Preparation method of vinylene carbonate

Abstract

The invention discloses a preparation method of vinylene carbonate, which comprises the following steps: by taking saturated dihydric alcohol as a solvent, reacting chloroethylene carbonate with ethylene glycol dialkali metal salt to obtain a vinylene carbonate crude product, and rectifying and crystallizing the vinylene carbonate crude product to obtain high-purity vinylene carbonate. An expensive catalyst is not adopted, and the reaction is homogeneous reaction, so that the heat and mass transfer effects are improved, the yield and purity of the product are improved, the generation of acid-containing wastewater is eliminated, and the requirement of clean production is met; and meanwhile, the production cost is reduced, and great economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The present application relates to a lithium battery electrolyte additive, and in particular to a method for preparing vinylene carbonate. Background Art

[0002] Vinylene carbonate is a colorless transparent liquid with a melting point of 19-22°C and a boiling point of 162°C. It easily absorbs water and hydrolyzes in humid air and shows strong acidity. It is thermally unstable and is a new type of organic film-forming additive and overcharge protection additive for lithium-ion batteries. When vinylene carbonate is added to the electrolyte of lithium batteries in small amounts as an additive, a dense SEI film can be formed at the negative electrode. This dense SEI film can improve the high and low temperature properties of the electrolyte, improve the cycle performance of lithium batteries at high temperatures, reduce the internal resistance of the battery, inhibit the decomposition of solutes and solvents, improve the cycle performance of the battery, and thus improve the performance of the battery. Therefore, it is one of the most ideal products among lithium battery electrolyte additives.

[0003] In the current technology, there is a process route for obtaining vinylene carbonate by reacting chloroethylene carbonate with a dechlorinating agent. The dechlorinating agent is selected from one of pyridine compounds, ammonia gas, liquid ammonia, and triethylamine, but all of them have defects.

[0004] When pyridine compounds are used as dechlorinating agents, they may cause respiratory irritation, damage the nervous system, and endanger liver and kidney functions. They are seriously harmful to human health, easily pollute the environment, and also pose safety risks.

[0005] When ammonia is used as a dechlorinating agent, additional solvent is required, and this process method has obvious disadvantages, not only the yield is low but also the cost is quite high.

[0006] Liquid ammonia is used as a dechlorinating agent and also as a solvent. However, the process is extremely complicated and the reaction time is long. In addition, the storage conditions for liquid ammonia are harsh and the transportation is difficult. The combination of many unfavorable factors has greatly reduced the economic efficiency of industrial production and made it impossible to achieve efficient economic output.

[0007] Triethylamine is used as a dechlorinating agent, and borohydride catalyst is required in the reaction process. A large amount of triethylamine is used, which is costly. In addition, triethylamine promotes the polymerization of vinylene carbonate, resulting in a low yield of vinylene carbonate. A large amount of solid salt is generated in the process, and the post-processing process is complicated.

[0008] Therefore, developing a clean, efficient and cost-effective process for producing vinylene carbonate is a major development need in this field. Summary of the invention

[0009] A method for preparing vinylene carbonate is provided to produce vinylene carbonate in a clean, efficient and cost-effective manner.

[0010] The above first invention objective of the present invention is achieved through the following technical solutions: A method for preparing vinylene carbonate is characterized in that a saturated diol is used as a solvent, vinylene carbonate is reacted with ethylene glycol dialkali metal salt to obtain a crude vinylene carbonate product, and the crude vinylene carbonate product can be distilled and crystallized to obtain high-purity vinylene carbonate.

[0011] By adopting the above technical scheme, the raw materials used in the preparation method of the present application are easily available, no expensive catalyst is used, the reaction is a homogeneous reaction, the heat and mass transfer effects are improved, the yield and purity of the product are increased, the generation of acid-containing wastewater is eliminated, and the requirements of clean production are met; at the same time, the production cost is reduced, which has great economic and social benefits.

[0012] Optionally, the specific steps of reacting ethylene chlorocarbonate with ethylene glycol dialkali metal salt are as follows: Ethylene glycol dialkali metal salt and saturated diol are mixed uniformly to obtain liquid phase A, and chloroethylene carbonate is added dropwise to liquid phase A to evaporate vinylene carbonate during the reaction. After the addition is completed and the reaction is continued until no distillate is produced, the reaction is stopped to obtain a crude vinylene carbonate product.

[0013] By adopting the above technical scheme, the preparation method of the present application continuously drips the raw materials and continuously evaporates the products under high vacuum, so that the residence time of the product in the kettle is greatly shortened, the risk of product polymerization and decomposition is reduced, and the yield is increased from 65% to more than 92%. In addition, the product vinyl carbonate is directly distilled out during the reaction process without the need for complicated post-processing, and the production efficiency and production cost are significantly improved and optimized.

[0014] Optionally: when vinyl chloride carbonate is added dropwise, the temperature of the reaction system is 50-80° C.; and the vacuum degree is 5-10 Torr.

[0015] Optional: the dripping time of chloroethylene carbonate is controlled within 1 to 4 hours.

[0016] Optionally, the molar ratio of the ethylene chloride carbonate to the ethylene glycol dialkali metal salt is 1:(0.54-0.6).

[0017] Optionally, the mass ratio of the ethylene chloride carbonate to the saturated diol solvent is 1:(2.5-3.5).

[0018] By adopting the above technical scheme, the yield and purity of the vinylene carbonate product obtained by the preparation method of the present application are good.

[0019] Optionally, the ethylene glycol dialkali metal salt is prepared by reacting ethylene glycol with an alkali metal hydroxide.

[0020] By adopting the above technical scheme, compared with the preparation of ethylene glycol dialkali metal salt by the reaction of active alkali metal and ethylene glycol, the reaction is milder, the reaction by-products are safer, and the preparation of ethylene glycol dialkali metal salt is more efficient and safer; compared with the preparation by alcoholysis, no alkali metal alkoxy derivatives are required as raw materials, the cost is more economical, and the reaction by-products are more environmentally friendly.

[0021] Optionally: the preparation method of the ethylene glycol dialkali metal salt is as follows, Ethylene glycol and mesitylene solvents are mixed, and alkali metal hydroxide is added under nitrogen protection, heated to react, and water is separated by reflux at normal pressure. When no water is separated, reduced pressure distillation is started to evaporate mesitylene to obtain crude ethylene glycol dialkali metal salt, which is then beaten with solvent, filtered and dried in vacuum to obtain ethylene glycol dialkali metal salt.

[0022] By adopting the above technical scheme, mesitylene is used as a diluent solvent, which can be soluble in ethylene glycol, reduce the compatibility of by-products in ethylene glycol, reduce the saturated vapor pressure of water on the surface of the reaction liquid phase, and thus accelerate the rapid distillation and transfer of water. At the same time, the boiling point of mesitylene is between water and ethylene glycol and has a certain gap with both, and the three do not form an azeotrope. Therefore, when water is distilled, the organic matter content in the fraction is low, the water separation and transfer efficiency is high, the yield of ethylene glycol dialkali metal salt is high, and the burden of wastewater treatment is reduced.

[0023] In summary, this application has at least the following beneficial effects: The invention uses ethylene glycol dialkali metal salt as a dechlorinating agent and saturated diol as a solvent, drips chloroethylene carbonate under certain temperature and vacuum conditions, and distills the product while reacting, so that the residence time of the product in the kettle is greatly shortened. The invention adopts the method of continuously dripping raw materials and continuously distilling the product under high vacuum, so that the residence time of the product in the kettle is greatly shortened, the risk of product polymerization and decomposition is reduced, and the yield is significantly improved; the product vinylene carbonate is directly distilled out during the reaction process, and no complicated post-treatment process is required; The raw materials of this method are easily available, no expensive catalyst is used, the reaction is a homogeneous reaction, the heat and mass transfer effects are improved, the yield and purity of the product are increased, the generation of acid-containing wastewater is eliminated, and the requirements of clean production are met; at the same time, the production cost is reduced, and great economic and social benefits are achieved. DETAILED DESCRIPTION

[0024] Preparation Example 1 Ethylene glycol disodium salt, the preparation method is as follows: Add 248.0 g of ethylene glycol and 1000 ml of mesitylene into a 2000 ml four-necked reaction flask with a water separator; Add 325g of sodium hydroxide under nitrogen protection, stir and heat, reflux at normal pressure to separate water, and when no water is separated, start reduced pressure distillation to evaporate mesitylene to obtain crude ethylene glycol disodium salt; The crude disodium ethylene glycol salt was slurried with 800 ml of mesitylene and filtered, and the filtrate was vacuum dried at 50° C. to obtain 406 g of disodium ethylene glycol salt.

[0025] Preparation Example 2 Ethylene glycol dipotassium salt, the preparation method is as follows: Add 248.0 g of ethylene glycol and 1000 ml of mesitylene into a 2000 ml four-necked reaction flask with a water separator; Add 455g potassium hydroxide under nitrogen protection, stir and heat, reflux at normal pressure to separate water, and when no water is separated, start reduced pressure distillation to evaporate mesitylene to obtain crude ethylene glycol dipotassium salt; The crude ethylene glycol dipotassium salt was slurried with 800 ml of mesitylene and filtered, and the filtrate was vacuum dried at 50° C. to obtain 528 g of ethylene glycol dipotassium salt.

[0026] In addition, ethylene glycol dialkali metal salts can be prepared by reacting active alkali metals with ethylene glycol, or by alcoholysis using alkali metal alkoxy derivatives as raw materials to react with ethylene glycol to prepare ethylene glycol dialkali metal salts.

[0027] However, the preparation time of using active alkali metals to react with ethylene glycol is long and the byproduct hydrogen has safety hazards. Therefore, the preparation of ethylene glycol dialkali metal salt by reacting ethylene glycol with alkali metal hydroxide is more gentle, the reaction byproduct is safer, and the preparation of ethylene glycol dialkali metal salt is more efficient and safe. The alcoholysis method has high preparation cost, and the byproduct is high molecular alcohol or aldehyde, which has a heavy burden on subsequent treatment. Therefore, it is better to prepare ethylene glycol dialkali metal salt by reacting ethylene glycol with alkali metal hydroxide.

[0028] Preparation Example 3 Ethylene glycol disodium salt, the preparation method is as follows: Add 248.0 g of ethylene glycol and 1000 ml of trimethylbenzene into a 2000 ml four-necked reaction flask with a water separator; Add 325g of sodium hydroxide under nitrogen protection, stir and heat for fractionation, remove water from the fraction and reflux, when no water is separated, start vacuum distillation, evaporate trimethylbenzene, and obtain crude ethylene glycol disodium salt; The crude disodium ethylene glycol salt was slurried and filtered with 800 ml of trimethylbenzene, and the filtrate was vacuum dried at 50° C. to obtain 406 g of disodium ethylene glycol salt.

[0029] Comparing the organic matter content in the water obtained by water separation during the preparation process of Preparation Example 1 and Preparation Example 3, the total organic matter content in the water obtained by water separation in Preparation Example 1 is 1.26wt%, and in Preparation Example 3 is 4.23wt%.

[0030] Therefore, in Preparation Example 1, mesitylene is used as the diluent solvent, which is miscible with ethylene glycol, reduces the compatibility of by-products in ethylene glycol, reduces the saturated vapor pressure of water on the surface of the reaction liquid phase, and thus accelerates the rapid distillation and transfer of water. At the same time, the boiling point of mesitylene is between water and ethylene glycol and has a certain gap with both, and the three do not form an azeotrope. Therefore, when water is distilled, the organic matter content in the fraction is low, the water separation and transfer efficiency is high, the yield of ethylene glycol dialkali metal salt is high, and the burden of wastewater treatment is small.

[0031] Example 1 A method for preparing vinylene carbonate, comprising the following steps: S1: In a 1000ml four-necked flask equipped with a thermometer, a stirrer and a distillation device, add 60.0g of ethylene glycol disodium salt (0.566mol) and 372g of ethylene glycol, replace the air in the reaction flask with nitrogen, then evacuate the flask to a vacuum degree of 5mmHg, and vigorously stir under nitrogen protection to obtain liquid phase A; S2: Heat the liquid phase A to 65° C., dropwise add 125 g (1 mol, 98 wt%) ethylene chlorocarbonate, and simultaneously evaporate the product vinylene carbonate. The dropwise addition time is 2 h. After the dropwise addition is complete, the reaction is stopped when no distillate is produced.

[0032] The reaction process is as follows: M is a metal ion.

[0033] Example 2 A method for preparing vinylene carbonate, comprising the following steps: S1: In a 1000ml four-necked flask equipped with a thermometer, a stirrer and a distillation device, add 60.0g of ethylene glycol disodium salt (0.566mol) and 456.6g of 1,3-propylene glycol, replace the air in the reaction flask with nitrogen, and then evacuate the flask to a vacuum degree of 5mmHg, and stir vigorously under nitrogen protection to obtain liquid phase A; S2: Heat the liquid phase A to 65°C, dropwise add 125 g (1 mol, content 98 wt%) of chloroethylene carbonate, and evaporate the product at the same time. The dropwise addition time is 2 h. After the dropwise addition is completed, the reaction is stopped when there is no distillate.

[0034] Example 3 A method for preparing vinylene carbonate, comprising the following steps: S1: In a 1000ml four-necked flask equipped with a thermometer, a stirrer and a distillation device, add 60.0g of ethylene glycol disodium salt (0.566mol) and 456.6g of 1,2-propylene glycol, replace the air in the reaction flask with nitrogen, and then evacuate the flask to a vacuum degree of 5mmHg, and stir vigorously under nitrogen protection to obtain liquid phase A; S2: Heat liquid phase A to 50°C, dropwise add 125g (1 mol, 98 wt%) ethylene chlorocarbonate, and distill off the product at the same time. The dropwise addition time is 2h, and the reaction is stopped when no distillate is produced.

[0035] Example 4 A method for preparing vinylene carbonate, comprising the following steps: S1: In a 1000ml four-necked flask equipped with a thermometer, a stirrer and a distillation device, add 60.0g of ethylene glycol disodium salt (0.566mol) and 945g of hexanediol, replace the air in the reaction flask with nitrogen, then evacuate the flask to a vacuum degree of 5mmHg, and stir vigorously under nitrogen protection to obtain liquid phase A; S2: Heat liquid phase A to 50°C, dropwise add 125g (1 mol, 98 wt%) ethylene chlorocarbonate, and distill off the product at the same time. The dropwise addition time is 2h, and the reaction is stopped when no distillate is produced.

[0036] Example 5 A method for preparing vinylene carbonate, comprising the following steps: S1: In a 1000ml four-necked flask equipped with a thermometer, a stirrer and a distillation device, add 60.0g of ethylene glycol disodium salt (0.566mol) and 372g of ethylene glycol, replace the air in the reaction flask with nitrogen, then evacuate the flask to a vacuum degree of 5mmHg, and vigorously stir under nitrogen protection to obtain liquid phase A; S2: Heat liquid phase A to 50° C., add 125 g (1 mol, content 98 wt%) of ethylene chlorocarbonate, and distill off the product at the same time. The addition time is 1 min. After the addition is complete, the reaction is stopped when there is no distillate.

[0037] Example 6 A method for preparing vinylene carbonate, which differs from Example 1 in that the vacuum degree in S1 is 2 Torr.

[0038] Example 7 A method for preparing vinylene carbonate, which differs from Example 1 in that the vacuum degree in S1 is 10 Torr.

[0039] Example 8 A method for preparing vinylene carbonate, which differs from Example 1 in that the liquid phase heating temperature in S2 is 40°C.

[0040] Example 9 A method for preparing vinylene carbonate, which differs from Example 1 in that the liquid phase heating temperature in S2 is 50°C.

[0041] Example 10 A method for preparing vinylene carbonate, which differs from Example 1 in that the liquid phase heating temperature in S2 is 80°C.

[0042] Embodiment 11 A method for preparing vinylene carbonate, which differs from Example 1 in that the liquid phase heating temperature in S2 is 90°C.

[0043] Example 12 A method for preparing vinylene carbonate is different from Example 1 in that the mass of ethylene glycol disodium salt added in S1 is 53 g, and the molar ratio of chloroethylene carbonate to ethylene glycol dialkali metal salt is 1:0.5.

[0044] Example 13 A method for preparing vinylene carbonate is different from Example 1 in that the mass of ethylene glycol disodium salt added in S1 is 57.24 g, and the molar ratio of chloroethylene carbonate to ethylene glycol dialkali metal salt is 1:0.54.

[0045] Embodiment 14 A method for preparing vinylene carbonate is different from Example 1 in that the mass of ethylene glycol disodium salt added in S1 is 63.6 g, and the molar ratio of chloroethylene carbonate to ethylene glycol dialkali metal salt is 1:0.6.

[0046] Embodiment 15 A method for preparing vinylene carbonate is different from Example 1 in that the mass of ethylene glycol disodium salt added in S1 is 74.2 g, and the molar ratio of chloroethylene carbonate to ethylene glycol dialkali metal salt is 1:0.7.

[0047] Example 16 A method for preparing vinylene carbonate is different from Example 1 in that the mass of ethylene glycol added in S1 is 245 g, and the molar ratio of chloroethylene carbonate to ethylene glycol in the reaction is 1:2.

[0048] Embodiment 17 A method for preparing vinylene carbonate is different from Example 1 in that the mass of ethylene glycol added in S1 is 306.25 g, and the molar ratio of chloroethylene carbonate to ethylene glycol in the reaction is 1:2.5.

[0049] Embodiment 18 A method for preparing vinylene carbonate, which is different from Example 1 in that the mass of ethylene glycol added in S1 is 428.75 g, and the molar ratio of chloroethylene carbonate to ethylene glycol in the reaction is 1:3.5.

[0050] Embodiment 19 A method for preparing vinylene carbonate is different from Example 1 in that the mass of ethylene glycol added in S1 is 490 g, and the molar ratio of chloroethylene carbonate to ethylene glycol is 1:4.

[0051] Embodiment 20 A method for preparing vinylene carbonate is disclosed, which differs from Example 1 in that in S1, dipotassium ethylene glycol is used instead of disodium ethylene glycol, and the amount of dipotassium ethylene glycol used is 75 g.

[0052] Embodiment 21 A method for preparing vinylene carbonate, which differs from Example 1 in that the dropping time in S2 is 0.5 h.

[0053] Embodiment 22 A method for preparing vinylene carbonate, which differs from Example 1 in that the dropping time in S2 is 1 hour.

[0054] Embodiment 23 A method for preparing vinylene carbonate, which differs from Example 1 in that the dropping time in S2 is 4 hours.

[0055] Embodiment 24 A method for preparing vinylene carbonate, which differs from Example 1 in that the dropping time in S2 is 5 hours.

[0056] Comparative Example 1 A method for preparing vinylene carbonate, comprising the following steps: S1: In a 1000ml four-necked flask equipped with a thermometer, a stirrer and a distillation device, 38.5g of sodium ethoxide and 372g of ethylene glycol were added, the air in the reaction flask was replaced with nitrogen, and then evacuated to a vacuum degree of 5mmHg, and stirred vigorously under nitrogen protection to obtain liquid phase A; S2: Heat the liquid phase A to 65°C, dropwise add 125 g (1 mol, 98 wt%) chloroethylene carbonate, and distill off the product at the same time. The dropwise addition time is 2 hours. After the dropwise addition is completed, continue the reaction until there is no distillate.

[0057] Comparative Example 2 A method for preparing vinylene carbonate, comprising the following steps: S1: In a 1000ml four-necked bottle equipped with a thermometer, a stirrer and a distillation device, add 67.9g of propylene glycol disodium salt and 456.5g of 1,3-propylene glycol, replace the air in the reaction bottle with nitrogen, then evacuate to a vacuum degree of 5mmHg, and stir vigorously under nitrogen protection to obtain liquid phase A; S2: Heat the liquid phase A to 65°C, dropwise add 125 g (1 mol, 98 wt%) chloroethylene carbonate, and distill off the product at the same time. The dropwise addition time is 2 hours. After the dropwise addition is completed, continue the reaction until there is no distillate.

[0058] The quality, yield and purity of the vinylene carbonate products obtained in Examples 1 to 24 and Comparative Examples 1 to 2 are shown in the following table.

[0059] Table 1. Record of product quality, yield and purity of Examples 1 to 24 and Comparative Examples 1 to 2 Combined with the above table, analysis of Example 1 and Comparative Examples 1-2: In Example 1, ethylene carbonate was dechlorinated with disodium ethylene glycol in an ethylene glycol environment to obtain vinylene carbonate; in Comparative Example 1, ethylene carbonate was dechlorinated with sodium ethoxide in an ethylene glycol environment to obtain vinylene carbonate; in Comparative Example 2, ethylene carbonate was dechlorinated with disodium propylene glycol in an 1,3-propylene glycol environment to obtain vinylene carbonate; In the test results, the purity and yield of the product of Example 1 are significantly better than those of Comparative Example 1; although the purity of the product obtained in Comparative Example 2 reaches more than 90wt%, the yield of Comparative Example 2 is significantly lower than that of Example 1.

[0060] Combined with Example 20, in Example 20, an equimolar amount of dipotassium ethylene glycol was used to replace the disodium ethylene glycol used in Example 1. The test results showed that the purity of the product obtained in Example 20 was similar to that in Example 1, both being higher than 95wt%, and the yield of Example 20 was similar to that of Example 1.

[0061] In the present application, ethylene glycol dialkali metal salt is selected to catalyze the dechlorination of chloroethylene carbonate in a saturated diol environment to prepare vinylene carbonate. The raw materials used in the preparation method are easily available, no expensive catalyst is used, the reaction is a homogeneous reaction, the heat and mass transfer effect is improved, the yield and purity of the product are increased, the generation of acid-containing wastewater is eliminated, and the requirements of clean production are met; the product vinylene carbonate is directly distilled out during the reaction process, and no complicated post-treatment process is required, the production efficiency and production cost are significantly improved and optimized, thereby reducing the production cost, and having great economic and social benefits.

[0062] In combination with Examples 1 to 4, the saturated diols used in Examples 1 to 4 are ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, and hexylene glycol, and the yields of vinylene carbonate obtained in Examples 1 to 4 are all higher than 92%, and the product purity is greater than 96wt%. Compared with Comparative Examples 1 to 2, the product purity and yield of Examples 2 to 4 are significantly improved, so the saturated diols in this application can be selected when the boiling point and viscosity are appropriate, for example, saturated diols of C2 to C6 are selected.

[0063] In combination with Example 1 and Example 5, ethylene chlorocarbonate is added dropwise in Example 1, and ethylene chlorocarbonate is added directly and quickly in Example 5. In the test results, the product purity and the quality of the obtained product in Example 1 are greater than those in Example 5, and the product yield in Example 1 is significantly higher than that in Example 5. Therefore, the preparation method of the present application continuously drops the raw materials under high vacuum and continuously evaporates the product, so that the residence time of the product in the kettle is greatly shortened, the risk of product polymerization and decomposition is reduced, and the yield is significantly improved.

[0064] Example 1 and Examples 21 to 24 compare and study the effect of the addition time of chloroethylene carbonate on the reaction process, wherein the addition time of Example 21 is 0.5h, the addition time of Example 22 is 1h, the addition time of Example 23 is 4h, and the addition time of Example 24 is 5h. In the test results, the yields are from high to low in the order of Example 23, Example 1, Example 24, Example 22, and Example 21, and the product purities are from high to low in the order of Example 1, Example 23, Example 24, Example 22, and Example 21. Combined with the reaction time and the actual purity value and yield value, when the addition time of Example 24 is extended, although the product yield and purity of Example 24 are better than those of Examples 22 and 21, they are not better than those of Examples 1 and 23 to bring about a high efficiency improvement, so the addition time in this application is preferably 1 to 4h.

[0065] In combination with Example 1 and Examples 6-7, a comparative study was conducted on the effect of the environmental vacuum degree when chloroethylene carbonate was separated in the preparation method of the present application. The vacuum degree of Example 1 was 5 Torr, the vacuum degree of Example 6 was 2 Torr, and the vacuum degree of Example 10 was 10 Torr. The yields of Examples 1 and Examples 6-7 were all higher than 92%, and the purities were all greater than 96wt%. The yields of Example 1 and Example 7 were equal to and better than Example 6, and the product purity of Example 1 and Example 6 was similar to and better than Example 7. Therefore, the vacuum degree has different trends on the product purity and product yield. In the present application, the selection range of the environmental vacuum degree when chloroethylene carbonate is separated is 2-10 Torr.

[0066] In combination with Example 1 and Examples 8 to 11, a comparative study was conducted on the effect of reaction temperature on the separation of chloroethylene carbonate in the preparation method of the present application. The reaction temperature of Example 1 was 65°C, the reaction temperature of Example 8 was 40°C, the reaction temperature of Example 9 was 50°C, the reaction temperature of Example 10 was 80°C, and the reaction temperature of Example 11 was 95°C. The yields in the test results were as follows: Example 1, Example 10, Example 9, Example 11, and Example 8 from high to low, and the product purities were as follows: Example 10, Example 1, Example 9, Example 8, and Example 11 from high to low, so the reaction temperature of 50 to 80°C in the present application is better.

[0067] In combination with Example 1 and Examples 12 to 15, a comparative study was conducted on the effect of the molar ratio of the reaction of ethylene chloride carbonate and ethylene glycol dialkali metal salt in the preparation method of the present application. In Example 1, the molar ratio of the reaction of ethylene chloride carbonate and ethylene glycol dialkali metal salt was 1:0.566, in Example 12, the molar ratio of the reaction of ethylene chloride carbonate and ethylene glycol dialkali metal salt was 1:0.5, in Example 13, the molar ratio of the reaction of ethylene chloride carbonate and ethylene glycol dialkali metal salt was 1:0.54, in Example 14, the molar ratio of the reaction of ethylene chloride carbonate and ethylene glycol dialkali metal salt was 1:0.6, and in Example 15, the molar ratio of the reaction of ethylene chloride carbonate and ethylene glycol dialkali metal salt was 1:0.7.

[0068] In the test results, the yields from high to low are Example 1, Example 14, Example 13, Example 15, and Example 12, and the product purities from high to low are Example 1, Example 14, Example 15, Example 13, and Example 12. Combined with the reaction time and the actual purity value and yield value, when the amount of ethylene glycol dialkali metal salt is increased in Example 15, although the purity of Example 15 is better than that of Example 13, the yield of Example 15 is lower than that of Example 1, Example 14, and Example 13, and the purity of the example is lower than that of Example 1 and Example 14. Therefore, considering the cost, the molar ratio of ethylene chloride carbonate to ethylene glycol dialkali metal salt in the present application is 1:(0.54-0.6) which is better.

[0069] In combination with Example 1 and Examples 16 to 19, a comparative study was conducted on the effect of the mass ratio of ethylene chloride carbonate to saturated diol solvent. The saturated diol solvent was used as the reaction phase system and solvent. In Example 1, the mass ratio of ethylene chloride carbonate to saturated diol solvent was 1:3.04, in Example 16, the mass ratio of ethylene chloride carbonate to saturated diol solvent was 1:2, in Example 17, the mass ratio of ethylene chloride carbonate to saturated diol solvent was 1:2.5, in Example 18, the mass ratio of ethylene chloride carbonate to saturated diol solvent was 1:3.5, and in Example 19, the mass ratio of ethylene chloride carbonate to saturated diol solvent was 1:4.

[0070] In the test results, the yields from high to low are Example 1, Example 17, Example 18, Example 19, and Example 16, and the product purities from high to low are Example 1, Example 19, Example 18, Example 17, and Example 16. Combined with the reaction time and the actual purity and yield values, when the amount of saturated diol solvent is increased in Example 19, the product yield of Example 19 is better than that of Example 16 but lower than that of Examples 1, 17, and 18. The product purity of Example 19 is better than that of Example 18 but lower than that of Example 1. Taking into account the mass ratio of ethylene chloride to saturated diol solvent in this application of 1:(2.5-3.5) is better.

[0071] The specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, as long as they are within the scope of protection required by the present invention, they are protected by the patent law.

Claims

1. A method for preparing vinylene carbonate, characterized in that: Using saturated diol as solvent, vinyl chloride carbonate and ethylene glycol dialkali metal salt react to obtain crude vinylene carbonate, and high-purity vinylene carbonate can be obtained after distillation and crystallization of the crude vinylene carbonate.

2. The method for preparing vinylene carbonate according to claim 1, characterized in that: The specific steps of the reaction of ethylene chlorocarbonate and ethylene glycol dialkali metal salt are as follows: Ethylene glycol dialkali metal salt and saturated diol are mixed uniformly to obtain liquid phase A, and chloroethylene carbonate is added dropwise to liquid phase A to evaporate vinylene carbonate during the reaction. After the addition is completed and the reaction is continued until no distillate is produced, the reaction is stopped to obtain a crude vinylene carbonate product.

3. The method for preparing vinylene carbonate according to claim 2, wherein: When vinyl chloride carbonate is added dropwise, the temperature of the reaction system is 50-80°C; the vacuum degree is 5-10 Torr.

4. The method for preparing vinylene carbonate as an electrolyte additive according to claim 2, characterized in that: The addition time of ethylene chloride carbonate is controlled within 1 to 4 hours.

5. The method for preparing vinylene carbonate according to claim 1, characterized in that: The molar ratio of the ethylene chloride carbonate to the ethylene glycol dialkali metal salt is 1:(0.54-0.6).

6. The method for preparing vinylene carbonate according to claim 1, characterized in that: The mass ratio of the ethylene chloride carbonate to the saturated diol solvent is 1:(2.5-3.5).

7. The method for preparing vinylene carbonate according to claim 1, wherein: The ethylene glycol dialkali metal salt is prepared by reacting ethylene glycol with an alkali metal hydroxide.

8. A method for preparing vinylene carbonate according to claim 7, characterized in that: The preparation method of the ethylene glycol dialkali metal salt is as follows: Ethylene glycol and mesitylene solvents are mixed, and alkali metal hydroxide is added under nitrogen protection, heated to react, and water is separated by reflux at normal pressure. When no water is separated, reduced pressure distillation is started to evaporate mesitylene to obtain crude ethylene glycol dialkali metal salt, which is then beaten with solvent, filtered and dried in vacuum to obtain ethylene glycol dialkali metal salt.

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