvinylamine was prepared with ((SCH-M) 0.5 (SCH-Z) 0.5 ), ((SCH-M) 0.5 (SCH-U) 0.5 ) to prepare a uniform casting solution

[0050] (4) The prepared uniform casting solution was coated on the hydrophilic modified MPSf membrane surface using a doctor blade to form PVAm / (SCH-M) 0.5 (SCH-Z) 0.5 / MPSf and PVAm / (SCH-M) 0.5 (SCH-U) 0.5 / MPSf MMMs.

[0051] Figure 3 The SEM images and EDS of the PVAm / (SCH-M) 0.5 (SCH-Z) 0.5 / MPSf and PVAm / (SCH-M) 0.5 (SCH-U) 0.5 / MPSf MMMs membrane surface show that the multi-MOF mixed matrix membrane is successfully prepared by using the doctor blade method, and the multi-MOF can be uniformly dispersed in the PVAm, and the membrane surface of the MMMS is dense and uniform.

[0052] Example 4:

[0053] (1) ZIF-8, MOF-74-Ni, UiO-66-NH2 were calcined by vacuum resistance to adjust the calcination current to prepare SCH-Z (110A (407 °C)), SCH-M (85A (294 °C)), SCH-U (110 (407 °C)), the calcination time was 2 h, and the whole process was cooled by circulating water.

[0054] (2) The hydrophilic modified MPSf membrane surface was prepared by coating 0.025wt% polyvinyl alcohol on the PDMS-coated polysulfone surface with an average pore size of 20-50 nm.

[0055] (3) 0.1wt% basic polymer polyvinylamine was prepared with ((SCH-M) 0.7 (SCH-Z) 0.3 ), ((SCH-M) 0.67 (SCH-U) 0.33 ) to form a uniform casting solution

[0056] (4) The prepared uniform casting solution was coated on the hydrophilic modified MPSf membrane surface using a doctor blade to form PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf and PVAm / (SCH-M) 0.67 (SCH-Z) 0.33 / MPSf MMMs membrane.

[0057] Figure 4 The adsorption isotherms of PVAm / (SCH-M) 0.7 (SCH-Z) 0.3 / MPSf and PVAm / (SCH-M) 0.67 (SCH-Z) 0.33 / MPSf MMMs for CH4 and N2 show that SCH-Z and SCH-M, SCH-U still have adsorption capacity, and the nanoparticles still have certain microporosity. The degree of reduction of adsorption performance is lower for CH4 than for N2. It is indicated that during the heat treatment under vacuum conditions, abundant metal sites and high mesoporous porous structure can be obtained. Such structure can provide additional transport channels and action sites for gas molecules, which can improve CH4 adsorption and selectivity.

Claims

1. A method for separating CH4 / N2 by high vacuum calcination of a multi-MOF mixed matrix membrane, characterized in that: The uniform mixture of basic high-molecular polyvinylamine, SCH-M / SCH-Z and SCH-M / SCH-U is prepared into a multi-metal organic framework mixed matrix membrane by a blade coating method to realize efficient separation of CH4 / N2; the steps are as follows: In step S1, zinc nitrate hexahydrate and 2-methylimidazole are dissolved in equal amounts of methanol and then mixed to react, obtaining white ZIF-8 nanoparticles; In step S2, nickel nitrate hexahydrate and 2,5-dihydroxyterephthalic acid are added to a mixed solution of N,N-dimethylformamide, ethanol and water to react; zirconium chloride and amino terephthalic acid are dissolved in concentrated hydrochloric acid and N,N-dimethylformamide, and yellow-green MOF-74-Ni and white UiO-66-NH2 nanoparticles are obtained by a solvothermal method; In step S3, the synthesized ZIF-8, MOF-74-Ni and UiO-66-NH2 nanoparticles are vacuum resistance calcined by a vacuum resistance evaporation coating instrument to form SCH-Z, SCH-M and SCH-U with carbonized and hardened surfaces; In step S4, polyvinyl alcohol is used to soak the surface of a polysulfone membrane with polydimethylsiloxane to prepare a hydrophilic modified MPSf membrane surface; Step S5, mixing the basic polymer polyvinylamine with SCH-MOF (SCH-Z, SCH-M, SCH-U), blade coating on the surface of the modified MPSf film, and interfacial self-assembly to form a PVAm / 48%(SCH-M) 0.7 (SCH-Z) 0.3 / MPSf mixed matrix film and PVAm / 45%(SCH-M) 0.67 (SCH-U) 0.33 / MPSf mixed matrix film; In step S1, the mass ratio of zinc nitrate hexahydrate to 2-methylimidazole is 9:10, and the reacted ZIF-8 nanoparticles are washed with anhydrous methanol solution for three days and dried in a vacuum oven at 60℃ for 12 h; In step S2, after the nickel nitrate hexahydrate and 2,5-dihydroxyterephthalic acid are completely dissolved in the mixed solution by ultrasonic treatment, they are transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, heated to 125℃ in a blast oven and reacted for 20 h; after washing with N,N-dimethylformamide for three times, the same step of centrifugation is performed after replacement with methanol, and the mixture is dried in a vacuum oven for 24 h; In step S2, 0.932 g of amino terephthalic acid and zirconium chloride are weighed out, and the amino terephthalic acid and zirconium chloride are dissolved in 24 mL of N,N-dimethylformamide and 0.665 mL of concentrated hydrochloric acid, and immediately stirred uniformly by a magnetic stirrer; then, the reaction is carried out at 220℃ for 24 hours, after which the mixture is washed with N,N-dimethylformamide and methanol for three times in succession, and then dried to obtain UiO-66-NH2 nanoparticles; In step S3, 15-20 mg of the nanoparticle material is placed in the groove of the tubular tungsten boat. The vacuum chamber is evacuated, and when the pressure in the chamber reaches 4.7 x 10 -3 Pa, the evaporation power is turned on and the current is passed through the tubular tungsten boat. In step S3, the calcination currents of MOF-74-Ni and UiO-66-NH2, ZIF-8 are 75 A (249℃), 110 A (407℃) and 100 A (362℃) respectively, and the calcination times are 5 min, 5 min and 15 min respectively; the whole process is cooled by circulating water; After the circulating water cooling process, SCH-MOF (SCH-M, SCH-U and SCH-Z) is obtained, which retains the original microporous characteristics of the metal organic framework, introduces additional mesoporous structures and unsaturated metal sites, has rich metal site active sites and exposed surface atoms, can improve the chemical activity and increase the contact efficiency with gas molecules.

2. The method of claim 1, wherein the high vacuum calcined multi-MOF mixed matrix membrane separates CH4 / N2. In step S4, the surface of the polysulfone membrane with polydimethylsiloxane was soaked with 0.025 wt% polyvinyl alcohol, 50-60 mL. Due to the rich hydroxyl groups in the polyvinyl alcohol, the polyvinyl alcohol interacts with the Si-O bond in the polydimethylsiloxane to form hydrogen bonds, enhancing the affinity between the polyvinyl alcohol layer and the polydimethylsiloxane layer; Completely dried at 30°C and 40% RH to obtain an MPSf membrane with a hydrophilic surface.

3. The method of claim 2, wherein the high vacuum calcined multi-MOF mixed matrix membrane separates CH4 / N2. In step S5, SCH-Z and SCH-M, SCH-M and SCH-U were mixed with 0.1 wt% PVAm aqueous solution to produce a uniform PVAm-MOF mixture.

4. The method of claim 3, wherein the high vacuum calcined multi-MOF mixed matrix membrane separates CH4 / N2. In step S5, the uniformly dispersed casting solution was uniformly coated on the MPSf membrane with a preset thickness of 400 μm using a doctor blade; the amount of SCH-MOF was adjusted to prepare casting solutions with different contents (such as Eq. (1)), MOF content (wt%) = (m(MOFs) / (m(MOFs) + m(PVAm))) x 100% (1); PVAm is a polar polymer, CH4 is a non-polar molecule with a polar bond, and according to the principle of similarity, the two can be fused to prepare MMMs, which can promote the adsorption efficiency of CH4, thereby achieving the separation effect.

5. The method of claim 4, wherein the high vacuum calcined multi-MOF mixed matrix membrane separates CH4 / N2. High vacuum calcination of multi-MOF mixed matrix membrane for gas separation.

Images