A metal-organic framework hybrid matrix membrane, and a preparation method and application thereof

Abstract

This invention relates to the field of gas membrane separation technology, specifically to a metal-organic framework hybrid matrix membrane, its preparation method, and its applications. The hybrid matrix membrane uses a water-stable metal-organic framework material Zn-bzc-2CH3 synthesized by a solvothermal method as the dispersed phase and cross-linked polyethylene glycol XLPEO as the continuous polymer matrix phase, prepared by ultraviolet cross-linking polymerization. The Zn-bzc-2CH3 material exhibits kinetic sieving ability for propylene / propane, thus the hybrid matrix membrane demonstrates enhanced propylene / propane separation performance.

Description

Technical Field

[0001] This invention belongs to the field of gas membrane separation technology, specifically relating to metal-organic framework hybrid matrix membranes, their preparation methods, and applications. Background Technology

[0002] Polymer-grade propylene (C3H6) with a purity exceeding 99.5% is a key raw material for polypropylene production, which is one of the world's most produced synthetic plastics. The main impurity in propylene is propane (C3H8), therefore, propane removal is a crucial step in obtaining high-purity propylene. Currently, industrial methods mainly rely on cryogenic distillation to separate propylene / propane, which involves high investment costs and energy consumption. Therefore, developing energy-efficient and effective propylene / propane separation methods is of great significance for energy conservation and emission reduction in chemical processes.

[0003] Compared to traditional separation methods, membrane separation is a more energy-efficient and effective separation technology. Among various types of membrane materials, hybrid matrix membranes combine the good processability of polymers with the excellent diffusion and sieving capabilities of novel porous materials. They hold promise for overcoming the limitations of polymer membrane separation performance while maintaining good potential for large-scale preparation and application, making them a type of separation membrane material expected to be applied in the near future. One of the core aspects of hybrid matrix membrane material design lies in the design and control of the packing structure and function. Metal-organic framework materials, as a novel type of nano- and micro-structured porous materials, have outstanding advantages in structural diversity, designability, and controllability, making them an ideal packing material for hybrid matrix membrane preparation. However, metal-organic framework hybrid matrix membranes with high propylene / propane separation performance are currently relatively scarce.

[0004] Therefore, the development of metal-organic framework hybrid matrix membrane materials that can efficiently separate propylene / propane is of great research significance and value. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a metal-organic framework hybrid matrix membrane, its preparation method, and its application.

[0006] This invention is achieved through the following technical solution:

[0007] A metal-organic framework hybrid matrix membrane, wherein the filler used in the preparation of the hybrid matrix membrane is a water-stable metal-organic framework material Zn-bzc-2CH3 with propylene / propane kinetic sieving capability, and the polymer matrix is ​​cross-linked polyethylene glycol.

[0008] The present invention also provides a method for preparing the metal-organic framework hybrid matrix membrane, comprising the following steps:

[0009] S1: Zn-bzc-2CH3 filler powder was uniformly dispersed in methanol by ultrasonic treatment to obtain suspension A;

[0010] S2: Add polyethylene glycol diacrylate oligomer PEGDA to suspension A, and mix the filler particles and oligomer evenly by stirring and ultrasonic treatment to obtain suspension B.

[0011] S3: Add a photoinitiator to suspension B, mix evenly by stirring and ultrasonic treatment, then evaporate the methanol in the resulting suspension B to increase the viscosity of the casting solution and reduce particle aggregation and sedimentation; then, drop the resulting casting solution between two quartz glass plates with a certain gap, and then place it in an ultraviolet crosslinking instrument for irradiation under ultraviolet light to crosslink and solidify the oligomers in the casting solution into a film;

[0012] S4: Remove the cross-linked and cured membrane from between the quartz glass plates and soak it in methanol for 3 days to fully dissolve the uncross-linked oligomers; then remove the membrane and slowly evaporate the solvent at room temperature to reduce stress-induced membrane curling and cracking; after the solvent has fully evaporated, vacuum treat the membrane to further evaporate the residual solvent, and then store the membrane in a vacuum environment.

[0013] Furthermore, the Zn-bzc-2CH3 packing used in step S1 includes the following steps:

[0014] (1) Dissolve 0.42 g of 3,5-dimethylpyrazole-4-carboxylic acid and 0.89 g of zinc nitrate hexahydrate in 40 mL of N,N-diethylformamide (DEF) to obtain reaction solution A;

[0015] (2) Add reaction solution A into a stainless steel reactor with a polytetrafluoroethylene liner, then place the reactor in a forced-air drying oven, and raise the temperature to 140°C in 6 hours by program control, maintain it for 12 hours, and then lower it to 30°C in 2 hours.

[0016] (3) Centrifuge the reaction solution, collect the crystals generated in the solution, and separate the crude Zn-bzc-2CH3 product; then, soak and centrifuge several times with methanol to remove unreacted metal salts and organic ligands, and obtain the Zn-bzc-2CH3 filler required for the preparation of the mixed matrix membrane.

[0017] Preferably, in step S2, the molecular weight of the PEGDA oligomer is 700 g / mol.

[0018] Preferably, in step S2, the mass ratio of Zn-bzc-2CH3 filler to PEGDA oligomer is 30:70.

[0019] Preferably, in step S3, the wavelength of the ultraviolet light used is 302 nm and the irradiation time is 90 s.

[0020] Preferably, in step S3, the photoinitiator used is 2,2-dimethoxy-2-phenylacetophenone (DMPA), and the amount used is 0.1 wt%.

[0021] The present invention also provides the application of the metal-organic framework hybrid matrix membrane in propylene / propane separation.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention uses a water-stable metal-organic framework material, Zn-bzc-2CH3, as a filler to prepare a hybrid matrix membrane. This membrane material, belonging to the hybrid matrix membrane category, combines the advantages of polymer membranes in terms of cost and large-scale preparation, and has promising application prospects. Furthermore, the high water stability of the filler material is beneficial for the application of the membrane material under real separation conditions.

[0024] 2. The Zn-bzc-2CH3 material used in this invention has kinetic sieving ability for propylene / propane, and the propylene / propane separation selectivity of the mixed matrix membrane is significantly improved compared with that of the pure XLPEO membrane. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the Zn-bzc-2CH3 material structure used in this invention;

[0026] Figure 2 These are the propylene and propane adsorption isotherms of the Zn-bzc-2CH3 material synthesized in this invention;

[0027] Figure 3 These are the propylene and propane kinetic adsorption curves of the Zn-bzc-2CH3 material synthesized in this invention;

[0028] Figure 4 The XRD patterns are those of the synthesized Zn-bzc-2CH3 material and the mixed matrix films prepared in Examples 1-5 and Comparative Example 1.

[0029] Figure 5 These are cross-sectional scanning electron microscope images of the hybrid matrix films prepared in Examples 1-5 and Comparative Example 1;

[0030] Figure 6 The propylene / propane separation performance of the mixed matrix membranes prepared in Examples 1-5 and Comparative Example 1 is shown. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] This invention provides a metal-organic framework hybrid matrix membrane, wherein the hybrid matrix membrane is prepared by ultraviolet crosslinking polymerization using water-stable metal-organic framework material Zn-bzc-2CH3 synthesized by solvothermal method as filler (dispersed phase) and crosslinked polyethylene glycol (XLPEO) as polymer matrix (continuous phase).

[0033] The method for preparing the metal-organic framework hybrid matrix membrane includes the following steps:

[0034] S1: Zn-bzc-2CH3 filler powder was uniformly dispersed in methanol by ultrasonic treatment to obtain suspension A;

[0035] S2: Add polyethylene glycol diacrylate (PEGDA) oligomer to suspension A, and mix the filler particles and oligomer evenly by stirring and ultrasonic treatment to obtain suspension B;

[0036] S3: Add a photoinitiator to suspension B, mix evenly by stirring and ultrasonic treatment, and then evaporate an appropriate amount of methanol in the resulting suspension B to increase the viscosity of the casting solution and reduce particle aggregation and sedimentation. Then, drop an appropriate amount of the obtained casting solution between two quartz glass plates with a certain gap, and then place it in an ultraviolet crosslinking instrument for irradiation under ultraviolet light to crosslink and solidify the oligomers in the casting solution into a film.

[0037] S4: Remove the cross-linked and cured membrane from between the quartz glass plates and soak it in methanol for 3 days to allow the insufficiently cross-linked oligomers to dissolve completely. Then remove the membrane and slowly evaporate the solvent at room temperature to reduce stress-induced membrane curling and breakage. After the solvent has fully evaporated, vacuum treat the membrane to further evaporate the residual solvent. Then store the membrane in a vacuum environment for characterization and testing.

[0038] The synthesis method of the Zn-bzc-2CH3 filler includes the following steps:

[0039] (i) Dissolve 0.42 g of 3,5-dimethylpyrazole-4-carboxylic acid and 0.89 g of zinc nitrate hexahydrate in 40 mL of N,N-diethylformamide (DEF) to obtain reaction solution A;

[0040] (ii) Add reaction solution A into a stainless steel reactor with a polytetrafluoroethylene liner (volume of 100 mL), then place the reactor in a forced-air drying oven, and raise the temperature to 140°C in 6 h by program control, maintain it for 12 h, and then lower it to 30°C in 2 h.

[0041] (iii) Centrifuge the reaction solution, collect the crystals generated in the solution, and separate the crude Zn-bzc-2CH3 product; then, soak and centrifuge several times with methanol to remove unreacted metal salts and organic ligands, and obtain the Zn-bzc-2CH3 filler required for the preparation of the mixed matrix membrane.

[0042] Example 1

[0043] S1: 0.6g of Zn-bzc-2CH3 powder was uniformly dispersed in 2.0g of methanol by ultrasonic treatment to obtain suspension A;

[0044] S2: Add 1.4g of polyethylene glycol diacrylate (PEGDA) oligomer to suspension A, and mix the filler particles and oligomer evenly by stirring and ultrasonic treatment to obtain suspension B;

[0045] S3: Add 0.004g of photoinitiator DMPA to suspension B. After mixing evenly by stirring and ultrasonic treatment, evaporate an appropriate amount of methanol in the resulting suspension B to increase the viscosity of the casting solution and reduce particle aggregation and sedimentation. Then, drop an appropriate amount of the obtained casting solution between two quartz glass plates with a certain gap, and place it in an ultraviolet crosslinker. Irradiate it under ultraviolet light with a wavelength of 302nm for 90s to crosslink and solidify the oligomers in the casting solution into a film.

[0046] S4: Remove the cross-linked and cured membrane from between the quartz glass plates and soak it in methanol for 3 days to fully dissolve the uncross-linked oligomers; then remove the membrane and slowly evaporate the solvent at room temperature to reduce membrane curling and cracking caused by stress; after the solvent has fully evaporated, vacuum process the membrane to further evaporate the residual solvent and obtain the metal-organic framework mixed matrix membrane.

[0047] Example 2

[0048] The difference between Example 2 and Example 1 is that the mass of Zn-bzc-2CH3 in step S1 is 0.2g, and the mass of PEGDA in step S2 is 1.8g, while the other conditions are exactly the same.

[0049] Example 3

[0050] The difference between Example 3 and Example 1 is that the mass of Zn-bzc-2CH3 in step S1 is 0.4g and the mass of PEGDA in step S2 is 1.6g, while the other conditions are exactly the same.

[0051] Example 4

[0052] The difference between Example 3 and Example 1 is that the mass of Zn-bzc-2CH3 in step S1 is 0.8g and the mass of PEGDA in step S2 is 1.2g, while the other conditions are exactly the same.

[0053] Example 5

[0054] The difference between Example 5 and Example 1 is that the mass of Zn-bzc-2CH3 in step S1 is 1.0g and the mass of PEGDA in step S2 is 1.0g, while the other conditions are exactly the same.

[0055] Comparative Example 1

[0056] The difference between Comparative Example 1 and Example 1 is that the mass of Zn-bzc-2CH3 in step S1 is 0g, and the mass of PEGDA in step S2 is 2.0g, while the other conditions are exactly the same.

[0057] The metal-organic framework hybrid matrix membrane of the present invention has the following structure of the metal-organic framework material Zn-bzc-2CH3 used in membrane preparation: Figure 1 As shown. The Zn-bzc-2CH3 material has a cage-like porous structure with large pores and small windows. The window size allows propylene and propane molecules to pass through, therefore the thermodynamic adsorption isotherms of this material for propylene and propane are approximately (see...). Figure 2 There is no obvious selectivity. However, propylene and propane molecules exhibit different diffusion behaviors when passing through smaller pores in the material (see [link to relevant documentation]). Figure 3 The relatively small propylene molecules can pass through the pores of the material more quickly. Therefore, this material has a high kinetic adsorption selectivity for propylene and propane (~17.1), and using this material as a packing material can improve the propylene / propane separation factor of the membrane.

[0058] Figure 4 The XRD spectra of the mixed matrix films prepared in Examples 1-5 and Comparative Example 1, as well as the synthesized Zn-bzc-2CH3 material, are shown. As can be seen from the figures, with the increase in the loading of Zn-bzc-2CH3 material, the characteristic peaks of the metal-organic framework material become increasingly prominent, while the characteristic peaks of the polymer gradually weaken. Figure 5 The images show scanning electron microscope (SEM) images of the cross-sections of the mixed matrix membranes prepared in Examples 1-5 and Comparative Example 1. The Zn-bzc-2CH3 material particles are uniformly distributed throughout the membrane. As the loading increases, more metal-organic framework particles can be observed in the images.

[0059] Tests on the propylene / propane separation performance of the mixed matrix membranes obtained in Examples 1-5 and Comparative Example 1

[0060] The propylene / propane separation performance of the mixed matrix membranes prepared in Examples 1-5 and Comparative Example 1 was tested using a 50:50 propylene / propane mixed gas at a pressure of 0.2 MPa. The test results are as follows: Figure 6As shown in Table 1, the hybrid matrix membrane obtained in Example 1 exhibits the highest propylene / propane separation factor. Higher doping levels tend to introduce defects into the membrane, thereby reducing its separation selectivity. Therefore, the preferred filler doping level for the Zn-bzc-2CH3 / XLPEO hybrid matrix membrane is 30 wt%.

[0061] Table 1. Test results of propylene / propane separation performance of the mixed matrix membranes obtained in Examples 1-5 and Comparative Example 1

[0062]

Claims

1. Use of a metal-organic framework hybrid matrix membrane in propylene / propane separation, characterized in that: The mixed matrix membrane is prepared by ultraviolet crosslinking polymerization, and is filled with a water-stable metal-organic framework material Zn-bzc-2CH3 as a filler dispersed phase and crosslinked polyethylene glycol XLPEO as a polymer matrix continuous phase. The preparation method of the metal-organic framework mixed matrix membrane comprises the following steps: S1: uniformly dispersing Zn-bzc-2CH3 filler powder in methanol by ultrasonic treatment to obtain a suspension A; S2: adding polyethylene glycol diacrylate PEGDA oligomers to the suspension A, uniformly mixing the filler particles and the oligomers by stirring and ultrasonic treatment to obtain a suspension B; S3: adding a photoinitiator to the suspension B, uniformly mixing by stirring and ultrasonic treatment, then volatilizing the methanol in the obtained suspension B, then dropping the obtained casting solution between two quartz glass plates, then placing the quartz glass plates in an ultraviolet crosslinking instrument, and irradiating under ultraviolet light to crosslink and solidify the oligomers in the casting solution into a film; S4: taking the crosslinked and solidified film from between the quartz glass plates, immersing the film in methanol for 3 days to fully dissolve the oligomers that are not sufficiently crosslinked, then taking out the film, slowly volatilizing the solvent at room temperature to reduce the film curling and fragmentation caused by stress, then performing vacuum treatment on the film to further volatilize the residual solvent, and then storing the film in a vacuum environment.

2. Use of the metal-organic framework hybrid matrix membrane according to claim 1 for propylene / propane separation, characterized in that: The preparation method of the metal-organic framework material Zn-bzc-2CH3 comprises the following steps: (1) dissolving 0.42g of 3,5-dimethylpyrazole-4-carboxylic acid and 0.89g of zinc nitrate hexahydrate in 40ml of N,N-dimethylformamide DEF to obtain a reaction solution A; (2) adding the reaction solution A into a polytetrafluoroethylene-lined stainless steel reaction kettle, then placing the reaction kettle in a blast drying oven, and raising the temperature to 140 DEG C at a programmed temperature for 6h, keeping the temperature for 12h, and then lowering the temperature to 30 DEG C for 2h; (3) centrifuging the reaction solution, collecting the generated crystals in the solution, and separating out Zn-bzc-2CH3 crude products; then, immersing and centrifugally washing the Zn-bzc-2CH3 crude products with methanol to remove unreacted metal salts and organic ligands, and obtaining Zn-bzc-2CH3 fillers required for the preparation of the mixed matrix membrane.

3. Use of the metal-organic framework hybrid matrix membrane according to claim 1 for propylene / propane separation, characterized in that: In step S2, the molecular weight of the PEGDA oligomers is 700g / mol.

4. Use of the metal-organic framework hybrid matrix membrane according to claim 1 for propylene / propane separation, characterized in that: In step S3, the wavelength of the ultraviolet light is 302nm, and the irradiation time is 90s.

5. Use of the metal-organic framework hybrid matrix membrane according to claim 1 for propylene / propane separation, characterized in that: In step S3, the photoinitiator is 2,2-dimethoxy-2-phenylphenylacetophenone DMPA, and the amount of the photoinitiator is 0.1wt%.

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