Preparation method of silane coupling agent modified nano ZSM-5 mixed matrix membrane

Abstract

The present application relates to the technical field of gas separation material, especially to a preparation method of silane coupling agent modified nano ZSM-5 mixed matrix membrane. The main steps of the method include preparation of nano ZSM-5, preparation of silane coupling agent modified nano ZSM-5, preparation of Pebax-1657 solution, preparation of silane coupling agent modified nano ZSM-5 filler, preparation of casting solution, treatment of the casting solution and preparation of the mixed matrix membrane. The purpose of the present application is to introduce silane coupling agent into nano ZSM-5 by blending to prepare silane coupling agent modified nano ZSM-5, which has excellent CO2 adsorption performance, thereby solving the problem of low CO2 / N2 permeability and selectivity of the membrane material, and comparing it with β-cyclodextrin (β-CD) which also has abundant CO2-philic groups, further illustrating the excellent permeability and high CO2 / N2 selectivity of the silane coupling agent modified nano ZSM-5 mixed matrix membrane.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of gas separation materials, in particular to a preparation method of a silane coupling agent modified nano ZSM-5 mixed matrix membrane. BACKGROUND

[0002] In order to meet the needs of industrial production, the combustion of a large amount of fossil fuels has caused the content of CO2 in the atmosphere to be far excessive, resulting in global warming, glacier melting and a series of problems. According to the report of the Energy Agency, in 2023, the global carbon dioxide emissions related to energy increased by 1.1%, an increase of 410 million tons, reaching a new high of 37.4 billion tons. However, CO2 is a carbon resource that exists on the earth and is abundant in storage. It is cheap, non-toxic and renewable. Reasonable utilization and capture of CO2 (CCS) is a sustainable technology with great prospects in energy saving and emission reduction. At present, the capture methods of CO2 include liquid absorption method, adsorption separation method, low-temperature distillation method and membrane separation method. Compared with the other three methods, the membrane separation method is favored by most researchers because of its simple operation, environmental friendliness, low energy consumption, high separation efficiency and other characteristics. In the gas separation membrane, the mixed matrix membrane (MMM) is widely concerned because it combines the advantages of inorganic separation membranes and organic separation membranes, and can theoretically break the restriction between permeability and selectivity. The inorganic filler not only provides additional gas adsorption sites, but also provides gas diffusion paths. At the same time, the inorganic filler itself or can be modified by functional groups to realize the interaction with the polymer chain, improve the interfacial compatibility and avoid the defects of not having gas selectivity.

[0003] ZSM-5 is a kind of topological type silicate molecular sieve, which is used in various places due to its unique pore structure, adjustable silicon-aluminum ratio, good hydrothermal stability, moderate acidity and high specific surface area. 3-aminopropyltriethoxysilane (APTES) is a common silane coupling agent, and beta-cyclodextrin (beta-CD) has rich CO2-philic groups. The modification of ZSM-5 using the two can positively affect the separation of CO2 to a certain extent. The CO2 / N2 separation performance of the mixed matrix membrane prepared from MOFs, HOFs and COFs materials has not reached the ideal state, and the cost is relatively high. Therefore, it is a challenging work to study an inorganic material with low price suitable for the field of gas separation, and it will be a new challenge to prepare a mixed matrix membrane with high selectivity and high permeability. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a preparation method of a silane coupling agent modified nano ZSM-5 mixed matrix membrane. The method is to prepare a nano ZSM-5 by introducing a silane coupling agent into the nano ZSM-5 through blending, and then prepare a mixed matrix membrane for CO2 separation by taking Pebax-1657 as a matrix. The purpose of the present application is to introduce a silane coupling agent into a nano ZSM-5 through blending to prepare a silane coupling agent modified nano ZSM-5, which has excellent CO2 adsorption performance, so as to solve the problems of low CO2 / N2 permeability and selectivity of the membrane material, and further illustrate the excellent permeability and high CO2 / N2 selectivity of the silane coupling agent modified nano ZSM-5 mixed matrix membrane by comparing with β-cyclodextrin (β-CD) which also has abundant CO2-philic groups. Therefore, the present application provides a preparation method of a silane coupling agent modified nano ZSM-5 mixed matrix membrane.

[0005] The technical scheme of the present application is as follows:

[0006] A preparation method of a silane coupling agent modified nano ZSM-5 mixed matrix membrane, comprising the following steps:

[0007] Step 1, weigh 1-1.5 parts of aluminum isopropoxide and dissolve it in 48-80 parts of an organic template agent, stir until the aluminum isopropoxide is fully dissolved, add 52-65 parts of silicon dioxide, and stir uniformly to obtain a micro-wet gel mixture. Then, the mixture is added to an open glass container, and then transferred to an inner liner of a hydrothermal reaction kettle. Deionized water is added outside the bottle mouth of the inner liner. After the hydrothermal reaction kettle is sealed and aged at room temperature for 24-72 hours, the hydrothermal reaction kettle is transferred to an electric heating constant temperature drying oven for crystallization treatment, and then a crystalline product is obtained. The product is centrifuged, washed, dried, and calcined to obtain a dried nano ZSM-5;

[0008] Step 2, add 50-150 parts of toluene to an A beaker, and then add 1-5 parts of 3-aminopropyl triethoxysilane dropwise to the toluene solution, so that the 3-aminopropyl triethoxysilane is fully dissolved in the toluene solution. Then, add 50-150 parts of toluene to a B beaker, and then add 0.05-1 parts of nano ZSM-5 to the B beaker. Then, the solution in the A beaker is added dropwise to the B beaker, and the stirring speed is 800 r / min. After stirring for 2-5 hours, the mixture is transferred to a round-bottom flask. After adding 1-5 drops of ultrapure water, the mixture is reacted in an 80-90℃ oil bath for 12-36 hours. After centrifugal washing and drying with toluene, a silane coupling agent modified nano ZSM-5 is obtained;

[0009] Step 3, add 0.2-0.5 parts of Pebax-1657 and 6.47-10 parts of ethanol to a flask, and heat the flask in an 85-95℃ oil bath for 6-12 hours to obtain a uniform concentration of Pebax solution;

[0010] Step 4, the silane coupling agent modified nano ZSM-5 is added as a filler into anhydrous ethanol, and after ultrasonic treatment for 2-6h, the mixture is placed on a stirring table for stirring for 24-72h to obtain a silane coupling agent modified nano ZSM-5 filler casting solution;

[0011] Step 5, 6-7 parts of the Pebax-1657 solution is weighed into a reagent bottle, and 0.2-1.5 parts of the silane coupling agent modified nano ZSM-5 filler casting solution is added dropwise into the reagent bottle, and the mixture is oscillated for 120-240min by using a turbine oscillator and ultrasonic treatment for 15-30min, and after the filler and the polymer solution are uniformly mixed, the casting solution is left to be deaerated, the prepared mixed matrix membrane solution is poured onto a polytetrafluoroethylene flat plate, and the flat plate is placed in a constant temperature oven at 60-80℃ for drying for 18-24h, and then the flat plate is placed in a vacuum oven at 60-80℃ for vacuumizing and continuing to remove the solvent for 18-30h to obtain a silane coupling agent modified nano ZSM-5 mixed matrix membrane.

[0012] Further, the mass ratio of the ethanol to water in step 3 is 6-10:1-4.

[0013] Further, the centrifuge in step 1 is used at a rotation speed of 7000-12000rpm for 5-15min.

[0014] Further, the content of the silane coupling agent modified nano ZSM-5 in the silane coupling agent modified nano ZSM-5 filler casting solution in step 4 is 1%-4%.

[0015] Further, the thickness of the silane coupling agent modified nano ZSM-5 mixed matrix membrane in step 5 is 30-70μm.

[0016] Further, the ultrasonic stirring mixing method in step 4 is stirring at a rotation speed of 300-600rpm for 30-60min at room temperature, and then ultrasonic dispersion for 15-45min.

[0017] Further, the crystallization temperature of the electric heating constant temperature drying oven in step 1 is 120-150℃ for 4-16h.

[0018] Further, the drying temperature in step 2 is 60-90℃ for 12-36h.

[0019] Further, according to the preparation method of the silane coupling agent modified nano ZSM-5 mixed matrix membrane according to any one of claims 1-8, the prepared mixed matrix membrane is used for CO2 / N2 gas separation.

[0020] Based on the above technical scheme, the prepared mixed matrix membrane is used for CO2 / N2 gas separation.

[0021] The structural formula of each of the above-mentioned substances is as follows:

[0022] The structural formula of ZSM-5 is:

[0023]

[0024] The structural formula of 3-aminopropyl triethoxysilane (APTES) is:

[0025]

[0026] The structural formula of β-CD (β-CD) is:

[0027]

[0028] The structural formula of pebax-1657 is:

[0029]

[0030] The present application uses pebax-1657 as a matrix material, and uses nano-ZSM-5 modified by 3-aminopropyl triethoxysilane as a silane coupling agent as a filler to prepare a mixed matrix membrane.

[0031] Firstly, it has superior mechanical properties. Pebax is formed by blending polyether segments (PE) and amide segments (PA) into block copolymers; the polyether segment exhibits rubbery characteristics, ensuring that the membrane material itself has a high free volume fraction, which can provide a good gas transmission channel and reduce the mass transfer resistance; at the same time, the large number of basic amine groups in the amide at the front end of the polyether have strong interaction ability with CO2, which can increase the solubility of CO2 in the membrane, thereby effectively improving the solubility selectivity of the membrane material for CO2 gas.

[0032] Secondly, the introduction of porous nano-ZSM-5 filler significantly improves the performance of the membrane. It is synthesized by tetrapropylammonium hydroxide template agent, so that there is a very compact fit between organic molecules and inorganic framework, and the organic structure directing agent only has one orientation in the pore or cage and cannot freely move to create a porous filler with a suitable pore size structure. Thus, it provides a transmission channel for CO2 in the membrane, which helps the effective permeation of CO2 and thus improves the mass transfer efficiency of the membrane. At the same time, the strong acidic sites and catalytic activity of ZSM-5 provide additional functions for the gas separation process. Porous nano-ZSM-5 also improves the mechanical and thermal stability of the membrane, enabling it to maintain performance under more severe operating conditions, while enhancing the anti-pollution ability of the membrane, reducing the accumulation of pollutants on the membrane surface, and prolonging the service life of the membrane. These characteristics, in combination, make it a key component for improving the performance of mixed matrix membranes, especially in the field of gas separation, where it can effectively improve the selectivity and permeability of the membrane for specific gases, meeting the demand for high-purity gases in industrial applications.

[0033] Finally, the siloxane group in 3-aminopropyl triethoxysilane can undergo condensation reaction with the hydroxyl groups on the surface of nano ZSM-5, forming stable chemical bonds, thereby enhancing the structural stability of nano ZSM-5. The functional groups such as amino groups on the surface of nano ZSM-5 modified by silane coupling agent can increase its adsorption capacity for specific substances. The amino groups in 3-aminopropyl triethoxysilane can form hydrogen bonds or chemical bonds with the organic polymer chains, thereby improving the dispersibility of porous nano ZSM-5 in organic polymers.

[0034] The silane coupling agent modified nano ZSM-5 mixed matrix membrane prepared in the application is compared with the nano ZSM-5 mixed matrix membrane modified by β-cyclodextrin (β-CD) which also has abundant CO2-philic groups, further demonstrating the excellent permeability and high CO2 / N2 selectivity of the silane coupling agent modified nano ZSM-5 mixed matrix membrane.

[0035] Through testing, the CO2 permeability PCO2 of the mixed matrix membrane prepared by using nano ZSM-5 as filler is 77.28 Barrer, and the CO2 / N2 selectivity is 71.08. The CO2 permeability PCO2 of the mixed matrix membrane prepared by using β-CD modified nano ZSM-5 as filler is 82.59 Barrer, and the CO2 / N2 selectivity reaches 78.23. The CO2 permeability PCO2 of the mixed matrix membrane prepared by using silane coupling agent modified nano ZSM-5 as filler is 110.96 Barrer, and the CO2 / N2 selectivity reaches a maximum of 87.56. The gas permeability and selectivity are significantly improved, which makes the silane coupling agent modified nano ZSM-5 based mixed matrix membrane have great application potential in industrial gas separation process, especially for improving the efficiency of CO2 capture and separation. This membrane not only effectively promotes the permeation of CO2, but also improves the permeation amount of CO2 while maintaining high CO2 / N2 selectivity, which is of great significance for reducing greenhouse gas emissions, improving energy utilization efficiency and realizing environmental sustainable development. In addition, this performance advantage also indicates the key role of silane coupling agent in improving the interfacial compatibility between nano filler and polymer matrix, which enhances the overall performance and stability of the membrane by enhancing the interaction between the two. Therefore, the silane coupling agent modified nano ZSM-5 filler provides a new strategy for the design and preparation of mixed matrix membranes, and is expected to be widely applied and further researched in the field of gas separation technology. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Scanning electron microscope image of the silane coupling agent modified nano ZSM-5 prepared in Example 1;

[0037] Figure 2 X-ray diffraction patterns of ZSM-5 prepared for Example 1 and Comparative Examples 2-5;

[0038] Figure 3 X-ray diffraction patterns of mixed matrix membranes prepared for Examples 1-4 and Comparative Example 1;

[0039] Figure 4 Performance diagrams of mixed matrix membranes prepared for Examples 1-4 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0040] The following illustrates the technical solutions in the present application by listing some specific examples, but the protection scope of the present application is not limited to the listed examples:

[0041] The materials used in the following examples are commercially available, wherein Pebax-1657 is purchased from Arkema, France; toluene, amorphous silica are purchased from Tianjin Damao Chemical Reagent Co., Ltd.; ethanol, aluminum isopropoxide, tetrapropylammonium hydroxide (TPAOH), 3-aminopropyltriethoxysilane (APTES), β-cyclodextrin (β-CD) are purchased from Aldrich Chemical Company, USA.

[0042] Example 1:

[0043] Step 1, by means of steam-assisted method, 1 g of silica and 0.017 g of aluminum isopropoxide are weighed according to the silicon aluminum ratio Si:Al = 200:1, and stirred until the aluminum isopropoxide is fully dissolved under the action of 0.7 mL of TPAOH. Then the silica is added, transferred into an open glass bottle, and then transferred into a polytetrafluoroethylene bottle. 5 mL of deionized water is added between the two, and then transferred into a reaction kettle. After aging at room temperature for 24 h, the reaction kettle is transferred into a 135℃ electric constant-temperature drying oven for reaction for 10 h. After centrifugal washing and drying in a blowing drying oven, calcination is carried out in a 570℃ muffle furnace to obtain nano ZSM-5;

[0044] Step 2, 50 mL of toluene is added to an A beaker, and 3 mL of APTES is added dropwise to it, so that the APTES is fully diffused in the toluene solution. 50 mL of toluene is added to a B beaker, and then 0.3136 g of nano ZSM-5 is added, so that the silicon content in the ZSM-5 and the silicon content in the APTES is 1:1.5. The solution in the A beaker is added dropwise into the B beaker, and the stirring speed is 800 r / min. After 2 hours of continuous stirring, the mixture is transferred to a round-bottom flask, and 2 drops of ultrapure water are added. After reaction in an 80℃ oil bath for 24 h, the mixture is washed by centrifugation with toluene and dried in a blowing drying oven. Finally, the silane coupling agent modified nano ZSM-5 is obtained;

[0045] Step 3, 22.85 g of ethanol and 9.79 g of distilled water were weighed and mixed, heated to 85℃ under stirring, then 1.01 g of Pebax-1657 was added to keep the temperature at 85℃ and stirred for 6 h to completely dissolve, to obtain a Pebax solution.

[0046] Step 4, 1 g of silane coupling agent modified nano ZSM-5 was taken in a glass bottle with a cover, 20 mL of anhydrous ethanol was added, and after ultrasonic treatment for 2 h, it was placed on a stirring table for stirring for 24 h to obtain a silane coupling agent modified nano ZSM-5 filler casting solution.

[0047] Step 5, 6.70 g of Pebax solution was taken in a reagent bottle, 0.2 mL of silane coupling agent modified nano ZSM-5 filler casting solution was added dropwise, and it was oscillated for 120 min using a vortex oscillator and ultrasonic treatment for 30 min, and then it was left to stand for 5 min to obtain a 5 wt.% mixed matrix membrane solution. The above-mentioned mixed matrix membrane solution was poured into a clean polytetrafluoroethylene mold, then the membrane was placed in a constant temperature oven for drying at 60℃ for 24 h, and finally it was dried for 24 h in a vacuum oven under vacuum to obtain a silane coupling agent modified nano ZSM-5 mixed matrix membrane. The thickness of the prepared mixed matrix membrane was 57-61 μm.

[0048] The separation performance of the above-mentioned mixed matrix membrane was tested, and the PCO2 was 87.62 Barrer and the αCO2 / N2 was 80.21. It can be clearly seen that the gas permeability and gas selectivity of the mixed matrix membrane are improved. Compared with the pure Pebax-1657 mixed matrix membrane, the CO2 permeation flux is increased by 56.52%, and the CO2 / N2 selectivity is increased by 101.89%; compared with the unmodified, the CO2 permeation flux is increased by 13.38%, and the CO2 / N2 selectivity is increased by 12.84%. Compared with the β-CD modified nano ZSM-5 mixed matrix membrane, the CO2 permeation flux is increased by 6.09%, and the CO2 / N2 selectivity is increased by 2.53%.

[0049] Figure 2 The XRD pattern of the nano ZSM-5 prepared in step 1 can be seen that the characteristic peaks appear at 2θ of 7.96°, 8.83°, 23.18°, 23.99° and 24.45°, which proves that the product prepared in step 1 has good crystallinity and is nano ZSM-5. Figure 1 The scanning electron microscope image of the silane coupling agent modified nano ZSM-5 prepared in step 2 can be seen from the figure that the nano ZSM-5 after modification by the silane coupling agent does not maintain the conventional morphology, but still maintains good dispersibility. Figure 3The X-ray diffraction spectrum of the nano ZSM-5 mixed matrix membrane modified by the silane coupling agent. The spectrum shows obvious diffraction peaks at 2θ angles of 7.96°, 8.83°, 23.18°, 23.99° and 24.45°, which confirms that the nano ZSM-5 is successfully introduced into the system of the mixed matrix membrane, and proves that the modification treatment of the silane coupling agent does not damage the crystal structure of the nano ZSM-5, but effectively maintains its crystal characteristics, which further verifies that the silane coupling agent modification method can enhance the interaction between the nano ZSM-5 and the polymer matrix while maintaining the integrity of the nano ZSM-5 crystal, thereby improving the overall performance of the mixed matrix membrane.

[0050] Example 2:

[0051] Step 1, by means of steam assisted method, 1g of silicon dioxide and 0.017g of aluminum isopropoxide were weighed according to the silicon aluminum ratio Si:Al=200:1, stirred until the aluminum isopropoxide was fully dissolved in 0.7mL of TPAOH, then the silicon dioxide was added, transferred into an open glass bottle, then the open glass bottle was transferred into a polytetrafluoro bottle, 5mL of deionized water was added between the two, then transferred into a reaction kettle, aged at room temperature for 24h, then the reaction kettle was transferred into a 135℃ electric heating constant temperature drying oven for reaction for 10h, centrifugal washing, drying in a blowing drying oven, calcination in a muffle furnace, to obtain nano ZSM-5;

[0052] Step 2, 50mL of toluene was added to A beaker, 3mL of APTES was added dropwise to it, and the APTES was fully diffused in the toluene solution; 50mL of toluene was added to B beaker, then 0.3136g of nano ZSM-5 was added, according to the silicon content in ZSM-5, the silicon content in ZSM-5 and APTES was 1:1.5, the solution in A beaker was added dropwise into B beaker, the stirring speed was 800r / min, and the stirring was continued for 2h, then the mixture was transferred to a round-bottom flask, 2 drops of ultrapure water were added, and the reaction was carried out at 85℃ oil bath for 24h, then the toluene was used for centrifugal washing, and the product was dried in a blowing drying oven, finally the silane coupling agent modified nano ZSM-5 was obtained;

[0053] Step 3, 22.85g of ethanol and 9.79g of distilled water were mixed, heated to 85℃ under stirring, then 1.01g of Pebax-1657 was added and kept at 85℃ for 6h to make it completely dissolved, to obtain a Pebax solution;

[0054] Step 4, 1g of silane coupling agent modified nano ZSM-5 was taken in a glass bottle with a lid, 20mL of ethanol was added, ultrasonic treatment was carried out for 2h, then it was placed on a stirring table for stirring for 24h, to obtain a silane coupling agent modified nano ZSM-5 filler casting solution;

[0055] Step 5, take 6.70 g of Pebax solution obtained in step 3 in a reagent bottle, and drop 0.4 mL of silane coupling agent modified nano ZSM-5 filler casting solution prepared in step 4 into it, and oscillate it with a vortex oscillator; 240 min and ultrasonic treatment; 30 min, and then stand for 5 min to obtain a 10 wt.% mixed matrix membrane solution. Pour the above-mentioned mixed matrix membrane solution into a clean polytetrafluoroethylene mold, and then place the membrane in a constant temperature oven at 60°C for drying for 24 h, and finally continue to dry in a vacuum oven under vacuum for 24 h to obtain a silane coupling agent modified nano ZSM-5 mixed matrix membrane. The thickness of the prepared mixed matrix membrane is 62-68 μm.

[0056] The separation performance of the above-mentioned mixed matrix membrane is tested to be PCO2= 110.96 Barrer, aCO2 / N2= 87.56, and it can be clearly seen that the gas permeability and gas selectivity of the mixed matrix membrane are improved. Compared with the pure Pebax-1657 mixed matrix membrane, the CO2 permeation flux is increased by 98.21%, and the CO2 / N2 selectivity is increased by 120.39%; compared with before modification, the CO2 permeation flux is increased by 43.58%, and the CO2 / N2 selectivity is increased by 23.19%; compared with the β-CD modified nano ZSM-5 mixed matrix membrane, the CO2 permeation flux is increased by 34.35%, and the CO2 / N2 selectivity is increased by 11.93%; at the same time, its performance breaks through the upper limit of Robbson in 2008.

[0057] Figure 3 The X-ray diffraction spectrum of the silane coupling agent modified nano ZSM-5 mixed matrix membrane. In the spectrum, there are obvious diffraction peaks at 2θ angles of 7.96°, 8.83°, 23.18°, 23.99° and 24.45°, which confirm that the nano ZSM-5 is successfully introduced into the system of the mixed matrix membrane, and prove that the modification treatment of the silane coupling agent does not cause damage to the crystal structure of the nano ZSM-5, but effectively maintains its crystal characteristics, which further verifies that the silane coupling agent modification method can enhance the interaction between the nano ZSM-5 and the polymer matrix while maintaining the integrity of the nano ZSM-5 crystal, thereby improving the overall performance of the mixed matrix membrane. In addition, the intensity of these characteristic peaks is higher than that of Example 1, which is due to the higher addition amount of the silane coupling agent modified nano ZSM-5 in Example 1.

[0058] Example 3:

[0059] Step 1, by means of steam-assisted method, 1 g of silicon dioxide and 0.017 g of aluminum isopropoxide were weighed according to the silicon aluminum ratio Si:Al = 200:1, and stirred until the aluminum isopropoxide was fully dissolved under the action of 0.7 mL of TPAOH, then the silicon dioxide was added, transferred into an open glass bottle, and then transferred into a polytetrafluoroethylene bottle, 5 mL of deionized water was added between the two, and then transferred into a reaction kettle, aged at room temperature for 24 h, then the reaction kettle was transferred into a 135°C electric heating constant temperature drying oven for reaction for 10 h, centrifugal washing, drying in a blowing drying oven, calcination in a muffle furnace, to obtain nano ZSM-5;

[0060] Step 2, 50 mL of toluene was added to an A beaker, and 3 mL of APTES was added dropwise, so that the APTES was fully diffused in the toluene solution; 50 mL of toluene was added to a B beaker, and then 0.3136 g of nano ZSM-5 was added, so that the silicon content in the ZSM-5 and the silicon content in the APTES was 1:1.5, the solution in the A beaker was added dropwise into the B beaker, and the stirring speed was 800 r / min; after 2 hours of continuous stirring, the mixture was transferred to a round-bottom flask, and then reacted in an 85°C oil bath for 24 h; then the mixture was washed with toluene and dried in a blowing drying oven, to obtain the silane coupling agent modified nano ZSM-5;

[0061] Step 3, 22.85 g of ethanol and 9.79 g of distilled water were weighed and mixed, and heated to 85°C under stirring, then 1.01 g of Pebax-1657 was added and stirred at 85°C for 6 h to completely dissolve, to obtain a Pebax solution;

[0062] Step 4, 1 g of the silane coupling agent modified nano ZSM-5 was taken in a glass bottle with a lid, 20 mL of ethanol was added, and ultrasonic treatment was performed for 2 h, then placed on a stirring table for stirring for 24 h, to obtain a silane coupling agent modified nano ZSM-5 filler casting solution;

[0063] Step 5, 6.70 g of the Pebax solution obtained in step 3 was taken in a reagent bottle, and 0.6 mL of the silane coupling agent modified nano ZSM-5 filler casting solution prepared in step 4 was added dropwise, and then oscillated for 240 min by using a vortex oscillator and ultrasonic treatment for 30 min, and then placed for 5 min, to obtain a 15 wt.% mixed matrix membrane solution; the mixed matrix membrane solution was poured into a clean polytetrafluoroethylene mold, then the membrane was placed in a constant temperature oven for drying at 60°C for 24 h, and finally vacuum drying was continued for 24 h in a vacuum oven to obtain a silane coupling agent modified nano ZSM-5 mixed matrix membrane. The thickness of the prepared mixed matrix membrane was 59-68 μm.

[0064] The separation performance of the mixed matrix membrane above was tested to be PCO2=95.84 Barrer, aCO2 / N2=83.65, which can be clearly seen that the gas permeability and gas selectivity of the mixed matrix membrane are improved. And compared with the pure Pebax-1657 mixed matrix membrane, the CO2 permeation flux is increased by 71.20%, and the CO2 / N2 selectivity is increased by 110.55%; compared with before modification, the CO2 permeation flux is increased by 24.02%, and the CO2 / N2 selectivity is increased by 17.68%; compared with the β-CD modified nano ZSM-5 mixed matrix membrane, the CO2 permeation flux is increased by 16.04%, and the CO2 / N2 selectivity is increased by 6.93%.

[0065] Figure 3 The X-ray diffraction spectrum of the nano ZSM-5 mixed matrix membrane modified by the silane coupling agent. In the spectrum, there are obvious diffraction peaks at 2θ angles of 7.96°, 8.83°, 23.18°, 23.99° and 24.45°, which confirm that the nano ZSM-5 is successfully introduced into the system of the mixed matrix membrane, and prove that the modification treatment of the silane coupling agent does not cause damage to the crystal structure of the nano ZSM-5, but effectively maintains its crystal characteristics, which further verifies that the silane coupling agent modification method can enhance the interaction between the nano ZSM-5 and the polymer matrix while maintaining the integrity of the nano ZSM-5 crystals, thereby improving the overall performance of the mixed matrix membrane. In addition, the intensity of these characteristic peaks is higher than that of Example 2, which is due to the higher addition amount of the nano ZSM-5 modified by the silane coupling agent than that of Example 2.

[0066] Example 4:

[0067] Step 1, by means of vapor assisted method, 1g of silicon dioxide and 0.017g of aluminum isopropanol were weighed according to the silicon aluminum ratio Si:Al=200:1, and stirred until the aluminum isopropanol was fully dissolved under the action of 0.7mL of TPAOH, then the silicon dioxide was added, and transferred into an open glass bottle, then the open glass bottle was transferred into a polytetrafluoroethylene bottle, 5mL of deionized water was added between the two, and then transferred into a reaction kettle, and aged at room temperature for 24h, then the reaction kettle was transferred into a 135℃ electric heating constant temperature drying oven for reaction for 10h, centrifugal washing, drying in a blowing drying oven, calcination in a muffle furnace, to obtain nano ZSM-5;

[0068] Step 2, 50 mL of toluene was added into a beaker A, 3 mL of APTES was added dropwise into the toluene solution, and the APTES was fully dispersed in the toluene solution; 50 mL of toluene was added into a beaker B, and then 0.3136 g of nano ZSM-5 was added, and the silicon content in the ZSM-5 was calculated to be 1:1.5 of the silicon content in the APTES, the solution in the beaker A was added dropwise into the beaker B, and the stirring speed was 800 r / min, and the stirring was continued for 2 hours, then the mixture was transferred to a round-bottom flask, 2 drops of ultrapure water were added, and the reaction was carried out at 85°C in an oil bath for 24 hours, then the mixture was washed by centrifugation with toluene and dried in a blast drying oven, and finally the nano ZSM-5 modified by the silane coupling agent was obtained;

[0069] Step 3, 22.85 g of ethanol and 9.79 g of distilled water were weighed and mixed, and heated to 85°C under stirring, then 1.01 g of Pebax-1657 was added and stirred at 85°C for 6 hours to completely dissolve, and a Pebax solution was obtained;

[0070] Step 4, 1 g of the nano ZSM-5 modified by the silane coupling agent was taken into a glass bottle with a lid, 20 mL of ethanol was added, and ultrasonic treatment was carried out for 2 hours, then the mixture was placed on a stirring table and stirred for 24 hours, and a casting solution of the nano ZSM-5 modified by the silane coupling agent was obtained;

[0071] Step 5, 6.70 g of the Pebax solution obtained in step 3 was taken into a reagent bottle, 0.8 mL of the casting solution of the nano ZSM-5 modified by the silane coupling agent was added dropwise, and the mixture was oscillated by a vortex oscillator for 240 minutes and ultrasonic treated for 30 minutes, and then was left to stand for 5 minutes, and a 20 wt.% mixed matrix membrane solution was obtained, the mixed matrix membrane solution was poured into a clean polytetrafluoroethylene mold, then the membrane was placed in a constant temperature oven and dried at 60°C for 24 hours, and finally the membrane was further dried in a vacuum oven under vacuum for 24 hours to obtain a mixed matrix membrane of the nano ZSM-5 modified by the silane coupling agent. The thickness of the prepared mixed matrix membrane was 61-67 μm.

[0072] The separation performance of the above-mentioned mixed matrix membrane was tested, and the PCO2 was 89.25 Barrer and the aCO2 / N2 was 81.13, which indicated that the gas permeability and gas selectivity of the mixed matrix membrane were improved. Compared with the pure Pebax-1657 mixed matrix membrane, the CO2 permeation flux was increased by 59.43%, and the CO2 / N2 selectivity was increased by 104.20%; compared with the unmodified one, the CO2 permeation flux was increased by 15.49%, and the CO2 / N2 selectivity was increased by 14.14%; compared with the nano ZSM-5 mixed matrix membrane modified by β-CD, the CO2 permeation flux was increased by 8.06%, and the CO2 / N2 selectivity was increased by 3.71%.

[0073] Figure 3 The X-ray diffraction spectrum of the nanometer ZSM-5 mixed matrix membrane modified by silane coupling agent. The spectrum shows obvious diffraction peaks at 2θ angles of 7.96°, 8.83°, 23.18°, 23.99° and 24.45°, which confirms that the nanometer ZSM-5 is successfully introduced into the system of the mixed matrix membrane, and proves that the modification treatment of the silane coupling agent does not damage the crystal structure of the nanometer ZSM-5, but effectively maintains its crystal characteristics, which further verifies that the silane coupling agent modification method can enhance the interaction between the nanometer ZSM-5 and the polymer matrix while maintaining the integrity of the nanometer ZSM-5 crystals, thereby improving the overall performance of the mixed matrix membrane. In addition, the intensity of these characteristic peaks is higher than that of Example 3, which is due to the higher amount of nanometer ZSM-5 modified by the silane coupling agent added in Example 3.

[0074] Comparative Example 1:

[0075] Step 1, 0.2g Pebax-1657 was placed in a flask with 6.47g ethanol in an oil bath at 85℃ for 6h to obtain a uniform concentration of Pebax solution;

[0076] Step 2, the above solution was treated by ultrasonic defoaming, and after standing, it was poured into a polytetrafluoroethylene mold, which was placed in a constant temperature oven at 60℃ for drying for 24h, and then placed in a vacuum oven for vacuuming to continue to remove the solvent for 24h, to obtain a pure Pebax mixed matrix membrane.

[0077] The separation performance of the pure Pebax-1657 mixed matrix membrane was tested to be PCO2=55.98 Barrer, αCO2 / N2=39.73.

[0078] Figure 3 The XRD spectrum of the pure Pebax-1657 mixed matrix membrane, as can be seen from the figure, shows a relatively wide diffraction peak at about 20°, which is mainly due to the diffraction of the PE segment in Pebax, which indicates that the Pebax-1657 polymer matrix itself has a lower crystal structure and a higher amorphous region. This amorphous structure helps the diffusion of gas molecules in the membrane, as they can pass through the disordered polymer chains more freely. In addition, this structural feature of the pure Pebax-1657 membrane also means that when fillers such as nanometer ZSM-5 are introduced, it may affect the crystallization behavior of the membrane, thereby affecting the gas separation performance of the membrane.

[0079] Comparative Example 2:

[0080] Step 1, by means of steam-assisted method, 1 g of silicon dioxide and 0.017 g of aluminum isopropoxide were weighed according to the silicon aluminum ratio Si:Al = 200:1, and stirred until the aluminum isopropoxide was fully dissolved under the action of 0.7 mL of TPAOH, then the silicon dioxide was added, transferred into an open glass bottle, and then transferred into a polytetrafluoroethylene bottle, a small amount of deionized water was added between the two, and then transferred into a reaction kettle, aged at room temperature for 24 h, then the reaction kettle was transferred into a 135°C electric constant-temperature drying oven for reaction for 10 h, centrifugal washing, drying in a blowing drying oven, calcination in a 570°C muffle furnace, and dry ZSM-5 nanoparticles were obtained.

[0081] Step 2, 1 g of the prepared ZSM-5 nanoparticles was added to 20 mL of ethanol, and after ultrasonic treatment for 2 h, it was placed on a stirring table for stirring for 24 h or more, to obtain a ZSM-5 casting solution;

[0082] Step 3, 22.85 g of ethanol and 9.79 g of distilled water were weighed and mixed, and heated to 85°C under stirring, then 1.01 g of Pebax-1657 was added and stirred at 85°C for 6 h to completely dissolve, to obtain a Pebax solution;

[0083] Step 4, 6.70 g of the Pebax solution obtained in step 2 was weighed in a reagent bottle, and 0.2 mL of the ZSM-5 casting solution prepared in step 2 was added dropwise, and a turbine oscillator was used for oscillation for 120-240 min and ultrasonic treatment for 15-30 min, and after the filler and the polymer solution were uniformly mixed, the 10 wt.% mixed matrix membrane solution was left to deaerate;

[0084] Step 5, the prepared mixed matrix membrane solution was poured into a polytetrafluoroethylene flat plate, placed in a 60°C constant-temperature oven for drying for 24 h, and then placed in a vacuum oven for vacuuming to continue solvent removal for 24 h, to obtain a ZSM-5 / Pebax mixed matrix membrane. The prepared mixed matrix membrane has a thickness of 48-69 μm.

[0085] The separation performance of the ZSM-5@Pebax-1657 mixed matrix membrane was tested to be PCO2= 77.28 Barrer, and aCO2 / N2= 71.08.

[0086] Figure 2 The XRD pattern of the nano ZSM-5 prepared in step 1 can be seen to have characteristic peaks at 2θ of 7.96°, 8.83°, 23.18°, 23.99°, and 24.45°, proving that the product prepared in step 1 has good crystallinity and is nano ZSM-5.

[0087] Comparative Example 3:

[0088] Step 1, by means of steam-assisted method, 1 g of silicon dioxide and 0.017 g of aluminum isopropoxide were weighed according to the silicon aluminum ratio Si:Al = 200:1, and stirred until the aluminum isopropoxide was fully dissolved under the action of 0.7 mL of TPAOH, then the silicon dioxide was added, transferred into an open glass bottle, and then transferred into a polytetrafluoroethylene bottle, a small amount of deionized water was added between the two, and then transferred into a reaction kettle, aged at room temperature for 24 h, then the reaction kettle was transferred into a 135°C electric heating constant temperature drying oven for reaction for 10 h, centrifugal washing, drying in a blowing drying oven, calcination in a muffle furnace, and dry ZSM-5 nanoparticles were obtained;

[0089] Step 2, the molar amount of ZSM-5: the molar amount of β-CD = 1:1.2, 50 mL of toluene was added to beaker A, then 2 mL of β-CD was added dropwise to promote the diffusion of β-CD in the toluene solution, 50 mL of toluene was added to beaker B, then 0.3675 g of pure ZSM-5 nanoparticles obtained in step 1 was added, the A and B beakers were stirred vigorously for 2 h, then transferred to a round-bottom flask, two drops of ultrapure water were added, then reacted in a 90°C oil bath for 24 h, then filtered and washed with toluene, and dried, finally β-CD modified nano ZSM-5 was obtained;

[0090] Step 3, 22.85 g of ethanol and 9.79 g of distilled water were mixed, heated to 85°C under stirring, then 1.01 g of Pebax-1657 was added and kept at 85°C for 6 h to completely dissolve, and a Pebax solution was obtained;

[0091] Step 4, 1 g of β-CD modified nano ZSM-5 nanoparticles obtained in step 2 was taken in a glass bottle with a lid, 20 mL of ethanol was added, ultrasonicated for 2 h, then placed on a stirring table for stirring for 24 h, and a β-CD modified nano ZSM-5 casting solution was obtained;

[0092] Step 5, 6.70 g of the Pebax solution obtained in step 3 was taken in a reagent bottle, 0.4 mL of the β-CD modified nano ZSM-5 casting solution prepared in step 4 was added dropwise, and vortexed for 120 min and ultrasonicated for 15 min, then stood for 5 min, and a 10 wt.% mixed matrix membrane solution was obtained;

[0093] Step 6, the above mixed matrix membrane solution was poured into a clean polytetrafluoroethylene mold, then the membrane was placed in a constant temperature oven for drying at 60°C for 24 h, and finally vacuum dried in a vacuum oven for 24 h to obtain a β-CD modified nano ZSM-5 mixed matrix membrane, and the prepared mixed matrix membrane had a thickness of 57-66 μm.

[0094] The separation performance of the tested β-CD modified nano ZSM-5 mixed matrix membrane was PCO2=82.59 Barrer, αCO2 / N2=78.23.

[0095] Figure 2 From the XRD pattern of the nano ZSM-5 prepared in step 1, it can be seen that characteristic peaks appear at 2θ of 7.96°, 8.83°, 23.18°, 23.99°, and 24.45°, proving that the product prepared in step 1 has good crystallinity and is nano ZSM-5.

[0096] Comparative Example 4:

[0097] Synthesis of ZSM-5 using APTES and TPAOH as dual templates:

[0098] Step 1: Mix 0.7 mL of TPAOH and 1.5 mL of APTES;

[0099] Step 2: Weigh 0.017 g of aluminum isopropoxide, mix it with the mixed solution obtained in step 1, and stir it thoroughly to dissolve it;

[0100] Step 3, weigh 1.01 g of silicon dioxide, mix it with the mixed solution obtained in step 2, and stir thoroughly;

[0101] Step 4: transfer the mixture to a reactor and age it at room temperature for 24 hours, then transfer the reactor to a 130°C oven and react for 4 hours;

[0102] Step 5: Wash the mixture three times by centrifugation with deionized water, and then dry it in a 60°C forced air drying oven;

[0103] Step 6: Grind the dried sample in a mortar and then calcine it in a muffle furnace at 570° C. to remove excess template.

[0104] like Figure 2 As shown in the XRD pattern, characteristic peaks do not appear at 2θ values ​​of 7.96°, 8.83°, 23.18°, 23.99°, or 24.45°. Instead, a broad, diffusely scattered peak appears. This indicates that the atomic arrangement of the sample lacks long-range order, exhibiting typical amorphous structural characteristics, and the product has not crystallized.

[0105] Comparative Example 5:

[0106] Synthesis of ZSM-5 using β-CD and TPAOH as dual templates:

[0107] Step 1: Mix 1 mL of TPAOH and 1.5 mL of β-CD;

[0108] Step 2: Weigh 0.017 g of aluminum isopropoxide, mix it with the mixed solution obtained in step 1, and stir it thoroughly to dissolve it;

[0109] Step 3, weigh 1.01 g of silicon dioxide, mix it with the mixed solution obtained in step 2, and stir thoroughly;

[0110] Step 4: transfer the mixture to a reactor and age it at room temperature for 24 hours, then transfer the reactor to a 130°C oven and react for 4 hours;

[0111] Step 5: Wash the mixture three times by centrifugation with deionized water, and then dry it in a 60°C forced air drying oven;

[0112] Step 6: Grind the dried sample in a mortar and then calcine it in a muffle furnace at 570° C. to remove excess template.

[0113] like Figure 2 As shown in the XRD pattern, characteristic peaks do not appear at 2θ values ​​of 7.96°, 8.83°, 23.18°, 23.99°, or 24.45°. Instead, a broad, diffusely scattered peak appears. This indicates that the atomic arrangement of the sample lacks long-range order, exhibiting typical amorphous structural characteristics, and the product has not crystallized.

[0114] Figure 4 This is a performance diagram of the mixed matrix membranes prepared in Examples 1 to 4 and Comparative Examples 1 to 3. As shown in the figure, the gas permeability and gas selectivity of the mixed matrix membranes of Examples 1 to 4 are generally higher than those of Comparative Examples 1 to 3, and Example 2 has the best gas permeability and gas selectivity, and its performance has exceeded the 2008 Robbson upper limit (black line in the figure).

[0115] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a silane coupling agent-modified nano-ZSM-5 mixed matrix membrane, characterized in that, The method comprises the following steps: Step 1, 1-1.5 parts of aluminum isopropyl alcohol is dissolved in 48-80 parts of organic template agent, and stirred until the aluminum isopropyl alcohol is fully dissolved, 52-65 parts of silica is added and stirred uniformly to obtain a micro-wet gel mixture, the mixture is added to an open glass container, and then transferred to an inner liner of a hydrothermal reaction kettle, deionized water is added outside the glass bottle mouth of the inner liner, after the hydrothermal reaction kettle is aged at room temperature for 24-72 hours, the hydrothermal reaction kettle is transferred to an electric heating constant temperature drying oven for crystallization treatment, and then a crystalline product is obtained, the product is centrifuged, washed, dried and calcined to obtain dry nano ZSM-5; Step 2, 50-150 parts of toluene is added to an A beaker, 1-5 parts of 3-aminopropyl triethoxysilane is added dropwise to the toluene solution, and the solution is fully dissolved in the toluene solution; 50-150 parts of toluene is added to a B beaker, and then 0.05-1 parts of nano ZSM-5 is added, the solution in the A beaker is added dropwise into the B beaker, and the process is continuously stirred at a speed of 800 r / min, and after 2-5 hours of continuous stirring, the mixture is transferred to a round-bottom flask, 1-5 drops of ultrapure water is added dropwise, and the mixture is reacted in an 80-90 ℃ oil bath for 12-36 hours, and then the mixture is washed and dried with toluene to obtain a silane coupling agent modified nano ZSM-5; Step 3, 0.2-0.5 parts of Pebax-1657 and 6.47-10 parts of ethanol are added to a flask, and the flask is heated in an 85-95 ℃ oil bath for 6-12 hours to obtain a uniform concentration of Pebax-1657 solution; Step 4, the silane coupling agent modified nano ZSM-5 is added to anhydrous ethanol as a filler, ultrasonic treatment is performed for 2-6 hours, and then the mixture is stirred on a stirring table for 24-72 hours to obtain a silane coupling agent modified nano ZSM-5 filler casting solution; Step 5, 6-7 parts of the Pebax-1657 solution is weighed in a reagent bottle, and 0.2-1.5 parts of the silane coupling agent modified nano ZSM-5 filler casting solution is added dropwise, a turbine oscillator is used for oscillation for 120-240 minutes and ultrasonic treatment for 15-30 minutes, the filler and the polymer solution are uniformly mixed, the casting solution is left to deaerate, the prepared mixed matrix membrane solution is poured onto a polytetrafluoroethylene flat plate, and then placed in a constant temperature oven at 60-80 ℃ for drying for 18-24 hours, and then placed in a vacuum oven at 60-80 ℃ for vacuumizing and continuing to remove solvent for 18-30 hours to obtain a silane coupling agent modified nano ZSM-5 mixed matrix membrane.

2. The method for preparing silane coupling agent modified nano ZSM-5 mixed matrix membrane according to claim 1, characterized in that, The mass ratio of the ethanol to water in step 3 is 6-10:1-4.

3. The method for preparing silane coupling agent modified nano ZSM-5 mixed matrix membrane according to claim 1, characterized in that, The centrifuge in step 1 uses a centrifuge with a speed of 7000-12000 rpm, and the centrifugation time is 5-15 minutes.

4. The method for preparing silane coupling agent modified nano ZSM-5 mixed matrix membrane according to claim 1, characterized in that, The content of the silane coupling agent modified nano ZSM-5 in the silane coupling agent modified nano ZSM-5 filler casting solution in step 4 is 1%-4%.

5. The method for preparing silane coupling agent modified nano ZSM-5 mixed matrix membrane according to claim 1, characterized in that, The thickness of the silane coupling agent modified nano ZSM-5 mixed matrix membrane in step 5 is 30-70 μm.

6. The method of claim 1, wherein the method is characterized by: The crystallization temperature of the electric heating constant temperature drying oven in step 1 is 120-150 DEG C, and the time is 4-16 h.

7. The method of claim 1, wherein the method is characterized by: The drying temperature in step 2 is 60-90 DEG C, and the time is 12-36 h.

8. The method for preparing silane coupling agent modified nano ZSM-5 mixed matrix membrane according to any one of claims 1-7, characterized in that, The prepared mixed matrix membrane is used for CO2 / N2 gas separation.

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