XLPEO / MIL-ZIF mixed matrix membrane as well as preparation method and application thereof

Abstract

The invention provides an XLPEO / MIL-ZIF mixed matrix membrane and a preparation method and application thereof.The XLPEO / MIL-ZIF mixed matrix membrane is prepared from an MIL-ZIF core-shell material with ZIF-8 as a shell and a polyethylene oxide material (PEO), MIL-101 (Cr) is modified with a surfactant, a ZIF-8 precursor smoothly grows on the surface of the MIL-101 (Cr) to form a shell, the MIL-ZIF core-shell material is formed, then the MIL-ZIF core-shell material is doped into a mixed solution of PEGMEA and PEGDA to be evenly dispersed, a membrane casting solution is formed, and the XLPEO / MIL-ZIF mixed matrix membrane is obtained. The two PEO polymers are crosslinked through ultraviolet irradiation to form the XLPEO / MIL-ZIF mixed matrix membrane, and the XLPEO / MIL-ZIF mixed matrix membrane has good CO2 / N2 separation performance and has good application prospects in the field of gas membrane separation.

Description

Technical Field

[0001] The present invention relates to the technical field of organic / inorganic hybrid membrane materials, and in particular to an XLPEO / MIL@ZIF mixed matrix membrane and its preparation method and application. Background Art

[0002] The sharp increase in greenhouse gases caused by the development of human industrialization has led to complex ecological environment chain effects. At present, it is urgent to promote the development of CCUS technology. Among them, membrane separation carbon capture technology has become the forefront of carbon capture technology due to its advantages such as low pollution, low energy consumption, small equipment floor area, and integrated design. Among many membrane materials, mixed matrix membranes can couple the advantages of organic matrices and inorganic fillers, and have the potential to break through the limitations of the "trade-off" effect of polymer membranes. However, there are still problems such as limited compatibility between fillers and matrices and separation performance not meeting industrial applications in mixed matrix membrane materials, which need to be further improved. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an XLPEO / MIL@ZIF mixed matrix membrane.

[0004] Another technical problem to be solved by the present invention is to provide a preparation method of the above XLPEO / MIL@ZIF mixed matrix membrane.

[0005] Another technical problem to be solved by the present invention is to provide an application of the above XLPEO / MIL@ZIF mixed matrix membrane.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A preparation method of an XLPEO / MIL@ZIF mixed matrix membrane is to use MIL-101(Cr) as the core and ZIF-8 as the shell to construct a MIL@ZIF core-shell material; combined with polyethylene oxide material (PEO) to obtain an XLPEO / MIL@ZIF mixed matrix membrane.

[0008] Preferably, the preparation method of the above XLPEO / MIL@ZIF mixed matrix membrane is specifically as follows:

[0009] (1) Using cetyltrimethylammonium bromide (CTAB) as a surfactant to modify MIL-101(Cr), so that the ZIF-8 precursor grows into a shell on the surface of MIL-101(Cr) to form a MIL@ZIF core-shell material;

[0010] (2) Incorporating it into a mixed solution of polyethylene glycol diacrylate (PEGMEA) and polyethylene glycol diacrylate (PEGDA) and dispersing it evenly to form a casting solution;

[0011] (3) Crosslink the two types of PEO polymers by ultraviolet irradiation to form an XLPEO / MIL@ZIF mixed matrix membrane.

[0012] Preferably, the preparation method of the above XLPEO / MIL@ZIF mixed matrix membrane is as follows:

[0013] (1) Mix 0.05 g of MIL-101(Cr), 0.0274 g of cetyltrimethylammonium bromide (CTAB), 0.1782 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O), and 2.709 g of 2-methylimidazole and disperse them in deionized water. After ultrasonic treatment and stirring, obtain the MIL@ZIF core-shell structure material;

[0014] (2) Disperse MIL@ZIF with mass loadings of 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% into a mixed liquid of PEGMEA (polyethylene glycol methyl ether acrylate) and PEGDA (polyethylene glycol diacrylate) with a mass ratio of 1:1. Then add 1 wt.% of 1-hydroxycyclohexyl phenyl ketone (HCPK) as a photoinitiator and stir to mix evenly to form a homogeneous casting solution;

[0015] (3) Pour the formed casting solution between two quartz glass plates and use ultraviolet light irradiation to crosslink the polymer into a film;

[0016] (4) Immerse the film in anhydrous methanol overnight and then vacuum dry it at 80 °C for 8 h to obtain the XLPEO / MIL@ZIF mixed matrix membrane.

[0017] Preferably, in the preparation method of the above XLPEO / MIL@ZIF mixed matrix membrane, during the synthesis of MIL@ZIF, divide the reactants into three solutions, namely: an aqueous solution of zinc nitrate hexahydrate in deionized water as solution A, a solution formed by cetyltrimethylammonium bromide (CTAB) and 2-methylimidazole and deionized water as solution B, and a solution formed by cetyltrimethylammonium bromide (CTAB) and MIL-101(Cr) as solution C; first mix solution A and solution B and ultrasonically treat for 5 min, then mix with solution C and ultrasonically treat again for 5 min. [[ID=B]]

[0018] In the preparation method of the above XLPEO / MIL@ZIF mixed matrix membrane, cetyltrimethylammonium bromide (CTAB) is mixed with MIL-101(Cr) and 2-methylimidazole respectively to activate the surface activity of the two, making it easier for them to combine.

[0019] Preferably, for the preparation method of the above-mentioned XLPEO / MIL@ZIF mixed matrix membrane, the stirring time of the casting solution is 24 h, and the casting solution needs to be ultrasonically treated for 30 min every 12 h of stirring to further promote the uniform dispersion of the filler in the casting solution.

[0020] Preferably, for the preparation method of the above-mentioned XLPEO / MIL@ZIF mixed matrix membrane, the ultraviolet cross-linking time is 7.5 min to ensure good cross-linking degree of the polymer.

[0021] An XLPEO / MIL@ZIF mixed matrix membrane is prepared by the above method.

[0022] The application of the above-mentioned XLPEO / MIL@ZIF mixed matrix membrane in gas membrane separation.

[0023] Preferably, for the above application, the gas is CO2 / N2.

[0024] The beneficial effects of the present invention are as follows:

[0025] The above-mentioned XLPEO / MIL@ZIF mixed matrix membrane is prepared by combining the MIL@ZIF core-shell material with a ZIF-8 shell and a poly(ethylene oxide) material (PEO). The surface of MIL-101(Cr) is modified with a surfactant to enable the ZIF-8 precursor to grow smoothly into a shell on the surface of MIL-101(Cr) to form a MIL@ZIF core-shell material. Subsequently, it is incorporated into a mixed solution of PEGMEA (polyethylene glycol diacrylate) and PEGDA (polyethylene glycol diacrylate) and dispersed evenly to form a casting solution. The two types of PEO polymers are cross-linked by ultraviolet irradiation to form an XLPEO / MIL@ZIF mixed matrix membrane, which has good CO2 / N2 separation performance and has good application prospects in the field of gas membrane separation. Compared with the prior art, it has the following advantages:

[0026] 1. Combining the excellent CO2 separation performance and easy preparation characteristics of the PEO polymer membrane, and the gas "screening-diffusion" fast mass transfer path of the MIL@ZIF core-shell material, the mixed matrix membrane has good gas separation performance.

[0027] 2. It has high CO2 separation performance in the temperature range of 25-45 °C and the pressure range of 0.1-0.3 MPa.

[0028] 3. The preparation processes of the two MOF materials used are simple, and the raw material prices are low, having good economy. Description of the Drawings

[0029] Figure 1 It is the synthesis route diagram of the XLPEO / MIL@ZIF mixed matrix membrane in Example 1.

[0030] Figure 2 Scanning electron microscope image of the MIL@ZIF filler in Example 1. Among them, the filler morphology is as follows:

[0031] (a) MIL-101(Cr), (b) ZIF-8, (c-d) MIL@ZIF.

[0032] Figure 3 CO2 / N2 separation performance of XLPEO / MIL@ZIF mixed matrix membranes with different MIL@ZIF loadings at 25 °C and 0.3 MPa in Example 2.

[0033] Figure 4 Effect of different operating temperatures and pressures on the performance of XLPEO / MIL@ZIF mixed matrix membranes in Example 3. Among them, (a) permeability, (b) selectivity. Detailed implementation manners

[0034] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners. The processes, conditions, reagents, experimental methods, etc. for implementing the present invention are all common knowledge and well-known common sense in the art except for the specifically mentioned content below, and there is no particularly restricted content.

[0035] Example 1

[0036] An XLPEO / MIL@ZIF mixed matrix membrane, as Figure 1 shown, includes the following steps:

[0037] (1) Preparation of MIL-101(Cr):

[0038] First, 3 g of chromium(III) nitrate nonahydrate (Cr(NO3)3·9H2O) and 1.23 g of terephthalic acid (H2BDC) were weighed separately and dispersed in 36 mL of deionized water. The mixture was stirred in a constant-temperature water bath at 40 °C for 30 min to ensure uniform mixing of the reactants. The solution was transferred to the PTFE liner of a 100 mL hydrothermal reactor. 0.375 mL of hydrofluoric acid (HF) was measured with a syringe and injected into the above solution, and stirring was continued for 30 min to ensure uniform mixing of the reactants. After stirring, the liner was placed in the hydrothermal reactor, and the reaction was carried out at 220 °C for 8 h. After the reaction, the solution in the liner was transferred to a 100 mL centrifuge tube and centrifuged at 5000 rpm for 10 min to obtain a green solid sample. Then, it was washed by centrifugation with N,N-dimethylformamide (DMF) to remove unreacted H2BDC. After repeating this three times, the solid sample was dispersed in a certain amount of DMF and stirred in an oil bath at 80 °C for 6 h. Then, the solid sample was washed with absolute ethanol more than three times to remove DMF, centrifuged and collected, and then dispersed in absolute ethanol and stirred in an oil bath at 60 °C for 3 h. After the oil bath stirring was completed, the solid sample was centrifuged and collected, placed in a blast drying oven at 60 °C. After the sample was completely dried into a block, it was ground into powder, and then placed in a vacuum drying oven and activated at 120 °C for 12 h to remove the guest molecules contained in the sample and open the pores. Finally, the green powder sample MIL-101(Cr) was collected and stored in a dark and dry place for future use.

[0039] (2) Preparation of MIL@ZIF:

[0040] 0.1782 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was dispersed in 25 mL of deionized water and stirred until the crystals were completely dissolved to form solution A. 0.0137 g of cetyltrimethylammonium bromide (CTAB) and 2.709 g of 2-methylimidazole were dispersed in 25 mL of deionized water and stirred until the powder and crystals were completely dissolved to form solution B. 0.0137 g of CTAB and 0.05 g of MIL-101(Cr) were dispersed in 25 mL of deionized water, and the mixture was ultrasonically treated for 5 - 10 min to ensure uniform dispersion of MIL-101(Cr) in water, and then stirred until the powder was completely dissolved to form solution C. Solution A was poured into solution B to form a mixed solution, which was ultrasonically treated for 5 min, and then solution C was poured into the above solution and ultrasonically treated for 5 min. The resulting solution was magnetically stirred at a speed of 500 rpm / min for 3 h. After stirring, it was washed by centrifugation with absolute methanol three times, and the obtained solid was dried to remove the liquid, then ground into powder, and then vacuum dried at 80 °C for 10 h. Finally, a gray-green powder was obtained, as Figure 2 shown, which was MIL@ZIF, and it was stored in a dry and dark place for future use.

[0041] (3) Preparation of XLPEO / MIL@ZIF mixed matrix membrane:

[0042] The total mass of the mixed matrix membrane was set to 1 g, and the mass loading of MIL@ZIF was set to 5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%, respectively. The total amount of PEGMEA and PEGDA can be obtained by subtracting the filler mass from the total mass of the mixed matrix membrane, and the mass ratio of PEGMEA to PEGDA is 1:1. A precalculated mass addition of MIL@ZIF powder was dispersed in a mixture of PEGMEA and PEGDA of the corresponding mass. A casting solution was then added containing 1 wt.% of 1-hydroxycyclohexyl phenyl ketone (a photoinitiator, representing 1 wt.% of the total mass of the mixed matrix membrane, but not included in the total mass of the membrane) and 30 wt.% of anhydrous methanol. The casting solution was magnetically stirred at 1000 rpm for 24 hours. After 12 hours of stirring, the casting solution was ultrasonically treated for 30 minutes to further mix the reactants and ensure a uniform distribution of the cross-linked network after film formation. After stirring, the casting solution was slowly poured onto the center of a quartz glass plate with Teflon tape of a certain thickness on both sides. The plate was then covered with another glass plate to spread the casting solution evenly between the two glass plates. The glass plate was irradiated with UV light for 7.5 minutes and turned over every 30 seconds to increase the degree of cross-linking of the PEO material (PEGMEA and PEGDA) inside the casting solution. After cross-linking, the glass plate was opened and the peeled membrane was immersed in anhydrous methanol for 12 hours to remove unreacted PEO. Finally, the membrane was placed in a vacuum oven at 60°C for drying and activation for 6-12 hours, resulting in a green and transparent XLPEO / MIL@ZIF mixed matrix membrane.

[0043] Example 2

[0044] The CO2 and N2 inlet pressures were set to 0.3 MPa, and the operating temperature was set to 25 °C.

[0045] The XLPEO / MIL@ZIF mixed matrix membrane described in Example 1 was vacuum dried at 80°C for 12 hours to remove residual guest molecules in the membrane, and then placed in a membrane pool. The upper chamber of the membrane pool was then tightly covered, covered with a heat shield, the vacuum pump was turned on, and the CO2 or N2 valve was opened. The relevant parameters such as membrane area, membrane thickness, test pressure and temperature were entered into the test software, and the upper and lower chambers were set to degas for 8 hours before the test began. After the degassing in the membrane pool reached a stable state, the system closed the vacuum passage of the lower chamber and began to fill the upper chamber with the set pressure of the test gas. Driven by the pressure difference, the gas permeated the membrane and entered the lower chamber. The pressure change in the lower chamber was detected by the pressure sensor. The software automatically calculated the membrane permeability coefficient and recorded the experimental results.

[0046] like Figure 3As shown, for the XLPEO / MIL@ZIF mixed matrix membrane with a MIL@ZIF loading of 20 wt.%, the CO2 permeability is 328 Barrer and the CO2 / N2 selectivity is 93.1.

[0047] Example 3

[0048] The CO2 separation performance of the XLPEO / MIL@ZIF mixed matrix membrane with a MIL@ZIF loading of 20 wt.% was tested at 25 - 45 °C and 0.1 - 0.3 MPa respectively. The testing method was the same as that in Specific Example 2.

[0049] As Figure 4 shown, at 25 °C, as the pressure increased from 0.1 MPa to 0.3 MPa, the CO2 permeability of the XLPEO / MIL@ZIF - 20 wt.% membrane increased from 312 Barrer to 328 Barrer, and its CO2 / N2 selectivity increased from 49.4 to 93.1. When the inlet pressure was 0.3 MPa, as the temperature increased from 25 °C to 45 °C, the CO2 permeability of the XLPEO / MIL@ZIF - 20 wt.% membrane increased from 328 Barrer to 493 Barrer, while the CO2 / N2 selectivity decreased from 93.1 to 39.6.

[0050] In summary, in the present invention, ZIF - 8 and MIL - 101(Cr) are constructed as core - shell fillers. By utilizing the microporous structure of the shell layer and the microporous - mesoporous structure of the core, a "screening - diffusion" gas mass transfer pathway can be formed within the membrane, thereby effectively enhancing the CO2 separation and purification performance of the polymer membrane. Based on the above statement, this method proposes a mixed matrix membrane with XLPEO as the polymer matrix and MIL@ZIF core - shell material as the filler for the separation of the CO2 / N2 system. The prepared XLPEO / MIL@ZIF mixed matrix membrane has excellent CO2 / N2 separation effects under various temperature and pressure environments. When the MIL@ZIF loading is 20 wt.%, the CO2 separation performance of the XLPEO / MIL@ZIF mixed matrix membrane reaches the best, which has good potential for industrial scale - up for the separation of the CO2 / N2 system.

[0051] The above - described embodiments are merely descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary engineering and technical personnel in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of an XLPEO / MIL@ZIF mixed matrix membrane, characterized in that: Using MIL-101(Cr) as the core and ZIF-8 as the shell, a MIL@ZIF core-shell material was constructed; combined with polyethylene oxide material, an XLPEO / MIL@ZIF mixed matrix membrane was obtained.

2. The preparation method of the XLPEO / MIL@ZIF mixed matrix membrane according to claim 1, characterized in that: The specific steps are as follows: (1) Using cetyltrimethylammonium bromide as a surfactant to modify MIL-101(Cr), enabling the ZIF-8 precursor to grow into a shell on the surface of MIL-101(Cr) to form a MIL@ZIF core-shell material; (2) Incorporating it into a mixed solution of polyethylene glycol diacrylate and polyethylene glycol diacrylate and dispersing it evenly to form a casting solution; (3) Crosslinking polyethylene glycol diacrylate and polyethylene glycol diacrylate by ultraviolet irradiation to form an XLPEO / MIL@ZIF mixed matrix membrane.

3. The preparation method of the XLPEO / MIL@ZIF mixed matrix membrane according to claim 1 or 2, wherein: The specific steps are as follows: (1) Mixing 0.05 g of MIL-101(Cr), 0.0274 g of cetyltrimethylammonium bromide, 0.1782 g of zinc nitrate hexahydrate, and 2.709 g of 2-methylimidazole and dispersing them in deionized water. After ultrasonic treatment and stirring, a MIL@ZIF core-shell structural material was obtained; (2) Dispersing MIL@ZIF with mass loadings of 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% into a mixed liquid of PEGMEA and PEGDA with a mass ratio of 1:1, and then adding 1 wt.% of 1-hydroxycyclohexyl phenyl ketone as a photoinitiator, and stirring and mixing evenly to form a homogeneous casting solution; (3) Pouring the formed casting solution between two quartz glass plates and using ultraviolet light irradiation to crosslink the polymer into a film; (4) Immersing the film in anhydrous methanol overnight and then drying it under vacuum at 80 °C for 8 h to obtain an XLPEO / MIL@ZIF mixed matrix membrane.

4. The preparation method of the XLPEO / MIL@ZIF mixed matrix membrane according to claim 3, wherein: During the synthesis of MIL@ZIF, the reactants were divided into three solutions, namely: an aqueous solution of zinc nitrate hexahydrate in deionized water as solution A, a solution formed by cetyltrimethylammonium bromide and 2-methylimidazole and deionized water as solution B, and a solution formed by cetyltrimethylammonium bromide and MIL-101(Cr) as solution C; first, mix solution A and solution B and perform ultrasonic treatment for 5 min, and then mix with solution C and perform ultrasonic treatment again for 5 min.

5. The preparation method of the XLPEO / MIL@ZIF mixed matrix membrane according to claim 3, characterized in that: The stirring time of the casting solution is 24 h, and the casting solution is ultrasonically treated for 30 min every 12 h of stirring.

6. The preparation method of the XLPEO / MIL@ZIF mixed matrix membrane according to claim 3, characterized in that: The ultraviolet crosslinking time is 7.5 min.

7. A kind of XLPEO / MIL@ZIF mixed matrix membrane, characterized in that: It is prepared by the method described in any one of claims 1-6.

8. Application of the XLPEO / MIL@ZIF mixed matrix membrane described in claim 7 in gas membrane separation.

9. The application according to claim 8, wherein: The gas is CO2 / N2.

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