A preparation method of fluoroethylene carbonate

Abstract

The present invention discloses a method for preparing fluoroethylene carbonate. Ethylene carbonate undergoes a fluorination reaction in the presence of a fluorination agent, an oxidant, and a phase transfer catalyst to produce the fluoroethylene carbonate. The oxidant is Oxone or nitrosotetrafluoroborate. The method uses a strong oxidant and a fluorination agent to oxidize the fluorination agent, slowly generating fluorine gas in situ, and then directly reacts the ethylene carbonate to synthesize the fluoroethylene carbonate. This method, for the first time, proposes a method for fluorination using solid raw materials to generate fluorine gas in situ. This method solves the problems of high equipment requirements, high risk, and poor gas-liquid mass transfer caused by the use of fluorine gas raw materials. Furthermore, the method utilizes low-cost raw materials, simple equipment, strong reaction selectivity, and high yield, thus possessing great industrial application value.

Description

Technical Field

[0001] The present invention relates to the field of organic synthesis, and in particular to a method for preparing fluoroethylene carbonate. Background Art

[0002] The key to developing and applying high-capacity lithium-ion batteries lies in addressing their safety. In addition to optimizing the positive and negative electrode materials, optimizing the electrolyte system is also crucial. The use of additives is a simple and easy method in developing and optimizing electrolyte systems. Different additives can effectively improve different battery properties.

[0003] Fluorinated organic carbonates are an important class of organofluorine compounds (organic fluorides) that can be used as solvents and solvent additives in lithium-ion batteries. They exhibit excellent solid electrolyte interface (SEI) properties, forming a dense structure without increasing impedance. They also prevent further electrolyte decomposition and act as flame retardants, improving the electrolyte's low-temperature performance, significantly increasing the battery's cycle life and enhancing battery safety. Fluorinated ethylene carbonate is a key product. The main synthesis routes for fluoroethylene carbonate include the following: The electrochemical fluorination method for the industrial production of organofluorine compounds was first implemented by 3M. This fluorination method, commonly known as the "Simons electrochemical fluorination process," requires electrolysis of an electrolyte solution containing liquid anhydrous hydrogen fluoride and an organic compound raw material. However, its disadvantages are high energy consumption and the need for anhydrous hydrogen fluoride. Another electrochemical fluorination method involves electrolysis in a salt melt (e.g., a potassium fluoride / hydrogen fluoride melt), known as the Phillips process. BASF Europe has improved this type of method in CN103261484A, using hydrogen fluoride complexes to replace anhydrous hydrogen fluoride or salt melts as fluorinating agents in electrolytes, and applying them to the preparation of fluorinated organic carbonates, but still need to consume a large amount of electricity in the process, and the cost is high. Another method for industrially producing fluorinated organic carbonates is the halogen exchange method, i.e., the method for synthesizing fluorinated organic carbonates by the Finkelstein halogen exchange reaction. This type of method generally involves chlorinating an organic compound to obtain chlorinated organic carbonates, which are then reacted with a fluorinating agent (HF or KF) after purification to obtain fluorinated organic carbonates. For example, the route for synthesizing monofluoroethylene carbonate using the halogen exchange method is as follows:

[0004]

[0005] The first step of chlorination has been reported in many reports, and the process is relatively mature and easy to operate and control relative to the fluorination reaction. However, since the synthesis of fluoroethylene carbonate by this route requires a two-step reaction, and in order to reduce the impurities in the halogen exchange reaction and obtain highly purified fluorinated organic carbonate, the intermediate chloroethylene carbonate needs to be subjected to a multi-step purification process including washing, neutralization, drying, and rectification, which makes the process complex and reduces production efficiency. In addition, according to existing reports, the total yield of preparing monofluoroethylene carbonate by the general two-step reaction is 60-65%, which is not ideal. Patent CN105541783A discloses a method for producing fluoroethylene carbonate. Fluoroethylene carbonate is prepared from ethylene carbonate through a three-step reaction of chlorination, elimination, and addition. The process route is shown below. The intermediates chloroethylene carbonate and vinylene carbonate both need to be purified (distillation to obtain chloroethylene carbonate and vacuum purification to obtain vinylene carbonate) before they can be used in the next reaction. Compared with the direct fluorination method, the number of reaction and process steps is significantly increased, production efficiency is reduced, and the yield of fluoroethylene carbonate is not improved compared with the halogen exchange method, and is only 56.5% based on chloroethylene carbonate.

[0006]

[0007] Another feasible process for synthesizing fluoroethylene carbonate is direct fluorination, which uses fluorine gas or a mixture of fluorine gas and an inert gas (such as nitrogen) to directly react with ethylene carbonate to synthesize fluoroethylene carbonate. For example, the route for synthesizing monofluoroethylene carbonate using direct fluorination is as follows:

[0008]

[0009] Fluorine gas is used in this reaction. Fluorine gas is a highly toxic gas that can irritate the eyes, skin, and respiratory mucosa. When it is exposed to the sun, it will begin to irritate the mucous membranes of the eyes, nose, and throat. If the exposure lasts for a long time, it may also cause pulmonary edema. Contact with the skin may cause burning of hair, coagulative necrosis of the contact area, carbonization of epithelial tissue, etc. Chronic contact may cause osteosclerosis and ligament calcification. To ensure personnel safety, the maximum allowable concentration in the air is 0.1ppm (0.2mg / m 3 Therefore, direct fluorination using fluorine gas places high demands on both equipment and process safety, including leak prevention and tail gas treatment facilities. Therefore, the reaction route using fluorine gas places high demands on equipment. Due to these reasons, there are few reports on the direct fluorination process, and its industrial application is also greatly limited.

[0010] In addition, the fluorination reaction using fluorine gas or a mixture of fluorine gas and inert gas as raw materials has the characteristic of large heat release compared to similar substitution reactions (such as chlorination, bromination, etc.), and has very high heat transfer requirements for the process, which increases the difficulty of process development.

[0011] Furthermore, existing processes for synthesizing fluoroethylene carbonates cannot achieve the goal of synthesizing a variety of different fluoroethylene carbonates and their mixtures using the same reactor simply by adjusting process parameters (for example, using ethylene carbonate as a raw material to synthesize monofluoroethylene carbonate; or using ethylene carbonate as a raw material to synthesize difluoroethylene carbonate; or using monofluoroethylene carbonate as a raw material to synthesize trifluoroethylene carbonate). The substitution reaction between fluorine gas and organic compounds is easy to occur and the process is violent. If the reaction is not properly controlled, it is easy to overreact, resulting in reduced selectivity and the formation of a mixture of products with different degrees of fluorination, which reduces the yield of the target product and increases the difficulty of separation and purification. Existing methods also cannot effectively solve the selectivity problem of direct fluorination reactions.

[0012] Fluorine gas is highly corrosive, corroding most metals and non-metals. Therefore, the direct fluorination method places stringent demands on the materials and structure of the reaction equipment. Furthermore, it requires that the fluorine gas be consumed as completely as possible during the process to improve fluorine conversion, minimize waste, and mitigate the risks of tail gas treatment. The direct fluorination reaction of ethylene carbonate with fluorine gas is a heterogeneous reaction involving two phases, gas and liquid. Such reactions typically involve a combination of mass transfer and reaction processes, with the macroscopic reaction rate being influenced by both the intrinsic reaction rate and the mass transfer rate. The fluorination reaction of ethylene carbonate with fluorine gas is a rapid reaction, significantly influenced by mass transfer factors. Therefore, sufficient contact and mixing of the gas and liquid phases are beneficial for a rapid and complete reaction. It is generally believed that in heterogeneous reactions, mixing is most effective when two phases of similar volume are mixed. However, in gas-liquid reactions, the volume difference between the gas and liquid phases is typically significant. For example, in the monofluorination reaction of ethylene carbonate with elemental fluorine (pure fluorine gas), the theoretical molar ratio of the gas-liquid volume is as high as 336:1. If a polyfluorination reaction is performed, the volume difference between the gas and liquid phases will increase exponentially. For example, in the difluorination reaction of ethylene carbonate with elemental fluorine (pure fluorine gas), the theoretical molar ratio is 672:1. Alternatively, if a mixture of fluorine and an inert gas is used as the fluorination reagent, the volume difference between the gas and liquid phases will be even greater. For example, in the monofluorination reaction of ethylene carbonate with a mixture of elemental fluorine and nitrogen at a volume concentration of 20%, the theoretical molar ratio is 1680:1. The gas / liquid dispersion specific surface area is generally used to measure the mixing effect of the gas and liquid phases. The larger the gas / liquid dispersion specific surface area, the better the gas-liquid mixing. In summary, although the direct fluorination method for synthesizing fluoroethylene carbonate has theoretical advantages (high fluorine reactivity, rapid reaction at low temperature, few reaction steps and high production efficiency), it also has obvious disadvantages: 1) the reaction controllability is very poor, as manifested in a large exotherm, the reaction is prone to runaway, and it is very dangerous; 2) due to the large volume difference between the gas and liquid phases in a heterogeneous reaction, it is difficult to achieve uniform mixing of the gas and liquid phases. The reaction places very high demands on the mass transfer of the reaction system, otherwise it is difficult to achieve a full reaction; 3) the process selectivity is poor and the flexibility is low. The exotherm and gas-liquid volume ratio of different fluorination reactions of the same raw material (for example, monofluorination, difluorination, trifluorination, tetrafluorination, etc.) vary greatly. In addition, the physical properties (for example, melting and boiling points, thermal conductivity, heat capacity, solubility, etc.) and reactivity of different raw materials are also very different. Therefore, the conditions for the corresponding fluorination reactions also vary greatly, making it difficult to control a certain degree of fluorination reaction to occur with high selectivity, and it is difficult for a single reactor to meet the synthesis conditions of multiple fluorinated products at the same time. Summary of the Invention

[0013] In view of the problems existing in the prior art of using fluorine gas as raw material, such as high risk, poor controllability, high equipment requirements, and poor mass transfer effect of heterogeneous reactions, the present invention provides a method for slowly releasing fluorine gas in situ to carry out a fluorination reaction. This method can prepare fluoroethylene carbonate (FEC) with high yield, high efficiency and environmental protection, with strong reaction selectivity, high yield and simple equipment.

[0014] The technical solution adopted in the present invention is:

[0015] A method for preparing fluoroethylene carbonate comprises the following steps: fluoroethylene carbonate is subjected to a fluorination reaction under the action of a fluorination agent, an oxidant and a phase transfer catalyst to prepare the fluoroethylene carbonate; the oxidant is Oxone or nitrosotetrafluoroborate.

[0016] Reaction equation of the present invention is as follows:

[0017]

[0018] The fluorination agent is a fluorinated alkaline salt, such as triethylamine hydrogen fluoride, pyridine polyfluoric acid, sodium fluoride, potassium fluoride, antimony fluoride, sodium bifluoride or potassium bifluoride.

[0019] Furthermore, the phase transfer catalyst is crown ether, quaternary ammonium salt or polyethylene glycol.

[0020] The crown ether is preferably 12-crown-6 or 18-crown-6; the molecular weight of the polyethylene glycol is between 400 and 2000, and the quaternary ammonium salt is preferably tetrabutylammonium bromide, tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium iodide, benzyltriethylammonium chloride (TEBA), tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride or tetradecyltrimethylammonium chloride, etc.

[0021] The molar ratio of the ethylene carbonate, the fluorination agent and the oxidant is 1:0.5-5:1-3, preferably 1:1-1.5:1-2.

[0022] The added mass of the phase transfer catalyst is 1 to 50% of the ethylene carbonate, preferably 3 to 35%.

[0023] In the present method, the fluorination agent is oxidized by an oxidant, slowly producing fluorine gas, which then fluorinates the ethylene carbonate in situ. The oxidant must be a strong oxidant, as conventional oxidants have low yields, contain high levels of impurities, or even fail to catalyze the reaction.

[0024] The oxidant used in the present invention is Oxone or nitrosotetrafluoroborate.

[0025] Oxone is a potassium peroxysulfate complex salt with a molecular formula of 2KHSO₅·KHSO₄·K₂SO₄ and a molecular weight of 614.7. Oxone is an inorganic peroxide, consisting of potassium monopersulfate (potassium peroxysulfate), potassium bisulfate, and potassium sulfate in a triple salt. Its active ingredient is KHSO₅, a salt of H₂SO₅. It is a white powdery solid that is easily soluble in water. It is generally stable in its solid state, decomposes slowly, is low in toxicity, and produces no harmful substances.

[0026] Nitrosinate tetrafluoroborate is a mild single electron transfer oxidant with an oxidation-reduction potential of 1.5 V for NO / NO+ in acetonitrile.

[0027] After extensive screening, the present invention discovered that fluorinated reagents, such as triethylamine hydrogen fluoride, pyridine polyfluoride, KF, NaF, SbF, NaHF2, KHF2 and other fluorinated alkaline salts, react with ethylene carbonate in the presence of Oxone or nitrosotetrafluoroborate to fluorinate, thereby synthesizing fluoroethylene carbonate with high selectivity.

[0028] Furthermore, preferably, in the method, the oxidant is added in batches.

[0029] The method of the present invention is preferably carried out in an organic solvent, and the organic solvent is preferably one or more of DMF, DMSO, sulfolane, dimethyl carbonate, diethyl carbonate, ethyl acetate, acetonitrile, dichloromethane, and dichloroethane.

[0030] The amount of the organic solvent used is preferably 10 to 30 mL / g based on the mass of ethylene carbonate.

[0031] The method is carried out under the protection of an inert gas, preferably nitrogen.

[0032] The reaction temperature is 10-200°C, preferably 40-100°C.

[0033] The reaction time is 5-20 hours.

[0034] 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.

[0035] Solid-liquid separation can be achieved by filtration. The filter cake can be washed with an organic solvent.

[0036] Specifically, the method of the present invention is preferably carried out according to the following steps:

[0037] Under nitrogen protection, ethylene carbonate, a fluorination agent, and a phase transfer catalyst are added to an organic solvent, and then an oxidant is added in batches. The temperature is controlled at 10-200°C to carry out a fluorination reaction. After the reaction is complete, the mixture is filtered, the filter cake is washed, and the solvent is evaporated from the filtrate, and the mixture is distilled to obtain fluoroethylene carbonate. The oxidant is Oxone or nitrosotetrafluoroborate.

[0038] The beneficial effects of the present invention are as follows: by using a strong oxidant and a fluorinating agent, the fluorinating agent can be oxidized to slowly generate fluorine gas in situ, thereby directly performing a substitution reaction on ethylene carbonate to synthesize fluoroethylene carbonate. Due to the strong oxidizing property of fluorine, the reduced fluoride ion is difficult to oxidize, which is also a technical problem that the prior art has not been able to find a raw material that can replace fluorine gas. The present invention proposes for the first time a method for fluorination reaction by in-situ generation of fluorine gas from solid raw materials, which solves the problems of high equipment requirements, high risk, and poor gas-liquid two-phase mass transfer caused by fluorine raw materials. In addition, the present invention has low raw materials, simple equipment, strong reaction selectivity, high yield, and great industrial application value. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0040] Example 1:

[0041] Take a 250ml tetrafluoroethylene bottle (the inner wall is coated with tetrafluoroethylene), add 8.8g of ethylene carbonate, under nitrogen protection, add 4.2g of sodium fluoride, 100ml of dimethyl carbonate, and 0.4g of tetrabutylammonium bromide, control the temperature at 10°C, and slowly add 60g of oxone in batches. After the reaction is completed by GC monitoring, filter, wash the filter cake with 30ml of dimethyl carbonate, and distill the filtrate to remove the solvent dimethyl carbonate. 9.5g of the product is distilled out, the content is >99%, and the yield is 89.6%.

[0042] 1 HNMR: 4.4-4.55(2H, m); 6.2-6.4(1H, d)

[0043] Example 2:

[0044] Take a 250ml tetrafluoroethylene bottle and add 8.8g of ethylene carbonate. Under nitrogen protection, add 5.8g of potassium fluoride, 0.5g of tetrabutylammonium iodide, and 100ml of dimethyl carbonate. Control the temperature at 30°C and slowly add 60g of oxone in batches. After GC monitoring, filter and wash the filter cake with 30ml of dimethyl carbonate. Distill the filtrate to remove the solvent dimethyl carbonate. Distill 9.8g of the product with a content of >99% and a yield of 92.5%.

[0045] Example 3:

[0046] Take a 250ml tetrafluoroethylene bottle, add 8.8g of ethylene carbonate, under nitrogen protection, add 3.9g of potassium bifluoride, add 0.4g of tetrabutylammonium hydrogen sulfate, and 100ml of diethyl carbonate. Control the temperature at 30°C and slowly add 60g of oxone in batches. After the reaction is completed under GC monitoring, filter, wash the filter cake with 30ml of diethyl carbonate, and distill the filtrate to remove the solvent diethyl carbonate. Distill 9.7g of the product with a content of >99% and a yield of 91.5%.

[0047] Example 4:

[0048] Take a 250ml tetrafluoroethylene bottle, add 8.8g of ethylene carbonate, under nitrogen protection, add 3.1g of sodium bifluoride, 100ml of diethyl carbonate, and 0.4g of benzyltriethylammonium chloride, control the temperature at 40℃, and slowly add 60g of oxone in batches. After the reaction is completed under GC monitoring, filter, wash the filter cake with 30ml of diethyl carbonate, and distill the filtrate to remove the solvent diethyl carbonate. 8.9g of the product is distilled out with a content of >99% and a yield of 83.6%. 1 HNMR: 4.4-4.55(2H, m); 6.2-6.4(1H, d)

[0049] Embodiment 5:

[0050] Take a 250ml tetrafluoroethylene bottle, add 8.8g of ethylene carbonate, under nitrogen protection, add 3.9g of potassium bifluoride, 100ml of DMSO, and 0.3g of 12-crown-6 ether, control the temperature at 30℃, and slowly add 60g of oxone in batches. After GC monitoring, filter and wash the filter cake with 30ml of diethyl carbonate. Distill the filtrate to remove the solvent and distill 9.7g of the product with a content of >99% and a yield of 91.5%.

[0051] Example 6:

[0052] Take a 250ml tetrafluoroethylene bottle, add 200g of ethylene carbonate, under nitrogen protection, add 3.9g of potassium bifluoride, 4g of 12-crown-6 ether, and 100g of cyclopentane sulfone, control the temperature at 60℃, and slowly add 60g of oxone in batches. Keep the temperature and react. After GC monitoring, filter and wash the filter cake with ethylene carbonate. Distill the filtrate to remove the solvent and distill 9.7g of the product with a content of >99% and a yield of 91.5%. 1 HNMR: 4.35-4.45(2H, m); 6.2-6.35(1H, d)

[0053] Embodiment seven:

[0054] Take a 250ml tetrafluoroethylene bottle, add 8.8g of ethylene carbonate, under nitrogen protection, add 3.9g of potassium bifluoride, 100ml of diethyl carbonate, and 3g of polyethylene glycol 2000, control the temperature at 30℃, and slowly add 60g of oxone in batches. After the reaction is completed under GC monitoring, filter, wash the filter cake with diethyl carbonate, and distill the filtrate to remove the solvent diethyl carbonate. Distill 9.5g of the product with a content of >99% and a yield of 89.6%.

[0055] Embodiment 8:

[0056] In a 250ml tetrafluoroethylene flask, 8.8g of ethylene carbonate, 5.8g of potassium fluoride, 100ml of dimethyl carbonate, and 0.4g of benzyltriethylammonium chloride were added. The temperature was maintained at 40°C, and oxygen was slowly introduced. After completion of the reaction, the reaction was monitored by GC, filtered, and the filter cake was washed with 30ml of dimethyl carbonate. The filtrate was distilled to remove the solvent dimethyl carbonate, and 8g of the product was distilled out with a content of >99% and a yield of 55.4%. It can be seen that the yield is lower when oxygen is used as the oxidant. The choice of oxidant is crucial to the progress and yield of the fluorination reaction of the present invention.

[0057] Embodiment 9:

[0058] Take a 250ml three-necked flask, add 4.4g of ethylene carbonate, add 2.9g of potassium fluoride, 100ml of dimethyl carbonate, and 0.5g of dodecyltrimethylammonium chloride. Add 5g of nitrosotetrafluoroborate in batches while stirring. Keep warm at 50℃. After the reaction is completed under GC monitoring, filter, wash the filtrate cake with 30ml of dimethyl carbonate, distill to remove the solvent dimethyl carbonate, and distill to obtain 4.1g of the product with a content of 98.5% and a yield of 77%.

[0059] Embodiment 10:

[0060] Take a 250ml three-necked flask, add 8.8g of ethylene carbonate, add 4.2g of sodium fluoride, 100ml of dimethyl carbonate, and 0.3g of tetrabutylammonium bromide. Add 10g of nitrosotetrafluoroborate in batches while stirring. Keep warm at 50°C. After the reaction is completed under GC monitoring, filter, wash the filter cake with 30ml of dimethyl carbonate, and distill the filtrate to remove the solvent dimethyl carbonate. 8.3g of the product is distilled out with a content of 98.5% and a yield of 78.3%.

[0061] Example 11:

[0062] Take a 250ml three-necked flask, add 8.8g of ethylene carbonate, add 3.9g of potassium bifluoride, 90ml of diethyl carbonate, and 0.4g of tetradecyltrimethylammonium chloride, and add 10g of nitrosotetrafluoroborate in batches while stirring. Keep warm at 50°C. After the reaction is completed under GC monitoring, filter, wash the filter cake with 30ml of diethyl carbonate, and distill the filtrate to remove the solvent diethyl carbonate. 8.5g of the product is distilled out with a content of 98.5% and a yield of 80.18%.

[0063] Example 12:

[0064] Take a 250ml three-necked flask, add 8.8g of ethylene carbonate, add 3.1g of sodium bifluoride, 90ml of diethyl carbonate, and 0.4g of tetrabutylammonium fluoride. Add 10g of nitrosotetrafluoroborate in batches while stirring, keep warm at 80℃, monitor the reaction by GC, filter, wash the filter cake with 30ml of diethyl carbonate, and distill the filtrate to remove the solvent diethyl carbonate. Distill 9g of the product with a content of 99.1% and a yield of 84.9%.

[0065] Example 13:

[0066] Take a 250ml three-necked flask, add 8.8g of ethylene carbonate, 5g of pyridine hydrogen fluoride, 90ml of ethyl acetate, 2g of 12-crown-6, and add 10g of nitrosotetrafluoroborate in batches while stirring. Keep warm at 40°C. After the reaction is completed under GC monitoring, filter, wash the filter cake with 30ml of ethyl acetate, and distill the filtrate to remove the solvent ethyl acetate. 9.5g of the product is distilled out with a content of 98.5% and a yield of 89.6%.

[0067] Example 14:

[0068] In a 250ml three-necked flask, add 8.8g of ethylene carbonate, 5g of pyridine hydrogen fluoride, 90ml of diethyl carbonate, and 3g of polyethylene glycol 2000. Add 10g of nitroso-tetrafluoroborate in portions while stirring. Maintain the mixture at 40°C. After completion of the reaction, monitor the reaction by GC, filter the mixture, wash the filter cake with 30ml of diethyl carbonate, and distill the filtrate to remove the diethyl carbonate solvent. 9.4g of the product is obtained with a content of 99.1% and a yield of 88.67%.

[0069] Embodiment 15:

[0070] Take a 250ml three-necked flask, add 8.8g of ethylene carbonate, add 4.3g of triethylamine hydrogen fluoride, 90ml of diethyl carbonate, and 3g of polyethylene glycol 600, and add 10g of nitrosotetrafluoroborate in batches while stirring. Keep warm at 40°C. After the reaction is completed under GC monitoring, filter, wash the filter cake with 30ml of diethyl carbonate, and distill the filtrate to remove the solvent diethyl carbonate. 9.3g of the product is distilled out with a content of 99.2% and a yield of 87.7%.

[0071] Example 16:

[0072] Take a 250ml three-necked flask, add 8.8g of ethylene carbonate, 5g of pyridine hydrogen fluoride, 100ml of ethyl acetate, and 0.4g of tetrabutylammonium fluoride, and add 10g of nitrosotetrafluoroborate in batches while stirring. Keep warm at 100℃. After the reaction is completed by GC monitoring, filter, wash the filter cake with 30ml of ethyl acetate, and distill the filtrate to remove the solvent ethyl acetate. 9.25g of the product is distilled out with a content of 98.4% and a yield of 87.2%.

[0073] Embodiment 17:

[0074] Take a 250ml three-necked flask, add 8.8g of ethylene carbonate, add 5g of pyridine hydrogen fluoride, 100ml of DMF, and 0.3g of benzyltriethylammonium chloride. Add 10g of nitrosotetrafluoroborate in batches while stirring. Keep warm at 100℃. After the reaction is completed, monitor by GC, filter, wash the filter cake with 30ml of ethyl acetate, and distill the filtrate to remove the solvent. 8.15g of the product with a content of 98.24% and a yield of 77.2% is obtained.

[0075] Embodiment 18:

[0076] Take a 250ml tetrafluoroethylene bottle, add 8.8g of ethylene carbonate, under nitrogen protection, add 3.9g of potassium bifluoride, 0.5g of trioctylmethylammonium chloride, and 100ml of sulfolane, control the temperature at 30℃, and slowly add 60g of oxone in batches. After GC monitoring, filter and wash the filter cake with ethyl acetate. The filtrate is distilled to remove the solvent, and 9.5g of the product is distilled out with a content of >99% and a yield of 89.6%.

[0077] Embodiment 19:

[0078] Take a 250ml tetrafluoroethylene bottle, add 8.8g of ethylene carbonate, under nitrogen protection, add 3.9g of potassium fluoride, 3g of 18-crown-6, and 100ml of DMF, control the temperature at 30℃, and slowly add 50g of oxone in batches. After the reaction is completed, monitor it with GC, filter, wash the filter cake with ethyl acetate, and distill the filtrate to remove the solvent. 9.1g of the product is distilled out with a content of >98% and a yield of 82.6%.

[0079] Embodiment 20:

[0080] In a 250ml PTFE flask, 8.8g of ethylene carbonate was added. Under nitrogen, 3.9g of potassium fluoride, 3g of 18-crown-6, and 100ml of DMF were added. The temperature was maintained at 30°C, and 50g of potassium peroxymonosulfate was slowly added in batches. The reaction heated rapidly, making temperature control difficult. GC monitoring of the reaction revealed excessive impurities, resulting in a product content of only 56.5%. No post-processing distillation was performed. The results showed that even though potassium peroxymonosulfate is the active ingredient of oxone, using potassium peroxymonosulfate alone resulted in a high impurity content and a low yield. Therefore, oxone cannot be replaced with potassium peroxymonosulfate.

[0081] Embodiment 21:

[0082] In a 250ml three-necked flask, 8.8g of ethylene carbonate, 4.3g of triethylamine hydrogen fluoride, 90ml of diethyl carbonate, and 3g of polyethylene glycol 600 were added. With stirring, 12g of potassium permanganate was added in portions. The reaction was maintained at 40°C and monitored by GC. No target product was produced. The results showed that potassium permanganate, a conventional oxidant, could not oxidize the reduced fluoride ion, preventing the fluorination reaction from proceeding.

[0083] Embodiment 22:

[0084] In a 250ml three-necked flask, 8.8g of ethylene carbonate, 4.3g of triethylamine hydrogen fluoride, 90ml of diethyl carbonate, and 3g of polyethylene glycol 2000 were added. With stirring, 8g of manganese dioxide was added in portions. The reaction was maintained at 40°C and monitored by GC. No target product was produced. The results showed that manganese dioxide could not oxidize the reduced fluoride ion, and the fluorination reaction could not proceed.

[0085] Embodiment 23:

[0086] In a 250ml three-necked flask, 8.8g of ethylene carbonate, 4.3g of triethylamine hydrogen fluoride, 90ml of diethyl carbonate, and 1g of tetrabutylammonium bromide were added. Ozone was slowly introduced with stirring. The temperature was maintained at 40°C. The reaction was monitored by GC. Excessive impurities and a product content of 60.4% were observed, and no further treatment was performed. Using ozone as an oxidant is not a good option due to the high impurities and low product yield.

[0087] Embodiment 24:

[0088] In a 250ml three-necked flask, add 8.8g of ethylene carbonate, 4.3g of triethylamine hydrogen fluoride, 90ml of diethyl carbonate, and 3g of polyethylene glycol 600. With stirring, add 11g of periodic acid in portions. Maintain the mixture at 40°C and monitor the reaction until complete using GC. Filter the mixture, wash the filter cake with ethyl acetate, and distill the filtrate to remove the solvent. 5.1g of the product (>98% content, 46.3% yield) is obtained. Using periodic acid as the oxidant yields a lower yield.

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, an oxidant and a phase transfer catalyst to prepare fluoroethylene carbonate; the oxidant is Oxone or nitrosotetrafluoroborate; the fluorination agent is triethylamine hydrogen fluoride, pyridine polyfluoric acid, sodium fluoride, potassium fluoride, antimony fluoride, sodium bifluoride or potassium bifluoride; and the reaction temperature is 30-100°C. The reaction equation is as follows: 。 2. The method according to claim 1, wherein The phase transfer catalyst is crown ether, quaternary ammonium salt or polyethylene glycol.

3. The method according to claim 2, wherein The crown ether is 12-crown-6 or 18-crown-6; the molecular weight of the polyethylene glycol is 400-2000; and the quaternary ammonium salt is tetrabutylammonium bromide, tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium iodide, benzyltriethylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride or tetradecyltrimethylammonium chloride.

4. The method according to claim 1, wherein The molar ratio of the ethylene carbonate, the fluorination agent and the oxidant is 1:0.5-5:1-3; and the added mass of the phase transfer catalyst is 1-50% of the ethylene carbonate.

5. The method according to claim 1, wherein The method is carried out in an organic solvent, and the organic solvent is one or more of DMF, DMSO, sulfolane, dimethyl carbonate, diethyl carbonate, ethyl acetate, acetonitrile, dichloromethane, and dichloroethane.

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

7. 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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