AZIF nanofiller, preparation method, homogeneous interface mediated mixed matrix membrane, and preparation method and application of homogeneous interface mediated mixed matrix membrane

Abstract

The invention belongs to the technical field of gas separation membranes, and particularly relates to an AZIF nano-filler, a preparation method, a homogeneous interface mediated mixed matrix membrane and a preparation method and application of the homogeneous interface mediated mixed matrix membrane. According to the preparation method of the homogeneous interface mediated mixed matrix membrane, a long molecular chain AOPIM-1 polymer is taken as a membrane matrix and is blended with an AZIF nanofiller to prepare the metal organic framework / intrinsic microporous polymer mixed matrix membrane. According to the homogeneous interface mediated mixed matrix membrane prepared by the invention, the interface compatibility between the filler and the membrane matrix is remarkably improved, the inherent pore channel screening characteristic of an organic framework material is maintained, rich selective nano diffusion channels are provided, and efficient separation of propylene / propane is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation membranes, and in particular relates to an AZIF nanofiller, a preparation method, a homogeneous interface-mediated mixed matrix membrane, and a preparation method and application thereof. Background Art

[0002] As a key raw material in the petrochemical industry, the demand for propylene is continuously driven by the demand for downstream industrial products, and the average annual demand growth rate is expected to remain at 3.4% by 2030. Since polymer-grade downstream products require propylene purity higher than 99.5%, it is crucial to separate and purify propylene from light hydrocarbon mixtures, especially from propane. Currently, the separation of propylene and propane mainly relies on cryogenic distillation technology, but this technology has the disadvantages of high energy consumption and low separation efficiency.

[0003] Membrane separation technology is a non-thermally driven separation method that can significantly reduce energy consumption compared to cryogenic distillation technology, making it a promising alternative for propylene and propane separation with low energy consumption and high efficiency. The development of high permeability and high selectivity membrane materials is crucial for propylene and propane separation. Metal-organic framework materials (MOFs) have shown good separation efficiency in adsorption-dominated breakthrough experiments due to their regular pore structure, high specific surface area and designable pore characteristics, which also reflects their good application prospects in the field of membrane separation. Mixed matrix membranes are expected to combine the excellent separation properties of MOFs materials and the advantages of polymer matrix processability, becoming a research hotspot for the development of efficient propylene / propane separation membranes. However, due to the difference in the physicochemical properties of the filler and the polymer membrane matrix, it is very easy to cause incompatibility between the polymer-filler interface, and the MOFs filler is usually unevenly dispersed in the membrane, resulting in the existence of non-selective defects. Therefore, the development of high-performance MOFs mixed matrix membranes is challenging. There are also proposals to functionalize MOFs materials to effectively improve their compatibility with polymer matrices, but the commonly used functionalization methods usually involve tedious post-processing and rely on the matching between MOFs and polymers, which limits their wide application. Therefore, the simple design of new high permeability and selectivity membrane materials is the key to achieve propylene / propane membrane separation. Summary of the invention

[0004] The purpose of the present invention is to provide an AZIF nanofiller and a preparation method, and to provide a homogeneous interface-mediated mixed matrix membrane and its preparation method and application in one step, so as to provide a simple strategy for solving the compatibility problem between the mixed matrix membrane filler and the polymer matrix and realize efficient propylene / propane separation.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] An AZIF nanofiller is obtained by the following preparation method: using amidoxime-modified self-microporous polymer AOPIM-1 oligomer as a regulator to perform in-situ coordination regulation on the synthesis and preparation of zeolite imidazole framework ZIF-8; the weight average molecular weight of the AOPIM-1 oligomer is 5.2kDa.

[0007] Furthermore, the mixed solution of AOPIM-1 oligomer and 2-methylimidazole was fully mixed and reacted with the solution of Zn(NO3)2·6H2O, and AZIF nanoparticles were obtained by post-treatment; the mass ratio of AOPIM-1 oligomer and Zn(NO3)2·6H2O in the reaction solution was 1:100-500.

[0008] Furthermore, the reaction is carried out at 30-50° C. for 1-2 hours.

[0009] The mass ratio of AOPIM-1 oligomer to 2-methylimidazole in the mixed solution of AOPIM-1 oligomer and 2-methylimidazole is 1:110-550.

[0010] The solution of Zn(NO3)2·6H2O is a solution of Zn(NO3)2·6H2O and 2-methylimidazole dissolved in dimethyl sulfoxide, wherein the molar concentration of Zn(NO3)2·6H2O in the solution is 0.25-0.35 mol / L, preferably 0.3 mol / L; the molar concentration of dimethylimidazole is 1.0-1.4 mol / L, preferably 1.2 mol / L.

[0011] The molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is preferably 1:4.

[0012] The post-treatment is to collect and wash the reaction product by centrifugation, and then vacuum dry it at 60-80° C. for 8-12 hours to obtain AZIF nanoparticles.

[0013] Specifically, Zn(NO3)2.6H2O and 2-methylimidazole are dissolved in dimethyl sulfoxide respectively, and magnetically stirred at room temperature for 5-10 minutes; AOPIM-1 oligomer is dissolved in 2-methylimidazole solution and stirred at room temperature for 1 hour; the mixed solution of AOPIM-1 oligomer and 2-methylimidazole is added dropwise to Zn(NO3)2.6H2O solution, and the mixed solution is reacted in a 30-50°C water bath for 1-2 hours; AZIF powder is collected by centrifugation, washed, and vacuum dried at 60-80°C for 8-12 hours to obtain AZIF nanoparticles.

[0014] The present invention further provides a method for preparing a homogeneous interface-mediated mixed matrix membrane, using a long molecular chain AOPIM-1 polymer as a membrane matrix and blending it with the AZIF nanofiller to prepare a metal organic framework / self-microporous polymer mixed matrix membrane.

[0015] Furthermore, the AZIF nanoparticles are fully dispersed in an organic solvent to obtain a dispersion with a mass concentration of 0.12-0.85 wt %, and then the AOPIM-1 polymer is dissolved in the dispersion; the mass concentration of the AZIF nanoparticles in the mixed matrix membrane is 5-20 wt %.

[0016] The organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0017] Furthermore, the AZIF nanoparticles were dispersed in an organic solvent, and stirring and ultrasonic treatment were performed alternately for 12-24 h; the AOPIM-1 polymer was dissolved in the AZIF dispersion, and stirring was continued for 24 h.

[0018] The resulting mixture solution can then be poured into a petri dish and dried in an oven at 80° C. for 24-48 hours. After the solvent evaporates, the mixed matrix membrane is obtained by vacuum drying at 80° C. for 12-24 hours.

[0019] The AOPIM-1 polymer and AOPIM-1 oligomer described in the present invention can be prepared according to the prior art.

[0020] More specifically, a method for preparing a homogeneous interface-mediated metal organic framework / self-microporous polymer mixed matrix membrane comprises the following steps:

[0021] 1) Preparation of AZIF nanoparticles: Zn(NO3)2.6H2O and 2-methylimidazole were dissolved in dimethyl sulfoxide, respectively, and magnetically stirred at room temperature for 5-10 min; AOPIM-1 oligomer was dissolved in 2-methylimidazole solution, and stirred at room temperature for 1 h; AOPIM-1 oligomer and 2-methylimidazole were added dropwise to Zn(NO3)2.6H2O solution, and the mixture was reacted in a 30-50°C water bath for 1-2 h; AZIF powder was collected by centrifugation, washed, and vacuum dried at 60-80°C for 8-12 h to obtain AZIF nanoparticles;

[0022] 2) Preparation of mixed matrix membrane: Disperse the AZIF nanoparticles obtained in step 1) in an organic solvent, and alternately stir and ultrasonicate for 12-24 hours; dissolve the AOPIM-1 polymer in the AZIF dispersion, and continue stirring for 24 hours; vacuum dry the mixture to remove the solvent to obtain a mixed matrix membrane.

[0023] The mixed matrix membrane has good application in propylene / propane gas separation.

[0024] The invention adopts amidoxime-modified self-microporous polymer (AOPIM-1) oligomer to carry out in-situ coordination regulation on the synthesis of zeolite imidazolate framework ZIF-8, so as to obtain functionalized AZIF nanoparticles with controllable size.

[0025] By using the AZIF nanoparticles prepared in the present invention as fillers and the long molecular chain AOPIM-1 polymer as a membrane matrix, a mixed matrix membrane with good interface compatibility, high permeability and selectivity can be constructed through a blending method.

[0026] There are multiple advantages in selecting the AZIF of the present invention as filler for preparing propylene / propane separation membrane:

[0027] First, the flexible pore structure of ZIF-8 makes its effective pore size between Suitable for propylene / propane screening; second, the amidoxime group of the AOPIM-1 oligomer side chain is sensitive to Zn 2+ The coordination effect can effectively reduce the surface energy of the crystals, inhibit the Ostwald ripening process of the crystal growth process, and make the nanoparticles obtain a uniform particle size distribution; third, the macromolecular structure of the AOPIM-1 oligomer prevents it from entering the pores of the metal organic framework, which can ensure the specific regulation of the surface properties of the filler and effectively maintain the inherent pore characteristics of ZIF-8; fourth, the AOPIM-1 oligomer on the AZIF surface and the membrane matrix AOPIM-1 polymer have the same structural characteristics, which is conducive to the construction of a homogeneous interface between the filler phase and the polymer phase; good interfacial compatibility can optimize the dispersion of the filler in the membrane, forming continuous nanopores that are conducive to the transmission of propylene molecules, and retaining the screening characteristics of propane molecules, thereby achieving effective separation of propylene / propane; fifth, the molecular entanglement of the AOPIM-1 oligomer and the polymer matrix at the phase interface can effectively limit the mobility of the polymer chain segments and improve the anti-aging and anti-plasticization properties of the membrane.

[0028] The present invention uses AOPIM-1 oligomer as a coordination regulator for ZIF-8 synthesis, realizing the one-step synthesis of functionalized organic framework materials (MOFs) and the simple design of high permeability and selectivity membrane materials. On the one hand, the ZIF-8 crystal growth process and surface characteristics are finely regulated without affecting its inherent pore characteristics; on the other hand, the AOPIM-1 oligomer on the surface of the nanofiller constructs a homogeneous interface between the filler and the membrane matrix.

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

[0030] The homogeneous interface-mediated mixed matrix membrane prepared by the present invention significantly improves the interfacial compatibility between the filler and the membrane matrix, while maintaining the inherent pore screening characteristics of the organic framework material, constructs a homogeneous interface between the metal organic framework filler and the self-microporous polymer matrix, optimizes the dispersion characteristics of the filler in the membrane and forms an interconnected network structure, provides abundant selective nano-diffusion channels, and realizes efficient separation of propylene / propane. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The SEM images of the cross sections of the mixed matrix membranes obtained in Example 1, Example 2, and Example 3 of the present invention;

[0032] Figure 2 This is a graph showing the long-term separation performance test of the mixed matrix membrane obtained in Example 2 of the present invention for propylene / propane mixed gas at different temperatures and pressures. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto: Embodiment 1

[0034] A method for preparing a metal organic framework / self-microporous polymer mixed matrix membrane mediated by AZIF nanoparticles and homogeneous interfaces, the steps are as follows:

[0035] 1) Weigh 1.786g of Zn(NO3)2.6H2O and 1.97g of 2-methylimidazole and dissolve them in 20.0mL of dimethyl sulfoxide (volume concentration 99.7%, the same below), respectively, and stir at room temperature for 10min. Weigh 0.004g of AOPIM-1 oligomer and dissolve it in 2-methylimidazole solution, stir at room temperature for 1h, and add the obtained mixed solution dropwise to the Zn(NO3)2.6H2O solution. Then, transfer the above mixed solution to a water bath and stir at 40°C for 1h. After the reaction is completed, collect the product by centrifugation, wash it thoroughly with anhydrous methanol, and vacuum dry it at 75°C overnight to obtain AZIF nanoparticles.

[0036] 2) Disperse 0.028g of the above nanoparticles into 8mL of N,N-dimethylformamide (volume concentration 99.5%, the same below), and alternately stir and ultrasonicate the dispersion for 12h. Then, weigh 0.25g of AOPIM-1 polymer and dissolve it in the above dispersion, stirring at room temperature for 24h. Pour the resulting mixture into a horizontal smooth Petri dish with a diameter of 6cm and place it in an oven at 80°C for 48h to evaporate the solvent. After the solvent evaporates, vacuum dry it at 80°C for 12h to completely remove the residual solvent. The resulting mixed matrix membrane is labeled AOPIM / AZIF-1.

[0037] Example 2

[0038] A method for preparing a metal organic framework / self-microporous polymer mixed matrix membrane mediated by AZIF nanoparticles and homogeneous interfaces, the steps are as follows:

[0039] 1) Weigh 1.786g of Zn(NO3)2.6H2O and 1.97g of 2-methylimidazole and dissolve them in 20.0mL of dimethyl sulfoxide, respectively, and stir at room temperature for 10min. Weigh 0.009g of AOPIM-1 oligomer and dissolve it in 2-methylimidazole solution, stir at room temperature for 1h, and add the obtained mixed solution dropwise to the Zn(NO3)2.6H2O solution. Then, transfer the above mixed solution to a water bath and stir at 40°C for 1h. After the reaction is completed, collect the product by centrifugation, wash it thoroughly with anhydrous methanol, and vacuum dry it at 75°C overnight to obtain AZIF nanoparticles.

[0040] 2) Disperse 0.044 g of the above nanoparticles in 8 mL of N,N-dimethylformamide, and alternately stir and ultrasonicate the dispersion for 12 h. Then, weigh 0.25 g of AOPIM-1 polymer and dissolve it in the above dispersion, stirring at room temperature for 24 h. Pour the resulting mixture into a horizontal smooth Petri dish with a diameter of 6 cm and place it in an oven at 80 ° C for 48 h to evaporate the solvent. After the solvent evaporates, vacuum dry it at 80 ° C for 12 h to completely remove the residual solvent. The resulting mixed matrix membrane is labeled AOPIM / AZIF-2.

[0041] Example 3

[0042] A method for preparing a metal organic framework / self-microporous polymer mixed matrix membrane mediated by AZIF nanoparticles and homogeneous interfaces, the steps are as follows:

[0043] 1) Weigh 1.786g of Zn(NO3)2.6H2O and 1.97g of 2-methylimidazole and dissolve them in 20.0mL of dimethyl sulfoxide, respectively, and stir at room temperature for 10min. Weigh 0.018g of AOPIM-1 oligomer and dissolve it in 2-methylimidazole solution, stir at room temperature for 1h, and add the obtained mixed solution dropwise to the Zn(NO3)2.6H2O solution. Then, transfer the above mixed solution to a water bath and stir at 40°C for 1h. After the reaction is completed, collect the product by centrifugation, wash it thoroughly with anhydrous methanol, and vacuum dry it at 75°C overnight to obtain AZIF nanoparticles.

[0044] 2) Disperse 0.044 g of the above nanoparticles in 8 mL of N,N-dimethylformamide, and alternately stir and ultrasonicate the dispersion for 12 h. Then, weigh 0.25 g of AOPIM-1 polymer and dissolve it in the above dispersion, stirring at room temperature for 24 h. Pour the resulting mixture into a horizontal smooth Petri dish with a diameter of 6 cm and place it in an oven at 80 ° C for 48 h to evaporate the solvent. After the solvent evaporates, vacuum dry it at 80 ° C for 12 h to completely remove the residual solvent. The resulting mixed matrix membrane is labeled AOPIM / AZIF-3.

[0045] Comparative Example 1

[0046] The preparation steps of unmodified ZIF-8 mixed matrix membrane are as follows:

[0047] 1) Weigh 1.786g of Zn(NO3)2.6H2O and 1.97g of 2-methylimidazole and dissolve them in 20.0mL of dimethyl sulfoxide, stir at room temperature for 10min, and then add the 2-methylimidazole solution dropwise to the Zn(NO3)2.6H2O solution. Then, transfer the mixed solution to a water bath and stir at 40°C for 1h. After the reaction is completed, the product is collected by centrifugation, washed thoroughly with anhydrous methanol, and vacuum dried at 75°C overnight to obtain ZIF-8 nanoparticles.

[0048] 2) Disperse 0.028 g of the above nanoparticles in 8 mL of N,N-dimethylformamide, and alternately stir and ultrasonicate the dispersion for 12 h. Then, weigh 0.25 g of AOPIM-1 polymer and dissolve it in the above dispersion, stirring at room temperature for 24 h. Pour the resulting mixture into a horizontal smooth Petri dish with a diameter of 6 cm and place it in an oven at 80 ° C for 48 h to evaporate the solvent. After the solvent evaporates, vacuum dry it at 80 ° C for 12 h to completely remove the residual solvent. The resulting mixed matrix membrane is labeled AOPIM / ZIF-8.

[0049] Comparative Example 2

[0050] The preparation steps of AOPIM-1 pure phase polymer membrane are as follows:

[0051] Weigh 0.25 g of AOPIM-1 polymer and dissolve it in N,N-dimethylformamide and stir it at room temperature for 24 h. Pour the resulting polymer solution into a horizontal smooth Petri dish with a diameter of 6 cm and place it in an oven at 80°C for 48 h to evaporate the solvent. After the solvent evaporates, vacuum dry it at 80°C for 12 h to completely remove the residual solvent. The resulting mixed matrix membrane is labeled AOPIM.

[0052] Table 1 shows the propylene and propane gas permeability coefficients and selectivities of the AOPIM / AZIF mixed matrix membranes prepared in Examples 1-3, the AOPIM / ZIF-8 and AOPIM membranes prepared in Comparative Examples 1-2, and gas separation membranes reported in the literature.

[0053] Table 1

[0054]

[0055] It can be seen from Table 1 that compared with the mixed matrix membranes reported in the literature (ZIF-67 / 6FDA-DAM, prepared by referring to Nat Mater. 19 (12) (2020) 1346-1353; Zr-fum-fcu-MOF / 6FDA-DAM, prepared by referring to Adv Mater. 31 (14) (2019) 1807513; UiO-66 / 6FDA-DAM, prepared by referring to Angew Chem Int Ed. 60 (23) (2021) 13081-13088; 6FDA-DAM / KAUST-7, prepared by referring to Adv Mater. 35 (25) (2023) 2300296; ZIF-8-CN / PIM-1, prepared by referring to Adv Mater. 34 (6) (2022) 2104606), the mixed matrix membrane prepared by the present invention not only maintains a high propylene / propane separation capacity, but also shows a high advantage in permeability. The permeability and selectivity of the mixed matrix membrane made of AZIF obtained by coordination regulation of AOPIM-1 oligomer are improved. The propylene permeability coefficient of Example 2 is increased to 267.6 Barrer, which is about 1.9 times that of Comparative Example 1, and the selectivity is increased to 27.3, which is about 1.5 times that of Comparative Example 1.

Claims

1. A method for preparing an AZIF nanofiller, characterized in that: The self-microporous polymer AOPIM-1 oligomer modified by amidoxime is used as a regulator to perform in-situ coordination regulation on the synthesis and preparation of the zeolite imidazole framework ZIF-8; the weight average molecular weight of the AOPIM-1 oligomer is 5.2 kDa.

2. The method for preparing the AZIF nanofiller according to claim 1, characterized in that: The mixed solution of AOPIM-1 oligomer and 2-methylimidazole was fully mixed and reacted with the solution of Zn(NO3)2·6H2O, and AZIF nanoparticles were obtained by post-treatment; the mass ratio of AOPIM-1 oligomer and Zn(NO3)2·6H2O in the reaction solution was 1:100~500.

3. The method for preparing the AZIF nanofiller according to claim 2, characterized in that, The mass ratio of AOPIM-1 oligomer to 2-methylimidazole in the mixed solution of AOPIM-1 oligomer and 2-methylimidazole is 1:110-550.

4. The AZIF nanofiller obtained by any one of the preparation methods of claims 1-3.

5. A method for preparing a homogeneous interface-mediated mixed matrix membrane, characterized in that: The long molecular chain AOPIM-1 polymer is used as the membrane matrix and is blended with the AZIF nanofiller described in claim 4 to prepare a metal organic framework / self-microporous polymer mixed matrix membrane.

6. The method for preparing a homogeneous interface-mediated mixed matrix membrane according to claim 5, characterized in that: The AZIF nanoparticles are fully dispersed in an organic solvent to obtain a dispersion with a mass concentration of 0.12-0.85wt%, and then the AOPIM-1 polymer is dissolved in the dispersion; the mass concentration of the AZIF nanoparticles in the mixed matrix membrane is 5-20wt%.

7. The method for preparing a homogeneous interface-mediated mixed matrix membrane according to claim 6, characterized in that: The organic solvent is one of N, N-dimethylformamide, N, N-dimethylacetamide and dimethyl sulfoxide.

8. The method for preparing a homogeneous interface-mediated mixed matrix membrane according to claim 6, characterized in that: The AZIF nanoparticles were dispersed in an organic solvent, and stirred and ultrasonicated alternately for 12-24 hours; the AOPIM-1 polymer was dissolved in the AZIF dispersion, and stirred for another 24 hours; the mixture was vacuum dried to remove the solvent to obtain a mixed matrix membrane.

9. A homogeneous interface mediated mixed matrix membrane obtained by any one of the preparation methods of claims 5-8.

10. Use of the mixed matrix membrane according to claim 9 in propylene / propane gas separation.

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