Preparation method of pervaporation membrane, and pervaporation membrane and application and refining method thereof in hydrogen chloride gas refining

Abstract

The application provides a preparation method of a pervaporation membrane, comprising the following steps: (1) adding a polymer membrane material into a first solvent to perform first dissolution, to obtain a first solution; (2) adding a p-aminophenyl compound and g-C3N4 into a second solvent to perform second dissolution, to obtain a second solution; (3) mixing and reacting the first solution and the second solution, to obtain a polymer casting solution; (4) sequentially performing film forming treatment and desolvent treatment on the polymer casting solution, to obtain the pervaporation membrane. The application also provides the pervaporation membrane, application of the pervaporation membrane in hydrogen chloride gas refining, a refining method and refined hydrogen chloride gas. The preparation method can prepare a pervaporation membrane for hydrogen chloride gas refining, the pervaporation membrane can purify hydrogen chloride gas generated in an isocyanate production process while recycling phosgene and chlorobenzene, and the refined hydrogen chloride gas has high purity.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation, specifically relating to the preparation method of pervaporation membrane, the application of pervaporation membrane in the purification of hydrogen chloride gas, and the purification method thereof. Background Technology

[0002] Isocyanates are important organic compounds widely used in industries such as construction, automotive, insulation, shoe soles, and adhesives. Most existing industrial production methods for isocyanates employ phosgenation, where a primary amine is mixed with an inert solvent and then reacted with phosgene to obtain a reaction solution containing the product, inert solvent, excess phosgene, and hydrogen chloride. The product is then purified through processes such as phosgene removal and solvent removal to finally obtain the final product.

[0003] In the phosgenation reaction of amines, to ensure the reaction efficiency between phosgene and amines and reduce the formation of the byproduct urea, it is usually necessary to add an excess of phosgene to enhance mixing. Unreacted phosgene mostly exists, at least partially, in gaseous form along with the released hydrogen chloride. To improve the economics of isocyanate production processes, it is important to recover excess phosgene, minimize its loss, and recycle it back into the phosgenation process. It is also necessary to separate the hydrogen chloride gas generated during production and utilize it appropriately; different specific applications require different purity levels of hydrogen chloride.

[0004] Potential uses of hydrogen chloride include the regeneration of hydrochloric acid in aqueous solution. Common methods for producing gaseous hydrogen chloride include oxidizing hydrogen chloride to chlorine gas and using hydrogen chloride as a byproduct of PVC production. All of these processes require the removal of residual phosgene, chlorobenzene and other large molecular impurities from the hydrogen chloride.

[0005] Existing technologies disclose methods for treating hydrogen chloride gas during the preparation of isocyanate. For example, in GB-A-827376, the amine phosgenation reaction is carried out at a pressure of 3 bar; the phosgene after the reaction is condensed from the gas phase, releasing hydrogen chloride which is then recovered. However, it is foreseeable that such a simple separation will result in a large amount of residual phosgene in the hydrogen chloride. In US3381025 A, after the phosgenation reaction is completed, phosgene and hydrogen chloride are distilled off together, and then chlorobenzene and phosgene are condensed and recycled back to the phosgenation reaction, while the hydrogen chloride containing a large amount of residual phosgene is sent to an absorber to remove phosgene. In this case, the separation of phosgene / hydrogen chloride in the two streams is incomplete, resulting not only in the loss of hydrogen chloride, but also in the presence of a large amount of hydrogen chloride in the phosgene, causing a large amount of hydrochloride to be generated during amine phosgenation.

[0006] The technologies described above not only have high investment and operating costs, requiring large amounts of steam and refrigerant to remove phosgene and chlorobenzene from hydrogen chloride to low levels, but also result in the formation of large amounts of hydrochloride during the phosgenation reaction due to the high hydrogen chloride content in the circulating phosgene, thus affecting product quality and the long-term operation of the equipment. Therefore, in the existing isocyanate production field, it is of great significance to develop a pervaporation membrane and removal method that offers high removal efficiency and is safe and reliable for removing phosgene and chlorobenzene from hydrogen chloride and achieving phosgene recovery. Summary of the Invention

[0007] The first objective of this invention is to provide a method for preparing a pervaporation membrane, which can obtain a pervaporation membrane that can be used for the purification of hydrogen chloride gas and the filtration to remove phosgene and chlorobenzene from the hydrogen chloride gas. The second objective of this invention is to provide a pervaporation membrane prepared by the aforementioned method, which can filter out phosgene and chlorobenzene from hydrogen chloride gas, thereby achieving purification of hydrogen chloride gas. The third objective of this invention is to provide a pervaporation membrane prepared by the aforementioned method and its application in the purification of hydrogen chloride gas. The fourth objective of this invention is to provide a pervaporation membrane prepared by the aforementioned preparation method and a purification method for purifying hydrogen chloride gas using the aforementioned pervaporation membrane.

[0008] The fifth object of the present invention is to provide a refined hydrogen chloride gas obtained by the aforementioned refining method.

[0009] To achieve the first objective of this invention, the following technical solution is adopted: A method for preparing a pervaporation membrane includes the following steps: (1) The polymer membrane material is added to the first solvent for first dissolution to obtain the first solution; (2) Add the p-aminophenyl compound and g-C3N4 to the second solvent for a second dissolution to obtain a second solution; (3) Mix and react the first solution obtained in step (1) and the second solution obtained in step (2) to obtain a polymer casting solution; (4) The polymer casting solution obtained in step (3) is subjected to film formation treatment and solvent removal treatment in sequence to obtain a pervaporation membrane.

[0010] In this invention, in step (2), no chemical reaction occurs between the aminophenyl compound and g-C3N4, but a more stable structure is formed through molecular forces, which helps to improve the stability of the pervaporation membrane during preparation.

[0011] The pervaporation membrane of the present invention can be applied to the purification of hydrogen chloride gas, and is preferably used for the removal of phosgene and chlorobenzene from hydrogen chloride gas. The hydrogen chloride gas is generated during the isocyanate production process. In one embodiment, the hydrogen chloride gas contains chlorobenzene at a mass concentration of 50-10000 ppm, such as 100 ppm, 200 ppm, 500 ppm, 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm, and 9000 ppm, and phosgene at a mass concentration of 500-100000 ppm, such as 1000 ppm, 2000 ppm, 5000 ppm, 10000 ppm, 20000 ppm, 30000 ppm, 40000 ppm, 50000 ppm, 60000 ppm, 70000 ppm, 80000 ppm, and 90000 ppm.

[0012] In one embodiment, in step (1), the polymer membrane material includes any one or a combination of polyvinylidene fluoride, polycarbonate, polyethylene, polypropylene, polysulfone, and polyethersulfone.

[0013] In one embodiment, in step (1), the first solvent includes any one or more combinations of dichloromethane, trichloromethane, benzene, tetrahydrofuran, acetone, ethanol, n-heptane, and n-hexane.

[0014] In one embodiment, in step (1), the mass concentration of the polymer membrane material in the first solution is 1-8 wt%, such as 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, and 7.5 wt%.

[0015] In one embodiment, in step (1), the first dissolution is carried out under stirring conditions, preferably for a stirring time of 0.5-3 h, such as 1 h, 1.5 h, 2 h and 2.5 h.

[0016] In one embodiment, in step (2), the p-aminophenyl compound includes any one or more combinations of p-aminophenyl-pyrene, p-aminophenyl ethanol, p-aminophenyl butyric acid and p-aminophenyl trimethoxysiloxane, preferably 1,3,6,8-tetra(p-aminophenyl)-pyrene (abbreviated as PyTTA).

[0017] Taking 1,3,6,8-tetra(p-aminophenyl)-pyrene (abbreviated as PyTTA) as an example, the mechanism of action of the present invention is as follows: On the one hand, PyTTA molecules have four amino units at their tail ends, and the g-C3N4 surface is rich in amino end groups, thus exhibiting strong selective permeability to phosgene and chlorobenzene, which can significantly increase membrane flux. When the two are combined, the adsorption capacity of the membrane can be significantly increased. On the other hand, PyTTA has a pyrene unit, which makes the monomer a potential candidate for supramolecular self-assembly driven by non-covalent effects and interactions of π-π stacking. Through the interaction with its own amino groups and the amino groups of g-C3N4, self-assembly can be achieved. This reconstruction process reduces the energy of the system by reconstructing the configuration and enhancing π-π interactions, thereby reducing membrane structural defects and improving membrane separation performance. Finally, the amino groups on the surfaces of PyTTA and g-C3N4 can undergo chemical coupling reactions with benzyl chloride groups in polymer membrane materials such as polysulfone, achieving chemical connection with the membrane substrate material and significantly improving the membrane's filtration, antifouling performance, and stability.

[0018] In one embodiment, in step (2), the second solvent includes any one or a combination of dichloromethane, chloroform, benzene, tetrahydrofuran, acetone, ethanol, n-heptane, and n-hexane.

[0019] In one embodiment, in step (2), the mass ratio of g-C3N4 to the p-aminophenyl compound is (0.3-12):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1 and 11.5:1.

[0020] In one embodiment, in step (2), the total mass concentration of the g-C3N4 and the p-aminophenyl compound in the second solution is 0.5-5 wt%, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt% and 4.5 wt%.

[0021] In one embodiment, in step (2), the second dissolution is carried out under ultrasonic and stirring conditions, preferably for an ultrasonic time of 0.5-2 h, such as 1 h and 1.5 h.

[0022] In one embodiment, in step (3), the mass ratio of the first solution to the second solution is (0.2-6):1, such as 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 and 5.5:1.

[0023] In one embodiment, in step (3), the reaction time is 5-10 h, such as 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h and 9.5 h; preferably, the reaction is carried out under ultrasonic conditions.

[0024] In one embodiment, in step (4), the film-forming process includes forming a film by using the polymer casting liquid obtained in step (3) by solution casting, scraping, dip coating or spin coating; preferably, the film-forming process is performed on a substrate, preferably the substrate is a PVDF (polyvinylidene fluoride) substrate.

[0025] Those skilled in the art will understand that the membrane obtained after the film-forming treatment contains solvent, which, if not removed, will cause contamination during use. In one embodiment, step (4) includes drying and curing the membrane obtained after the film-forming treatment to remove the solvent and obtain a pervaporation membrane; preferably, the drying temperature is 30-120 ℃, such as 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃ and 115 ℃; preferably, the drying pressure is -0.9~-0.1 barg, such as -0.2 barg, -0.3 barg, -0.4 barg, -0.5 barg, -0.6 barg, -0.7 barg and -0.8 barg. For example, it is carried out in a vacuum oven.

[0026] To achieve the second objective of this invention, a pervaporation membrane prepared using the aforementioned method is also provided.

[0027] To achieve a third objective of the present invention, an application of the aforementioned pervaporation membrane in the purification of hydrogen chloride gas is also provided. Preferably, the hydrogen chloride gas contains chlorobenzene and phosgene.

[0028] To achieve the fourth objective of this invention, a purification method for purifying hydrogen chloride gas using the aforementioned pervaporation membrane is also provided, wherein the hydrogen chloride gas contains chlorobenzene and phosgene; characterized in that the purification method includes the following steps: (a) Install the pervaporation membrane into a membrane separation device; (b) The hydrogen chloride gas is passed into the membrane separation device obtained in step (a) for membrane separation, and a permeate gas containing chlorobenzene and phosgene is output, as well as a residual gas as purified hydrogen chloride gas.

[0029] The purification method of the present invention can remove chlorobenzene and phosgene from hydrogen chloride gas.

[0030] In one embodiment, the purification method further includes step (c), in which the permeate gas obtained in step (b) is condensed and the chlorobenzene and phosgene are recovered.

[0031] Those skilled in the art will understand that the condensation is carried out through a condenser, which can be a heat exchanger commonly used in industry, such as a shell-and-tube heat exchanger and a plate heat exchanger.

[0032] In one embodiment, in step (b), the operating temperature of the membrane separation device is -10 to 80 °C, such as -5 °C, 0 °C, 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, and 75 °C.

[0033] In one embodiment, in step (b), the membrane separation device is a multi-stage membrane separation device, such as a 2-stage, 3-stage, or 4-stage membrane separation device.

[0034] In one embodiment, the membrane separation device is defined as an n-stage membrane separation device, where n ≥ 3; In step (b), the membrane separation process is as follows: The hydrogen chloride gas is passed into the primary membrane separation unit of the membrane separation device obtained in step (a) for primary membrane separation, and primary permeate gas and primary residual permeate gas are output. The primary permeate gas is fed into the secondary membrane separation unit for secondary membrane separation, and the output is secondary permeate gas and secondary permeate gas; … The n-1 stage permeate gas is fed into the n-stage membrane separation unit for n-stage membrane separation, and the n-stage permeate gas and purified hydrogen chloride gas, which is the n-stage permeate gas, are output. In step (c), the first-stage permeate gas, the second-stage permeate gas...n-stage permeate gas are fed into the condenser via a vacuum pump and condensed to recover chlorobenzene and phosgene.

[0035] In one embodiment, in step (c), the condensation temperature is -20 to 20 °C, such as -15 °C, -10 °C, -5 °C, 0 °C, 5 °C, 10 °C, and 15 °C.

[0036] In one embodiment, the hydrogen chloride gas contains chlorobenzene at a mass concentration of 50-10000 ppm, such as 100 ppm, 200 ppm, 500 ppm, 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm, and 9000 ppm, and phosgene at a mass concentration of 500-100000 ppm, such as 1000 ppm, 2000 ppm, 5000 ppm, 10000 ppm, 20000 ppm, 30000 ppm, 40000 ppm, 50000 ppm, 60000 ppm, 70000 ppm, 80000 ppm, and 90000 ppm.

[0037] To achieve the fifth objective of this invention, a refined hydrogen chloride gas obtained by the aforementioned refining method is also provided; Preferably, in the refined hydrogen chloride gas, the mass concentration of chlorobenzene is ≤5 ppm and the mass concentration of phosgene is ≤8 ppm.

[0038] The beneficial effects of this invention are as follows: The method for preparing the pervaporation membrane of the present invention can produce a pervaporation membrane for the purification of hydrogen chloride gas. This pervaporation membrane can purify the hydrogen chloride gas generated during isocyanate production while recovering phosgene and chlorobenzene. When phosgene and chlorobenzene are separated and removed from the hydrogen chloride gas by membrane separation, the permeate gas on the permeate side is phosgene and chlorobenzene, which can be recovered and reused after condensation. The residual gas on the permeate side is the purified hydrogen chloride gas product, which can be used as a raw material for PVC, etc. Through the membrane recovery process, the system energy consumption is effectively reduced, excess raw materials are fully recycled, the equipment service life is extended, and the safety risks of production are reduced. Detailed Implementation

[0039] The technical solution and effects of the present invention will be further described below with reference to specific embodiments. The following embodiments are for illustrative purposes only, and the invention is not limited to the described embodiments or examples. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0040] In the following examples and comparative examples, the sources of raw materials and equipment are as follows: g-C3N4, Xi'an Qiyue Biotechnology Co., Ltd.; 1,3,6,8-Tetra(p-aminophenyl)-pyrene (PyTTA), Xi'an Qiyue Biotechnology Co., Ltd. Polysulfone, Solvay T-3500 (USA); Dichloromethane, purity > 98%, Shanghai Titan Technology Co., Ltd. Polypropylene, Wanhua Chemical Group Co., Ltd.; Benzene, Shanghai Titan Technology Co., Ltd.; p-Aminophenylethanol, purity >99%, Hubei Dibai Chemical Co., Ltd.; Ethanol, Shanghai Titan Technology Co., Ltd.; Polycarbonate, Wanhua Chemical Group Co., Ltd.; Tetrahydrofuran, purity > 99%, Shanghai Titan Technology Co., Ltd.; p-Aminophenylbutyric acid, purity >97%, Hubei Rishengchang New Material Technology Co., Ltd.; Acetone, purity > 99%, Shanghai Titan Technology Co., Ltd. Detector: Agilent 7890A; chromatographic column: HP-5 (30 m × 0.25 μm × 320 μm); chromatographic conditions: (1) Column temperature: 50 ℃ for 0.5 min, 5 ℃ / min to 80 ℃ for 1 min; 10 ℃ / min to 280 ℃ for 10 min; (2) Injector temperature: 280 ℃; (3) Detector temperature: 295 ℃; (4) Septum purge gas flow rate: 3.0 mL / min; (5) Carrier gas (nitrogen) flow rate: 3 mL / min; (6) Air flow rate: 350 mL / min; (7) Hydrogen flow rate: 35 mL / min; (8) Make-up gas (nitrogen) flow rate: 25 mL / min, split injection, split ratio 1:10, injection volume 0.5 μL.

[0041] The testing method is as follows: (1) Method for determining the chlorobenzene content in hydrogen chloride gas: Activated carbon was used to adsorb hydrogen chloride gas, and carbon disulfide was used for analysis after adsorption. The chlorobenzene content could be obtained by Agilent chromatography 7890A.

[0042] (2) Method for determining the phosgene content in hydrogen chloride gas: Phosgene in hydrogen chloride gas was absorbed by chlorobenzene liquid to obtain a photochemical liquid containing phosgene; then, it was derivatized with methanol and measured by gas chromatography, and its concentration was calculated using a standard curve and converted into phosgene content.

[0043] (a) Preparation of pervaporation membrane Example 1 (S1) The pervaporation membrane A1 is prepared according to the method for preparing the pervaporation membrane of the present invention, comprising the following steps: (1) 8 g of polysulfone (polymer membrane material) was added to 192 g of dichloromethane (first solvent) for first dissolution to obtain 200 g of first solution; wherein, the mass concentration of polysulfone in the first solution was 4 wt%; (2) 4 g of PyTTA (a p-aminophenyl compound) and 4 g of g-C3N4 were added to 192 g of dichloromethane (a second solvent) for a second dissolution, and then sonicated for 1 h to obtain 200 g of a second solution; wherein, the total mass concentration of PyTTA and g-C3N4 in the second solution was 4 wt%; (3) The first solution obtained in step (1) and the second solution obtained in step (2) are mixed and reacted under ultrasonic conditions at a mass ratio of 1:1 for 8 h to obtain a polymer casting solution; (4) The polymer casting solution obtained in step (3) is cast onto a PVDF substrate for film formation treatment, and then placed in a vacuum oven at 80 ℃ and a pressure of -0.3 barg to dry to constant weight (solvent removal treatment) to obtain pervaporation membrane A1.

[0044] Example 2 (S2) The pervaporation membrane A2 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (1), the amount of polysulfone is 6 g and the amount of dichloromethane is 194 g; in the first solution, the mass concentration of polysulfone is 3 wt%. In step (2), PyTTA is 1.5 g, g-C3N4 is 2.5 g, and dichloromethane is 196 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 2 wt%. In step (3), the reaction time is 10 h; In step (4), the drying temperature is 70 ℃.

[0045] Example 3 (S3) The pervaporation membrane A3 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (1), the polysulfone content is 10 g and the dichloromethane content is 190 g; in the first solution, the polysulfone concentration is 5 wt%. In step (4), the drying pressure is -0.5 barg.

[0046] Example 4 (S4) The pervaporation membrane A4 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (1), the polymer membrane material is 2 g of polypropylene, and the first solvent is 198 g of benzene; the mass concentration of polypropylene in the first solution is 1 wt%. In step (2), the p-aminophenyl compound is 4 g of p-aminophenyl ethanol and the second solution is 192 g of ethanol.

[0047] Example 5 (S5) The pervaporation membrane A5 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (1), the polymer membrane material is 16 g of polycarbonate, the first solvent is 184 g of tetrahydrofuran, and the mass concentration of polycarbonate in the first solution is 8 wt%. In step (2), the p-aminophenyl compound is 4 g of p-aminophenylbutyric acid and the second solution is 192 g of acetone.

[0048] Example 6 (S6) The pervaporation membrane A6 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (2), PyTTA is 0.65 g, g-C3N4 is 7.35 g, and dichloromethane is 196 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 4 wt%.

[0049] Example 7 (S7) The pervaporation membrane A7 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (2), PyTTA is 6 g, g-C3N4 is 2 g, and dichloromethane is 196 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 4 wt%.

[0050] Example 8 (S8) The pervaporation membrane A8 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (2), PyTTA is 0.5 g, g-C3N4 is 0.5 g, and dichloromethane is 199 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 0.5 wt%.

[0051] Example 9 (S9) The pervaporation membrane A9 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (2), PyTTA is 5 g, g-C3N4 is 5 g, and dichloromethane is 190 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 4 wt%.

[0052] Example 10 (S10) The pervaporation membrane A10 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (3), the first solution and the second solution are mixed at a mass ratio of 3:1.

[0053] Example 11 (S11) The pervaporation membrane A11 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (3), the first solution and the second solution are mixed at a mass ratio of 0.2:1.

[0054] Example 12 (S12) The pervaporation membrane A12 was prepared according to the preparation method of Example 1, with the only difference from Example 1 in the following aspects: In step (3), the first solution and the second solution are mixed at a mass ratio of 6:1.

[0055] Comparative Example 1 (D1) The pervaporation membrane A1' was prepared according to the preparation method of Example 3, with the only difference from Example 3 in the following aspects: In step (2), PyTTA is 0 g, g-C3N4 is 4 g, and dichloromethane is 196 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 2 wt%.

[0056] Comparative Example 2 (D2) The pervaporation membrane A2' was prepared according to the preparation method of Example 3, with the only difference from Example 3 in the following aspects: In step (2), PyTTA is 0 g, g-C3N4 is 8 g, and dichloromethane is 192 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 4 wt%.

[0057] Comparative Example 3 (D3) The pervaporation membrane A3' was prepared according to the preparation method of Example 3, with the only difference from Example 3 in the following aspects: In step (2), PyTTA is 4 g, g-C3N4 is 0 g, and dichloromethane is 196 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 2 wt%.

[0058] Comparative Example 4 (D4) The pervaporation membrane A4' was prepared according to the preparation method of Example 3, with the only difference from Example 3 in the following aspects: In step (2), PyTTA is 8 g, g-C3N4 is 0 g, and dichloromethane is 192 g; in the second solution, the total mass concentration of PyTTA and g-C3N4 is 4 wt%.

[0059] (ii) Purification of hydrogen chloride gas Examples 13-26 (S13-26) and Comparative Examples 5-8 (D5-8) Hydrogen chloride gas containing chlorobenzene and phosgene was purified using pervaporation membranes A1-12 and A1'-4' of Examples 1-12 (S1-12) and Comparative Examples 1-4 (D1-4), respectively, to obtain purified hydrogen chloride gas and recover chlorobenzene and phosgene; the steps are as follows: (a) Install the pervaporation membrane into a three-stage membrane separation device; (b) The hydrogen chloride gas is passed into the primary membrane separation unit of the membrane separation device obtained in step (a) for primary membrane separation, and primary permeate gas and primary residual permeate gas are output; The primary permeate gas is fed into the secondary membrane separation unit for secondary membrane separation, and the output is secondary permeate gas and secondary permeate gas; The secondary permeate gas is fed into a tertiary membrane separation unit for tertiary membrane separation, and the output is tertiary permeate gas and refined hydrogen chloride gas product as tertiary permeate gas. (c) The primary, secondary, and tertiary permeate gases obtained in step (b) are fed into a condenser via a vacuum pump and condensed to recover chlorobenzene and phosgene; The purification conditions and purification results of Examples 13-26 (S13-26) and Comparative Examples 5-8 (D5-8) are shown in Table 1.

[0060] Table 1. Refining conditions and results for S13-26 and D5-8

[0061] According to Table 1, the only difference between Examples 18-26 and Comparative Examples 5-8 and Example 15 is the pervaporation membrane used.

[0062] According to the comparison between Examples 13-26 (S13-26) and Comparative Examples 5-8 (D5-8) and Table 1, it can be seen that: When the pervaporation membrane A1'-4' obtained in Comparative Examples 1-4 was used to purify hydrogen chloride gas containing chlorobenzene and phosgene, the separation effect of chlorobenzene and phosgene was limited. The content of phosgene in the purified hydrogen chloride gas product was reduced to only 80-200 ppm and the content of chlorobenzene was reduced to only 280-300 ppm. When the pervaporation membrane A1-12 obtained in Examples 1-12 of this invention is used to purify hydrogen chloride gas containing chlorobenzene and phosgene, the chlorobenzene and phosgene can be separated to a great extent. The content of chlorobenzene and phosgene in the purified hydrogen chloride gas product is reduced to less than 2 ppm, which is a hundred times different from that when the pervaporation membrane A1'-4' obtained in Comparative Examples 1-4 is used.

[0063] (III) Stability of the pervaporation membrane The contents of chlorobenzene and phosgene in the purified hydrogen chloride gas products obtained in Example 15 (S15), Comparative Example 5 (D5), and Comparative Example 7 (D7) at different operating times (200 h, 2000 h, and 4000 h) were tested to examine the stability of the pervaporation membranes A3, A1', and A3'. The results are shown in Table 2.

[0064] Table 2. Stability results of pervaporation membranes A3, A1', and A3'

[0065] As shown in Table 2, when purifying hydrogen chloride gas containing chlorobenzene and phosgene, the pervaporation membrane obtained by the method of this invention exhibits relatively stable chlorobenzene and phosgene content in the purified hydrogen chloride gas product after 200 h, 2000 h, and 4000 h of operation. However, when using the pervaporation membrane obtained in the comparative example, the chlorobenzene and phosgene content in the purified hydrogen chloride gas product increases several times over after 200 h, 2000 h, and 4000 h of operation. These data indicate that the pervaporation membrane obtained by the method of this invention has good stability, while the pervaporation membrane obtained in the comparative example has poor stability.

Claims

1. A method for preparing a pervaporation membrane, characterized in that, The preparation method includes the following steps: (1) The polymer membrane material is added to the first solvent for first dissolution to obtain the first solution; (2) Add the p-aminophenyl compound and g-C3N4 to the second solvent for a second dissolution to obtain a second solution; (3) Mix and react the first solution obtained in step (1) and the second solution obtained in step (2) to obtain a polymer casting solution; (4) The polymer casting solution obtained in step (3) is subjected to film-forming treatment and solvent removal treatment in sequence to obtain a pervaporation membrane; wherein, In step (2), the p-aminophenyl compounds include any one or more combinations of 1,3,6,8-tetrakis(p-aminophenyl)-pyrene, p-aminophenylethanol, and p-aminophenylbutyric acid; In step (2), the mass ratio of g-C3N4 to the p-aminophenyl compound is (0.3-12):1; In step (2), the total mass concentration of the g-C3N4 and the p-aminophenyl compound in the second solution is 0.5-5 wt%. In step (3), the mass ratio of the first solution to the second solution is (0.2-6):

1.

2. The preparation method according to claim 1, characterized in that, In step (1), the polymer membrane material includes any one or more combinations of polyvinylidene fluoride, polycarbonate, polyethylene, polypropylene, polysulfone, and polyethersulfone; and / or In step (1), the first solvent includes any one or more combinations of dichloromethane, trichloromethane, benzene, tetrahydrofuran, acetone, ethanol, n-heptane, and n-hexane; and / or In step (1), the mass concentration of the polymer membrane material in the first solution is 1-8 wt%; and / or In step (1), the first dissolution is carried out under stirring conditions for 0.5-3 h.

3. The preparation method according to claim 1 or 2, characterized in that, In step (2), the second solvent includes any one or a combination of dichloromethane, chloroform, benzene, tetrahydrofuran, acetone, ethanol, n-heptane and n-hexane; In step (2), the second dissolution is carried out under ultrasonic and stirring conditions.

4. The preparation method according to claim 3, characterized in that, In step (2), the ultrasound time is 0.5-2 h.

5. The preparation method according to any one of claims 1, 2, and 4, characterized in that, In step (3), the reaction time is 5-10 h.

6. The preparation method according to claim 5, characterized in that, In step (3), the reaction is carried out under ultrasonic conditions.

7. The preparation method according to any one of claims 1, 2, 4 and 6, characterized in that, In step (4), the film-forming process includes forming a film by using the polymer casting solution obtained in step (3) through solution casting, scraping, dip coating or spin coating.

8. The preparation method according to claim 7, characterized in that, In step (4), the film formation process is performed on the substrate.

9. The preparation method according to claim 8, characterized in that, In step (4), the substrate is a PVDF substrate.

10. The preparation method according to claim 7, characterized in that, In step (4), the solvent removal process includes drying and curing the membrane obtained after the film-forming process to obtain a pervaporation membrane.

11. The preparation method according to claim 10, characterized in that, In step (4), the drying temperature is 30-120 ℃.

12. The preparation method according to claim 10, characterized in that, In step (4), the drying pressure is -0.9~-0.1 barg.

13. A pervaporation membrane prepared by any one of claims 1-12.

14. The application of the pervaporation membrane as described in claim 13 in the purification of hydrogen chloride gas.

15. A purification method for purifying hydrogen chloride gas using a pervaporation membrane as described in claim 13, wherein the hydrogen chloride gas contains chlorobenzene and phosgene; characterized in that, The refining method includes the following steps: (a) Install the pervaporation membrane into a membrane separation device; (b) The hydrogen chloride gas is passed into the membrane separation device obtained in step (a) for membrane separation, and a permeate gas containing chlorobenzene and phosgene is output, as well as a residual gas as purified hydrogen chloride gas.

16. The refining method according to claim 15, characterized in that, The purification method further includes step (c), in which the permeate gas obtained in step (b) is condensed and chlorobenzene and phosgene are recovered.

17. The refining method according to claim 15, characterized in that, In step (b), the operating temperature of the membrane separation device is -10 to 80 ℃.

18. The refining method according to claim 16, characterized in that, In step (c), the condensation temperature is -20 to 20 ℃.

19. The refining method according to any one of claims 15-18, characterized in that, The hydrogen chloride gas contains chlorobenzene at a mass concentration of 50-10000 ppm and phosgene at a mass concentration of 500-100000 ppm.

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