A method for preparing a metal-organic framework gel hybrid matrix membrane and its application in CO2 / CH4 separation.

Abstract

This invention discloses a method for preparing a metal-organic framework (MOF) gel hybrid matrix membrane and its application in CO2 / CH4 separation, belonging to the field of gas separation membrane technology. The method involves dispersing a metal-organic framework (MOF) gel in a solvent to obtain a solution containing an MOF gel network. Subsequently, diamine and dianhydride monomers are added sequentially to this solution, and a polymerization reaction is carried out to directly obtain a hybrid matrix casting solution. Next, the casting solution is uniformly coated onto a glass culture dish, and after heat treatment, washing, and drying, the hybrid matrix membrane is finally obtained. This invention features mild preparation conditions and simple operation. By using MOF gel as the filler, constructing continuous transport channels in the solvent, and performing in-situ polymerization to form a polyimide matrix, this method not only significantly improves the permeate flux of the separation membrane but also effectively enhances the interfacial compatibility between the filler and the matrix. The prepared hybrid matrix membrane exhibits excellent CO2 / CH4 separation performance.

Description

Technical Field

[0001] This invention relates to a method for preparing a metal-organic framework gel hybrid matrix membrane and its application in CO2 / CH4 separation, specifically belonging to the field of gas separation membrane technology. Background Technology

[0002] Guided by the "dual carbon" goal, an energy revolution is gradually advancing, aiming to reduce the proportion of mainstream carbon-emitting energy sources such as coal and oil in energy consumption and develop high-quality renewable energy. Biogas, as a clean and renewable energy source, shows promising application prospects in power generation, heating, and natural gas substitution. However, the large amount of CO2 present in biogas not only reduces its calorific value but may also lead to corrosion of transportation and storage equipment. Therefore, efficient separation of CO2 and CH4 is of great significance for improving biogas quality, reducing greenhouse gas emissions, and promoting the development of carbon capture and storage technologies.

[0003] Traditional separation methods, such as cryogenic distillation and chemical absorption, while achieving efficient separation, suffer from high energy consumption, high cost, and potential secondary pollution. In recent years, membrane separation technology has shown great potential in CO2 / CH4 separation due to its advantages of low energy consumption, ease of operation, and easy scale-up. Mixed matrix membranes (MMMs), a research hotspot in gas separation membranes, combine the excellent separation performance of inorganic membranes with the ease of processing and manufacturing of polymer materials, exhibiting excellent permeability, selectivity, and mechanical strength. However, manufacturing defect-free MMMs remains challenging because insufficient compatibility between the packing material and the polymer often leads to the formation of non-selective interfacial voids, adversely affecting membrane performance.

[0004] Therefore, this invention designs a hybrid matrix membrane using metal-organic framework (MOF) gel as filler and in-situ polymerization to form a polymer matrix. The MOF gel is dispersed in a solvent to construct continuous transport channels; then diamine and dianhydride monomers are added sequentially, and polyimide matrix is ​​formed by in-situ polymerization around the gel network, which enhances the interfacial compatibility between the filler and the matrix, effectively avoids the generation of non-selective interfacial voids, and obtains a high-performance hybrid matrix membrane. Summary of the Invention

[0005] The purpose of this invention is to provide a simple and reliable preparation method for preparing mixed matrix membranes (MMMs) capable of efficiently separating CO2 / CH4. These MMMs use MOF gel as the filler and polyimide as the polymer matrix; the gel network provides a continuous and effective transport channel for gas molecules, and the in-situ polymerization method ensures good interfacial compatibility between the filler and the matrix, thereby endowing the MMMs with high separation performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A MOF gel-mixed matrix membrane for CO2 / CH4 separation is prepared by in-situ polymerization using MOF gel as filler and polyimide as polymer matrix.

[0008] The in-situ polymerization method refers to dispersing MOF gel in a solvent, and then dissolving diamine and dianhydride monomers in the solvent system in sequence, so that these monomers undergo in-situ polymerization around the MOF gel network to form a polyimide matrix, and directly obtaining a mixed matrix casting solution.

[0009] A method for preparing a MOF gel-mixed matrix membrane for CO2 / CH4 separation specifically includes the following steps:

[0010] S1: Disperse a certain mass of metal-organic framework (MOF) gel into a solvent and stir until homogeneous;

[0011] S2: Dissolve a certain mass of diamine monomer in the solution obtained in S1, then add a certain mass of dianhydride monomer and react for several hours;

[0012] S3: Add a certain amount of catalyst and dehydrating agent to carry out an imidization reaction to obtain a mixed matrix casting solution;

[0013] S4: Take a certain mass of casting solution and evenly coat it on a glass petri dish, then place it in an oven for heat treatment;

[0014] S5: Peel the heat-treated film off the culture dish, immerse it in a methanol solution, and dry it thoroughly to obtain the UiO-66 gel-mixed matrix film.

[0015] In step S1, the MOF gel is UiO-66 gel with a mass of 0.05 g-0.12 g; the solvent is N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone, preferably N,N-dimethylformamide (DMF); the solvent volume is 11 mL.

[0016] In step S2, the diamine monomer is 4,4'-diaminodiphenyl ether (ODA), with a mass of 0.4 g; the dianhydride monomer is 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA), with a mass of 0.91 g. The reaction apparatus is a three-necked flask, and the reaction is carried out under an argon or nitrogen atmosphere at a temperature of 0 °C for 6-12 h.

[0017] In step S3, the catalyst is triethylamine, and the amount used is 0.27-1.2 mL; the dehydrating agent is acetic anhydride, and the amount used is 0.71-3.2 mL; the imidization reaction temperature is room temperature, and the reaction time is 12-24 h.

[0018] In step S4, the mass of the casting solution is 0.5-1.5 g, the inner diameter of the glass culture dish is 5 cm, and the heat treatment temperature is 120-220 ℃.

[0019] In step S5, the soaking time is 24-48 h; the drying conditions are 120 °C under vacuum for 24 h.

[0020] The aforementioned MOF gel-mixed matrix membrane is used for CO2 / CH4 separation.

[0021] The beneficial effects of this invention are: 1) The MOF gel is uniformly dispersed in the polymer matrix, constructing a continuous and effective gas molecule transport channel, which significantly enhances the permeation flux of MMMs; 2) The abundant metal sites and organic linkers in the MOF gel can attract diamine and dianhydride monomers through coordination and hydrogen bonding, causing them to undergo polymerization reactions around the gel network, enhancing the compatibility between the filler and the polymer, and avoiding the generation of non-selective interfacial voids. Attached Figure Description

[0022] Figure 1 (a) is a scanning electron microscope (SEM) image of the polyimide film in Comparative Example 2; Figure 1 (b) is a scanning electron microscope cross-sectional view of the polyimide film in Comparative Example 2.

[0023] Figure 2 (a) is a scanning electron microscope (SEM) view of the hybrid matrix membrane in Example 3; Figure 2 (b) is a scanning electron microscope cross-sectional view of the mixed matrix membrane in Example 3.

[0024] Figure 3 The images show the FTIR spectra of the mixed matrix film in Example 3 and the polyimide film in Comparative Example 2.

[0025] Figure 4 The results are from long-term performance tests of the hybrid matrix membrane prepared in Example 2. Detailed Implementation Example 1

[0026] (1) Preparation of MOF gel. 0.2332 g ZrCl4 and 0.1661 g terephthalic acid were mixed and placed in natural air for 12 h. Then, the mixture was completely dissolved in 40 mL DMF by sonication. 5 mL glacial acetic acid was added and the mixture was sonicated for 5 min. The solution was then placed in a 100 mL reaction vessel and reacted at 120 °C for 24 h to obtain solidified UiO-66 gel. After thorough centrifugation, washing, and activation, the gel was put into use. DMF was used as both the washing and activation reagents.

[0027] (2) Disperse 0.05 g of UiO-66 gel into 11 mL of DMF and stir until homogeneous.

[0028] (3) Transfer the above UiO-66 gel solution to a three-necked flask, use an ice-water bath under an argon atmosphere, and stir at 600 rpm; first add 0.4 g ODA and stir for 0.5 h; then add 0.91 g 6FDA and continue stirring for 6 h.

[0029] (4) At room temperature, add 1.2 mL of triethylamine and 3.2 mL of acetic anhydride, and continue stirring for 12 h to obtain a mixed matrix casting solution.

[0030] (5) Take 1.0 g of mixed matrix casting solution and apply it evenly to the bottom of a glass culture dish with an inner diameter of 5 cm. Place it in an oven at 120℃ for 12 h.

[0031] (6) Peel the heat-treated film off the petri dish and soak it in methanol solution for 24 h; then place the film in a vacuum oven and dry it at 120 °C for 24 h to obtain the final mixed matrix film.

[0032] The mixed matrix membrane prepared in this embodiment was subjected to a CO2 / CH4 mixed gas permeation experiment, with a CO2 to CH4 volume ratio of 1:1, an inlet pressure of 1 bar, and a test temperature of 35 °C. The test results showed that the CO2 permeation coefficient was 15.06 Barrer and the CO2 / CH4 separation selectivity was 69.53.

[0033] Comparative Example 1

[0034] (1) Take 11 mL of DMF into a three-necked flask, use an ice-water bath under an argon atmosphere, and stir at 600 rpm; first add 0.4 g of ODA and stir for 0.5 h; then add 0.91 g of 6FDA and continue stirring for 6 h.

[0035] (2) At room temperature, add 1.2 mL of triethylamine and 3.2 mL of acetic anhydride, and continue stirring for 12 h to obtain polyimide casting solution.

[0036] (3) Take 1.0 g of polyimide casting solution and apply it evenly to the bottom of a glass culture dish with an inner diameter of 5 cm. Place it in an oven at 120℃ for 12 h.

[0037] (4) Peel the heat-treated film off the petri dish and soak it in methanol solution for 24 h; then place the film in a vacuum oven and dry it at 120 °C for 24 h to obtain the final polyimide film.

[0038] The polyimide membrane prepared in this embodiment was subjected to a CO2 / CH4 mixed gas permeation experiment, wherein the volume ratio of CO2 to CH4 was 1:1, the inlet pressure was 1 bar, and the test temperature was 35 °C. The test results showed that the CO2 permeation coefficient was 7.13 Barrer and the CO2 / CH4 separation selectivity was 22.44. Example 2

[0039] (1) Preparation of MOF gel. Same as in Example 1.

[0040] (2) Disperse 0.05 g of UiO-66 gel into 11 mL of DMF and stir until homogeneous.

[0041] (3) Transfer the above UiO-66 gel solution to a three-necked flask, use an ice-water bath under an argon atmosphere, and stir at 600 rpm; first add 0.4 g ODA and stir for 0.5 h; then add 0.91 g 6FDA and continue stirring for 12 h.

[0042] (4) At room temperature, add 0.27 mL of triethylamine and 0.72 mL of acetic anhydride, and continue stirring for 12 h to obtain a mixed matrix casting solution.

[0043] (5) Take 1.0 g of mixed matrix casting solution and apply it evenly to the bottom of a glass culture dish with an inner diameter of 5 cm. Place it in an oven at 120℃ for 12 h.

[0044] (6) Peel the heat-treated film off the petri dish and soak it in methanol solution for 24 h; then place the film in a vacuum oven and dry it at 120 °C for 24 h to obtain the final mixed matrix film.

[0045] The mixed matrix membrane prepared in this embodiment was subjected to a CO2 / CH4 mixed gas permeation experiment, with a CO2 to CH4 volume ratio of 1:1, an inlet pressure of 1 bar, and a test temperature of 35 °C. The test results showed that the CO2 permeation coefficient was 29.64 Barrer and the CO2 / CH4 separation selectivity was 81.97. Example 3

[0046] (1) Preparation of MOF gel. Same as in Example 1.

[0047] (2) Disperse 0.075 g of UiO-66 gel into 11 mL of DMF and stir until homogeneous.

[0048] (3) Transfer the above UiO-66 gel solution to a three-necked flask, use an ice-water bath under an argon atmosphere, and stir at 600 rpm; first add 0.4 g ODA and stir for 0.5 h; then add 0.91 g 6FDA and continue stirring for 12 h.

[0049] (4) At room temperature, add 0.27 mL of triethylamine and 0.72 mL of acetic anhydride, and continue stirring for 12 h to obtain a mixed matrix casting solution.

[0050] (5) Take 1.0 g of mixed matrix casting solution and apply it evenly to the bottom of a glass culture dish with an inner diameter of 5 cm. Place it in an oven at 120℃ for 12 h.

[0051] (6) Peel the heat-treated film off the petri dish and soak it in methanol solution for 24 h; then place the film in a vacuum oven and dry it at 120 °C for 24 h to obtain the final mixed matrix film.

[0052] The mixed matrix membrane prepared in this embodiment was subjected to a CO2 / CH4 mixed gas permeation experiment, where the volume ratio of CO2 to CH4 was 1:1, the inlet pressure was 1 bar, and the test temperature was 35 °C. The test results showed that the CO2 permeation coefficient was 30.90 Barrer, and the CO2 / CH4 separation selectivity was 135.54. Example 4

[0053] (1) Preparation of MOF gel. Same as in Example 1.

[0054] (2) Disperse 0.10 g of UiO-66 gel into 11 mL of DMF and stir until homogeneous.

[0055] (3) Transfer the above UiO-66 gel solution to a three-necked flask, use an ice-water bath under an argon atmosphere, and stir at 600 rpm; first add 0.4 g ODA and stir for 0.5 h; then add 0.91 g 6FDA and continue stirring for 12 h.

[0056] (4) At room temperature, add 0.27 mL of triethylamine and 0.72 mL of acetic anhydride, and continue stirring for 12 h to obtain a mixed matrix casting solution.

[0057] (5) Take 1.0 g of mixed matrix casting solution and apply it evenly to the bottom of a glass culture dish with an inner diameter of 5 cm. Place it in an oven at 120℃ for 12 h.

[0058] (6) Peel the heat-treated film off the petri dish and soak it in methanol solution for 24 h; then place the film in a vacuum oven and dry it at 120 °C for 24 h to obtain the final mixed matrix film.

[0059] The mixed matrix membrane prepared in this embodiment was subjected to a CO2 / CH4 mixed gas permeation experiment, where the volume ratio of CO2 to CH4 was 1:1, the inlet pressure was 1 bar, and the test temperature was 35 °C. The test results showed that the CO2 permeation coefficient was 21.17 Barrer and the CO2 / CH4 separation selectivity was 90.69.

[0060] Comparative Example 2

[0061] (1) Take 11 mL of DMF into a three-necked flask, use an ice-water bath under an argon atmosphere, and stir at 600 rpm; first add 0.4 g of ODA and stir for 0.5 h; then add 0.91 g of 6FDA and continue stirring for 12 h.

[0062] (2) At room temperature, add 0.27 mL of triethylamine and 0.72 mL of acetic anhydride, and continue stirring for 12 h to obtain polyimide casting solution.

[0063] (3) Take 1.0 g of polyimide casting solution and apply it evenly to the bottom of a glass culture dish with an inner diameter of 5 cm. Place it in an oven at 120℃ for 12 h.

[0064] (4) Peel the heat-treated film off the petri dish and soak it in methanol solution for 24 h; then place the film in a vacuum oven and dry it at 120 °C for 24 h to obtain the final polyimide film.

[0065] The polyimide membrane prepared in this embodiment was subjected to a CO2 / CH4 mixed gas permeation experiment, wherein the volume ratio of CO2 to CH4 was 1:1, the inlet pressure was 1 bar, and the test temperature was 35 °C. The test results showed that the CO2 permeation coefficient was 9.90 Barrer and the CO2 / CH4 separation selectivity was 51.85.

[0066] Figure 1 (a) is a scanning electron microscope (SEM) image of the polyimide film in Comparative Example 2; Figure 1 (b) is a cross-sectional view of the polyimide film in Comparative Example 2. From... Figure 1 As can be seen from (a) and (b), the polyimide film prepared in Comparative Example 2 has a smooth and defect-free surface, and a uniform and continuous internal matrix distribution.

[0067] Figure 2 (a) is a scanning electron microscope (SEM) view of the hybrid matrix membrane in Example 3; Figure 2 (b) is a cross-sectional view of the hybrid matrix membrane in Example 3. Figure 2As can be seen from (a) and (b), the polyimide film prepared in Example 3 has a smooth surface, and the UiO-66 gel is evenly and continuously distributed on the surface and inside, without any agglomeration or defects, indicating that the UiO-66 gel has good compatibility with the polyimide matrix.

[0068] Figure 3 The FTIR spectra are those of the mixed matrix film in Example 3 and the polyimide film in Comparative Example 2. In the spectra of Example 3 and Comparative Example 2, 1784 cm⁻¹... －1 (-C=O, asymmetric stretching vibration), 1720 cm －1 (-C=O, symmetric stretching vibration) and 1373 cm －1 The characteristic peak at (-CN, stretching vibration) confirms the successful preparation of polyimide, 1236 cm⁻¹. －1 (=COC=, stretching vibration) and 1498 cm －1 The absorption band at (C=C) is attributed to the vibration of the ODA cells in the polyimide (6FDA-ODA).

[0069] Figure 4 The results show the long-term performance test results of the hybrid matrix membrane prepared in Example 2. Figure 4 It can be seen that the prepared mixed matrix membrane has stable permeation and separation performance over a long period of time.

[0070] The above embodiments are merely illustrative of the implementation methods of the present invention and to disclose certain characteristics of its methods and applications, and should not be considered as limiting the scope of protection of the present invention. It should be understood that various changes and adjustments can be made without departing from the basic concept of the present invention, and all such changes and adjustments fall within the protection scope of the present invention.

Claims

1. A method for preparing a metal-organic framework gel hybrid matrix membrane, characterized in that, Includes the following steps: S1: A certain mass of metal-organic framework (MOF) gel is dispersed in a solvent and stirred until homogeneous; the MOF gel is UiO-66 gel. S2: Dissolve a certain mass of diamine monomer in the solution obtained in S1, then add a certain mass of dianhydride monomer and react for several hours; S3: Add a certain amount of catalyst and dehydrating agent to carry out an imidization reaction to obtain a mixed matrix casting solution; S4: Take a certain mass of casting solution and evenly coat it on a glass petri dish, then place it in an oven for heat treatment; S5: Peel the heat-treated film off the culture dish, immerse it in a methanol solution, and dry it thoroughly to obtain the UiO-66 gel-mixed matrix film.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass of UiO-66 gel is 0.01g-0.12g; the solvent is N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone; and the solvent volume is 11mL.

3. The preparation method according to claim 1, characterized in that, In step S2, the diamine monomer is 4,4'-diaminodiphenyl ether with a mass of 0.4 g; the dianhydride monomer is 4,4'-(hexafluoroisopropene)phthalic anhydride with a mass of 0.91 g; the reaction apparatus is a three-necked flask, the reaction is carried out under an argon or nitrogen atmosphere, the reaction temperature is 0 ℃, and the reaction time is 6-12 h.

4. The preparation method according to claim 1, characterized in that, In step S3, the catalyst is triethylamine, and the amount used is 0.27-1.2 mL; the dehydrating agent is acetic anhydride, and the amount used is 0.72-3.2 mL; the imidization reaction temperature is room temperature, and the reaction time is 12-24 h.

5. The preparation method according to claim 1, characterized in that, In step S4, the mass of the casting solution is 0.5-1.5g, the inner diameter of the glass culture dish is 5 cm, and the heat treatment temperature is 120-220 ℃.

6. The preparation method according to claim 1, characterized in that, In step S5, the soaking time is 24-48 h; the drying conditions are 120 °C under vacuum for 24 h.

7. A metal-organic framework gel hybrid matrix membrane, characterized in that, It is prepared by any one of the preparation methods described in claims 1-6 and used for CO2 / CH4 separation.

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