Preparation method for fluoroethylene carbonate

Abstract

The present invention relates to the technical field of lithium ion battery electrolyte additive synthesis, and provides a method for preparing fluoroethylene carbonate. In the present invention, chloroethylene carbonate, a polymerization inhibitor, a catalyst, and liquid hydrogen fluoride are mixed to perform a fluorination reaction to obtain fluoroethylene carbonate. In the present invention, a polymerization inhibitor and a catalyst are added at the same time, thus the rate of reaction is increased, while avoiding the occurrence of side reactions such as material polymerization, thereby increasing the conversion rate and product yield. In the present invention, liquid hydrogen fluoride is used as a fluorination reagent, which is low in cost, easy to use, and convenient for continuous production. In the present invention, a trifluorotoluene compound is used as a solvent, and the trichlorotoluene compound is used to effectively utilize the remaining hydrogen fluoride, which is conducive to achieving full utilization of resources and reducing production costs. The fluorination reaction of the present invention can be carried out in a microchannel reactor, and can achieve continuous and automated production. In summary, the preparation method provided by the present invention is an efficient, economical, green, and environmentally friendly method with broad prospects.

Description

A preparation method of fluoroethylene carbonate

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on January 24, 2024, with application number CN202410101101.1 and invention name “A Method for Preparing Fluorinated Ethylene Carbonate”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The invention relates to the technical field of synthesis of lithium ion battery electrolyte additives, in particular to a method for preparing fluoroethylene carbonate. Background Art

[0003] Lithium-ion batteries consist of a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte, known as the "blood" of a lithium-ion battery, conducts electrons between the positive and negative electrodes. The manufacturing cost of the electrolyte accounts for 14% of the total cost of a lithium battery, making it the most expensive component, aside from the positive electrode material. The electrolyte is made up of a solvent, solute (i.e., lithium salt), and additives, all formulated in specific proportions. Generally, the solvent accounts for 80-90%, the lithium salt for approximately 8%, and the additives for 5-10%. In terms of manufacturing cost, the solute is the most expensive, accounting for nearly 50%, while the solvent accounts for approximately 30%, and the additives for approximately 10%. There are many different types of additives, each with its own distinct functions, such as improving conductivity, overcharge safety, storage performance, flame retardancy, and stability. Different lithium-ion battery manufacturers have different battery applications and performance requirements, and their additive selection priorities vary accordingly. As battery performance requirements continue to increase, the importance of additives becomes even more pronounced.

[0004] Fluoroethylene carbonate is an organic film-forming additive and overcharge protection additive for lithium-ion battery electrolyte. It has good high and low temperature performance and anti-flatulence function, which can improve the capacity and cycle life of lithium-ion batteries.

[0005] The main methods for producing fluoroethylene carbonate are as follows:

[0006] Patent US6010806 discloses a method using dimethyl carbonate and 3,3,3-trifluoro-1,2-propylene oxide as reactants in the presence of sodium bicarbonate. This method uses expensive raw materials and a long reaction time, making it unsuitable for industrial production. Patent CN108250176A provides a rapid continuous flow synthesis process for fluoroethylene carbonate, in which a F2 / N2 gas mixture is used to react with ethylene carbonate. F2 is highly toxic and highly reactive, making it prone to loss of control and presenting a high risk of failure. The process also produces numerous byproduct impurities that are difficult to separate and purify, resulting in high production costs. Patent WO98115024 uses chloroethylene carbonate and potassium fluoride as raw materials. This method is also a relatively mature synthesis method used in the domestic industry, but it is a heterogeneous reaction, which is time-consuming and has low conversion rates. It also requires high particle size and activity of solid potassium fluoride, making it expensive. The large amount of solid potassium fluoride used is labor-intensive, making automation difficult, and it produces a large amount of mixed potassium chloride and potassium fluoride as solid waste, resulting in high costs for the three wastes. Patent CN101774923B discloses a method for preparing fluoroethylene carbonate, which involves a substitution reaction between chloroethylene carbonate and a fluorinating agent in the presence of an organic solvent and an acid-binding agent to produce fluoroethylene carbonate. This method uses a solvent, which increases costs, involves a cumbersome post-processing process, and exhibits a low yield of only approximately 85%. Patents CN105968083A and CN114874179A disclose methods for preparing fluoroethylene carbonate, which utilize hydrogen fluoride as a fluorine source and are prepared using a microchannel process. Repeated experiments have shown that the actual conversion rate and product yield of this method are very limited, failing to meet the requirements for industrial application. Patent CN116178333A discloses a method for preparing fluoroethylene carbonate using chloroethylene carbonate as a raw material, hydrogen fluoride as a fluorine source, and a mixture of SbCl5 and MoCl5 in a certain proportion as a catalyst. However, due to the high level of by-product impurities in this method, the product yield and quality are not guaranteed. The yield is less than 85%, and the product purity is less than 99.5%, which does not meet the purity requirement of 99.95% or above required for electronic-grade lithium battery additives.

[0007] In summary, existing preparation methods generally have problems such as low conversion rate and product yield, low product purity and high cost, and are not suitable for industrial production.

[0008] Summary of the Invention

[0009] In view of this, the present invention provides a method for preparing fluoroethylene carbonate. The preparation method provided by the present invention has high raw material conversion rate, high product yield and purity, and low preparation cost.

[0010] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0011] A method for preparing fluoroethylene carbonate comprises the following steps:

[0012] Chloroethylene carbonate, a polymerization inhibitor, a catalyst and liquid hydrogen fluoride are mixed to carry out a fluorination reaction to obtain fluoroethylene carbonate; the catalyst comprises one or more of metal fluoride, metal chloride and tetrabutylammonium fluoride; the polymerization inhibitor comprises one or more of amine polymerization inhibitor, phenol polymerization inhibitor and piperidine nitroxide free radical polymerization inhibitor.

[0013] Preferably, a solvent is added during the mixing, and the solvent is a trifluorotoluene compound; the structural formula of the trifluorotoluene compound is shown in Formula I:

[0014] In formula I: n is an integer of 0 to 5, R is one or more of alkyl, phenyl and halogen;

[0015] The molar ratio of the chloroethylene carbonate to the solvent is 1:(0.2-2).

[0016] Preferably, the fluorination reaction is carried out in an autoclave.

[0017] Preferably, the fluorination reaction comprises: adding chloroethylene carbonate, a solvent, a catalyst, a polymerization inhibitor and liquid hydrogen fluoride into an autoclave, and then heating to carry out the fluorination reaction under certain temperature and pressure conditions;

[0018] During the fluorination reaction, generated hydrogen chloride gas is discharged while the reaction is taking place, and the discharged hydrogen chloride gas is absorbed by water to produce by-product hydrochloric acid; the pressure of the fluorination reaction is controlled by the discharge amount of the hydrogen chloride gas; during the fluorination reaction, the generated gaseous hydrogen fluoride and gaseous solvent are condensed, collected, and then returned to the autoclave.

[0019] Preferably, after the fluorination reaction is completed, the method further comprises mixing the obtained reaction solution with a trichlorotoluene compound, reacting the trichlorotoluene compound with the remaining hydrogen fluoride in the reaction solution to obtain a mixed reaction solution of fluoroethylene carbonate and trifluorotoluene compounds; distilling and desolventizing the mixed reaction solution to obtain a concentrated solution and trifluorotoluene compounds; recycling the trifluorotoluene compounds obtained by distillation and desolventizing; and sequentially rectifying and melt crystallizing the concentrated solution to obtain a fluoroethylene carbonate product.

[0020] The structure of the trichlorotoluene compound is shown in Formula II:

[0021] In formula II, n is an integer of 0 to 5, and R is one or more of an alkyl group, a phenyl group, and a halogen group.

[0022] Preferably, the fluorination reaction is carried out in a microchannel reactor.

[0023] Preferably, the fluorination reaction comprises:

[0024] Mixing ethylene chlorocarbonate, a catalyst and a polymerization inhibitor to obtain a mixed solution; or mixing ethylene chlorocarbonate, a catalyst, a polymerization inhibitor and a solvent to obtain a mixed solution;

[0025] The mixed liquid and liquid hydrogen fluoride are introduced into a microchannel reactor to carry out a fluorination reaction.

[0026] Preferably, after the fluorination reaction, the process further comprises: performing gas-liquid separation on the generated gas-liquid mixture to obtain a reaction liquid and a mixed gas; the mixed gas comprises hydrogen fluoride and hydrogen chloride; the mixed gas is condensed to recover hydrogen fluoride, and the remaining hydrogen chloride is absorbed with water to prepare hydrochloric acid.

[0027] Preferably, the device used in the fluorination reaction further includes a liquid hydrogen fluoride storage tank 1, a mixed liquid storage tank 2, a gas-liquid separator 4, a condenser 5, a reaction liquid receiving tank 6 and a liquid hydrogen fluoride recovery tank 7;

[0028] The outlet of the liquid hydrogen fluoride storage tank 1 and the outlet of the mixed liquid storage tank 2 are connected to the inlet of the microchannel reactor 3;

[0029] The inlet of the gas-liquid separator 4 is connected to the outlet of the microchannel reactor 3;

[0030] The inlet of the condenser 5 is connected to the gas outlet of the gas-liquid separator 4;

[0031] The inlet of the reaction liquid receiving tank 6 is connected to the liquid outlet of the gas-liquid separator 4;

[0032] The inlet of the liquid hydrogen fluoride recovery tank 7 is connected to the liquid outlet of the condenser 5 .

[0033] Preferably, the temperature of the fluorination reaction is 30° C. to 80° C., and the pressure is 0.1 to 1.5 MPa.

[0034] Preferably, the polymerization inhibitor includes one or more of phenothiazine, polymerization inhibitor 701, p-tert-butylcatechol, hydroquinone, diphenylamine and polymerization inhibitor 705;

[0035] The molar ratio of the chloroethylene carbonate to the polymerization inhibitor is 1:(0.0001-0.001);

[0036] The molar ratio of the chloroethylene carbonate to the liquid hydrogen fluoride is 1:(1-5).

[0037] Preferably, the catalyst includes one or more of potassium fluoride, ferric chloride, antimony trichloride, tungsten hexachloride, antimony pentachloride, tin tetrachloride, titanium tetrachloride and tetrabutylammonium fluoride; and the molar ratio of the chloroethylene carbonate to the catalyst is 1:(0.001-0.01).

[0038] Preferably, the kettle temperature of the distillation is 90°C to 110°C, the top temperature is 60°C to 80°C, and the pressure is below 15 mmHg; the melt crystallization includes: cooling the product collected after distillation to 18°C ​​to 20°C, crystallizing for 10 to 16 hours, then releasing the uncrystallized material, and heating the remaining crystallized material to 35°C to 40°C for melting to obtain a fine product of fluoroethylene carbonate.

[0039] The invention provides a preparation method of fluoroethylene carbonate, comprising the following steps: mixing chloroethylene carbonate (CEC), a polymerization inhibitor, a catalyst and liquid hydrogen fluoride to carry out a fluorination reaction to obtain fluoroethylene carbonate (FEC); the catalyst comprises one or more of metal fluoride, metal chloride and tetrabutylammonium fluoride; and the polymerization inhibitor comprises one or more of amine polymerization inhibitors, phenol polymerization inhibitors and piperidine nitroxide free radical polymerization inhibitors. The present invention simultaneously adds a polymerization inhibitor and a catalyst to the fluorination reaction, thereby preventing side reactions such as material polymerization and improving the reaction rate, thereby improving the conversion rate and product yield. Example results show that the molar yield of the fluoroethylene carbonate of the present invention can reach more than 90%, and the product purity can reach more than 99.95%. In addition, the present invention uses liquid hydrogen fluoride as a fluorination reagent. Compared with fluorination reagents such as potassium fluoride and fluorine gas, liquid hydrogen fluoride is cheaper, safer, easier to use, easier to realize automated control, reduces the labor intensity of workshop workers, and has low production costs. At the same time, liquid hydrogen fluoride has higher mass transfer efficiency than gaseous hydrogen fluoride, which is conducive to improving the conversion rate and product yield.

[0040] Furthermore, the present invention uses trifluorotoluene compounds as solvents for the fluorination reaction. Trifluorotoluene compounds have high stability, are not easy to decompose, and will not interfere with the fluorination reaction. At the same time, they have excellent solubility and can dissolve a small amount of polymer generated by the reaction, preventing the polymer from adhering to the wall or clogging the pipeline, thereby improving the yield and purity of the product. In addition, trifluorotoluene compounds are easy to separate and recover and can be recycled, which is conducive to further reducing production costs.

[0041] Furthermore, after the fluorination reaction is completed, the present invention adds trichlorotoluene compounds to the reaction solution to react with the remaining hydrogen fluoride in the system. This not only effectively utilizes the excess hydrogen fluoride to prepare trifluorotoluene compounds, but also avoids the need for post-treatment to neutralize with alkali to remove hydrogen fluoride, thereby greatly reducing production costs.

[0042] Furthermore, in the present invention, the hydrogen chloride gas generated during the reaction process can be absorbed by water to prepare hydrochloric acid as a by-product, thereby realizing waste gas utilization and having obvious economic benefits.

[0043] Furthermore, the amount of catalyst used in the present invention is very small, only 0.1% to 1% of the molar amount of ethylene chloride carbonate. The main reasons are as follows: the use of a polymerization inhibitor in combination with the catalyst can greatly reduce the production of polymers. The catalyst cannot be dissolved in the reaction system. If a large amount of polymer is produced, it will wrap the catalyst and affect the catalytic effect. The present invention can improve the catalytic activity by combining the polymerization inhibitor with the catalyst. The above reasons greatly reduce the amount of catalyst used in the present invention. Catalysts are generally relatively expensive. The present invention reduces the amount of catalyst used, thereby greatly reducing production costs.

[0044] Furthermore, the present invention adopts a microchannel reactor to carry out the fluorination reaction, which can realize continuous and automated production, greatly reduces the operation risk, and is safer.

[0045] Furthermore, the present invention reduces the generation of side reaction polymers due to the use of a polymerization inhibitor during the reaction process, thereby generating less hazardous waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic diagram of the structure of the device when a microchannel reactor is used for the reaction in the present invention; in Figure 1: 1-liquid hydrogen fluoride storage tank, 2-mixed liquid storage tank, 3-microchannel reactor, 4-gas-liquid separator, 5-condenser, 6-reaction liquid receiving tank, 7-liquid hydrogen fluoride recovery tank, 8-liquid hydrogen fluoride feed pump, 9-mixed liquid feed pump;

[0047] FIG2 is an HPLC spectrum of fluoroethylene carbonate prepared in Example 1;

[0048] FIG3 is a hydrogen NMR spectrum of fluoroethylene carbonate prepared in Example 1;

[0049] FIG4 is the C NMR spectrum of the fluoroethylene carbonate prepared in Example 1. DETAILED DESCRIPTION

[0050] The present invention provides a method for preparing fluoroethylene carbonate, comprising the following steps:

[0051] Chloroethylene carbonate, a polymerization inhibitor, a catalyst and liquid hydrogen fluoride are mixed to carry out a fluorination reaction to obtain fluoroethylene carbonate; the catalyst comprises one or more of metal fluoride, metal chloride and tetrabutylammonium fluoride; the polymerization inhibitor comprises one or more of amine polymerization inhibitor, phenol polymerization inhibitor and piperidine nitroxide free radical polymerization inhibitor.

[0052] In the present invention, a solvent is preferably added during the mixing, and the solvent is preferably a trifluorotoluene compound; the structural formula of the trifluorotoluene compound is preferably as shown in Formula I:

[0053] In Formula I: n is an integer of 0 to 5, more preferably 0, 1, 2, 3, 4 or 5, further preferably 0 or 1. Specifically, n represents the total number of all R groups on the benzene ring. When n is greater than 1, the R groups may be the same or different. R is one or more of an alkyl group, a phenyl group and a halogen group. The number of carbon atoms of the alkyl group is preferably 1 to 10, more preferably 1 to 5. Specifically, R is more preferably one or more of a methyl group, a phenyl group, F, Cl, Br and I. In a specific embodiment of the present invention, the trifluorotoluene compound is preferably trifluorotoluene (i.e., n is 0), or preferably a compound of the structure shown in Formula I-1:

[0054] In formula I-1: R is preferably one of methyl and Cl.

[0055] In a specific embodiment of the present invention, the solvent is most preferably trifluorotoluene or para-chlorotrifluorotoluene.

[0056] In the present invention, the molar ratio of the ethylene chlorocarbonate to the solvent is preferably 1:(0.2-2), more preferably 1:(0.2-1.5), and further preferably 1:0.22; the purity of the ethylene chlorocarbonate is preferably 90 wt% to 95 wt%.

[0057] In the present invention, the polymerization inhibitor preferably includes one or more of phenothiazine, polymerization inhibitor 701, p-tert-butylcatechol, hydroquinone, diphenylamine and polymerization inhibitor 705; the molar ratio of the chloroethylene carbonate to the polymerization inhibitor is preferably 1:(0.0001-0.001), more preferably 1:(0.0002-0.0005), and further preferably 1:0.0004; the catalyst includes one or more of metal fluoride, metal chloride and tetrabutylammonium fluoride, preferably at least two; specifically, the catalyst preferably includes potassium fluoride, ferric chloride, antimony trichloride, tungsten hexachloride, antimony pentachloride, tin tetrachloride, tetrabutylammonium fluoride, One or more of titanium chloride and tetrabutylammonium fluoride, more preferably at least two; the molar ratio of the ethylene chloride carbonate to the catalyst is preferably 1:(0.001-0.01), more preferably 1:(0.002-0.005), and even more preferably 1:0.003; in the present invention, when there are two catalysts, preferably titanium tetrachloride and tungsten hexachloride, the molar ratio of titanium tetrachloride to tungsten hexachloride is preferably (1-5):1, more preferably 2:1; or preferably tungsten hexachloride and tin tetrachloride, the molar ratio of tungsten hexachloride to tin tetrachloride is preferably 1:(1-5), more preferably 1:(2.2-2.3). The present invention preferably uses at least two catalysts for compounding, which can further enhance the catalytic activity and thus improve the product yield.

[0058] In the present invention, the molar ratio of the ethylene chlorocarbonate to the liquid hydrogen fluoride is preferably 1:(1-5), more preferably 1:(1-3), and further preferably 1:1.5; the liquid hydrogen fluoride is preferably obtained by liquefying anhydrous hydrogen fluoride gas.

[0059] In the present invention, the fluorination reaction is preferably carried out in an autoclave; when the fluorination reaction is carried out in an autoclave, the fluorination reaction preferably includes: adding chloroethylene carbonate, a solvent, a catalyst, an inhibitor and liquid hydrogen fluoride into the autoclave, then heating, and carrying out the fluorination reaction at a certain temperature and pressure; in a specific embodiment of the present invention, it is preferred that chloroethylene carbonate, a solvent, a catalyst and an inhibitor are first added into the autoclave, and then liquid hydrogen fluoride is added under stirring conditions.

[0060] In the present invention, during the fluorination reaction, the generated hydrogen chloride gas is discharged while the reaction is taking place, and the discharged hydrogen chloride gas is absorbed by water to produce by-product hydrochloric acid; the pressure of the fluorination reaction is preferably controlled by the discharge amount of the hydrogen chloride gas, specifically by controlling the discharge amount of the hydrogen chloride gas by controlling the tail gas regulating valve; during the fluorination reaction, the generated gaseous hydrogen fluoride and gaseous solvent are condensed and collected, and then returned to the autoclave; the condensation is preferably carried out in a condenser, and the condensed product is preferably collected in a hydrogen fluoride intermediate tank. In the present invention, the discharged hydrogen chloride gas is preferably used to prepare hydrochloric acid by a falling film absorption method; the condensation is preferably carried out using a condenser; the temperature of the fluorination reaction is preferably 30°C to 80°C, more preferably 60°C to 70°C, the pressure of the fluorination reaction is preferably 0.1 to 1.5 MPa, more preferably 0.3 to 1.5 MPa, and further preferably 0.6 to 0.8 MPa; the time of the fluorination reaction is preferably 3 to 6 hours. The present invention controls the fluorination reaction temperature to 30°C to 80°C, which enables efficient reaction and reduces the occurrence of side reactions. If the reaction temperature exceeds 80°C, byproducts will increase and the product purity will decrease. After the fluorination reaction is completed, the reaction solution is preferably cooled to room temperature and the pressure is restored to normal pressure.

[0061] In the present invention, the reaction formula of the fluorination reaction is shown in Formula A:

[0062] In the present invention, after the fluorination reaction is completed, the present invention preferably mixes the obtained reaction liquid with a trichlorotoluene compound, and the trichlorotoluene compound reacts with the remaining hydrogen fluoride in the reaction liquid to obtain a mixed reaction liquid of fluoroethylene carbonate and trifluorotoluene compounds; the mixed reaction liquid is distilled and desolvated to obtain a concentrated liquid and trifluorotoluene compounds respectively; the trifluorotoluene compounds are recycled; and the concentrated liquid is sequentially subjected to rectification and melt crystallization to obtain fluoroethylene carbonate.

[0063] In the present invention, the structure of the trichlorotoluene compound is preferably as shown in Formula II:

[0064] In formula II: n is an integer of 0 to 5, more preferably 0, 1, 2, 3, 4 or 5, further preferably 0 or 1, and the meaning of n is the same as in formula I and is not repeated here; R is one or more of alkyl, phenyl and halogen, more preferably one or more of methyl, phenyl, F, Cl, Br and I, further preferably one of methyl and Cl. In a specific embodiment of the present invention, the trichlorotoluene compound is most preferably trichlorotoluene; the molar ratio of the trichlorotoluene compound to chloroethylene carbonate is preferably (0.1 to 4):1, more preferably (0.5 to 3):1, further preferably 1:1; the reaction formula of the reaction of the trichlorotoluene compound and the remaining hydrogen fluoride in the reaction solution is shown in formula B:

[0065] In the present invention, the temperature for reacting the trichlorotoluene compound with the remaining hydrogen fluoride in the reaction solution is preferably 20°C to 70°C, more preferably 50°C to 60°C, the pressure is preferably 1 to 2 MPa, more preferably 1.5 to 1.8 MPa, and the reaction time is preferably 2 to 3 hours; during the reaction, the generated hydrogen chloride gas is preferably discharged while the reaction is taking place, and the hydrogen chloride gas is preferably absorbed by a falling film to produce hydrochloric acid as a by-product; the gaseous hydrogen fluoride generated during the reaction is condensed by a condenser and collected in a hydrogen fluoride intermediate tank, and then returned to the autoclave. When the hydrogen fluoride in the system is completely consumed and the pressure in the autoclave no longer increases, the reaction is considered complete. After the reaction is completed, the present invention preferably exhausts the gas and reduces the pressure to obtain a mixed reaction solution of fluoroethylene carbonate and trifluorotoluene compounds. The present invention has no special requirements for the method of distilling and desolvating the mixed reaction liquid, and methods well known to those skilled in the art can be used. In the present invention, the kettle temperature of the concentrated liquid distillation is preferably 90°C to 110°C, the top temperature is preferably 60°C to 80°C, and the pressure is preferably below 15 mmHg, more preferably below 10 mmHg. The melt crystallization preferably includes: cooling the product collected after distillation to 18°C ​​to 20°C, crystallizing for 10 to 16 hours, then releasing the uncrystallized material, and heating the remaining crystallized material to 35°C to 40°C for melting to obtain a fine fluoroethylene carbonate. The purity of the fine fluoroethylene carbonate is above 99.95%.

[0066] In the present invention, the fluorination reaction is preferably carried out in a microchannel reactor; when the fluorination reaction is carried out in a microchannel reactor, the fluorination reaction preferably includes: mixing ethylene chlorocarbonate, a catalyst and an inhibitor to obtain a mixed liquid; or mixing ethylene chlorocarbonate, a catalyst, an inhibitor and a solvent to obtain a mixed liquid; and passing the mixed liquid and liquid hydrogen fluoride into the microchannel reactor for the fluorination reaction. In the present invention, the amount ratio of the chloroethylene carbonate, catalyst, inhibitor and solvent is the same as that of the above-mentioned scheme, which will not be repeated here; the flow rate of the mixed solution in the microchannel reactor is preferably 60-80 g / min, and the residence time is preferably 20-30 min, the flow rate of the liquid hydrogen fluoride in the microchannel reactor is preferably 35-45 g / min, and the residence time is preferably 20-30 min; the flow ratio of chloroethylene carbonate and liquid hydrogen fluoride in the mixed solution is preferably 6:(1-5), more preferably 6:3.5; the temperature of the fluorination reaction is preferably 30°C-80°C, more preferably 60°C-70°C, and the pressure of the fluorination reaction is preferably 0.1-1.5 MPa, more preferably 0.1-1.0 MPa, and further preferably 0.2-0.4 MPa. In a specific embodiment of the present invention, the liquid hydrogen fluoride and the mixed solution are preferably introduced into the microchannel reactor by a pressure pump.

[0067] In the present invention, when the fluorination reaction is carried out in a microchannel reactor, the gas-liquid mixture produced by the fluorination reaction is preferably subjected to gas-liquid separation to obtain a reaction liquid and a mixed gas; the mixed gas includes hydrogen fluoride and hydrogen chloride; the mixed gas is condensed to recover hydrogen fluoride, and the remaining hydrogen chloride is absorbed with water to prepare by-product hydrochloric acid; the absorption method is preferably falling film absorption; in the present invention, when the mixed liquid does not include a solvent, the reaction liquid obtained by the gas-liquid separation is preferably directly distilled and then melt crystallized to obtain fluoroethylene carbonate; when the mixed liquid includes a solvent, the reaction liquid obtained by the gas-liquid separation is preferably first distilled and desolvated to obtain a concentrated liquid, and then the concentrated liquid is distilled and then melt crystallized to obtain fluoroethylene carbonate; the distillation and melt crystallization methods are consistent with the above-mentioned scheme and will not be repeated here.

[0068] In the present invention, when the fluorination reaction is carried out in a microchannel reactor, the device used in the fluorination reaction further includes a liquid hydrogen fluoride storage tank 1, a mixed liquid storage tank 2, a gas-liquid separator 4, a condenser 5, a reaction liquid receiving tank 6 and a liquid hydrogen fluoride recovery tank 7; the outlet of the liquid hydrogen fluoride storage tank 1 and the outlet of the mixed liquid storage tank 2 are connected to the inlet of the microchannel reactor 3; the inlet of the gas-liquid separator 4 is connected to the outlet of the microchannel reactor 3; the inlet of the condenser 5 is connected to the gas outlet of the gas-liquid separator 4; the inlet of the reaction liquid receiving tank 6 is connected to the liquid outlet of the gas-liquid separator 4; the inlet of the liquid hydrogen fluoride recovery tank 7 is connected to the liquid outlet of the condenser 5; the pipeline connecting the liquid hydrogen fluoride storage tank 1 and the microchannel reactor 3 is preferably provided with a liquid hydrogen fluoride feed pump 8, and the pipeline connecting the mixed liquid storage tank 2 and the microchannel reactor 3 is preferably provided with a mixed liquid feed pump 9; the liquid hydrogen fluoride feed pump 8 and the mixed liquid feed pump 9 are both pressurized pumps.

[0069] FIG1 is a schematic diagram of the structure of the device when a microchannel reactor is used for the reaction in the present invention. The specific reaction process is described below in conjunction with FIG1: liquid hydrogen fluoride flows out of the liquid hydrogen fluoride storage tank 1 and is passed into the microchannel reactor 3 under the action of a liquid hydrogen fluoride feed pump 8. A mixed liquid (prepared by ethylene chlorocarbonate, a catalyst and an inhibitor, or prepared by ethylene chlorocarbonate, a catalyst, an inhibitor and a solvent) flows out of the mixed liquid storage tank 2 and is passed into the microchannel reactor 3 under the action of a mixed liquid feed pump 9. The gas-liquid mixture produced by the reaction is discharged from the microchannel reactor 3. The outlet of the reactor 3 flows out and enters the gas-liquid separator 4 for gas-liquid separation. The liquid produced by the separation is the reaction liquid. It flows out from the liquid outlet of the gas-liquid separator 4 and enters the reaction liquid receiving tank 6 for subsequent distillation and purification. The gas produced by the separation is a mixed gas of hydrogen fluoride and hydrogen chloride. It flows out from the gas outlet of the gas-liquid separator 4 and enters the condenser 5 for condensation. The liquid hydrogen fluoride produced by the condensation enters the liquid hydrogen fluoride recovery tank 7 for subsequent recycling. The remaining hydrogen chloride gas is discharged from the gas outlet of the condenser 5 and is subsequently absorbed in the tail gas absorption tower to prepare hydrochloric acid.

[0070] The present invention addresses the common problems of large hazardous waste emissions, low product yields and high raw material costs in existing synthesis process routes. It provides a preparation method for fluoroethylene carbonate with low "hazardous waste" generation, high yield and low raw material costs. At the same time, when a microchannel reactor is used for the fluorination reaction, continuous and automated production can be achieved, greatly improving production efficiency.

[0071] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0072] Example 1

[0073] To a 2000mL autoclave were added 600g (MW 122.5, 4.65mol) of 95% chloroethylene carbonate, 150g (MW 146.1, 1.03mol) of trifluorotoluene, 0.6g (MW 166.2, 0.003mol) of p-tert-butylcatechol, 5g (MW 189.6, 0.026mol) of titanium tetrachloride, and 5g (MW 396.5, 0.013mol) of tungsten hexachloride. Stirring was initiated, and 280g (MW 20, 14mol) of liquid hydrogen fluoride was added. After the addition of the liquid hydrogen fluoride was complete, the mixture was slowly heated to 60°C to 70°C, the pressure was controlled at 0.6-0.8MPa, and the reaction was carried out for 5 hours, while hydrogen chloride gas was discharged during the reaction. Samples were taken for testing, and the FEC purity was 90.2%, the CEC purity was 3.8%, and the conversion rate was 95.9%.

[0074] After the reaction, the temperature was lowered to 15°C to 25°C, the mixture was vented to normal pressure, 450g of trichlorotoluene (MW195.47, 2.30mol) was added, the pressure was controlled to 1.5-1.8MPa, the temperature was controlled at 50°C to 60°C, and the reaction was kept warm for 4h, while the generated hydrogen chloride gas was discharged. After the reaction was completed, the mixture was discharged to obtain a mixed solution of FEC and trifluorotoluene. Then, 470g of by-product trifluorotoluene was obtained through distillation and desolventization, with a purity of 99.7% and a molar yield of 95.09%. The concentrated solution was rectified at a still temperature of 90°C, a top temperature of 60°C, and a pressure of less than 15mmHg. The collected product after the rectification was cooled to 18°C ​​and crystallized for 10h. The uncrystallized material was then discharged, and the remaining crystallized material was heated to 35°C and melted to obtain about 468g of fine fluoroethylene carbonate with a purity of 99.98% and a molar yield of 95.0%.

[0075] The HPLC spectrum of the fluoroethylene carbonate prepared in this example is shown in FIG2 , and the spectrum data are shown in Table 1:

[0076] Table 1 HPLC spectrum data

[0077] The H-NMR spectrum of the fluoroethylene carbonate prepared in this example is shown in FIG3 , and the H-NMR data are as follows: 1 HNMR (400 MHz, DMSO) δ 6.67-6.50 (d, 1H, CH), 4.79-4.59 (m, 2H, CH2); the C NMR spectrum of the fluoroethylene carbonate prepared in this example is shown in FIG4 .

[0078] Example 2

[0079] To a 2000mL autoclave were added 600g (MW 122.5, 4.41mol) of 90% chloroethylene carbonate, 150g (MW 146.1, 1.03mol) of trifluorotoluene, 0.6g (MW 166.2, 0.003mol) of p-tert-butylcatechol, 5g (MW 396.5, 0.013mol) of tungsten hexachloride, and 6g (MW 206.5, 0.029mol) of tin tetrachloride. The mixture was stirred, and 280g (MW 20, 14mol) of liquid hydrogen fluoride was added. After the addition of the liquid hydrogen fluoride, the mixture was slowly heated to 60°C to 70°C, and the pressure was controlled at 0.6-0.8MPa for 5 hours. The hydrogen chloride gas was discharged during the reaction. Sampling and testing showed that the FEC purity was 91.2%, the CEC purity was 3.0%, and the conversion rate was 96.8%.

[0080] After the reaction, the temperature was lowered to 15°C to 25°C, the mixture was vented to normal pressure, 450g of trichlorotoluene (MW195.47, 2.30mol) was added, the pressure was controlled to 1.5-1.8MPa, the temperature was controlled at 50°C to 60°C, and the reaction was kept warm for 3h, while the generated hydrogen chloride gas was discharged during the reaction. After the reaction was completed, the mixture was discharged to obtain a mixed solution of FEC and trifluorotoluene. Then, 475g of by-product trifluorotoluene was obtained through distillation and desolventization, with a purity of 99.5% and a molar yield of 96.5%. The concentrated solution was further subjected to rectification and melt crystallization (the conditions of rectification and melt crystallization were the same as those in Example 1) to obtain about 445g of fine fluoroethylene carbonate, with a purity of 99.97% and a molar yield of 95.1%.

[0081] Example 3

[0082] To a 2000mL autoclave were added 600g (MW 122.5, 4.65mol) of 95% chloroethylene carbonate, 180g (MW 180.5, 1.0mol) of parachlorobenzotrifluoride, 0.6g (MW 166.2, 0.003mol) of p-tert-butylcatechol, 5g (MW 189.6, 0.026mol) of titanium tetrachloride, and 5g (MW 396.5, 0.013mol) of tungsten hexachloride. The mixture was stirred, and 280g (MW 20, 14mol) of liquid hydrogen fluoride was added. After the addition of the liquid hydrogen fluoride was completed, the mixture was slowly heated to 60°C to 70°C, and the pressure was controlled at 0.6-0.8MPa for 5 hours. The reaction was carried out while venting hydrogen chloride gas. Sampling and testing showed that the FEC purity was 91.2%, the CEC purity was 3.5%, and the conversion rate was 96.3%.

[0083] After the reaction, the temperature was lowered to 15°C to 25°C, the mixture was vented to normal pressure, 530g of para-chlorobenzotrichloride (MW229.9, 2.31mol) was added, the pressure was controlled to 1.5-1.8MPa, the temperature was controlled at 50°C to 60°C, and the reaction was kept warm for 3h, while the generated hydrogen chloride gas was discharged. After the reaction was completed, the mixture was discharged to obtain a mixed solution of FEC and para-chlorobenzotrifluoride. Then, 570g of the by-product para-chlorobenzotrifluoride was obtained by distillation and desolventization, with a purity of 99.5% and a molar yield of 95.6%. The concentrated solution was further subjected to rectification and melt crystallization (the conditions of rectification and melt crystallization were the same as those in Example 1) to obtain about 465g of fine fluoroethylene carbonate, with a purity of 99.97% and a molar yield of 94.3%.

[0084] Example 4

[0085] 6 g of p-tert-butylcatechol (MW 166.2, 0.03 mol), 50 g of titanium tetrachloride (MW 189.6, 0.26 mol), and 50 g of tungsten hexachloride were dissolved in 6000 g of 95% ethylene chlorocarbonate (MW 122.5, 46.5 mol), and the mixed solution was placed in mixed solution storage tank 2. The jacket heating system of the microchannel reactor 3 was turned on to control the temperature to 60° C. to 70° C., and the mixed liquid feed pump 9 and the liquid hydrogen fluoride feed pump 8 were started at the same time. The flow ratio of CEC and liquid hydrogen fluoride was controlled to be 6:3.5. The material was slowly introduced into the microchannel for reaction. The pressure of the microchannel reactor 3 was controlled to 0.2 to 0.4 MPa by controlling the opening of the outlet valve. The gas-liquid mixture obtained by the reaction was separated by the gas-liquid separator 4, and the obtained mixed gas was condensed by the condenser 5. The excess hydrogen fluoride entered the liquid hydrogen fluoride recovery tank 7 for reuse, and the hydrogen chloride was absorbed to prepare the by-product hydrochloric acid. The reaction liquid obtained by gas-liquid separation entered the reaction liquid receiving tank 6, and then after rectification and melt crystallization (the conditions of rectification and melt crystallization were the same as those in Example 1), a fine fluoroethylene carbonate was obtained with a purity of 99.97% and a molar yield of 95.7%.

[0086] Example 5

[0087] To a 2000mL autoclave were added 600g of 90% chloroethylene carbonate (MW 122.5, 4.41 mol), 150g of trifluorotoluene (MW 146.1, 1.03 mol), 0.6g of p-tert-butylcatechol (MW 166.2, 0.003 mol), and 5g of tungsten hexachloride (MW 396.5, 0.013 mol) in sequence, with stirring. 280g of liquid hydrogen fluoride (MW 20, 14 mol) was then added. After the addition of the liquid hydrogen fluoride, the mixture was slowly heated to 60°C to 70°C, the pressure was controlled at 0.6-0.8 MPa, and the reaction was continued for 5 hours, while hydrogen chloride gas was discharged during the reaction. Sampling and testing showed an FEC purity of 84.6%, a CEC purity of 8.9%, and a conversion rate of 90.4% (the conversion rate was relatively low).

[0088] After the reaction, the temperature was lowered to 15°C to 25°C, the mixture was vented to normal pressure, 450g of trichlorotoluene (MW 195.47, 2.30mol) was added, the pressure was controlled at 1.5-1.8MPa, the temperature was controlled at 50°C to 60°C, and the reaction was kept warm for 3-4h, while the generated hydrogen chloride gas was discharged during the reaction. After the reaction was completed, the mixture was discharged to obtain a mixed solution of FEC and trifluorotoluene. Then, 473g of the by-product trifluorotoluene was obtained through distillation and desolventization, with a purity of 99.5% and a molar yield of 97.2%. The concentrated solution was rectified and melt crystallized (the conditions of rectification and melt crystallization were the same as those in Example 1) to obtain about 408g of fine fluoroethylene carbonate, with a purity of 99.95% and a molar yield of 87.3%.

[0089] Comparative Example 1 uses diethyl carbonate as solvent

[0090] To a 2000mL autoclave were added 600g (MW 122.5, 4.41mol) of 90% chloroethylene carbonate, 120g (MW 118.1, 1.03mol) of diethyl carbonate, 0.6g (MW 166.2, 0.003mol) of p-tert-butylcatechol, 5g (MW 396.5, 0.013mol) of tungsten hexachloride, and 6g (MW 206.5, 0.029mol) of tin tetrachloride. The mixture was stirred, and 280g (MW 20, 14mol) of liquid hydrogen fluoride was added. After the addition of the liquid hydrogen fluoride was completed, the mixture was slowly heated to 60°C to 70°C, and the pressure was controlled at 0.6-0.8MPa for 5h. The reaction was carried out while emitting hydrogen chloride gas. Sampling and testing showed that the purity of FEC was 80.1%, the purity of CEC was 8.9%, and the conversion rate was 90% (low conversion rate).

[0091] After the reaction is completed, the temperature is lowered to 15°C to 25°C, the mixture is vented to normal pressure, 450g of trichlorotoluene (MW195.47, 2.32mol) is added, the pressure is controlled to 1.5-1.8MPa, the temperature is controlled at 50°C to 60°C, and the reaction is kept warm for 3-4h, while the generated hydrogen chloride gas is discharged. After the reaction is completed, the mixture is discharged to obtain a mixed solution of FEC, trifluorotoluene and diethyl carbonate. Then, 445g of a mixed solvent of by-product trifluorotoluene and diethyl carbonate is obtained by distillation and desolventization. The concentrated solution is then subjected to rectification and melt crystallization (the conditions of rectification and melt crystallization are the same as those in Example 1) to obtain about 402g of fine fluoroethylene carbonate, with a purity of 99.4% (the purity is low and it is difficult to reach electronic grade purity), and a molar yield of 85.9% (the yield is low).

[0092] Comparative Example 2 Fluorination reaction temperature increased

[0093] To a 2000mL autoclave were added 600g of 90% chloroethylene carbonate (MW 122.5, 4.41 mol), 150g of trifluorotoluene (MW 146.1, 1.03 mol), 0.6g of p-tert-butylcatechol (MW 166.2, 0.003 mol), 5g of tungsten hexachloride (MW 396.5, 0.013 mol), and 6g of tin tetrachloride (MW 206.5, 0.029 mol), followed by stirring. 280g of liquid hydrogen fluoride (MW 20, 14 mol) was then added. After the addition of the liquid hydrogen fluoride was complete, the mixture was slowly heated to 85°C to 95°C, the pressure was controlled at 0.6-0.8 MPa, and the reaction was continued for 5 hours, while venting hydrogen chloride gas. Sampling and testing revealed an FEC purity of 78.5%, a CEC purity of 1.8%, and a conversion rate of 98.1%. (Although the conversion rate was high, the product purity was low and by-product impurities increased.)

[0094] After the reaction is completed, the temperature is lowered to 15°C to 25°C, the mixture is vented to normal pressure, 450g of trichlorotoluene (MW195.47, 2.30mol) is added, the pressure is controlled to 1.5-1.8MPa, the temperature is 50°C to 60°C, and the reaction is kept warm for 4h, while the generated hydrogen chloride gas is discharged. After the reaction is completed, the mixture is discharged to obtain a mixed solution of FEC and trifluorotoluene. Then, 470g of by-product trifluorotoluene is obtained through distillation and desolventizing, with a purity of 99.5% and a molar yield of 96.6%. The concentrated solution is then subjected to rectification and melt crystallization (the conditions of rectification and melt crystallization are the same as those in Example 1) to obtain about 330g of fine fluoroethylene carbonate, with a purity of 99.3% (the product purity is low) and a molar yield of 70.5% (due to the high reaction temperature, there is a lot of polymer in the still residue, and the product yield is low).

[0095] Comparative Example 3: Omitting the polymerization inhibitor

[0096] To a 2000mL autoclave were added 600g (MW 122.5, 4.41mol) of 90% chloroethylene carbonate, 150g (MW 146.1, 1.03mol) of trifluorotoluene, 5g (MW 396.5, 0.013mol) of tungsten hexachloride, and 6g (MW 206.5, 0.029mol) of tin tetrachloride. The mixture was stirred, and 280g (MW 20, 14mol) of liquid hydrogen fluoride was added. After the addition of the liquid hydrogen fluoride was completed, the mixture was slowly heated to 60°C to 70°C, and the pressure was controlled at 0.6-0.8MPa for 5 hours. The reaction was carried out while venting hydrogen chloride gas. Sampling and testing showed that the FEC purity was 91.2%, the CEC purity was 3.0%, and the conversion rate was 96.8%.

[0097] After the reaction, the temperature was lowered to 15°C to 25°C, the mixture was vented to atmospheric pressure, and 450g of trichlorotoluene (MW 195.47, 2.30 mol) was added. The pressure was controlled to 1.5-1.8 MPa, the temperature was controlled at 50°C to 60°C, and the reaction was kept warm for 3 hours, while the generated hydrogen chloride gas was discharged. After the reaction was completed, the mixture was discharged to obtain a mixture of FEC and trifluorotoluene. Then, 464g of the by-product trifluorotoluene was obtained through distillation and desolventization, with a purity of 99.5% and a molar yield of 95.4%. The concentrated solution was further subjected to rectification and melt crystallization (the conditions of rectification and melt crystallization were the same as in Example 1) to obtain approximately 363g of fine fluoroethylene carbonate with a purity of 99.97% and a molar yield of 77.5%. (The yield was low due to partial polymerization due to the lack of polymerization inhibitor).

[0098] Comparative Example 4 Omitting the Catalyst

[0099] To a 2000mL autoclave were added 600g of 90% chloroethylene carbonate (MW 122.5, 4.41mol), 150g of trifluorotoluene (MW 146.1, 1.03mol), and 0.6g of p-tert-butylcatechol (MW 166.2, 0.003mol), followed by stirring. 280g of liquid hydrogen fluoride (MW 20, 14mol) was then added. After the addition of the liquid hydrogen fluoride was complete, the mixture was slowly heated to 60°C to 70°C and maintained at a pressure of 0.6-0.8MPa for 5 hours, with hydrogen chloride gas being discharged during the reaction. Samples were taken for testing, and the FEC purity was 56.6%, the CEC purity was 35.3%, and the conversion rate was 61.6%.

[0100] After the reaction is complete, the temperature is lowered to 15°C to 25°C, vented to normal pressure, 450g of trifluorotoluene (MW195.47, 2.30mol) is added, the pressure is controlled to 1.5 to 1.8MPa, the temperature is controlled at 50°C to 60°C, and the reaction is kept warm for 3h, while the generated hydrogen chloride gas is discharged. After the reaction is complete, the blowing obtains a mixed solution of FEC and trifluorotoluene. Then, 473g of by-product trifluorotoluene is obtained through distillation and precipitation, with a purity of 99.5% and a molar yield of 97.2%. The concentrated solution is then subjected to rectification and melt crystallization (the conditions of rectification and melt crystallization are consistent with those of Example 1) to obtain about 235g of fluoroethylene carbonate product, with a purity of 99.2% and a molar yield of 50.2%. (Due to the lack of a catalyst, the conversion rate is low, the raw material residue is large, and the product purity is unqualified).

[0101] In summary, the preparation method of fluoroethylene carbonate provided by the present invention has high conversion rate, high product yield and purity, low raw material cost, low hazardous waste output, easy to achieve continuous and automated production, and has broad prospects.

[0102] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A preparation method of fluorinated ethylene carbonate, characterized in that, It includes the following steps: Vinyl chloroformate, inhibitor, catalyst and liquid hydrogen fluoride are mixed for a fluorination reaction to obtain vinyl fluorocarbonate; the catalyst includes one or more of metal fluorides, metal chlorides and tetrabutylammonium fluoride; the inhibitor includes one or more of amine inhibitors, phenolic inhibitors and piperidine nitroxide inhibitors.

2. The preparation method according to claim 1, wherein A solvent is also added during the mixing, and the solvent is a trifluorotoluene compound; the structural formula of the trifluorotoluene compound is shown in Formula I: In Formula I: n is an integer from 0 to 5, and R is one or more of alkyl, phenyl and halogen; The molar ratio of the vinyl chloroformate to the solvent is 1:(0.2 - 2).

3. The preparation method according to claim 2, wherein The trifluorotoluene compound is trifluorotoluene or p-chlorotrifluorotoluene.

4. The preparation method according to claim 2, characterized in that, The fluorination reaction is carried out in an autoclave.

5. The preparation method according to claim 4, characterized in that, The fluorination reaction includes: adding vinyl chloroformate, solvent, catalyst, inhibitor and liquid hydrogen fluoride into an autoclave, then heating, and carrying out the fluorination reaction under certain temperature and pressure conditions; During the fluorination reaction, hydrogen chloride gas generated is discharged while reacting, and the discharged hydrogen chloride gas is absorbed by water to make by-product hydrochloric acid; the pressure of the fluorination reaction is controlled by controlling the discharge amount of hydrogen chloride gas; during the fluorination reaction, gaseous hydrogen fluoride and gaseous solvent generated are condensed and collected, and then returned to the autoclave.

6. The preparation method according to claim 5, wherein After the fluorination reaction is completed, it further includes mixing the obtained reaction solution with a trichlorotoluene compound, and the trichlorotoluene compound reacts with the remaining hydrogen fluoride in the reaction solution to obtain a mixed reaction solution of vinyl fluorocarbonate and a trifluorotoluene compound; the mixed reaction solution is distilled to remove the solvent to obtain a concentrated solution and a trifluorotoluene compound respectively; the trifluorotoluene compound obtained by distilling off the solvent is recycled; the concentrated solution is subjected to rectification and melt crystallization in sequence to obtain a vinyl fluorocarbonate product; The structure of the benzotrichloride compound is shown in Formula II: In Formula II: n is an integer from 0 to 5, and R is one or more of alkyl, phenyl and halogen.

7. The preparation method according to claim 1 or 2, characterized in that, The fluorination reaction is carried out in a microchannel reactor.

8. The preparation method according to claim 7, wherein The fluorination reaction includes: Mixing vinyl chloroformate, catalyst and inhibitor to obtain a mixed solution; or mixing vinyl chloroformate, catalyst, inhibitor and solvent to obtain a mixed solution; Feeding the mixed solution and liquid hydrogen fluoride into a microchannel reactor for a fluorination reaction.

9. The preparation method according to claim 8, characterized in that, The flow rate ratio of vinyl chloroformate to liquid hydrogen fluoride in the mixed solution is 6:(1 - 5).

10. The preparation method according to claim 8, characterized in that, After the fluorination reaction, it further includes: carrying out gas-liquid separation on the generated gas-liquid mixture to obtain a reaction solution and a mixed gas; the mixed gas includes hydrogen fluoride and hydrogen chloride; the mixed gas is condensed to recover hydrogen fluoride, and the remaining hydrogen chloride is absorbed by water to prepare hydrochloric acid.

11. The preparation method according to claim 7, wherein, The device used for the fluorination reaction further includes a liquid hydrogen fluoride storage tank (1), a mixed solution storage tank (2), a gas-liquid separator (4), a condenser (5), a reaction solution receiving tank (6) and a liquid hydrogen fluoride recovery tank (7); The outlet of the liquid hydrogen fluoride storage tank (1) and the outlet of the mixed solution storage tank (2) are connected to the inlet of the microchannel reactor (3); The inlet of the gas-liquid separator (4) is connected to the outlet of the microchannel reactor (3); The inlet of the condenser (5) is connected to the gas outlet of the gas-liquid separator (4); The inlet of the reaction liquid receiving tank (6) is connected to the liquid outlet of the gas-liquid separator (4); The inlet of the liquid hydrogen fluoride recovery tank (7) is connected to the liquid outlet of the condenser (5).

12. The preparation method according to claim 1, characterized in that, The temperature of the fluorination reaction is 30°C to 80°C, and the pressure is 0.1 to 1.5 MPa.

13. The preparation method according to claim 1, characterized in that, The polymerization inhibitor includes one or more of phenothiazine, polymerization inhibitor 701, p-tert-butylcatechol, hydroquinone, diphenylamine, and polymerization inhibitor 705; The molar ratio of the chloroethylene carbonate to the polymerization inhibitor is 1:(0.0001 - 0.001); The molar ratio of the chloroethylene carbonate to the liquid hydrogen fluoride is 1:(1 - 5).

14. The preparation method according to claim 13, characterized in that, The catalyst includes one or more of potassium fluoride, ferric chloride, antimony trichloride, tungsten hexachloride, antimony pentachloride, tin tetrachloride, titanium tetrachloride, and tetrabutylammonium fluoride; the molar ratio of the chloroethylene carbonate to the catalyst is 1:(0.001 - 0.01).

15. The preparation method according to claim 14, characterized in that, The catalyst is titanium tetrachloride and tungsten hexachloride, and the molar ratio of titanium tetrachloride to tungsten hexachloride is (1 - 5):1; or the catalyst is tungsten hexachloride and tin tetrachloride, and the molar ratio of tungsten hexachloride to tin tetrachloride is 1:(1 - 5).

16. The preparation method according to claim 6, characterized in that, The bottom temperature of the rectification is 90°C to 110°C, the top temperature is 60°C to 80°C, and the pressure is below 15 mmHg; the melt crystallization includes: cooling the product collected after rectification to 18°C to 20°C, crystallizing for 10 to 16 h, then discharging the uncrystallized material, and heating the remaining crystallized material to 35°C to 40°C for melting to obtain high-purity fluoroethylene carbonate.

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