A method for preparing a zr-based metal-organic framework-based mixed matrix membrane

Abstract

The application discloses a preparation method of a Zr-based metal-organic framework-based mixed matrix membrane, and relates to the field of gas separation membranes.The mixed matrix membrane is prepared by taking a defect-exchanged Zr-based metal-organic framework material as a filler and polyimide 6FDA-DAM as a polymer matrix.The application overcomes the defects of the prior art, and o-TBA-U iO is prepared by dispersing a defect state U iO-66 in an N,N-dimethylformamide solution of o-TBA (o-Tri-fluoromethyl benzoic acid) and then performing a heating reaction, followed by centrifugation, washing and drying in sequence.Then, the o-TBA-U iO is mixed with 6FDA-DAM in a chloroform solution, and a mixed matrix membrane is prepared by a solvent evaporation method.The application has the advantages and benefits that the MOF-based mixed matrix gas separation membrane has good C3H6 permeability and ultrahigh C3H6 / C3H8 ideal selectivity, and the main reason is that the introduction of o-Tri-fluoromethyl benzoic acid enhances the molecular sieving ability of the membrane for C3H6 / C3H8 and the preferential diffusion rate of C3H6.

Description

Technical Field

[0001] This invention relates to the field of gas separation membranes, and more particularly to a method for preparing a Zr-based metal-organic framework hybrid matrix membrane. Background Technology

[0002] Propylene (C3H6) is one of the basic raw material components used in the petrochemical industry to produce various polymers and plastics, and its market value is considerable. However, polymer-grade C3H6 requires a purity of 99.5%, while chemical-grade C3H6 requires a purity higher than 92%. Separating C3H6 from C3H6 / C3H8 mixtures is crucial for obtaining pure C3H6 in the petrochemical industry. C3H6 / C3H8 (C3) separation typically employs cryogenic distillation; however, cryogenic distillation requires a significant amount of energy to separate C3.

[0003] Due to the similar physicochemical properties of C3H6 and C3H8, it is difficult to use other alternative methods for C3 separation. Compared with other methods, membrane separation technology has attracted much attention due to its green and low-energy consumption, high efficiency, sustainability, small footprint, and high separation efficiency. Therefore, the development of high-performance C3H6 / C3H8 separation membranes has significant practical implications.

[0004] Metal-organic frameworks (MOFs) are an emerging type of porous material. They are coordination polymers with a periodic network structure assembled from inorganic metal ions and organic ligands. They possess characteristics such as high porosity, large specific surface area, and adjustable pore size, and have broad application prospects in gas separation, electrochemistry, catalysis, and medicine. UiO-66, due to its high porosity, functionality, and excellent physicochemical stability, is widely used in gas separation.

[0005] Therefore, based on the above, and drawing on years of experience in design, development and actual production in the relevant industry, the inventor has studied and improved the existing structure and its shortcomings, and provided a method for preparing a Zr-based metal-organic framework hybrid matrix membrane, in order to achieve a more practical purpose. Summary of the Invention

[0006] To address the problems mentioned in the background section, this invention provides a method for preparing a Zr-based metal-organic framework hybrid matrix membrane.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a Zr-based metal-organic framework hybrid matrix membrane, the method comprising the following steps:

[0009] S1. Raw material mixing: Mix and dissolve the raw materials according to the specified proportions to obtain a mixed solution;

[0010] S2. Heat treatment: Place the mixed solution in a container and heat the container to obtain powder;

[0011] S3. Centrifugal washing: Collect the powder by centrifugation, and wash and dry the collected powder to obtain intermediate product powder;

[0012] S4. Synthetic defect exchange: The intermediate product powder is placed in the reaction solution to carry out the synthetic defect exchange process;

[0013] S5. Secondary washing: Collect the powder after the defect exchange process and wash it.

[0014] S6. Mixed matrix membrane generation: The secondary washing product is dispersed in an organic solvent to form a dispersion, and a polymer is added. The mixed matrix membrane is obtained by solvent evaporation.

[0015] Preferably, the raw materials in step S1 include zirconium tetrachloride, terephthalic acid, deionized water, N,N-dimethylformyl and formic acid in a molar ratio of 1:1:3:350:100.

[0016] Preferably, in step S2, the container is a tetrafluoroethylene reactor, and the tetrafluoroethylene reactor is heated in an oven at 120°C for 72 hours.

[0017] Preferably, in step S3, clean N,N-dimethylformyl and acetone solvents are used to wash the powder three times.

[0018] Preferably, in step S3, the washed powder is dried in a vacuum oven at 60°C for 24 hours to obtain intermediate product powder dU i O-66.

[0019] Preferably, in step S4, the reaction solution is a DMF solution of o-trifluoromethylbenzoic acid, and the mass ratio of the intermediate product powder dU i O-66 to o-trifluoromethylbenzoic acid is 1:1. After the intermediate product powder is placed in the reaction solution, it is reacted at 60°C for 24 hours.

[0020] Preferably, in step S4, the reaction solution undergoes a defect exchange reaction with m-trifluoromethylbenzoic acid and dU i O-66 to obtain m-TBA-U iO.

[0021] Preferably, in step S4, the reaction solution is prepared by reacting p-trifluoromethylbenzoic acid with dU i O-66 to synthesize defect exchange, thereby obtaining p-TBA-U iO.

[0022] Preferably, in step S5, the powder is washed three times with DMF and acetone, and the washed powder is dried in a vacuum oven at 60°C for 24 hours to obtain o-TBA-U iO.

[0023] Preferably, in step S6, the organic solvent is a chloroform solution and is ultrasonically dispersed to achieve uniform dispersion. The polymer is 6FDA-DAM powder, and the mixture is stirred at room temperature for 24 hours to obtain a mixed matrix membrane by solvent evaporation.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention discloses a method for preparing a Zr-based metal-organic framework hybrid matrix membrane. In this invention, o-trifluoromethylbenzoic acid (o-TBA) is grafted into the framework of dU iO-66. The resulting o-TBA-U iO is combined with 6FDA-DAM to prepare a hybrid matrix membrane with high-performance C3H6 / C3H8 separation performance, which has good application prospects. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 These are the XRD patterns of 2-4 of this invention;

[0028] Figure 2 These are the N2 adsorption isotherms at 77K from the present invention 2-4. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] 150 mg of 6FDA-DAM powder was dissolved in 3 mL of chloroform solution, and a pure polymer film was obtained by solvent evaporation, denoted as 6FDA-DAM.

[0032] Example 2

[0033] A method for preparing a Zr-based metal-organic framework hybrid matrix membrane, the specific steps of which are as follows:

[0034] S1. Weigh out 4431 mg of ZrCl4 and 307.5 mg of H2BDC and dissolve them in 50 mL of DMF. Add 100 μL of deionized water to the above solution.

[0035] S2. After complete dissolution, transfer to a polytetrafluoroethylene reactor and heat in a 120°C oven for 72 hours.

[0036] S3. The obtained powder was collected by centrifugation and washed three times with clean DMF and acetone solvents to remove unreacted reactants. The washed powder was dried in a vacuum oven at 60°C for 24 hours to completely remove the solvent, and U iO-66 was obtained.

[0037] S4. Weigh 40 mg of the above U iO-66 powder and disperse it in 3 mL of chloroform solution. Disperse it evenly by ultrasonication. Then add 160 mg of 6FDA-DAM powder to the above dispersion and stir at room temperature for 24 h. Obtain the mixed matrix membrane by solvent evaporation method, which is recorded as 20 wt% U i O-66 / 6FDA-DAM.

[0038] Example 3

[0039] A method for preparing a Zr-based metal-organic framework hybrid matrix membrane, the specific steps of which are as follows:

[0040] S1. Weigh out 4431 mg of ZrCl4 and 307.5 mg of H2BDC and dissolve them in 50 mL of DMF. Add 100 μL of deionized water and 14 mL of formic acid to the above solution.

[0041] S2. After complete dissolution, transfer to a polytetrafluoroethylene reactor and heat in a 120°C oven for 72 hours.

[0042] S3. The obtained powder was collected by centrifugation and washed three times with clean DMF and acetone solvents to remove unreacted reactants. The washed powder was dried in a vacuum oven at 60°C for 24 hours to completely remove the solvent, and dU iO-66 was obtained.

[0043] Weigh 40 mg of the above dU iO-66 powder and disperse it in 3 mL of chloroform solution. Disperse it evenly by ultrasonication. Then add 160 mg of 6FDA-DAM powder to the above dispersion and stir at room temperature for 24 h. Obtain the mixed matrix membrane by solvent evaporation method, which is denoted as 20 wt% dU iO-66 / 6FDA-DAM.

[0044] Example 4

[0045] A method for preparing a Zr-based metal-organic framework hybrid matrix membrane, the specific steps of which are as follows:

[0046] S1. Weigh 443 mg of ZrCl4 and 307.5 mg of H2BDC3 and dissolve them in 50 mL of DMF. Add 100 μL of deionized water and 14 mL of formic acid to the above solution.

[0047] S2. After complete dissolution, transfer to a polytetrafluoroethylene reactor and heat in a 120°C oven for 72 hours.

[0048] S3. The obtained powder was collected by centrifugation and washed three times with clean DMF and acetone solvents to remove unreacted reactants. The washed powder was dried in a vacuum oven at 60°C for 24 hours to completely remove the solvent, and dU iO-66 was obtained.

[0049] S4. The above-mentioned dU i O-66 powder is dispersed in a DMF solution of o-trifluoromethylbenzoic acid (o-TBA) (mass ratio 1:1) and reacted at 60°C for 24 hours to realize the defect exchange process in the subsequent synthesis.

[0050] S5. Collect the powder after the above reaction is completed, wash it three times with DMF and acetone to remove unreacted reactants, and finally dry it in a vacuum oven at 60°C for 24 hours to obtain o-TBA-U iO.

[0051] S6. Weigh 40 mg of the above o-TBA-U iO powder and disperse it in 3 mL of chloroform solution. Disperse it evenly by ultrasonication. Then add 160 mg of 6FDA-DAM powder to the above dispersion and stir at room temperature for 24 h. Obtain the mixed matrix membrane by solvent evaporation method, which is recorded as 20 wt% o-TBA-U iO / 6FDA-DAM.

[0052] Example 5

[0053] The preparation method of Example 5 is basically the same as that of Example 3, except that in step S4, o-trifluoromethylbenzoic acid (o-TBA) is replaced with m-trifluoromethylbenzoic acid (m-TBA), and the resulting mixed matrix membrane is denoted as 20wt% m-TBA-UiO / 6FDA-DAM.

[0054] Example 6

[0055] The preparation method of Example 6 is basically the same as that of Example 3, except that in step S4, o-trifluoromethylbenzoic acid (o-TBA) is replaced with p-trifluoromethylbenzoic acid (p-TBA), and the resulting mixed matrix membrane is denoted as 20wt% p-TBA-UiO / 6FDA-DAM.

[0056] The gas permeability tests of the mixed matrix membranes obtained in Examples 1-3 and Example 6 were conducted using C3H6 and C3H8. The specific test results are shown in the table below:

[0057] <![CDATA[C3H6(Barrer)]]> <![CDATA[C3H8(Barrer)]]> <![CDATA[α(C3H6 / C3H8)]]> Example 1 59.36 7.78 7.55 Example 2 105.23 14.49 7.25 Example 3 244.90 29.29 8.36 Example 4 292.96 2.82 103.87

[0058] As can be seen from the table above, the gas permeation rate of the MOF-based mixed matrix membrane increases compared to the 6FDA-DAM pure membrane. Compared to Examples 1 and 2, gas permeability increases with the introduction of defects in the MOF, but the selectivity does not change significantly. Compared to Examples 2 and 3, gas permeability is improved to some extent, but the C3H6 / C3H8 selectivity increases sharply from 8.36 to 103.87. This indicates that the introduction of defects can increase gas permeability, and the introduction of o-trifluoromethylbenzoic acid into defect UiO-66 increases the C3H6 / C3H8 selectivity. The reason for this is that the increased porosity in defect UiO-66 increases the number of gas transport channels, thereby increasing the gas transport flux. Furthermore, grafting o-trifluoromethylbenzoic acid into defect UiO-66 improves the MOF's sieving ability for C3H6 and C3H8, resulting in a C3H6 / C3H8 selectivity of 103.87.

[0059] To further investigate the reason for the ultra-high C3H6 / C3H8 selectivity of the o-TBA-UiO / 6FDA-DAM hybrid matrix membrane, the C3H6 and C3H8 gas permeability tests were conducted on the hybrid matrix membranes obtained in Examples 3 and 5-6 above. The specific test results are shown in the table below:

[0060] <![CDATA[C3H6(Barrer)]]> <![CDATA[C3H8(Barrer)]]> <![CDATA[α(C3H6 / C3H8)]]> Example 3 292.96 2.82 103.87 Example 4 166.5 4.06 41.03 Example 5 143.87 5.25 27.23

[0061] As can be seen from the table above, compared with Example 3, the gas permeability and C3H6 / C3H8 selectivity of Examples 4 and 5 are reduced to a certain extent. The reason for this may be that the trifluoromethyl groups at different substitution positions have different degrees of adjustment on the window size of the MOF. The meta and para trifluoromethyl groups have a greater restriction on the window size, resulting in a lower gas permeability coefficient and lower selectivity.

[0062] Example 7

[0063] The preparation method of Example 7 is basically the same as that of Example 1, except that in step S4, the mass ratio of o-TBA-U iO to 6FDA-DAM is 2:18; the resulting mixed matrix membrane is denoted as 10wt% o-TBA-U iO / 6FDA-DAM.

[0064] Example 8

[0065] The preparation method of Example 7 is basically the same as that of Example 1, except that in step S4, the mass ratio of o-TBA-U iO to 6FDA-DAM is 3:17; the resulting mixed matrix membrane is denoted as 15wt% o-TBA-U iO / 6FDA-DAM.

[0066] Example 9

[0067] The preparation method of Example 9 is basically the same as that of Example 1, except that in step S4, the mass ratio of o-TBA-U iO to 6FDA-DAM is 5:15. The resulting mixed matrix membrane is denoted as 25wt% o-TBA-U iO / 6FDA-DAM.

[0068] To further evaluate the role of o-TBA-U iO as a filler in the mixed matrix membrane, gas permeability tests were conducted on Examples 1, 2, and 7-9 using C3H6 and C3H8. The specific test results are shown in the table below:

[0069] <![CDATA[C3H6(Barrer)]]> <![CDATA[C3H8(Barrer)]]> <![CDATA[α(C3H6 / C3H8)]]> Example 1 59.36 7.78 7.55 Example 7 70.72 1.97 35.95 Example 8 124.29 2.79 44.54 Example 2 292.93 2.82 103.72 Example 9 532.68 16.87 31.58

[0070] The above tests show that gas permeability increases with increasing filler loading, and the selectivity of C3H6 / C3H8 increases within the loading range of 0-20wt%. The selectivity of the 25wt% mixed matrix membrane drops sharply from 103.72 to 31.58, indicating that excessively high filler loading may lead to non-selectivity defects, which in turn cause the mixed matrix membrane to exhibit low selectivity.

[0071] In summary, this application presents a method for preparing and applying a Zr-based metal-organic framework-based hybrid matrix membrane. It utilizes formic acid to create defects in situ, and leverages the readily substituted nature of formic acid to graft o-trifluoromethylbenzoic acid into the framework via post-synthetic defect exchange, yielding o-TBA-UiO. This successfully functionalizes the framework while preserving its defect degree. The resulting hybrid matrix membrane is prepared by combining it with polyimide 6FDA-DAM, achieving an ideal C3H6 / C3H8 selectivity of up to 103.72.

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a Zr-based metal-organic framework-based mixed matrix membrane, characterized in that, The method comprises the following steps: S1, raw material mixing: the raw materials are mixed and dissolved according to the proportion to obtain a mixed solution, wherein the raw materials include zirconium tetrachloride, terephthalic acid, deionized water, N,N-dimethylformamide and formic acid in a molar ratio of 1:1:3:350:100; S2, heating treatment: the mixed solution is placed in a container, and the container is heated to obtain a powder; S3, centrifugal washing: the powder is collected by centrifugation, and the collected powder is washed and dried to obtain an intermediate product powder d-UiO-66; S4, synthesis defect exchange: the intermediate product powder is placed in a reaction solution for a synthesis defect exchange process, wherein the reaction solution contains one of o-trifluoromethylbenzoic acid, m-trifluoromethylbenzoic acid or p-trifluoromethylbenzoic acid; S5, secondary washing: the powder after the synthesis defect exchange process is collected and washed; S6, mixed matrix membrane generation: the secondary washing product is dispersed in an organic solvent to form a dispersion liquid, and a polymer is added to obtain a mixed matrix membrane by a solvent evaporation method.

2. The method of claim 1, wherein the Zr-based metal-organic framework-based mixed matrix membrane is prepared by: In step S2, the container is a tetrafluoroethylene reaction kettle, which is heated in a 120℃ oven for 72h.

3. The method of claim 1, wherein the Zr-based metal-organic framework-based mixed matrix membrane is prepared by: In step S3, clean N,N-dimethylformamide and acetone solvents are used to wash the powder three times in sequence.

4. The method for preparing a Zr-based metal-organic framework hybrid matrix membrane as described in claim 1, characterized in that... In step S3, the washed powder is dried in a 60℃ vacuum oven for 24h to obtain the intermediate product powder d-UiO-66.

5. The method of claim 4, wherein the Zr-based metal-organic framework-based mixed matrix membrane is prepared by: In step S4, the reaction solution is a DMF solution of o-trifluoromethylbenzoic acid, and the mass ratio of the intermediate product powder d-UiO-66 to o-trifluoromethylbenzoic acid is 1:

1. After the intermediate product powder is placed in the reaction solution, it is placed in a 60℃ oven for 24h.

6. The method of claim 5, wherein the Zr-based metal-organic framework-based mixed matrix membrane is prepared by: In step S5, the powder is washed three times in sequence with DMF and acetone, and the washed powder is dried in a 60℃ vacuum oven for 24h to obtain o-TBA-UiO.

7. The method for preparing a Zr-based metal-organic framework hybrid matrix membrane as described in claim 1, characterized in that: In step S4, the reaction solution is used for post-synthesis defect exchange between m-trifluoromethylbenzoic acid and d-UiO-66 to obtain m-TBA-UiO.

8. The method of claim 1, wherein the Zr-based metal-organic framework-based mixed matrix membrane is prepared by: In step S4, the reaction solution is used for post-synthesis defect exchange between p-trifluoromethylbenzoic acid and d-UiO-66 to obtain p-TBA-UiO.

9. The method for preparing a Zr-based metal-organic framework hybrid matrix membrane as described in claim 1, characterized in that: In step S6, chloroform solution is used as the organic solvent, and ultrasonic dispersion is used to make the dispersion uniform. 6FDA-DAM powder is used as the polymer, and stirring is carried out at room temperature for 24h. A mixed matrix membrane is obtained by a solvent evaporation method.

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