Preparation method of fluoroethylene carbonate

Abstract

The invention discloses a preparation method of fluoroethylene carbonate, and belongs to the technical field of organic synthesis. According to the method, a three-in-one catalytic system of a fluorine source, a promoter and a phase transfer catalyst is constructed, so that the technical bottleneck of a traditional fluorination process is broken through. The method for in-situ generation of hydrogen fluoride comprises the following steps: taking a fluoro basic salt (such as potassium fluoride) as a fluorine source and concentrated sulfuric acid as a promoter to generate hydrogen fluoride (HF) in situ, and avoiding direct use of dangerous fluorine gas; reaction conditions are optimized: mild reaction and uniform precipitation of a byproduct (potassium chloride) are realized by adopting a composite fluorinating agent, and solid-liquid separation is facilitated. The method is high in reaction selectivity, and the yield reaches 93.5%. Raw materials are cheap and easy to obtain, equipment requirements are low, and large-scale production is facilitated. The FEC purity after rectification is gt; the lithium ion battery electrolyte additive meets the requirements of lithium ion battery electrolyte additives, and is especially suitable for the field of high-performance lithium ion batteries.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing fluoroethylene carbonate. Background Art

[0002] As a highly advantageous chemical power source with high energy density, lithium-ion batteries have been extensively and deeply studied worldwide. The electrolyte system, as a core component of lithium-ion batteries, has also undergone continuous development and optimization with the advancement of battery technology. This development process not only involves the innovation of electrolyte lithium salts, but also includes the development of new organic solvents and in-depth research on electrolyte additives. Among them, electrolyte additives are becoming increasingly important as a key factor in optimizing battery performance. By introducing specific functional additives into the basic electrolyte, the performance of lithium-ion batteries in different working environments can be significantly improved, such as increasing cycle life, enhancing thermal stability, improving rate performance, and improving safety performance.

[0003] Lithium-ion battery electrolyte additives can be divided into two categories: organic and inorganic. Organic additives are more widely used due to their good compatibility with the electrolyte, significant optimization effect and ease of use. Among them, unsaturated carbonate derivatives, such as ethylene carbonate (VC), vinyl ethylene carbonate (VEC) and fluoroethylene carbonate (FEC) and other vinyl structure-containing additives, can form a protective film on the electrode surface and significantly improve the battery's cycle performance. Ester additives, such as carboxymethyl cellulose (CMC), can also optimize the electrode-electrolyte interface and improve battery performance.

[0004] The industrial synthesis routes of fluoroethylene carbonate can be mainly summarized into three categories: electrochemical fluorination, direct fluorination and halogen exchange. In the electrochemical fluorination system, the Simons process is the earliest typical process to achieve industrial production (developed by 3M). Its core is to achieve fluorination by electrolysis in a mixed electrolyte system of liquid anhydrous hydrogen fluoride and organic compounds. However, this method has significant defects, including high energy consumption and dependence on highly corrosive anhydrous hydrogen fluoride. In order to improve the reaction medium conditions, the subsequently developed Philips process uses a potassium fluoride / hydrogen fluoride molten salt system as the electrolysis environment, but it is essentially still in the category of high-temperature molten salt electrolysis.

[0005] Notably, BASF SE proposed an innovative improvement in patent CN103261484A, successfully applying this electrochemical technology to the synthesis of fluorinated organic carbonates by introducing a hydrogen fluoride complex to replace anhydrous hydrogen fluoride or molten salt systems in traditional electrolytes. Despite this, such electrochemical methods still face the common technical bottleneck of excessive energy consumption during the electrolysis process.

[0006] The direct fluorination method uses ethylene carbonate as a raw material and directly replaces fluorine with fluorine gas or other fluorinating agents. This method synthesizes fluoroethylene carbonate in a single step, resulting in low production costs. However, due to the use of highly reactive and toxic fluorine gas, the reaction process is difficult to control and requires very high equipment and production processes, limiting its application in industrial production.

[0007] Another important synthetic route is the Finkelstein halogen exchange reaction-driven, step-by-step process. This technical route consists of two key stages: first, a chlorinated organic carbonate intermediate is prepared through a chlorination reaction. After purification, a halogen exchange reaction with fluorine gas is performed to produce the target fluorinated product. While this method circumvents the high energy consumption of the electrolysis process, continuous optimization is still needed in terms of process economics and safety. Summary of the Invention

[0008] The existing methods using fluorine gas as raw materials are characterized by high risk, poor controllability, and high equipment requirements. The present invention innovatively develops an improved fluorination process system based on halogen exchange, and achieves a technological breakthrough by constructing a ternary synergistic system of "fluorination reagent-cocatalyst-phase transfer catalyst". The core innovations include: ① Using a composite fluorination reagent to replace the gaseous fluorine source, the efficient activation and transfer of fluorine atoms is achieved under the catalytic effect of concentrated sulfuric acid, and the reaction selectivity is increased to more than 95%; ② Through molecular structure regulation, the by-product potassium chloride is formed into ultrafine particles, which shortens the filtration time by 50% compared with the traditional process; ③ The reaction system can be completed under mild conditions of normal pressure and 80-100 °C. Compared with the fluorine gas method, this process shows significant advantages in safety, economy and product purity, and provides a reliable technical path for industrial production.

[0009] The technical solution adopted by the present invention is: a method for preparing fluoroethylene carbonate, wherein the method comprises the following steps: fluoroethylene carbonate is subjected to a fluorination reaction under the action of a fluorination reagent, a co-catalyst and a phase transfer catalyst to prepare the fluoroethylene carbonate; the co-catalyst is concentrated sulfuric acid.

[0010] Reaction equation of the present invention is as follows:

[0011] The fluorination agent is a fluorinated alkaline salt, such as triethylamine trihydrofluoride, sodium fluoride, potassium fluoride, antimony trifluoride, sodium bifluoride or potassium bifluoride.

[0012] The phase transfer catalyst is crown ether, quaternary ammonium salt, quaternary phosphonium salt or polyethylene glycol.

[0013] The crown ether is preferably 12-crown-6 or 18-crown-6; the molecular weight of the polyethylene glycol is between 400 and 2000; the quaternary ammonium salt is preferably tetrabutylammonium bromide, tetra-n-octylammonium bromide, tetrabutylammonium chloride, etc.; the quaternary phosphonium salt is preferably triphenylmethylphosphonium chloride, tetraphenylphosphonium bromide, or methyltriphenylphosphonium bromide.

[0014] Preferably, the fluorination reagents are two fluorinated alkaline salts, one is antimony trifluoride, and the other is potassium fluoride, sodium fluoride or triethylamine trihydrofluoride, and the phase transfer catalyst is crown ether or polyethylene glycol.

[0015] The molar ratio of the chloroethylene carbonate and the fluorination agent is 1:0.1-5, preferably 1:1-2.

[0016] The added mass of the phase transfer catalyst is 0.1-10% of the ethylene chlorocarbonate, preferably 0.1-1%. The added mass of the co-catalyst is 0.01-10% of the ethylene chlorocarbonate, preferably 0.01-1%.

[0017] The method of the present invention is preferably carried out in an organic solvent, and the organic solvent is preferably one or more of tetrahydrofuran, dimethyl carbonate, ethyl acetate, acetonitrile, and methyl tert-butyl ether.

[0018] The amount of the organic solvent used is 1 to 50 mL / g, preferably 1 to 2 mL / g, based on the mass of chloroethylene carbonate.

[0019] The method is carried out under the protection of an inert gas, preferably nitrogen.

[0020] The reaction temperature is 30-200°C, preferably 60-100°C.

[0021] The reaction time is 3 to 20 h, preferably 6 to 10 h.

[0022] After the reaction is completed, the obtained reaction liquid is post-treated to obtain fluoroethylene carbonate. The post-treatment method of the reaction liquid is: solid-liquid separation, taking the liquid product and evaporating the solvent, and then performing rectification and purification to obtain fluoroethylene carbonate.

[0023] Solid-liquid separation can be achieved by filtration. The filter cake can be washed with an organic solvent.

[0024] Specifically, the method of the present invention is preferably carried out according to the following steps: Place 50.0 g of CEC (86% purity) into a constant-pressure dropping funnel. Add the corresponding equivalent (e.g., 2.0 eq.) of fluorinating agent (pre-ground to a fine powder) to a 250 ml three-necked flask. Mix 0.1 g of a phase transfer catalyst with 80 ml of solvent. Add 1 ml of concentrated sulfuric acid dropwise. Stir at room temperature for 2 hours, then raise the temperature to 90°C. Slowly add CEC dropwise (allowing for approximately 15 minutes). After the reaction is complete, filter, wash the filter cake, and evaporate the filtrate to remove the solvent. Distill the filtrate to obtain fluoroethylene carbonate.

[0025] The present invention has the beneficial effect of slowly generating hydrogen fluoride in situ through the action of concentrated sulfuric acid and a fluorination agent, avoiding the direct use of hazardous fluorine gas, thereby directly reacting ethylene carbonate to synthesize fluoroethylene carbonate. By dropwise addition of chloroethylene carbonate (CEC), combined with a phase transfer catalyst (such as polyethylene glycol or crown ether) and a polar solvent (such as acetonitrile), and an improved fluorination agent, a composite fluorinating agent is employed to achieve a mild reaction and uniform precipitation of the byproduct (potassium chloride), facilitating solid-liquid separation. Furthermore, the dropwise addition of CEC into the reaction system offers a milder reaction than the traditional one-pot method, resulting in a more uniform and finer potassium chloride solid, facilitating subsequent filtration. This invention, for the first time, proposes a method for fluorination reaction using in situ generation of hydrogen fluoride from solid raw materials, addressing the issues of high equipment requirements, high risk, and poor gas-liquid mass transfer associated with the use of fluorine gas raw materials. Furthermore, the present invention utilizes low-cost raw materials, simple equipment, strong reaction selectivity, and high yield, making it highly valuable for industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram of the experimental setup of this method.

[0027] Figure 2 This is the NMR spectrum of fluoroethylene carbonate.

[0028] Figure 3 This is a GC-MS spectrum.

[0029] Figure 4 This is the mass spectrum of fluoroethylene carbonate. DETAILED DESCRIPTION

[0030] The technical solutions of the present invention are further described below through examples.

[0031] Unless otherwise specified, the terms used in the present invention generally have the meanings commonly understood by those skilled in the art.

[0032] In the following examples, various processes and methods not described in detail are conventional methods well known in the art. At the same time, not all preparation methods are described in detail, and typical examples are taken to illustrate the specific process steps of the present invention. Example 1

[0033] To a 250 ml three-necked flask, under nitrogen, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 34.8 g of the product was distilled out with a conversion rate of >99%, a selectivity of 95.2%, an assay of 95.1%, and a yield of 93.5%. Example 2

[0034] To a 250 ml three-necked flask, under nitrogen, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of tetrahydrofuran and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of tetrahydrofuran, and the solvent was removed by distillation of the filtrate. 29.0 g of the product was distilled out with a conversion rate of 87.6%, a selectivity of 92.6%, a content of 81.1%, and a yield of 78.1%. Example 3

[0035] To a 250 ml three-necked flask, under nitrogen, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of ethyl acetate and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of ethyl acetate, and the filtrate was distilled to remove the solvent. 32.8 g of the product was distilled out with a conversion rate of 97.6%, a selectivity of 95.3%, a content of 93.0%, and a yield of 88.1%. Example 4

[0036] To a 250 ml three-necked flask, under nitrogen, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of dimethyl carbonate and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of dimethyl carbonate, and the solvent was removed by distillation of the filtrate. 18.6 g of the product was distilled out with a conversion rate of 61.1%, a selectivity of 96.9%, a content of 57.6%, and a yield of 49.7%. Example 5

[0037] To a 250 ml three-necked flask, under nitrogen, was added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of methyl tert-butyl ether and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of methyl tert-butyl ether, and the solvent was removed by distillation of the filtrate. 12.6 g of the product was distilled out with a conversion rate of 45.7%, a selectivity of 88.2%, a content of 40.3%, and a yield of 33.7%. Example 6

[0038] To a 250 ml three-necked flask, under nitrogen protection, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of 18-crown-6 ether, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 30.1 g of the product was distilled out with a conversion rate of 91.6%, a selectivity of 94.2%, a content of 86.3%, and a yield of 80.6%. Example 7

[0039] To a 250 ml three-necked flask, under nitrogen, was added 32.6 g of sodium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of 12-crown-6 ether, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 30.1 g of the product was distilled out with a conversion rate of 94.7%, a selectivity of 89.1%, a content of 84.4%, and a yield of 78.9%. Example 8

[0040] To a 250 ml three-necked flask, under nitrogen, was added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of tetrabutylammonium bromide, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 10.8 g of the product was distilled out with a conversion of 56.3%, a selectivity of 76.9%, a content of 34.4%, and a yield of 28.9%. Example 9

[0041] To a 250 ml three-necked flask, under nitrogen, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of triphenylmethylphosphonium chloride, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 18.9 g of the product was distilled out with a conversion rate of 69.1%, a selectivity of 82.3%, a content of 56.9%, and a yield of 50.7%. Example 10

[0042] To a 250 ml three-necked flask, under nitrogen, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of triphenylphosphonium bromide, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 16.6 g of the product was distilled out with a conversion of 67.0%, a selectivity of 79.3%, a content of 53.1%, and a yield of 44.3%. Example 11

[0043] To a 250 ml three-necked flask, under nitrogen, were added 45.0 g of potassium fluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of tetraphenylphosphonium bromide, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 19.2 g of the product was distilled out with a conversion rate of 64.8%, a selectivity of 88.3%, a content of 57.2%, and a yield of 51.3%. Example 12

[0044] To a 250 ml three-necked flask, under nitrogen protection, was added 60.5 g of potassium bifluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 1.2 g of the product was distilled out with a conversion rate of 8.3%, a selectivity of 86.7%, a content of 7.2%, and a yield of 3.3%. Example 13

[0045] To a 250 ml three-necked flask, under nitrogen protection, was added 48.1 g of sodium bifluoride (ground in advance), 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 3.4 g of the product was distilled out with a conversion rate of 16.8%, a selectivity of 63.1%, a content of 10.6%, and a yield of 9.1%. Example 14

[0046] To a 250 ml three-necked flask, under nitrogen protection, were added 41.7 g of triethylamine trihydrofluoride, 0.5 g of antimony trifluoride, 0.1 g of polyethylene glycol, and a mixture of 80 ml of acetonitrile and 0.1 g of concentrated sulfuric acid. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and slowly added dropwise CEC (50 g, 86% purity, controlled to be complete in about 15 min) in a constant pressure dropping funnel. The reaction was monitored by GC-MS. After 8 h of reaction, the mixture was filtered, the filter cake was washed with 50 ml of acetonitrile, and the solvent was removed by distillation of the filtrate. 24.4 g of the product was distilled out with a conversion rate of 77.3%, a selectivity of 93.3%, a content of 72.1%, and a yield of 65.3%.

[0047] The above embodiments are only used to illustrate the present invention. Any equivalent transformations and improvements based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.

[0048] in conclusion By comparing the schemes and experimental data of Example 1 with those of Examples 2 to 5, it is not difficult to see that when potassium fluoride is selected as the fluorination reagent, a highly polar solvent can promote the dissolution of potassium fluoride, thereby achieving a higher reaction conversion rate.

[0049] By comparing the schemes and experimental data of Example 1 with those of Examples 6, 8, 9, 10, and 11, it is not difficult to see that when potassium fluoride is selected as the fluorination agent, polyethylene glycol 600 has excellent catalytic performance. The reason for this can be attributed to the fact that the linear ether chain of polyethylene glycol can encapsulate fluoride ions ( ), enhanced Its solubility in the organic phase (acetonitrile) promotes nucleophilic substitution reactions. Its amphiphilic structure reduces the liquid-liquid interfacial tension and accelerates interphase mass transfer (CEC and The contact probability is increased), which is the key to the CEC conversion rate approaching 99.9%.

[0050] By comparing the schemes and experimental data of Example 1 with those of Examples 12 to 14, it is not difficult to see that the selectivity and conversion rate of the KF-acetonitrile-polyethylene glycol 600 system are higher than those of other systems. The reason can be attributed to the fact that KF partially dissolves in acetonitrile to form free Active sites promote the halogen exchange reaction of CEC, making it easier to approach CEC molecules and improving reaction kinetics.

Claims

1. A method for preparing fluoroethylene carbonate, characterized in that: The method comprises the following steps: ethylene carbonate is subjected to a fluorination reaction under the action of a fluorination agent, a co-catalyst and a phase transfer catalyst to prepare fluoroethylene carbonate; the co-catalyst is concentrated sulfuric acid; The reaction equation is as follows: 。 2. The method according to claim 1, wherein The fluorination agent is a fluorinated alkaline salt selected from one or more of triethylamine trihydrofluoride, sodium fluoride, potassium fluoride, antimony trifluoride, sodium bifluoride or potassium bifluoride.

3. The method according to claim 1, wherein The phase transfer catalyst is crown ether, quaternary ammonium salt, quaternary phosphonium salt or polyethylene glycol.

4. The method according to claim 3, wherein The crown ether is 12-crown-6 or 18-crown-6; the molecular weight of the polyethylene glycol is 400-2000; the quaternary ammonium salt is tetrabutylammonium bromide, tetra-n-octylammonium bromide, or tetrabutylammonium chloride; and the quaternary phosphonium salt is triphenylmethylphosphonium chloride, tetraphenylphosphonium bromide, or methyltriphenylphosphonium bromide.

5. The method according to claim 1, wherein The fluorination reagents are two fluorinated alkaline salts, one is antimony trifluoride, and the other is potassium fluoride, sodium fluoride or triethylamine trihydrofluoride. The phase transfer catalyst is crown ether or polyethylene glycol.

6. The method according to claim 1, wherein The molar ratio of the chloroethylene carbonate and the fluorinated reagent is 1:1-2; the added mass of the phase transfer catalyst is 0.1-1% of the chloroethylene carbonate; and the added mass of the co-catalyst is 0.01-1% of the mass of the chloroethylene carbonate.

7. The method according to claim 1, wherein The method is carried out in an organic solvent, which is one or more of tetrahydrofuran, dimethyl carbonate, ethyl acetate, acetonitrile, and methyl tert-butyl ether; the amount of the organic solvent used is 1 to 2 mL / g based on the mass of chloroethylene carbonate.

8. The method according to claim 1, wherein The method is carried out under the protection of inert gas.

9. The method according to claim 1, wherein The reaction temperature is 60-100°C.

10. The method according to claim 1, wherein After the reaction is completed, the obtained reaction liquid is post-treated to obtain fluoroethylene carbonate. The post-treatment method of the reaction liquid is: solid-liquid separation, taking the liquid product and evaporating the solvent, and then performing rectification and purification to obtain fluoroethylene carbonate.

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