A nanofiltration membrane based on transition crystalline monolayer nanosheets and a preparation method and application thereof

Abstract

This invention provides a nanofiltration membrane based on a transition-phase monolayer nanosheet, its preparation method, and its application. The nanofiltration membrane exhibits good mechanical strength, excellent chemical and physical stability, high shape selectivity for gas molecules, and low gas mass transfer resistance. The purifier utilizes the nanofiltration membrane to achieve rapid and efficient removal of impurities related to the production and use of environmentally friendly insulating gases. The purifier has a simple structure, extremely low energy consumption, and is easy to operate. A miniature in-situ impurity gas purification and separation device developed based on this purifier, when installed in production or electrical equipment, can selectively remove trace impurities from environmentally friendly insulating gases, achieving deep purification during the production and use of these gases. It is easy to maintain and has low cost. Due to the very low mass transfer resistance of the nanofiltration membrane, the system requires a low pressure differential for operation. All of these factors significantly reduce the production and use costs of environmentally friendly insulating gases, effectively promoting their large-scale application and widespread adoption in the power industry.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification technology, specifically relating to a nanofiltration membrane based on transitional crystalline phase monolayer nanosheets, its preparation method, and its application. Background Technology

[0002] In electrical equipment, insulating gases are used in large quantities. SF6 gas, due to its excellent insulation and arc-quenching properties, is currently the most widely used electrical insulating gas. However, SF6 gas has an extremely high greenhouse effect and has been listed as one of the six greenhouse gases with restricted emissions under the Kyoto Protocol. Especially with the intensification of global climate change and the accelerated construction of the global energy internet in recent years, countries have placed higher demands on the environmental friendliness of insulating gases. Perfluoroisobutyronitrile (C4) and perfluoropentacarbonyl (C5) are the most promising alternatives to SF6, significantly reducing their greenhouse effect, and are currently being extensively researched and applied in various electrical equipment. However, the production routes for C4 and C5 are long and complex, and the gases often contain many reaction impurities. Furthermore, C4 and C5 are more prone to decomposition during ionization in electrical equipment, generating various byproduct impurities. These impurities have a significant impact on the electrical properties of insulating gases. Conventional separation and purification methods include low-temperature distillation and molecular sieve sieving, but these methods require large equipment, consume high energy, and are cumbersome to use. Developing simple, convenient, and economical environmentally friendly insulating gas purification technologies and devices is of great significance for the practical application of environmentally friendly insulating gases. It can effectively reduce the production and use costs of environmentally friendly insulating gases and promote their commercial application.

[0003] Therefore, it is currently necessary to address the problems of existing filter membranes having low shape selectivity for environmentally friendly insulating gas molecules, high gas mass transfer resistance, and complex environmentally friendly insulating gas purifiers. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of low shape selectivity of existing filter membranes, high gas mass transfer resistance, and complexity of environmentally friendly insulating gas purifiers. It provides a nanofiltration membrane based on transition phase monolayer nanosheets, its preparation method, and its application. This nanofiltration membrane has excellent mechanical strength and chemical and physical stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a nanofiltration membrane based on transitional crystalline phase monolayer nanosheets involves mixing a nanosheet suspension with a polymer solution to obtain a mixed coating solution; coating the mixed coating solution onto a supporting membrane material to obtain a coating layer; removing the coating layer from the supporting membrane material, drying it, and aging it to obtain a nanofiltration membrane based on transitional crystalline phase monolayer nanosheets.

[0007] Furthermore, the nanosheet suspension is prepared by mixing transition phase monolayer nanosheets with ethanol to obtain a nanosheet suspension; the polymer solution is prepared by mixing a water-soluble polymer with water or mixing an alcohol-soluble polymer with ethanol to obtain a polymer solution; the water-soluble polymer is PVA, polyacrylamide, polyethylene glycol or sodium carboxymethyl cellulose; the alcohol-soluble polymer is PVP.

[0008] Furthermore, the mass concentration of the nanosheet suspension is 5-100 mg / L, the mass concentration of the polymer solution is 50-1000 mg / L, and the mass ratio of the nanosheet suspension to the polymer solution is 1:1-10:1.

[0009] Furthermore, the supporting membrane material has several micropores, the aging temperature is 50-90℃, and the aging time is 10-40 minutes.

[0010] Furthermore, the support film material is circular, the coating is performed by adding 10-500 μL of mixed coating solution to the support film material per square centimeter, the coating method is spin coating, and the thickness of the coating is 50-500 nm.

[0011] Furthermore, the mixed coating solution is diluted 10 times with alcohol before being coated onto the support film material. The support film material is strip-shaped. The coating involves adding 20-400 μL of the mixed coating solution to each square centimeter of support film material. The coating method is roller coating or spray coating. The thickness of the coating is 5-100 nm.

[0012] A nanofiltration membrane based on a transitional crystalline phase monolayer nanosheet is prepared using the preparation method described above, and the nanofiltration membrane has controllable single-molecule-sized micropores.

[0013] An insulating and environmentally friendly gas separation and purification device based on a nanofiltration membrane of a transitional crystalline phase monolayer nanosheet is disclosed. The separation and purification device includes a support body in which a plurality of nanofiltration membranes are installed. The support body is provided with an air inlet and an air outlet.

[0014] Furthermore, the support body is a cylindrical structure or a multi-layer sandwich structure, the air inlet is set as a raw material gas inlet, and the air outlet is set as a purified gas outlet and a waste gas outlet.

[0015] Furthermore, the nanofiltration membranes are arranged in parallel.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] This invention provides a method for preparing a nanofiltration membrane based on transition-phase monolayer nanosheets. The method involves combining a nanosheet suspension with a polymer solution, coating the resulting solution onto a porous support membrane material with high mechanical strength to form a coating layer. After drying and aging, a continuous and dense nanofiltration membrane is obtained. By selecting a porous support membrane material with high mechanical strength, the final nanofiltration membrane exhibits high mechanical strength and durability. This nanofiltration membrane possesses good mechanical strength, good chemical and physical stability, high gas molecule shape selectivity, and low gas mass transfer resistance.

[0018] This invention utilizes transition-phase monolayer nanosheets to prepare nanofiltration membranes with controllable single-molecule-sized micropores, achieving the separation and purification of impurities formed in insulating and environmentally friendly gases during preparation and use in high-voltage electrical equipment. The nanofiltration membrane based on transition-phase monolayer nanosheets provided by this invention achieves deep purification of environmentally friendly insulating gases during production and use by leveraging the extremely high uniformity of layer thickness and the controllable structure and shape of the nanopores.

[0019] The nanofiltration membrane-based insulating and environmentally friendly gas separation and purification device provided by this invention has the advantages of simple structure, low energy consumption, convenient operation and maintenance, and low cost. When the raw gas flows through the nanofiltration membrane, impurities with smaller molecular sizes seep out from the pores of the nanofiltration membrane, thus separating them from the insulating gas. The nanofiltration membrane based on transition crystal phase monolayer nanosheets has high molecular shape selectivity and low mass transfer resistance. The system requires a low pressure difference to operate, which can meet the needs of online and in-situ separation and purification of insulating and environmentally friendly gases. The complexity of the device is greatly reduced, which significantly reduces the production and use costs of insulating and environmentally friendly gases, and can effectively promote the large-scale application and popularization of insulating and environmentally friendly gases in the power industry.

[0020] This invention provides an insulating and environmentally friendly gas separation and purification device. The purifier is based on a parallel-arranged transition-phase monolayer nanosheet nanofiltration membrane. The environmentally friendly insulating gas feedstock flows in through the feedstock gas inlet of the support structure. Impurity gases flow out through the micropores of the transition-phase monolayer nanosheets as they pass through the nanofiltration membrane and escape through the exhaust outlet. This purification process achieves rapid and efficient removal of impurities related to the production and use of environmentally friendly insulating gases. The purification device has a simple structure, extremely low energy consumption, and is easy to operate. Based on this purifier, a miniature in-situ impurity gas purification and separation device can be installed in production or electrical equipment to selectively remove trace impurities from insulating and environmentally friendly gases, achieving deep purification during the production and use of these gases. It is easy to maintain and has low cost. Attached Figure Description

[0021] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is an electron microscope image of the transition crystal phase material of the present invention.

[0023] Figure 2 Electron micrograph of the transition crystalline phase monolayer nanosheets prepared by exfoliation of the transition crystalline phase material of the present invention.

[0024] Figure 3 An atomic force microscope image of the transitional crystalline monolayer nanosheets prepared by exfoliation of the transitional crystalline material of this invention. Detailed Implementation

[0025] The present invention will be further explained in detail below with reference to the accompanying drawings:

[0026] This invention provides a convenient and efficient insulating and environmentally friendly gas separation and purification device. Based on a parallel-arranged transition-phase ultrathin nanosheet nanofiltration membrane, this device achieves rapid and efficient removal of impurities related to the production and use of environmentally friendly insulating gases. The purification device has a simple structure, extremely low energy consumption, and is easy to operate. The nanofiltration membrane features good mechanical strength, good chemical and physical stability, high shape selectivity for gas molecules, and low gas mass transfer resistance. A miniature in-situ impurity gas purification and separation device developed based on this purifier, when installed in production or electrical equipment, can selectively remove trace impurities from environmentally friendly insulating gases, achieving deep purification during the production and use of these gases. It is easy to maintain and has low cost. Due to the very low mass transfer resistance of the nanofiltration membrane, the system requires a low pressure differential for operation. All of these factors significantly reduce the production and use costs of environmentally friendly insulating gases, effectively promoting their large-scale application and widespread use in the power industry.

[0027] This invention provides an insulating and environmentally friendly gas separation and purification device based on a nanofiltration membrane prepared from transition-phase monolayer nanosheets. The transition-phase ultrathin nanosheets have a thickness of 1-10 nanometers and extremely high uniformity. Based on molecular size simulation and nanosheet micropore size screening, transition-phase monolayer nanosheets with micropores of 0.5-2 nm are prepared. These nanosheets are then combined with a water-soluble polymer and coated onto a porous support membrane material with high mechanical strength, forming a coating with a thickness of 50-500 nm. After drying and aging, a continuous and dense membrane layer is obtained. By selecting a porous support membrane material with high mechanical strength, the final nanofiltration membrane possesses high mechanical strength and durability. The nanofiltration membrane is placed within an airtight support structure, which has a feed gas inlet, a purified gas outlet, and a waste gas outlet. When the feed gas flows through the nanofiltration membrane, smaller impurity gases permeate through the pores on the nanofiltration membrane nanosheets, thus separating from the insulating gas. Because the nanofiltration membrane has a high shape selectivity for gas molecules and low mass transfer resistance, the device can operate at lower pressures, meeting the needs for online and in-situ separation and purification of insulating and environmentally friendly gases.

[0028] Furthermore, the preparation of the aforementioned transitional crystalline phase monolayer nanosheets includes the following steps:

[0029] (1) Preparation of transition phase material: Tricarboxylic acid of the bicyclic oxacalix[2]arene[2]triazine core and metal ion salts, such as chromium salts, manganese salts, iron salts, cobalt salts, nickel salts, copper salts, zinc salts, zirconium salts and cadmium salts, are added to the reactor at a ratio of 1:2-10. A reaction solvent is added, the temperature is raised and controlled for a certain time, and after the crystal product is precipitated, the mother liquor is filtered off and washed to obtain the transition phase material. For example Figure 1 The image shown is an electron microscope image of a transition phase material.

[0030] (2) Preparation of transition phase monolayer nanosheets: A certain amount of transition phase material is taken, and an appropriate amount of exfoliating solvent (any two of methanol, dichloromethane, chloroform, ethanol, acetone, and n-propanol) is added. After ball milling, ultrasonic treatment is performed to achieve batch preparation of transition phase monolayer nanosheets. The obtained transition phase monolayer nanosheets have high uniformity of layer thickness, large size, and smooth surface, with a thickness between 1-5 nm. Figure 2 The image shown is an electron microscope (EM) image of a transitional crystalline monolayer nanosheet prepared by exfoliation of a transitional crystalline material. Figure 3 Atomic force microscopy image of a transitional crystalline monolayer nanosheet prepared by exfoliation of a transitional crystalline material.

[0031] Furthermore, the preparation of the above-mentioned nanofiltration membrane includes the following steps:

[0032] (1) The ultrathin nanosheets obtained by exfoliation are prepared into a nanosheet suspension of 5-100 mg / L with ethanol.

[0033] (2) Prepare a polymer solution of 50-1000 mg / L by mixing water-soluble or alcohol-soluble polymers such as PVA, PVP, polyacrylamide, polyethylene glycol, sodium carboxymethyl cellulose with water or ethanol.

[0034] (3) Mix the nanosheet suspension and the polymer solution in a ratio of 1:1 to 10:1 to prepare a mixed coating solution.

[0035] (4) Spin-coat the nanosheet mixed coating solution onto the circular porous support membrane material. Add 10-500ul of mixed coating solution to each square centimeter of circular porous support membrane material. After coating evenly, remove the coating and let it dry. Then age it at 50-90℃ for 10-40 minutes.

[0036] (5) Alternatively, dilute the mixed coating solution with alcohol by 10 times and roll or spray it onto the strip porous support membrane material. Add 20-400 μL of the mixed coating solution diluted with alcohol by 10 times per square centimeter of strip porous support membrane material. After coating evenly, let the coating dry and then age it at 50-90℃ for 10-40 minutes.

[0037] (6) The thickness of the obtained nanofiltration membrane on the porous support membrane material is 5-100 nm.

[0038] Furthermore, the construction of an environmentally friendly insulating gas separation and purification device includes the following steps:

[0039] (1) The prepared nanofiltration membrane is installed in an airtight support, which has a raw gas inlet, a purified gas outlet and a waste gas outlet.

[0040] (2) The environmentally friendly insulating gas raw material gas flows in from the raw material gas inlet of the support, and the impurity gas flows out from the micropores of the transition crystal phase ultrathin nanosheets when it flows through the nanofiltration membrane and escapes from the waste gas outlet. The purified environmentally friendly insulating gas flows out from the purified gas outlet, thereby realizing the rapid and efficient removal of relevant impurities in the production and use of environmentally friendly insulating gas.

[0041] The invention will be further explained in detail below with reference to implementation examples:

[0042] Example 1

[0043] Preparation of bicyclic oxacalix[2]arene[2]triazine tricarboxylic acid:

[0044] 0.05 mol cyanuric chloride and 0.065 mol anhydrous aluminum trichloride were added to a 250 mL round-bottom flask, followed by 100 mL toluene. The mixture was stirred for 5-10 hours, quenched with ice water, and recrystallized from the organic phase to obtain intermediate a. 3.6 g of intermediate a, 1.5 g of phloroglucinol, and 5.0 g of cesium carbonate were reacted at room temperature for 3-5 hours in dimethyl sulfoxide as solvent. The mixture was extracted and separated by column chromatography to obtain intermediate b. 0.5 g of intermediate b, 120 mg of chromium trioxide, and 320 mg of periodic acid were added to a 100 mL round-bottom flask, followed by 40 mL of acetonitrile as solvent. The mixture was stirred at room temperature for 8-10 hours, extracted, and the solvent was evaporated to obtain a white solid, which is the carboxylic acid ligand.

[0045] Preparation of Mn-based transition phase monolayer nanosheets:

[0046] Carboxylic acid ligands and anhydrous manganese chloride were added to THF, and the temperature was raised to 90°C at a rate of 0.1°C / min and held for a period of time. Then, the temperature was cooled to room temperature at a rate of 1°C / min and filtered to obtain a transparent crystalline transition phase material. After soaking in a mixed solvent (methanol and dichloromethane), ultrathin Mn-MOF nanosheets with a thickness of 1-5 nm were obtained in large quantities after ball milling, sonication, and standing. The nanosheets were mainly monolayers.

[0047] Preparation of Mn-based transition crystal phase monolayer nanosheet nanofiltration membranes:

[0048] The prepared Mn-MOF nanosheets were weighed and prepared into a nanosheet suspension with ethanol. Polyacrylamide with a molecular weight of 5 million was prepared into a polyacrylamide aqueous solution. The nanosheet suspension and the polyacrylamide aqueous solution were mixed in proportion to prepare a mixed solution. Then, 2 ml of the mixed solution was rolled onto a strip-shaped PTFE-supported microporous membrane (30 cm * 2 cm). After even coating, the coating was removed and dried. Then, the membrane was aged to obtain a strip-shaped nanofiltration membrane.

[0049] Fabrication of a gas separator based on a Mn-based transition crystal phase monolayer nanosheet nanofiltration membrane:

[0050] A gas separator was fabricated by installing the prepared elongated nanofiltration membrane in a gas filter. The filter has a multi-layer sandwich structure. When a mixture of C4 and nitrogen is passed through the gas separator, experiments show that only nitrogen permeates out of the nanofiltration membrane.

[0051] Example 2

[0052] 0.05 mol cyanuric chloride and 0.065 mol anhydrous aluminum trichloride were added to a 250 mL round-bottom flask, followed by 100 mL toluene. The mixture was stirred for 5-10 hours, quenched with ice water, and recrystallized from the organic phase to obtain intermediate a. 3.6 g of intermediate a, 1.5 g of phloroglucinol, and 5.0 g of cesium carbonate were reacted at room temperature for 3-5 hours in dimethyl sulfoxide as solvent. The mixture was extracted and separated by column chromatography to obtain intermediate b. 0.5 g of intermediate b, 120 mg of chromium trioxide, and 320 mg of periodic acid were added to a 100 mL round-bottom flask, followed by 40 mL of acetonitrile as solvent. The mixture was stirred at room temperature for 8-10 hours, extracted, and the solvent was evaporated to obtain a white solid, which is the carboxylic acid ligand.

[0053] Preparation of Mn-based transition phase monolayer nanosheets:

[0054] Carboxylic acid ligands and anhydrous manganese chloride were added to DMF, and the temperature was raised to 90°C at a rate of 0.1°C / min and held for a period of time. Then, the temperature was cooled to room temperature at a rate of 1°C / min and filtered to obtain a transparent crystalline transition phase material. After soaking in a mixed solvent (methanol and chloroform), the material was ball-milled, sonicated, and allowed to stand to obtain ultrathin Mn-MOF nanosheets in large quantities with a thickness of 1-5 nm, mainly in monolayer form.

[0055] Preparation of Mn-based transition crystal phase monolayer nanosheet nanofiltration membranes:

[0056] The prepared Mn-MOF nanosheets were weighed and prepared into a nanosheet suspension with ethanol. PVA with a molecular weight of 42,000 was prepared into a PVA ethanol solution. The nanosheet suspension and the PVA ethanol solution were mixed in proportion to prepare a mixed solution. Then, 2 ml of the mixed solution was spin-coated onto a PTFE-supported microporous membrane with a diameter of 5 cm. After coating evenly, the coating was removed and dried. Then, the membrane was aged to obtain a nanofiltration membrane.

[0057] Fabrication of a gas separator based on a Mn-based transition crystal phase monolayer nanosheet nanofiltration membrane:

[0058] The prepared circular nanofiltration membrane was installed in a gas filter. The filter has a cylindrical structure with two air inlets at the top and one at the bottom. A mixture of C4 and nitrogen was passed through the membrane material, and experiments showed that only nitrogen could pass through.

[0059] Example 3

[0060] Preparation of Mn-based transition phase monolayer nanosheets:

[0061] 0.05 mol cyanuric chloride and 0.065 mol anhydrous aluminum trichloride were added to a 250 mL round-bottom flask, followed by 100 mL toluene. The mixture was stirred for 5-10 hours, quenched with ice water, and recrystallized from the organic phase to obtain intermediate a. 3.6 g of intermediate a, 1.5 g of phloroglucinol, and 5.0 g of cesium carbonate were reacted at room temperature for 3-5 hours in dimethyl sulfoxide as solvent. The mixture was extracted and separated by column chromatography to obtain intermediate b. 0.5 g of intermediate b, 120 mg of chromium trioxide, and 320 mg of periodic acid were added to a 100 mL round-bottom flask, followed by 40 mL of acetonitrile as solvent. The mixture was stirred at room temperature for 8-10 hours, extracted, and the solvent was evaporated to obtain a white solid, which is the carboxylic acid ligand.

[0062] Carboxylic acid ligands and anhydrous manganese chloride were added to THF, heated at a rate of 0.1℃ / min and held for a period of time, then cooled to room temperature at a rate of 1℃ / min and filtered to obtain a transparent crystalline transition phase material. After soaking in a mixed solvent (chloroform and ethanol), ultrathin Mn-MOF nanosheets with a thickness of 1-5 nm were obtained in large quantities after ball milling, sonication and standing. The nanosheets were mainly monolayers.

[0063] Preparation of Mn-based transition crystal phase monolayer nanosheet nanofiltration membranes:

[0064] The prepared Mn-MOF nanosheets were weighed and prepared into a nanosheet suspension with ethanol. Sodium carboxymethyl cellulose with a molecular weight of 5 million was prepared into an aqueous solution of sodium carboxymethyl cellulose. The nanosheet suspension and the sodium carboxymethyl cellulose aqueous solution were mixed in proportion to prepare a mixed solution. Then, 2 ml of the mixed solution was sprayed onto a strip-shaped PTFE-supported microporous membrane (30 cm * 2 cm). After even coating, the coating was removed and dried. Then, the membrane was aged to obtain a strip-shaped nanofiltration membrane.

[0065] Fabrication of a gas separator based on a Mn-based transition crystal phase monolayer nanosheet nanofiltration membrane:

[0066] A gas separator was fabricated by installing the prepared elongated nanofiltration membrane in a gas filter. The filter has a multi-layer sandwich structure. When a mixture of C4 and nitrogen is passed through the gas separator, experiments show that only nitrogen permeates out of the nanofiltration membrane.

[0067] Example 4

[0068] 0.05 mol cyanuric chloride and 0.065 mol anhydrous aluminum trichloride were added to a 250 mL round-bottom flask, followed by 100 mL toluene. The mixture was stirred for 5-10 hours, quenched with ice water, and recrystallized from the organic phase to obtain intermediate a. 3.6 g of intermediate a, 1.5 g of phloroglucinol, and 5.0 g of cesium carbonate were reacted at room temperature for 3-5 hours in dimethyl sulfoxide as solvent. The mixture was extracted and separated by column chromatography to obtain intermediate b. 0.5 g of intermediate b, 120 mg of chromium trioxide, and 320 mg of periodic acid were added to a 100 mL round-bottom flask, followed by 40 mL of acetonitrile as solvent. The mixture was stirred at room temperature for 8-10 hours, extracted, and the solvent was evaporated to obtain a white solid, which is the carboxylic acid ligand.

[0069] Preparation of Cu-based transition phase monolayer nanosheets:

[0070] The prepared carboxylic acid ligand and copper nitrate hexahydrate were added to a DMSO solution. The mixed solution was then placed in a sealed glass tube and heated at a rate of 0.1 °C / min for a period of time. The mixture was then cooled to room temperature at a rate of 1 °C / min, filtered, and washed with solvent to obtain a blue blocky substance, which was the prepared transition phase material. After soaking in a mixed solvent (ethanol and acetone), the material was ball-milled, sonicated, and allowed to stand to obtain ultrathin Cu-MOF nanosheets in large quantities.

[0071] Preparation of Cu-based transition phase monolayer nanosheet nanofiltration membranes:

[0072] The prepared Cu-MOF nanosheets were prepared into a nanosheet suspension using ethanol. Polyethylene glycol with a molecular weight of 20,000 was used to prepare a polyethylene glycol aqueous solution. The nanosheet suspension and the polyethylene glycol aqueous solution were mixed in a certain proportion to prepare a mixed solution. Then, 2 ml of the mixed solution was sprayed onto a strip-shaped support microporous membrane (30 cm * 2 cm). After even coating, the coating was removed and dried. Then, the membrane was aged to obtain a Cu-based transition crystal phase monolayer nanosheet nanofiltration membrane.

[0073] Fabrication of a gas separator based on a Cu-based transition-phase monolayer nanosheet nanofiltration membrane:

[0074] A gas separator was fabricated by installing the prepared elongated nanofiltration membrane in a gas filter. The filter has a multi-layer sandwich structure. When a mixture of C4 and nitrogen is passed through the gas separator, experiments show that only nitrogen permeates out of the nanofiltration membrane.

[0075] Example 5

[0076] 0.05 mol cyanuric chloride and 0.065 mol anhydrous aluminum trichloride were added to a 250 mL round-bottom flask, followed by 100 mL toluene. The mixture was stirred for 5-10 hours, quenched with ice water, and recrystallized from the organic phase to obtain intermediate a. 3.6 g of intermediate a, 1.5 g of phloroglucinol, and 5.0 g of cesium carbonate were reacted at room temperature for 3-5 hours in dimethyl sulfoxide as solvent. The mixture was extracted and separated by column chromatography to obtain intermediate b. 0.5 g of intermediate b, 120 mg of chromium trioxide, and 320 mg of periodic acid were added to a 100 mL round-bottom flask, followed by 40 mL of acetonitrile as solvent. The mixture was stirred at room temperature for 8-10 hours, extracted, and the solvent was evaporated to obtain a white solid, which is the carboxylic acid ligand.

[0077] Preparation of Cu-based transition phase monolayer nanosheets:

[0078] The prepared carboxylic acid ligand and copper nitrate hexahydrate were added to a DMF solution. The mixed solution was then placed in a sealed glass tube and heated at a rate of 0.1 °C / min for a period of time. The mixture was then cooled to room temperature at a rate of 1 °C / min, filtered, and washed with solvent to obtain a blue blocky substance, which was the prepared transition phase material. After soaking in a mixed solvent (dichloromethane and acetone), the material was ball-milled, sonicated, and allowed to stand to obtain ultrathin Cu-MOF nanosheets in large quantities.

[0079] Preparation of Cu-based transition phase monolayer nanosheet nanofiltration membranes:

[0080] The prepared Cu-MOF nanosheets were prepared into a nanosheet suspension using ethanol. PVP with a molecular weight of 20,000 was prepared into a PVP alcohol solution. The nanosheet suspension and the PVP alcohol solution were mixed in proportion to prepare a mixed solution. Then, 2 ml of the mixed solution was spin-coated onto a PTFE-supported microporous membrane with a diameter of 5 cm. After coating evenly, the coating was removed and dried. Then, the membrane was aged to obtain a Cu-based transition crystal phase monolayer nanosheet nanofiltration membrane.

[0081] Fabrication of a gas separator based on a Cu-based transition-phase monolayer nanosheet nanofiltration membrane:

[0082] The prepared circular nanofiltration membrane was installed in a gas filter. The filter has a cylindrical structure with two air inlets at the top and one at the bottom. A mixture of C4 and nitrogen was passed through the membrane material, and experiments showed that only nitrogen could pass through.

[0083] The main parameter controls for Examples 1-5 are shown in the table below:

[0084]

[0085]

[0086] In the table, " / " indicates that the item was not performed;

[0087] The test results of the gas separators based on transition phase monolayer nanosheet nanofiltration membranes prepared in Examples 1-5 are as follows:

[0088] Purification of environmentally friendly insulating gas products using a gas separator based on a transition-phase monolayer nanosheet nanofiltration membrane:

[0089] Using the fabricated gas separator, the C4 feed gas prepared by the catalytic process is purified by passing it through a three-stage gas scrubber consisting of water, sodium hydroxide, and concentrated sulfuric acid. The system pressure is maintained at 1.2-4 atmospheres. Experiments show that the purity of the purified C4 gas can reach 99.9%.

[0090] Purification of environmentally friendly insulating gas products using a gas separator based on a transition-phase monolayer nanosheet nanofiltration membrane:

[0091] Using the prepared gas separator, the C5 feed gas prepared by the catalytic process is washed by a two-stage gas scrubber of sodium hydroxide and concentrated sulfuric acid, and then purified by the gas separator. The system pressure is maintained at 1.2-4 atmospheres. Experiments show that the purity of the purified C5 gas can reach 99.8%.

[0092] Purification of environmentally friendly insulating gases in use by a gas separator based on a transition-phase monolayer nanosheet nanofiltration membrane:

[0093] A gas separator and a micro-circulation pump were installed on a C4 insulating gas-based ring main unit. The C4 insulating gas in the ring main unit was circulated in the gas separator for 0.5 hours every 24 hours by the circulation pump. The pressure in the gas separator was maintained at 1.2-3 atmospheres. After 60 days of operation, the purity of the C4 insulating gas in the ring main unit was still 99.9%.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A perfluoroisobutane or perfluoropentanone gas separation purifier based on a nanofiltration membrane of transition crystalline phase monolayer nanosheets, characterized in that, The separation purifier comprises a support body, a plurality of nanofiltration membranes are installed in the support body, and the support body is provided with an air inlet and an air outlet. The preparation method of the nanofiltration membrane comprises: Step one: toluene is added to a mixture of cyanuric chloride and anhydrous aluminum chloride, stirred and quenched with ice water, and the organic phase is recrystallized to obtain intermediate a; intermediate a, m-benzene triol and cesium carbonate are reacted at room temperature in dimethyl sulfoxide as a solvent, and then extracted and separated by column chromatography to obtain intermediate b; intermediate b, chromium trioxide and periodic acid are mixed, acetonitrile is added as a solvent, stirred at room temperature, and then extracted and evaporated to obtain a bisepoxy hetero calix[2]arene [2] triazine tricarboxylic acid ligand; Step two: the ligand and metal ion salt are added to a solvent to obtain a transition crystal phase material, then a delamination solvent is added for soaking, and then ball milling, ultrasonic treatment and standing are performed to obtain a transition crystal phase monolayer nanosheet; Step three: the transition crystal phase monolayer nanosheet is mixed with ethanol to obtain a nanosheet suspension, a water-soluble polymer is mixed with water or an alcohol-soluble polymer is mixed with ethanol to obtain a polymer solution, and the nanosheet suspension and the polymer solution are mixed to obtain a mixed coating solution; the mixed coating solution is coated on a support film material to obtain a coating layer, the coating layer is removed from the support film material, dried and aged to obtain a nanofiltration membrane based on the transition crystal phase monolayer nanosheet, and the nanofiltration membrane has controllable monomolecular size micropores.

2. The perfluoroisobutyronitrile or perfluoropentanone gas separation purifier of claim 1, wherein, The support body is in a cylindrical structure or a multi-layer sandwich structure, the air inlet is arranged as a raw material gas inlet, and the air outlet is arranged as a purified gas outlet and a waste gas outlet.

3. The gas separation and purification apparatus of perfluoroisobutyronitrile or perfluoropentanone according to claim 1, characterized by, The nanofiltration membranes are arranged in parallel.

4. The gas separation and purification apparatus of perfluoroisobutyronitrile or perfluoropentanone according to claim 1, characterized by, The water-soluble polymer is PVA, polyacrylamide, polyethylene glycol or sodium carboxymethyl cellulose, and the alcohol-soluble polymer is PVP.

5. The gas separation and purification apparatus of perfluoroisobutyronitrile or perfluoropentanone according to claim 1, characterized by, The mass concentration of the nanosheet suspension is 5-100 mg / L, the mass concentration of the polymer solution is 50-1000 mg / L, and the mass ratio of the nanosheet suspension to the polymer solution is 1:1-10:

1.

6. The gas separation and purification apparatus for perfluoroisobutyronitrile or perfluoropentanone according to claim 1, characterized by, The aging temperature is 50-90 DEG C, and the aging time is 10-40 minutes.

7. The gas separation and purification apparatus for perfluoroisobutyronitrile or perfluoropentanone according to claim 1, characterized by, The support film material is circular, 10-500 ul of the mixed coating solution is added dropwise on each square centimeter of the support film material, the coating method is spin coating, and the thickness of the coating layer is 50-500 nm.

8. The gas separation and purification apparatus of perfluoroisobutyronitrile or perfluoropentanone according to claim 1, characterized by, The mixed coating solution is diluted by 10 times with alcohol before being coated on the support film material, the support film material is strip-shaped, 20-400 ul of the mixed coating solution is added dropwise on each square centimeter of the support film material, the coating method is roller coating or spraying, and the thickness of the coating layer is 5-100 nm.

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