A method for solvent-free preparation of vinylene carbonate

Abstract

The application provides a method for preparing vinylene carbonate without solvent. The method comprises the following steps: mixing chlorovinyl carbonate with a catalyst, heating to a reaction temperature, introducing a protective gas, and carrying out a dechlorination reaction; after the reaction is completed, filtering the reaction solution, and subjecting the filtrate to rectification, crystallization and melting to obtain vinylene carbonate; the catalyst is a supported Schiff base metal complex catalyst, which comprises an A12O3 carrier and an active component supported on the carrier, and the active component is one or more of Cu(II) Schiff base complex, Mn(II) Schiff base complex and Co(II) Schiff base complex. The method has the characteristics of high selectivity, high product conversion rate, low energy consumption and low discharge amount of three wastes; the reaction condition is mild, and the method has the characteristics of high activity, high selectivity, few side reactions, high yield, simple post-treatment, recyclable catalyst and green production process.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery electrolyte additive technology, specifically relating to a solvent-free method for preparing vinylene carbonate. Background Technology

[0002] Lithium-ion batteries are one of the most widely used chemical energy storage methods, and are already extensively applied in consumer digital electronic devices, new energy vehicles, energy storage base stations, aerospace, and military equipment. Electrolyte, as a crucial material in lithium-ion batteries, directly determines the battery's energy density, power density, cycle life, safety performance, and wide operating temperature range, ensuring the high voltage and high specific energy of lithium-ion batteries. It is generally formulated by mixing high-purity organic solvents, electrolytes, and additives in specific proportions under certain conditions. Additives, in particular, are characterized by small dosages and significant effects, changing production efficiency with minimal increase in production costs.

[0003] Vinyl carbonate (VC) is a core additive in the electrolyte, capable of forming a solid electrolyte interphase (SEI) film on the negative electrode surface during the initial charge-discharge cycle of a lithium-ion battery through an electrochemical reaction. The SEI film separates the electrode material from the electrolyte, allowing lithium ions to transport within it and enter the electrode surface for insertion or extraction. Conversely, the SEI film also prevents the passage of solvent molecules from the electrolyte, effectively preventing co-intercalation and avoiding damage to the electrode material caused by solvent molecule co-intercalation. This film exhibits stable electrochemical performance and effectively inhibits solvent molecule intercalation, thereby preventing solvation reactions in the electrode material and the resulting performance degradation during battery cycling.

[0004] Currently, the main methods for synthesizing vinylene carbonate are: (1) using chloroethylene carbonate as a raw material to undergo a dechlorination reaction to obtain vinylene carbonate; and (2) using ethylene carbonate as a raw material to obtain vinylene carbonate by heating with a catalyst to remove hydrogen. The first method is the most commonly used method. The selection of dehalogenating agents during the dechlorination process is the research focus of preparing vinylene carbonate from chloroethylene carbonate. Currently, commonly used dehalogenating agents include alkali metal hydroxides, ammonia, triethylamine, pyridines and other acid-binding agents, supported catalysts such as metal oxides, chlorides, sulfates, etc., and quaternary ammonium ion exchange resins, etc. For example, Sun Yuhan et al. first added chloroethylene carbonate and ethylene carbonate to a reaction flask, raised the water bath temperature to 50°C, and then added sodium hydroxide solution (the molar ratio of ethylene carbonate to sodium hydroxide was 1:1.5), controlling the addition to be completed within 15 minutes. The reaction was then continued at the temperature for 2 hours. The crude product was then subjected to vacuum distillation, and ethylene carbonate was finally obtained in a yield of 70%. Although this method can greatly shorten the reaction time, it generates more byproducts, and the method cannot fully utilize the role of inorganic bases. Wang Xiaolong et al. mixed chloroethylene carbonate with ethyl acetate, then added a composite metal catalyst consisting of copper oxide, zinc oxide, and nickel oxide in a mass ratio of 5:4:1, and triethylamine. The reaction was carried out at 0°C for 5 hours to produce crude ethylene carbonate. The reaction solution was filtered, and the filter residue was washed with hexane and stirred. After centrifugation, the crystals were freeze-dried under vacuum to obtain ethylene carbonate in 90% yield. The use of composite metals can reduce the reaction time and increase the product yield, but the production cost is too high, making it unsuitable for industrial production. Chinese patent document CN111808064A discloses a method for preparing vinylene carbonate, including the following steps: mixing chloroethylene carbonate and a catalyst, heating to a set temperature, and then bubbling the reaction under nitrogen conditions. The byproduct is hydrogen chloride. After the reaction is completed, the reaction solution is filtered, the filtrate is distilled, the fraction is collected, and the collected fraction is crystallized to obtain vinylene carbonate. The catalyst is iron oxide-alumina-titanium oxide nanofibers. However, iron oxide-alumina-titanium oxide nanofibers are brittle, and their stability decreases with increasing temperature, resulting in a lower recycling rate. Further research and exploration are needed for industrial production.

[0005] Therefore, researching and developing new methods for synthesizing vinylene carbonate to obtain environmentally friendly, safe, high-yield, and high-purity vinylene carbonate products is of great significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a solvent-free method for preparing vinylene carbonate. The method of this invention features mild reaction conditions, high product yield, and is free of solvents and amine residues, thus reducing production costs and making it suitable for industrial applications.

[0007] The technical solution of the present invention is as follows:

[0008] A solvent-free method for preparing vinylene carbonate includes the following steps:

[0009] After mixing chloroethylene carbonate with the catalyst, the mixture is heated to the reaction temperature and a protective gas is introduced to carry out the dechlorination reaction. After the reaction is completed, the reaction solution is filtered, and the filtrate is distilled, crystallized, and melted to obtain vinylene carbonate. The catalyst is a supported Schiff base metal complex catalyst, comprising an Al2O3 support and an active component supported on the support. The active component is one or more of Cu(II) Schiff base complex, Mn(II) Schiff base complex, and Co(II) Schiff base complex.

[0010] According to a preferred embodiment of the present invention, the active component is a Mn(II) Schiff base complex.

[0011] According to a preferred embodiment of the present invention, the catalyst is prepared by the following method:

[0012] (1) Preparation of Schiff base complexes

[0013] Under stirring conditions, acetylacetone was added dropwise to an ethanol solution of 1,2-bis(o-aminophenoxy)ethane. After the addition was complete, the mixture was refluxed at 90–100 °C for 8–12 h. After the reaction was completed, the solvent was removed from the resulting reaction solution, and the resulting solid was recrystallized from ethanol and dried under vacuum to obtain a Schiff base complex.

[0014] (2) Preparation of active components

[0015] An ethanol solution of a metal chloride, wherein the metal chloride is one or more of CuCl2, MnCl2, and CoCl2, is added dropwise to a chloroform solution of a Schiff base complex. After the addition is complete, the mixture is left at room temperature for 8-10 days, filtered, and dried to obtain the metal Schiff base complex, which is the active component.

[0016] (3) Catalyst preparation

[0017] Weigh out an Al2O3 support, then add water droplets to the support until it is just saturated with water, and record the volume of water used. Add the active component to the water to prepare an impregnation solution of equal volume, and add the impregnation solution droplets to the support to uniformly load the active component onto the Al2O3 support. After standing, drying, and calcining, the catalyst is obtained.

[0018] According to a preferred embodiment of the present invention, the concentration of the ethanol solution of 1,2-bis(o-aminophenoxy)ethane in step (1) is 0.03 to 0.08 mmol / mL.

[0019] According to a preferred embodiment of the present invention, the molar ratio of acetylacetone to 1,2-bis(o-aminophenoxy)ethane in step (1) is 2:1; and the dropping time of acetylacetone is 20-30 min.

[0020] According to a preferred embodiment of the present invention, the vacuum drying temperature in step (1) is 120-130°C and the vacuum drying time is 2-4 hours.

[0021] According to a preferred embodiment of the present invention, the concentration of the chloroform solution of the Schiff base complex in step (2) is 0.01–0.015 mmol / mL; the concentration of the ethanol solution of the metal chloride is 0.01–0.015 mmol / mL; and the molar ratio of the metal chloride to the Schiff base complex is 1:1.

[0022] According to a preferred embodiment of the present invention, the drying in step (2) is performed at 100-120°C for 2-3 hours.

[0023] According to a preferred embodiment of the present invention, the mass of the active component in step (3) is 10-15% of the mass of the Al2O3 support.

[0024] According to a preferred embodiment of the present invention, the standing in step (3) is to stand at 25-30°C for 6-7 hours; the drying is to dry at 100-110°C for 8-10 hours; and the calcination is to calcinate at 500-600°C for 4-6 hours.

[0025] According to a preferred embodiment of the present invention, the mass of the catalyst is 2 to 8% of the mass of ethylene chlorocarbonate, more preferably 4 to 6%.

[0026] According to a preferred embodiment of the present invention, the reaction temperature is 40–60°C.

[0027] According to a preferred embodiment of the present invention, the protective gas is nitrogen or argon, more preferably nitrogen; the flow rate of the protective gas is 1.0–4.0 m³ / s. 3 / h.

[0028] According to a preferred embodiment of the present invention, the dechlorination reaction time is 4 to 6 hours, more preferably 4.5 to 5 hours.

[0029] According to a preferred embodiment of the present invention, the distillation is vacuum distillation, with a distillation pressure of 10-20 kPa and a temperature of 55-70°C; that is, the fraction obtained during the distillation process at 55-70°C / 10-20 kPa is the crude product, vinylene carbonate.

[0030] According to a preferred embodiment of the present invention, the crystallization temperature is 12-15°C; and the melting temperature is 30-40°C.

[0031] According to the present invention, the obtained vinylene carbonate is a high-purity electronic-grade product.

[0032] The technical features and beneficial effects of this invention are as follows:

[0033] Compared with existing technologies, this invention has the following advantages: The method of this invention uses a specific type of catalyst, which can improve reaction selectivity, increase product conversion rate, and reduce energy consumption and emissions of waste gas, wastewater, and solid waste; using Schiff alkali metal complexes as catalysts results in mild reaction conditions, making it particularly suitable for temperature-sensitive compounds such as vinylene carbonate; the method of this invention features high activity, high selectivity, few side reactions, and high yield; the method of this invention has simple post-processing, and the catalyst can be recycled multiple times, making production green and environmentally friendly. Furthermore, the catalyst has low corrosiveness to reaction equipment, which can extend the service life of the equipment, enhance its production capacity, and save production costs. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the content therein is for illustrative purposes only and is not intended to limit the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally carried out under conventional conditions or as recommended by the manufacturer.

[0035] Preparation Example 1

[0036] The catalyst preparation method includes the following steps:

[0037] (1) Preparation of active components

[0038] 20 mL of an ethanol solution of 1,2-bis(o-aminophenoxy)ethane with a concentration of 0.05 mmol / mL was added to the reaction flask. 2 mmol of acetylacetone was slowly added dropwise with stirring over a period of 25 min. After the addition was complete, the mixture was refluxed at 94 °C for 10 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The solvent was removed by rotary evaporation. The residue was recrystallized from ethanol and dried under vacuum at 128 °C for 2 h to obtain a white solid, which was the Schiff base complex.

[0039] Add 10 mL of a chloroform solution of the Schiff base complex with a concentration of 0.01 mmol / mL to the reaction flask, and slowly add 10 mL of an ethanol solution of 0.01 mmol / mL MnCl2 with stirring over a period of 12 min. After the addition is complete, let it stand at room temperature for 10 days. Filter the solution, and dry the filter cake at 120 °C for 2 h to obtain colorless crystals, which are the Mn(II) Schiff base complex.

[0040] (2) Preparation of catalyst

[0041] Weigh 10g of Al2O3 support, then slowly add distilled water dropwise to the support until the support is saturated with water, using a volume of 15mL of distilled water; add 0.12g of Mn(II) Schiff base complex to water to prepare 15mL of impregnation solution, and add the obtained impregnation solution dropwise to 10g of Al2O3 support to uniformly load the active component onto the Al2O3 support; after standing at 25℃ for 6h, place it in an oven and dry at 110℃ for 8h, then place it in a muffle furnace and calcine at 550℃ for 5h to obtain the supported Schiff base metal complex catalyst, denoted as the Mn / Al2O3 Schiff base metal complex.

[0042] Preparation Example 2

[0043] The catalyst was prepared as described in Preparation Example 1, except that MnCl2 was replaced with CoCl2 in step (1), and the resulting catalyst was denoted as a Schiff base metal complex of Co / Al2O3.

[0044] Preparation Example 3

[0045] The catalyst was prepared as described in Preparation Example 1, except that MnCl2 was replaced with CuCl2 in step (1), and the resulting catalyst was denoted as a Schiff base metal complex of Cu / Al2O3.

[0046] Preparation Example 4

[0047] The catalyst was prepared as described in Preparation Example 1, except that MnCl2 was replaced with NiCl2 in step (1), and the resulting catalyst was denoted as a Ni / Al2O3 Schiff base metal complex.

[0048] Example 1

[0049] A solvent-free method for preparing vinylene carbonate includes the following steps:

[0050] Add 3.7g of catalyst (a Schiff metal complex of Mn / Al₂O₃) to 123.6g of ethylene chloride carbonate (80wt% purity), heat to 50°C, and then purge with nitrogen gas at a rate of 3m³ / h. 3 A continuous flow rate of / h was introduced, and the reaction was carried out for 4.5h. After the reaction, the mixture was filtered, and the filtrate was subjected to vacuum distillation to collect the fraction at 55-70℃ under a distillation pressure of 10-20 kPa. The distillate was cooled to 12-15℃ and crystallized. After no crystals precipitated, the mixture was filtered. The crystals were completely dissolved at 35℃ to obtain 58.8g of colorless and transparent vinylene carbonate liquid with a purity of 99.9%, a water content of 3ppm, and a yield of 84.7%.

[0051] The yield was calculated as follows: mass of vinylene carbonate / (mass of chloroethylene carbonate * purity / 122.51 * 86.05) * 100%, the same applies below.

[0052] Example 2

[0053] A solvent-free method for preparing vinylene carbonate includes the following steps:

[0054] 8.4 g of catalyst (a Schiff metal complex of Mn / Al₂O₃) was added to 168.4 g of ethylene chloride carbonate (80 wt% purity), heated to 50 °C, and nitrogen gas was introduced at a rate of 3 m³ / s. 3 A continuous flow rate of / h was introduced, and the reaction was carried out for 4.5h. After the reaction, the mixture was filtered, and the filtrate was subjected to vacuum distillation to collect the fraction at 55-70℃ under a distillation pressure of 10-20 kPa. The fraction obtained from distillation was cooled to 12-15℃ for crystallization. After no crystals precipitated, the mixture was filtered. The crystals were completely dissolved at 35℃ to obtain 84.4g of colorless and transparent vinylene carbonate liquid with a purity of 99.9%, a water content of 2ppm, and a yield of 89.2%.

[0055] Example 3

[0056] A solvent-free method for preparing vinylene carbonate is described in Example 1, except that the mass of the catalyst is 7% of the mass of chloroethylene carbonate.

[0057] The vinylene carbonate product obtained in this example has a purity of 99.9%, a moisture content of 2 ppm, and a yield of 85.1%.

[0058] Example 4

[0059] A solvent-free method for preparing vinylene carbonate is described in Example 2, the difference being that a Schiff base metal complex of Co / Al2O3 is used as the catalyst, resulting in vinylene carbonate with a purity of 99.7%, a water content of 8 ppm, and a yield of 87.6%.

[0060] Example 5

[0061] A solvent-free method for preparing vinylene carbonate is described in Example 2, the difference being that a Cu / Al₂O₃ Schiff base metal complex is used as the catalyst, resulting in vinylene carbonate with a purity of 99.3%, a water content of 5 ppm, and a yield of 84.5%.

[0062] Comparative Example 1

[0063] A solventless method for preparing vinylene carbonate is described in Example 2, the difference being that: instead of using a Schiff base metal complex of Mn / Al2O3 as the catalyst, a composite metal catalyst consisting of copper oxide, zinc oxide, and nickel oxide in a mass ratio of 5:4:1 is used, resulting in vinylene carbonate with a purity of 98.2% and a yield of 77.6%.

[0064] Comparative Example 2

[0065] A solvent-free method for preparing vinylene carbonate is described in Example 2, the difference being that a Ni / Al2O3 Schiff base metal complex is used as the catalyst, resulting in vinylene carbonate with a purity of 98.4%, a water content of 10 ppm, and a yield of 81.8%.

[0066] Comparative Example 3

[0067] A solvent-free method for preparing vinylene carbonate is described in Example 2, the difference being that: the amount of catalyst used is 16.8 g, the purity of the vinylene carbonate obtained is 98.7%, and the yield is 78.3%.

[0068] Comparative Example 4

[0069] A solvent-free method for preparing vinylene carbonate is described in Example 2, the difference being that Al2O3 is used as the catalyst and the raw materials in this comparative example are essentially unreacted.

[0070] Comparative Example 5

[0071] A solvent-free method for preparing vinylene carbonate is described in Example 2, the difference being that no catalyst is added; in this comparative example, no catalyst is added so that the raw materials cannot react.

[0072] The present invention has been described in detail above to explain some of its features. Its purpose is to enable those skilled in the art to understand and implement the content of the present invention. However, it should not be construed as limiting the scope of protection of the present invention. Moreover, the present invention is not limited to the above-described embodiments. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A solvent-free method for preparing vinylene carbonate, comprising the following steps: Vinyl chlorinated carbonate was mixed with a catalyst and heated to the reaction temperature. A protective gas was introduced to carry out the dechlorination reaction. After the reaction was completed, the reaction solution was filtered, and the filtrate was distilled, crystallized, and melted to obtain vinylene carbonate. The catalyst was a supported Schiff base metal complex catalyst, including an Al2O3 support and an active component supported on the support. The active component was one or more of Cu(II) Schiff base complex, Mn(II) Schiff base complex, and Co(II) Schiff base complex. The catalyst was prepared according to the following method: (1) Preparation of Schiff base complexes Under stirring conditions, acetylacetone was added dropwise to an ethanol solution of 1,2-bis(o-aminophenoxy)ethane. After the addition was complete, the mixture was refluxed at 90-100°C for 8-12 hours. After the reaction was completed, the solvent was removed from the resulting reaction solution, and the resulting solid was recrystallized from ethanol and dried under vacuum to obtain a Schiff base complex. (2) Preparation of active components An ethanol solution of a metal chloride, wherein the metal chloride is one or more of CuCl2, MnCl2, and CoCl2, is added dropwise to a chloroform solution of a Schiff base complex. After the addition is complete, the mixture is left at room temperature for 8-10 days, filtered, and dried to obtain the metal Schiff base complex, which is the active component. (3) Preparation of catalyst Weigh out an Al2O3 support, then add water droplets to the support until it is just saturated with water, and record the volume of water used. Add the active component to the water to prepare an impregnation solution of equal volume, and add the impregnation solution droplets to the support to uniformly load the active component onto the Al2O3 support. After standing, drying, and calcining, the catalyst is obtained.

2. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The active component is a Mn(II) Schiff base complex.

3. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The concentration of the ethanol solution of 1,2-bis(o-aminophenoxy)ethane in step (1) is 0.03~0.08 mmol / mL; The molar ratio of acetylacetone to 1,2-bis(o-aminophenoxy)ethane is 2:1; the dropping time of acetylacetone is 20-30 min. The vacuum drying temperature is 120~130℃, and the vacuum drying time is 2~4h.

4. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, In step (2), the concentration of the chloroform solution of the Schiff base complex is 0.01~0.015 mmol / mL; the concentration of the ethanol solution of the metal chloride is 0.01~0.015 mmol / mL; the molar ratio of the metal chloride to the Schiff base complex is 1:1; and the drying is carried out at 100~120℃ for 2~3 hours.

5. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The mass of the active component in step (3) is 10-15% of the mass of the carrier; The standing period is 6-7 hours at 25-30°C; the drying period is 8-10 hours at 100-110°C; and the calcination period is 4-6 hours at 500-600°C.

6. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The mass of the catalyst is 2-8% of the mass of chloroethylene carbonate.

7. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The mass of the catalyst is 4 to 6% of the mass of chloroethylene carbonate.

8. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The reaction temperature is 40~60℃; the protective gas is nitrogen or argon; the flow rate of the protective gas is 1.0~4.0 m³ / s. 3 / h.

9. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The dechlorination reaction takes 4 to 6 hours.

10. The method for preparing vinylene carbonate without solvent according to claim 1, characterized in that, The distillation is a vacuum distillation, with a pressure of 10~20 kPa and a temperature of 55~70℃; the crystallization temperature is 12~15℃; and the melting temperature is 30~40℃.