Preparation method of fluoroethylene carbonate

Abstract

The invention discloses a preparation method of fluoroethylene carbonate, and relates to the technical field of chemical production, and the preparation method comprises the following steps: treating chloroethylene carbonate by a 3A molecular sieve adsorption tower, and controlling free acid to be less than or equal to 30ppm; the method comprises the following steps: mixing crown ether, tetrabutylammonium bromide, tetrabutylammonium bromide and mesoporous silica to prepare a composite catalyst; 2, continuously feeding inert gas into the reaction kettle, after air replacement in the reaction kettle is completed, feeding the pretreated chloroethylene carbonate, the compound chelating agent, the solvent and the composite catalyst in the step 1 into the reaction kettle, stirring and mixing, and then adding fluoride salt in 10 times to prepare a fluoroethylene carbonate crude product; and leaching, filtering and rectifying the fluoroethylene carbonate crude product to obtain the finished fluoroethylene carbonate. Therefore, by compounding the chelating agent, redundant metal ions in the reaction are effectively reduced, and the purity of the final product is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical production, and particularly relates to a preparation method of fluoroethylene carbonate. Background Art

[0002] Fluoroethylene carbonate (FEC) has better electronegativity and electron-withdrawing ability because its molecule contains a C—F bond more than ethylene carbonate (EC). Quantum chemical calculations show that the lowest unoccupied molecular orbital energy of FEC (-0.3108) is much lower than that of EC (-0.29512). Therefore, it can be reduced at a lower reduction potential to form a good SEI film (Solid Electrolyte Interface) on the surface of the negative electrode, so that the cycle stability, normal temperature capacity at the same rate, and high temperature stability of lithium-ion batteries can be improved.

[0003] At present, the synthesis methods of fluoroethylene carbonate mainly include direct fluorination with fluorine gas and halogen exchange method. Among them, the halogen exchange method often uses fluorinated salts, chloroethylene carbonate or ethylene carbonate as raw materials, and fluoroethylene carbonate is generated under the catalysis of a catalyst. However, this method is prone to over-fluorination to generate polyfluorinated by-products.

[0004] For this reason, Chinese Patent with publication number CN114621177A discloses "a preparation method of fluoroethylene carbonate", and its technical solution is "the preparation method includes the following steps: S1. Mixing materials, adding a metal fluoride salt and a solvent into a reaction vessel, and mixing evenly to obtain a mixed material; S2. Fluorination, adding chloroethylene carbonate to the mixed material in step S1, and reacting under the protection of an inert gas to obtain a crude product of fluoroethylene carbonate; S3. Separation, separating the crude product of fluoroethylene carbonate obtained in step S2 to obtain a finished product of fluoroethylene carbonate and a by-product metal chloride salt. This application has the effects of high conversion rate, high selectivity, renewable and recyclable fluorine source, and no need for a catalyst by limiting specific fluorine sources and preparation processes".

[0005] In the above solution, the metal fluoride salt used is one of cobalt salt, zinc salt, copper salt, and nickel salt. Although the metal ions in the above solution will combine with chloride ions, there will be a situation where some metal ions do not combine with chloride ions, which may lead to excessive heavy metal ions in fluoroethylene carbonate. Summary of the Invention

[0006] Aiming at the above defects, the purpose of the present invention is to provide a preparation method of fluoroethylene carbonate, aiming to solve the problem of excessive heavy metal ions in fluoroethylene carbonate in the prior art.

[0007] To solve the above technical problems, the technical solution of the present invention is as follows: A preparation method of fluorinated ethylene carbonate, comprising the following steps: Step 1, pretreatment; The chlorinated ethylene carbonate is treated by a 3A molecular sieve adsorption tower, and the free acid is controlled to be ≤ 30 ppm; Step 2, catalyst preparation; A composite catalyst is prepared by mixing crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica; Step 3, fluorination reaction; An inert gas is continuously fed into the reaction kettle. After the air replacement in the reaction kettle is completed, the pretreated chlorinated ethylene carbonate, compound chelating agent, solvent, and composite catalyst are fed into the reaction kettle, stirred and mixed. The temperature in the reaction kettle is raised to 50 - 70 °C, and then the fluoride salt is added in 10 portions at intervals of not less than 30 min. Subsequently, the temperature in the reaction kettle is raised to 70 - 80 °C and kept warm for reaction for 4 - 5 h to obtain the crude fluorinated ethylene carbonate; the crude fluorinated ethylene carbonate is filtered, rinsed, desolvated, and rectified to obtain the finished product of fluorinated ethylene carbonate.

[0008] Among them, in Step 2, the mass ratio of crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.2 - 1.5:1.2 - 1.5:10 - 15.

[0009] Among them, in Step 2, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: the mesoporous silica is vacuum dried; γ-aminopropyltriethoxysilane, anhydrous ethanol, and dibutyltin dilaurate are mixed according to a mass ratio of 1:30:0.3 to obtain a modifier; the mesoporous silica and the modifier are mixed according to a mass ratio of 1:20, and magnetically stirred at a constant temperature of 70 - 80 °C for 1 - 2 h under nitrogen protection to obtain a reaction solution; the reaction solution is centrifuged at high speed, and then washed with deionized water and vacuum dried to obtain the modified mesoporous silica.

[0010] Among them, the pore diameter of the modified mesoporous silica is 5 - 10 nm.

[0011] Among them, in Step 3, the mass ratio of chlorinated ethylene carbonate, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.3 - 1.5:2.5 - 3:0.2 - 0.3:0.05 - 0.1.

[0012] Among them, the fluoride salt is one of potassium fluoride, magnesium fluoride, zinc fluoride, copper fluoride, nickel fluoride, cobalt fluoride, and sodium fluoride.

[0013] Among them, the solvent is composed of acetonitrile and dimethyl carbonate according to a mass ratio of 1.2 - 1.5:1.6 - 1.8.

[0014] Among them, step three includes the following stages: In the first stage, at room temperature, an inert gas is continuously fed into the reaction kettle to displace the air in the reaction kettle. In the second stage, the pretreated ethylene chlorocarbonate, compound chelating agent, solvent and composite catalyst are fed into the reaction kettle, stirred and mixed, and the temperature in the reaction kettle is raised to 50-70°C. Subsequently, the fluoride salt is added in 10 portions at intervals of not less than 30 minutes. In this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, the remaining compound chelating agent is added dropwise into the reaction kettle, and the temperature in the reaction kettle is raised to 70-80°C. After the addition is completed, the reaction is carried out under heat preservation for 4-5 hours.

[0015] Among them, the compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid according to a mass ratio of 1.2-2:1.

[0016] Among them, in step three, the crude product of vinyl fluorocarbonate is washed and filtered to remove the solid salt therein. The filter cake is dried to recover the solvent, and the dried product of chloride salt is disposed of after identification, and the filtrate goes to the rectification process. Under normal temperature and pressure, the filtrate is transported to the stripping tower, and stripped and desolvated under the conditions of a vacuum degree of -0.09 MPa and a tower kettle temperature of 80-90°C. The recovered solvent collected at the top of the tower is recycled to the fluorination process, and the tower kettle liquid is transported to the rough distillation tower. The rough distillation tower is distilled under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 100-145°C. The crude distillate is taken out from the top of the tower and sent to the light component removal tower, and the tower kettle residue is collected uniformly and incinerated. The light component removal tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 95-100°C. The fraction of vinylene carbonate is taken out from the top of the tower and sold as a by-product, and the tower kettle liquid is taken out and transported to the product tower. The product tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 105-110°C. The fraction of vinyl fluorocarbonate is taken out from the top of the tower and stored as a finished product, and the tower kettle liquid is taken out and transported to the post-treatment tower.

[0017] After adopting the above technical solution, the beneficial effects of the present invention are: First, in the composite catalyst, crown ether, tetrabutylphosphonium bromide, and tetrabutylammonium bromide cooperate and synergize with each other, suppressing side reactions and maximizing the purity of the final product. Among them, crown ether optimizes mass transfer and reaction selectivity by selectively complexing metal ions; tetrabutylphosphonium bromide forms ion pairs with cations, enhancing the solubility of fluoride ions in the organic phase, thereby improving the reaction efficiency. At the same time, tetrabutylphosphonium bromide can stabilize intermediates through hydrogen bonding and inhibit the formation of by-products; the role of tetrabutylammonium bromide is to promote the transfer of fluoride ions in the aqueous phase to the organic phase, accelerate the fluorination reaction, significantly increase the reaction rate and product yield. At the same time, by adjusting the local charge environment, it can also reduce the decomposition of organic solvents and lower the formation of by-products. Second, by compounding chelating agents, the excess metal ions in the reaction are effectively reduced, ensuring the purity of the final product. Detailed implementation mode

[0018] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] A method for preparing fluoroethylene carbonate, comprising the following steps: Step 1, pretreatment; The chlorofluoroethylene carbonate is treated by a 3A molecular sieve adsorption tower, and the free acid is controlled to be ≤ 30 ppm; Step 2, catalyst preparation; Crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica are mixed to prepare a composite catalyst; Step 3, fluorination reaction; An inert gas is continuously fed into the reaction kettle. After the air replacement in the reaction kettle is completed, the pretreated chlorofluoroethylene carbonate, compounded chelating agent, solvent, and composite catalyst are fed into the reaction kettle, stirred and mixed. The temperature in the reaction kettle is raised to 50 - 70 °C, and then the fluoride salt is added in 10 portions at intervals of not less than 30 min. Subsequently, the temperature in the reaction kettle is raised to 70 - 80 °C and kept warm for reaction for 4 - 5 h to obtain the crude fluoroethylene carbonate; the crude fluoroethylene carbonate is filtered, rinsed, desolvated, and rectified to obtain the finished fluoroethylene carbonate.

[0020] In step 2, the mass ratio of crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.2 - 1.5:1.2 - 1.5:10 - 15.

[0021] In Step 2, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: vacuum-dry the mesoporous silica; mix γ-aminopropyltriethoxysilane, anhydrous ethanol, and dibutyltin dilaurate in a mass ratio of 1:30:0.3 to obtain a modifier; mix the mesoporous silica and the modifier in a mass ratio of 1:20, and magnetically stir at a constant temperature of 70-80°C for 1-2 h under nitrogen protection to obtain a reaction solution; subject the reaction solution to high-speed centrifugal separation, then wash with deionized water and vacuum-dry to obtain the modified mesoporous silica.

[0022] The pore diameter of the modified mesoporous silica is 5-10 nm.

[0023] In Step 3, ethylene carbonate chloride, fluoride salt, solvent, composite catalyst, and compound chelating agent are in a mass ratio of 1:1.3-1.5:2.5-3:0.2-0.3:0.05-0.1.

[0024] The fluoride salt is one of potassium fluoride, magnesium fluoride, zinc fluoride, copper fluoride, nickel fluoride, cobalt fluoride, and sodium fluoride.

[0025] The solvent is composed of acetonitrile and dimethyl carbonate in a mass ratio of 1.2-1.5:1.6-1.8.

[0026] Step 3 includes the following stages: In the first stage, at room temperature, continuously feed an inert gas into the reaction kettle to displace the air in the reaction kettle. In the second stage, feed the pretreated ethylene carbonate chloride, compound chelating agent, solvent, and composite catalyst into the reaction kettle, stir and mix, heat the temperature in the reaction kettle to 50-70°C, and then add the fluoride salt in 10 portions at intervals of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, add the remaining compound chelating agent dropwise into the reaction kettle, heat the temperature in the reaction kettle to 70-80°C, and keep the temperature for 4-5 h after the dropping is completed.

[0027] Among them, the compound chelating agent is prepared by mixing disodium ethylenediaminetetraacetate and citric acid in a mass ratio of 1.2-2:1.

[0028] Among them, in Step 3, the crude fluoroethylene carbonate is washed and filtered to separate the solid salts therein. The filter cake is dried to recover the solvent, and the dried product of the chloride salt is disposed of after identification. The filtrate goes to the rectification process. Under normal temperature and pressure, the filtrate is transported to the stripping tower, and stripped and desolvated by rectification under the conditions of a vacuum degree of -0.09 MPa and a bottom temperature of 80 - 90 °C. The recovered solvent collected at the top of the tower is recycled to the fluorination process, and the bottom liquid is transported to the rough distillation tower. The rough distillation tower distills under the conditions of a vacuum degree of -0.098 MPa and a bottom temperature of 100 - 145 °C. The rough distillate taken from the top of the tower goes to the light component removal tower, and the bottom residue is collected uniformly and incinerated. The light component removal tower rectifies under the conditions of a vacuum degree of -0.098 MPa and a bottom temperature of 95 - 100 °C. The fraction of vinylene carbonate taken from the top of the tower is sold as a by-product, and the bottom liquid taken out is transported to the product tower. The product tower rectifies under the conditions of a vacuum degree of -0.098 MPa and a bottom temperature of 105 - 110 °C. The fraction of fluoroethylene carbonate taken from the top of the tower is stored as a finished product, and the bottom liquid taken out is transported to the post-treatment tower.

[0029] Example 1: Using the above scheme to produce fluoroethylene carbonate, where: In Step 2, the mass ratio of the crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.2:1.2:10. In Step 2, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: the mesoporous silica is vacuum dried; γ-aminopropyltriethoxysilane, absolute ethanol, and dibutyltin dilaurate are mixed according to a mass ratio of 1:30:0.3 to prepare a modifier; the mesoporous silica and the modifier are mixed according to a mass ratio of 1:20, and magnetically stirred at a constant temperature of 70 °C for 1 h under nitrogen protection to obtain a reaction solution; the reaction solution is centrifuged at high speed, and then washed with deionized water and vacuum dried to obtain the modified mesoporous silica.

[0030] In Step 3, the mass ratio of ethylene chlorocarbonate, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.3:2.5:0.2:0.05.

[0031] The solvent is composed of acetonitrile and dimethyl carbonate according to a mass ratio of 1.2:1.6.

[0032] The fluoride salt is potassium fluoride.

[0033] Step 3 includes the following stages: In the first stage, at room temperature, an inert gas is continuously fed into the reaction kettle to displace the air in the reaction kettle. In the second stage, chlorinated ethylene carbonate, a compound chelating agent, a solvent, and a composite catalyst are fed into a reaction kettle, stirred and mixed, and the temperature in the reaction kettle is raised to 50 °C. Subsequently, a fluoride salt is added in 10 portions at intervals of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, the remaining compound chelating agent is added dropwise into the reaction kettle, the temperature in the reaction kettle is raised to 70 °C, and after the addition is completed, the reaction is kept warm for 4 h.

[0034] The compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid according to a mass ratio of 1.2:1.

[0035] In step three, the crude product of fluoroethylene carbonate is washed and filtered to separate and remove the solid salt therein. The filter cake is dried to recover the solvent, the dried product of the chloride salt is identified and then disposed of, and the filtrate goes to the rectification process; the filtrate is transported to a stripping tower under normal temperature and pressure, and stripped and desolvated by rectification under the conditions of a vacuum degree of -0.09 MPa and a tower bottom temperature of 80 °C. The recovered solvent is collected at the top of the tower and applied to the fluorination process, and the tower bottom liquid is transported to a rough distillation tower; the rough distillation tower is distilled under the conditions of a vacuum degree of -0.098 MPa and a tower bottom temperature of 100 °C, and the rough distillate is taken out from the top of the tower and sent to a light component removal tower, and the tower bottom residue is collected uniformly and then incinerated; the light component removal tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower bottom temperature of 95 °C, and the fraction of vinylene carbonate is taken out from the top of the tower and sold as a product, and the tower bottom liquid is taken out and transported to a product tower; the product tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower bottom temperature of 105 °C, and the fraction of fluoroethylene carbonate is taken out from the top of the tower and stored as a finished product, and the tower bottom liquid is taken out and transported to a post-treatment tower.

[0036] Example 2: The difference between this example and Example 1 is as follows: In step two, the mass ratio of crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.3:1.3:12; in step two, the mesoporous silica is modified mesoporous silica, and its modification method is: the mesoporous silica is vacuum dried; γ-aminopropyltriethoxysilane, absolute ethanol, and dibutyltin dilaurate are mixed according to a mass ratio of 1:30:0.3 to prepare a modifier; the mesoporous silica and the modifier are mixed according to a mass ratio of 1:20, and magnetically stirred at a constant temperature of 74 °C for 1.2 h under nitrogen protection to obtain a reaction solution; the reaction solution is centrifuged at high speed, and then washed with deionized water and vacuum dried to obtain the modified mesoporous silica.

[0037] In step three, the mass ratio of chlorinated ethylene carbonate, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.34:2.7:0.24:0.06.

[0038] The solvent consists of acetonitrile and dimethyl carbonate in a mass ratio of 1.3:1.65.

[0039] The fluoride salt is magnesium fluoride.

[0040] Step 3 includes the following stages: In the first stage, at room temperature, inert gas is continuously introduced into the reactor to replace the air in the reactor; In the second stage, ethylene chloride carbonate, compound chelating agent, solvent and composite catalyst are put into the reactor, stirred and mixed, and the temperature in the reactor is raised to 55°C, and then fluoride salt is added in 10 times, with an addition interval of not less than 30 minutes; in this stage, the amount of compound chelating agent used is 70% of the total amount of compound chelating agent added; In the third stage, the remaining compound chelating agent was added dropwise into the reactor, and the temperature in the reactor was raised to 75° C. After the addition was completed, the reaction was kept warm for 4.5 hours.

[0041] The compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid in a mass ratio of 1.4:1.

[0042] In step 3, the crude fluoroethylene carbonate is washed and filtered to remove the solid salt therein, the filter cake is dried to recover the solvent, the dried product chloride salt is identified and disposed of, and the filtrate is sent to the distillation process; the filtrate is transported to the desolventizing tower at room temperature and pressure, and the distillation and desolventizing is carried out under the conditions of vacuum degree -0.09MPa and tower bottom temperature 84°C, the solvent is collected and recovered at the top of the tower and applied to the fluorination process, and the tower bottom liquid is transported to the crude distillation tower; the crude distillation tower is distilled under the conditions of vacuum degree -0.098MPa and tower bottom temperature 110°C The crude distillate is taken out from the top of the tower and sent to the lightness removal tower, and the residual liquid in the bottom of the tower is collected and incinerated; the lightness removal tower is distilled under the conditions of vacuum degree -0.098MPa and tower bottom temperature 96℃, and the vinylene carbonate fraction is taken out from the top of the tower and sold as the product, and the bottom liquid is taken out and transported to the product tower; the product tower is distilled under the conditions of vacuum degree -0.098MPa and tower bottom temperature 106℃, and the fluoroethylene carbonate fraction is taken out from the top of the tower and stored as the finished product, and the bottom liquid is taken out and transported to the post-treatment tower.

[0043] Embodiment 3: The difference between this embodiment and embodiment 1 is that: In Step 2, the mass ratio of the crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.4:1.4:14; in Step 2, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: vacuum-dry the mesoporous silica; mix γ-aminopropyltriethoxysilane, absolute ethanol, and dibutyltin dilaurate in a mass ratio of 1:30:0.3 to obtain a modifier; mix the mesoporous silica and the modifier in a mass ratio of 1:20, and carry out magnetic stirring at a constant temperature of 78 °C for 1.8 h under nitrogen protection to obtain a reaction solution; subject the reaction solution to high-speed centrifugal separation, then wash it with deionized water and vacuum-dry it to obtain the modified mesoporous silica.

[0044] In Step 3, the mass ratio of ethylene carbonate chloride, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.4:2.9:0.28:0.08.

[0045] The solvent is composed of acetonitrile and dimethyl carbonate in a mass ratio of 1.4:1.7.

[0046] The fluoride salt is zinc fluoride.

[0047] Step 3 includes the following stages: In the first stage, at room temperature, continuously feed an inert gas into the reaction kettle to displace the air in the reaction kettle. In the second stage, feed ethylene carbonate chloride, compound chelating agent, solvent, and composite catalyst into the reaction kettle, stir and mix, raise the temperature in the reaction kettle to 65 °C, and then add the fluoride salt in 10 portions at intervals of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, add the remaining compound chelating agent dropwise into the reaction kettle, raise the temperature in the reaction kettle to 78 °C, and keep the temperature for reaction for 4.8 h after the addition is completed.

[0048] The compound chelating agent is prepared by mixing disodium ethylenediaminetetraacetate and citric acid in a mass ratio of 1.8:1.

[0049] In Step 3, the crude fluoroethylene carbonate is washed and filtered to remove the solid salts therein. The filter cake is dried to recover the solvent, and the dried product, the chloride salt, is disposed of after identification. The filtrate goes to the rectification process. Under normal temperature and pressure, the filtrate is transported to the solvent stripping column, and stripped and rectified under the conditions of a vacuum degree of -0.09 MPa and a column bottom temperature of 88 °C. The recovered solvent collected at the top of the column is recycled to the fluorination process, and the column bottom liquid is transported to the rough distillation column. The rough distillation column is distilled under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 140 °C. The rough distillate taken from the top of the column goes to the light component removal column, and the column bottom residue is collected uniformly and incinerated. The light component removal column is rectified under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 98 °C. The vinyl carbonate fraction taken from the top of the column is sold as a product, and the column bottom liquid is taken out and transported to the product column. The product column is rectified under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 108 °C. The fluoroethylene carbonate fraction taken from the top of the column is stored as a finished product, and the column bottom liquid is taken out and transported to the post-treatment column.

[0050] Example 4: The difference between this example and Example 1 is as follows: In Step 2, the mass ratio of the crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.5:1.5:15. In Step 2, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: The mesoporous silica is dried under vacuum; γ-aminopropyltriethoxysilane, absolute ethanol, and dibutyltin dilaurate are mixed in a mass ratio of 1:30:0.3 to prepare a modifier; the mesoporous silica and the modifier are mixed in a mass ratio of 1:20, and magnetically stirred at a constant temperature of 80 °C for 2 h under nitrogen protection to obtain a reaction solution; the reaction solution is centrifuged at high speed, and then washed with deionized water and dried under vacuum to obtain the modified mesoporous silica.

[0051] In Step 3, the mass ratio of the chloroethylene carbonate, the fluoride salt, the solvent, the composite catalyst, and the compound chelating agent is 1:1.5:3:0.3:0.1.

[0052] The solvent consists of acetonitrile and dimethyl carbonate in a mass ratio of 1.5:1.8.

[0053] The fluoride salt is copper fluoride.

[0054] Step 3 includes the following stages: In the first stage, at room temperature, an inert gas is continuously fed into the reaction kettle to displace the air in the reaction kettle. In the second stage, the chloroethylene carbonate, the compound chelating agent, the solvent, and the composite catalyst are fed into the reaction kettle, stirred and mixed, and the temperature in the reaction kettle is raised to 70 °C, and then the fluoride salt is added in 10 portions at intervals of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, the remaining compound chelating agent is added dropwise into the reaction kettle, the temperature in the reaction kettle is raised to 80 °C, and after the addition is completed, it is kept warm and reacted for 5 h.

[0055] The compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid according to a mass ratio of 2:1.

[0056] In step three, the crude fluorinated ethylene carbonate is washed and filtered to remove the solid salt therein. The filter cake is dried to recover the solvent, and the dried product is identified and then disposed of after chlorination. The filtrate goes to the rectification process. Under normal temperature and pressure, the filtrate is transported to the stripping tower, and stripped and desolvated under the conditions of a vacuum degree of -0.09 MPa and a tower kettle temperature of 90 °C. The recovered solvent collected at the top of the tower is recycled to the fluorination process, and the tower kettle liquid is transported to the rough distillation tower. The rough distillation tower is distilled under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 145 °C. The rough distillate collected at the top of the tower goes to the light component removal tower, and the tower kettle residue is collected uniformly and then incinerated. The light component removal tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 100 °C. The vinyl carbonate fraction collected at the top of the tower is sold as a product, and the tower kettle liquid is collected and then transported to the product tower. The product tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 110 °C. The fluorinated ethylene carbonate fraction collected at the top of the tower is stored as a finished product, and the tower kettle liquid is collected and then transported to the post-treatment tower.

[0057] Example 5: The difference between this example and Example 1 is: In step two, the mass ratio of the crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.3:1.3:12; in step two, the mesoporous silica is modified mesoporous silica, and its modification method is: the mesoporous silica is vacuum dried; γ-aminopropyltriethoxysilane, absolute ethanol, and dibutyltin dilaurate are mixed according to a mass ratio of 1:30:0.3 to prepare a modifier; the mesoporous silica and the modifier are mixed according to a mass ratio of 1:20, and magnetically stirred at a constant temperature of 74 °C for 1.2 h under nitrogen protection to obtain a reaction solution; the reaction solution is centrifuged at high speed, and then washed with deionized water and vacuum dried to obtain the modified mesoporous silica.

[0058] In step three, the mass ratio of chloroethylene carbonate, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.34:2.7:0.24:0.06.

[0059] The solvent consists of acetonitrile and dimethyl carbonate in a mass ratio of 1.3:1.65.

[0060] The fluoride salt is nickel fluoride.

[0061] Step three includes the following stages: In the first stage, at room temperature, an inert gas is continuously fed into the reaction kettle to displace the air in the reaction kettle; In the second stage, ethylene chlorocarbonate, a compound chelating agent, a solvent, and a composite catalyst are fed into a reaction kettle, stirred and mixed, and the temperature in the reaction kettle is raised to 55 °C. Subsequently, a fluoride salt is added in 10 portions with an interval of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, the remaining compound chelating agent is added dropwise into the reaction kettle, and the temperature in the reaction kettle is raised to 75 °C. After the addition is completed, the reaction is carried out under insulation for 4.5 h.

[0062] The compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid according to a mass ratio of 1.4:1.

[0063] In step three, the crude product of fluoroethylene carbonate is washed and filtered to separate and remove the solid salt therein. The filter cake is dried to recover the solvent, and the dried product of the chloride salt is disposed of after identification, and the filtrate goes to the rectification process; the filtrate is transported to a stripping tower under normal temperature and pressure, and stripped and desolvated by rectification under the conditions of a vacuum degree of -0.09 MPa and a tower kettle temperature of 84 °C. The recovered solvent is collected at the top of the tower and applied to the fluorination process, and the tower kettle liquid is transported to a rough distillation tower; the rough distillation tower is distilled under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 110 °C, and the rough distillate is taken out from the top of the tower and sent to a de-light tower, and the tower kettle residue is collected uniformly and incinerated; the de-light tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 96 °C, and the fraction of vinylene carbonate is taken out from the top of the tower and sold as a product, and the tower kettle liquid is taken out and transported to a product tower; the product tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 106 °C, and the fraction of fluoroethylene carbonate is taken out from the top of the tower and stored as a finished product, and the tower kettle liquid is taken out and transported to a post-treatment tower.

[0064] Example 6: The difference between this example and Example 1 is as follows: In step two, the mass ratio of crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.3:1.3:12; in step two, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: the mesoporous silica is vacuum dried; γ-aminopropyltriethoxysilane, absolute ethanol, and dibutyltin dilaurate are mixed according to a mass ratio of 1:30:0.3 to prepare a modifier; the mesoporous silica and the modifier are mixed according to a mass ratio of 1:20, and magnetically stirred at a constant temperature of 74 °C for 1.2 h under nitrogen protection to obtain a reaction solution; the reaction solution is centrifuged at high speed, and then washed with deionized water and vacuum dried to obtain the modified mesoporous silica.

[0065] In step three, the mass ratio of ethylene chlorocarbonate, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.34:2.7:0.24:0.06.

[0066] The solvent is composed of acetonitrile and dimethyl carbonate in a mass ratio of 1.3:1.65.

[0067] The fluoride salt is cobalt fluoride.

[0068] Step 3 includes the following stages: In the first stage, at room temperature, an inert gas is continuously fed into the reaction kettle to displace the air in the reaction kettle. In the second stage, ethylene carbonate chloride, the compound chelating agent, the solvent, and the composite catalyst are fed into the reaction kettle, stirred and mixed, and the temperature in the reaction kettle is raised to 55 °C. Subsequently, the fluoride salt is added in 10 portions at intervals of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, the remaining compound chelating agent is added dropwise to the reaction kettle, and the temperature in the reaction kettle is raised to 75 °C. After the addition is completed, the reaction is carried out under insulation for 4.5 h.

[0069] The compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid in a mass ratio of 1.4:1.

[0070] In step 3, the crude product of vinyl fluorocarbonate is washed and filtered to separate and remove the solid salt therein. The filter cake is dried to recover the solvent, and the dried product of chloride salt is disposed of after identification. The filtrate goes to the rectification process; the filtrate is transported to the stripping tower at normal temperature and pressure, and stripped and desolvated under the conditions of a vacuum degree of -0.09 MPa and a tower kettle temperature of 84 °C. The recovered solvent is collected at the top of the tower and applied to the fluorination process, and the tower kettle liquid is transported to the rough distillation tower; the rough distillation tower is distilled under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 110 °C, and the crude distillate is taken out from the top of the tower and sent to the light component removal tower, and the tower kettle residue is collected uniformly and incinerated; the light component removal tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 96 °C, and the fraction of vinylene carbonate is taken out from the top of the tower and sold as a product, and the tower kettle liquid is taken out and transported to the product tower; the product tower is rectified under the conditions of a vacuum degree of -0.098 MPa and a tower kettle temperature of 106 °C, and the fraction of vinyl fluorocarbonate is taken out from the top of the tower and stored as a finished product, and the tower kettle liquid is taken out and transported to the post-treatment tower.

[0071] Example 7: The difference between this example and Example 1 is: In Step 2, the mass ratio of crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.5:1.5:15; in Step 2, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: vacuum dry the mesoporous silica; mix γ-aminopropyltriethoxysilane, absolute ethanol, and dibutyltin dilaurate according to a mass ratio of 1:30:0.3 to prepare a modifier; mix the mesoporous silica and the modifier according to a mass ratio of 1:20, and magnetically stir at a constant temperature of 80 °C for 2 h under nitrogen protection to obtain a reaction solution; centrifuge the reaction solution at high speed, then wash it with deionized water and vacuum dry it to obtain modified mesoporous silica.

[0072] In Step 3, the mass ratio of ethylene carbonate chloride, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.5:3:0.3:0.1.

[0073] The solvent is composed of acetonitrile and dimethyl carbonate in a mass ratio of 1.5:1.8.

[0074] The fluoride salt is sodium fluoride.

[0075] Step 3 includes the following stages: In the first stage, at room temperature, continuously feed an inert gas into the reaction kettle to displace the air in the reaction kettle. In the second stage, feed ethylene carbonate chloride, compound chelating agent, solvent, and composite catalyst into the reaction kettle, stir and mix, raise the temperature in the reaction kettle to 70 °C, and then add the fluoride salt in 10 portions at intervals of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added. In the third stage, add the remaining compound chelating agent dropwise into the reaction kettle, raise the temperature in the reaction kettle to 80 °C, and keep the temperature for 5 h after the addition is completed.

[0076] The compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid according to a mass ratio of 2:1.

[0077] In Step 3, the crude fluoroethylene carbonate is washed and filtered to remove the solid salts therein. The filter cake is dried to recover the solvent, and the dried product of chloride salt is disposed of after identification. The filtrate goes to the rectification process. Under normal temperature and pressure, the filtrate is transported to the solvent stripping column and stripped and desolvated by rectification under the conditions of a vacuum degree of -0.09 MPa and a column bottom temperature of 90°C. The recovered solvent collected at the top of the column is recycled to the fluorination process, and the column bottom liquid is transported to the rough distillation column. The rough distillation column distills under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 145°C. The rough distillate collected at the top of the column goes to the light component removal column, and the column bottom residue is collected uniformly and incinerated. The light component removal column rectifies under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 100°C. The fraction of vinylene carbonate collected at the top of the column is sold as a product, and the column bottom liquid is taken out and transported to the product column. The product column rectifies under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 110°C. The fraction of fluoroethylene carbonate collected at the top of the column is stored as a finished product, and the column bottom liquid is taken out and transported to the post-treatment column.

[0078] Comparative Example 1: The difference between this comparative example and Example 1 is that the compound chelating agent is not used.

[0079] Comparative Example 2: The difference between this comparative example and Example 1 is that the mass ratio of ethylene chlorocarbonate, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.3 - 1.5:2.5 - 3:0.2 - 0.3:0.01.

[0080] Comparative Example 3: The difference between this comparative example and Example 1 is that the compound chelating agent is added entirely in the second stage, and at the same time, the third stage is omitted.

[0081] The products in Examples 1 - 7 and Comparative Examples 1 - 3 are taken for detection respectively, and the detection method is as follows: (1) Method summary: By gas chromatography, on a capillary chromatographic column, fluoroethylene carbonate and organic impurity components are separated, detected by a flame ionization detector (FID), and quantified by the area normalization method.

[0082] (2) Instruments: ① Gas chromatograph: Shimadzu GC2014C or equivalent chromatograph; ② Detector: Flame ionization detector (FID); ③ Workstation: LabSolutions; ④ Chromatographic column: HP - 5; 50.0 m × 0.32 mm × 0.52 μm or equivalent column; (3) Chromatographic conditions: ① Injector temperature: 260°C; ② Detector temperature: 280 °C; ③ Carrier gas (N2) pressure: 0.07 (Mpa); ④ Hydrogen flow rate: 30 ml / min; Air flow rate: 300 ml / min; Tail gas blow flow rate: 40 ml / min; ⑤ Split ratio: 50:1; ⑥ Programmed temperature rise: Initial temperature 50 °C, hold for 3 minutes, increase to 200 °C at 15 °C per minute, hold for 15 minutes; ⑦ Injection volume: 0.4 μl.

[0083] (4) Test procedure: Inject 0.4 μL of the reference substance, inject one needle; Inject 0.4 μL of the sample solution, inject two needles, and the running time for each needle is 28 min. The retention time of the main peak of the sample to be measured should be the same as that of the reference substance.

[0084] (5) Calculation: ; Where: w1 is the purity of fluoroethylene carbonate (%); A1 is the peak area of fluoroethylene carbonate; ∑A is the total peak area.

[0085] (6) Precision: The difference between the two determination results of fluoroethylene carbonate is not more than 0.2%, and the average value is taken as the determination result.

[0086] Calculated according to the above formula, the results are shown in the following table:

[0087] It can be seen from the comparison between Examples 1-7 and Comparative Examples 1 and 2 that the compound chelating agent can effectively reduce the content of metal ions in the final product. For example, in Comparative Example 2, although the dosage of the compound chelating agent did not reach the standard, the content of metal ions in its product still decreased.

[0088] It can be seen from Comparative Example 3 that after omitting the third stage, although the content of metal ions in its product is greatly reduced under the action of the compound chelating agent, due to the omission of the heat preservation reaction, the conversion rates of chloroethylene carbonate and fluoroethylene carbonate both decrease significantly, which also causes the yield of the final product to decrease.

[0089] It can be seen from Comparative Examples 1 and 2 that the compound chelating agent has a certain influence on the yield of fluoroethylene carbonate, but the influence is not significant. After analysis, it is known that this is because the compound chelating agent can reduce the metal ion concentration in the reaction process, which speeds up the reaction rate of the fluoride salt and improves its reaction participation degree, and finally slightly increases the yield of fluoroethylene carbonate.

[0090] The key point of the compound chelating agent is that after the compound chelating agent is used, metal ions in the product are chelated and removed, and finally the purity of fluorinated ethylene carbonate is improved.

[0091] In summary, the advantages of this solution are as follows: First, in the composite catalyst, crown ether, tetrabutylphosphonium bromide, and tetrabutylammonium bromide cooperate and synergize with each other to inhibit side reactions and maximize the purity of the final product. Among them, crown ether optimizes mass transfer and reaction selectivity by selectively complexing metal ions; tetrabutylphosphonium bromide forms an ion pair with cations to enhance the solubility of fluoride ions in the organic phase, thereby improving the reaction efficiency. At the same time, tetrabutylphosphonium bromide can stabilize the intermediate through hydrogen bond interaction and inhibit the formation of by-products; the role of tetrabutylammonium bromide is to promote the transfer of fluoride ions in the aqueous phase to the organic phase, accelerate the fluorination reaction, significantly improve the reaction rate and product yield. At the same time, by adjusting the local charge environment, it can also reduce the decomposition of organic solvents and reduce the formation of by-products. Second, through the compound chelating agent, the excess metal ions in the reaction are effectively reduced, ensuring the purity of the final product.

[0092] The present invention is not limited to the above specific embodiments. Those of ordinary skill in the art starting from the above concepts and making various changes without creative labor fall within the protection scope of the present invention.

Claims

1. A method for preparing fluorinated ethylene carbonate, characterized in that, It includes the following steps: Step 1, pretreatment; Chlorinated ethylene carbonate is treated through a 3A molecular sieve adsorption tower, controlling the free acid ≤ 30 ppm; Step 2, catalyst preparation; A composite catalyst is prepared by mixing crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica; Step 3, fluorination reaction; An inert gas is continuously fed into the reaction kettle. After the air replacement in the reaction kettle is completed, the pretreated chlorinated ethylene carbonate, compound chelating agent, solvent, and composite catalyst are fed into the reaction kettle, stirred and mixed. The temperature in the reaction kettle is raised to 50 - 70 °C, and then the fluoride salt is added in 10 portions at intervals of not less than 30 min. Subsequently, the temperature in the reaction kettle is raised to 70 - 80 °C, and the reaction is carried out under insulation for 4 - 5 h to obtain the crude product of fluoroethylene carbonate; the crude product of fluoroethylene carbonate is filtered, rinsed, desolvated, and rectified to obtain the finished product of fluoroethylene carbonate; The compound chelating agent is prepared by compounding disodium ethylenediaminetetraacetate and citric acid according to a mass ratio of 1.2 - 2:

1.

2. The method for preparing fluorinated ethylene carbonate according to claim 1, characterized in that, In Step 2, the mass ratio of crown ether, tetrabutylphosphonium bromide, tetrabutylammonium bromide, and mesoporous silica is 6:1.2 - 1.5:1.2 - 1.5:10 - 15.

3. The method for preparing fluorinated ethylene carbonate according to claim 1, characterized in that, In Step 2, the mesoporous silica is modified mesoporous silica, and its modification method is as follows: the mesoporous silica is vacuum dried; γ-aminopropyltriethoxysilane, anhydrous ethanol, and dibutyltin dilaurate are mixed according to a mass ratio of 1:30:0.3 to obtain a modifier; the mesoporous silica and the modifier are mixed according to a mass ratio of 1:20, and magnetically stirred at a constant temperature of 70 - 80 °C under nitrogen protection for 1 - 2 h to obtain a reaction solution; the reaction solution is centrifuged at high speed, and then washed with deionized water and vacuum dried to obtain the modified mesoporous silica.

4. The method for preparing fluorinated ethylene carbonate according to claim 3, characterized in that, The pore diameter of the modified mesoporous silica is 5 - 10 nm.

5. The method for preparing fluorinated ethylene carbonate according to claim 1, characterized in that, In Step 3, the mass ratio of chlorinated ethylene carbonate, fluoride salt, solvent, composite catalyst, and compound chelating agent is 1:1.3 - 1.5:2.5 - 3:0.2 - 0.3:0.05 - 0.

1.

6. The method for preparing fluorinated ethylene carbonate according to claim 1, characterized in that, The fluoride salt is one of potassium fluoride, magnesium fluoride, zinc fluoride, copper fluoride, nickel fluoride, cobalt fluoride, and sodium fluoride.

7. The method for preparing fluorinated ethylene carbonate according to claim 1, characterized in that, The solvent is composed of acetonitrile and dimethyl carbonate according to a mass ratio of 1.2 - 1.5:1.6 - 1.

8.

8. The method for preparing fluorinated ethylene carbonate according to claim 1, characterized in that, In Step 3 It includes the following stages: The first stage, at room temperature, an inert gas is continuously fed into the reaction kettle to replace the air in the reaction kettle; The second stage, the pretreated chlorinated ethylene carbonate, compound chelating agent, solvent, and composite catalyst are fed into the reaction kettle, stirred and mixed. The temperature in the reaction kettle is raised to 50 - 70 °C, and then the fluoride salt is added in 10 portions at intervals of not less than 30 min; in this stage, the dosage of the compound chelating agent is 70% of the total amount of the compound chelating agent added; The third stage, the remaining compound chelating agent is added dropwise into the reaction kettle, and the temperature in the reaction kettle is raised to 70 - 80 °C. After the addition is completed, the reaction is carried out under insulation for 4 - 5 h.

9. The method for preparing fluorinated ethylene carbonate according to claim 1, characterized in that, In Step 3, the crude fluorinated ethylene carbonate is washed and filtered to remove the solid salts therein. The filter cake is dried to recover the solvent, and the dried product of chloride salt is disposed of after identification. The filtrate goes to the rectification process. Under normal temperature and pressure, the filtrate is transported to the solvent stripping column, and stripped and rectified under the conditions of a vacuum degree of -0.09 MPa and a column bottom temperature of 80 - 90 °C. The recovered solvent collected at the top of the column is recycled to the fluorination process, and the column bottom liquid is transported to the rough distillation column. The rough distillation column is distilled under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 100 - 145 °C. The rough distillate is taken out from the top of the column and sent to the light component removal column, and the column bottom residue is collected uniformly and incinerated. The light component removal column is rectified under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 95 - 100 °C. The fraction of vinylene carbonate is taken out from the top of the column and sold as a by-product, and the column bottom liquid is taken out and transported to the product column. The product column is rectified under the conditions of a vacuum degree of -0.098 MPa and a column bottom temperature of 105 - 110 °C. The fraction of fluorinated ethylene carbonate is taken out from the top of the column and stored as a finished product, and the column bottom liquid is taken out and transported to the post-treatment column.

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