A process for the preparation of 2,2-difluoroethyl acetate

Abstract

The application discloses a preparation method of acetic acid 2,2-difluoroethyl ester and belongs to the technical field of battery electrolyte additives. The application takes alkali metal acetate and 2,2-difluoro-1-chloroethane as reaction raw materials, prepares acetic acid 2,2-difluoroethyl ester in dimethyl sulfoxide, and then adopts a post-treatment process of extracting the reaction liquid first and then distilling, so that the problem that the interaction between dimethyl sulfoxide and the product is difficult to distill is effectively avoided, and problems, such as the decomposition of dimethyl sulfoxide at high temperature to reduce the purity of the product and the combination of the decomposition product and the product, are also avoided. Meanwhile, the reaction condition of the application is mild, the operation is simple, a complex catalytic system is not needed, and the application does not depend on specific reaction equipment, so the application has a good large-scale industrial production prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing 2,2-difluoroethyl acetate, belonging to the field of battery electrolyte additive technology. Background Technology

[0002] With the rapid development of electric vehicles, higher energy density, wider operating temperature range, better safety, higher rate performance, and lower price are the main development directions for lithium batteries in the future. Fluorinated solvents are excellent battery electrolyte additives. They form a thin and flexible solid electrolyte interphase (SEI) film in lithium batteries, which can better withstand the shrinkage and expansion of the battery caused by lithium deposition and lithium extraction during battery cycling. Furthermore, the SEI surface film formed by fluorinated solvents ensures uniform, dendrite-free lithium deposition, thereby ensuring the reversible behavior of the lithium anode and improving the short circuit caused by lithium dendrite growth piercing the separator.

[0003] 2,2-Difluoroethyl acetate (FEA) is an important fluorinated compound with wide applications and promising prospects in pharmaceutical intermediates, as a catalyst for cyclization, oxidation, and halogenation reactions. It is particularly valuable in agricultural chemistry and pharmaceuticals, possessing a broad range of applications and a promising market outlook. 2,2-Difluoroethyl acetate is a fluorinated solvent with a boiling point of 105℃ and a density of 1.203 g / cm³. 3 Its high boiling point and density allow it to maintain a stable physical state at high temperatures, thus contributing to improved high-temperature cycle performance of batteries. As an additive in battery electrolytes, 2,2-difluoroethyl acetate can significantly improve the charge-discharge efficiency, cycle performance, and capacity retention of lithium batteries. In high-performance lithium-ion batteries, 2,2-difluoroethyl acetate can replace the traditional methyl ethyl fluoride solvent, improving electrolyte conductivity and capacity retention. Therefore, its synthesis process is crucial for the effective development and utilization of 2,2-difluoroethyl acetate.

[0004] Chinese invention patent application CN113698295A, published on November 26, 2021, discloses a method for synthesizing 2,2-difluoroethyl acetate, which involves reacting 2,2-difluoroethanol with acetyl chloride via an acylation reaction in the presence of an acid scavenger. While the reaction process is simple and mild, the reactant acetyl chloride is highly susceptible to hydrolysis in water and is chemically unstable, requiring immediate preparation and use, leading to complex operations and potential waste.

[0005] Chinese invention patent application CN116003252A, published on April 25, 2023, discloses a method and apparatus for preparing difluoroethyl acetate. The preparation method includes the following steps: adding acetate to a reaction vessel and evacuating the vacuum; adding excess 2,2-difluoro-1-haloethane, heating and maintaining the temperature for reaction; after the reaction is complete, introducing the gaseous material into a distillation column, collecting the unreacted 2,2-difluoro-1-haloethane at the top of the column for reuse; collecting crude difluoroethyl acetate at the bottom of the column; after collection, cooling the reaction vessel to room temperature and releasing the solid potassium chloride inside the reaction vessel. This preparation method does not use any solvent, produces few byproducts, has simple reaction components, and facilitates the purification of the target product. However, the reaction depends on the relevant reaction apparatus, and the requirements for the airtightness and pressure resistance of the reaction apparatus are high, which is not conducive to large-scale promotion and application.

[0006] Chinese invention patent application CN116969837A, published on October 31, 2023, discloses a method for preparing electronic-grade 2,2-difluoroethyl acetate. The method uses 2-chloro-1,1-difluoroethane (R142) as a raw material and potassium acetate as a base, and involves a high-temperature reaction in a dimethyl sulfoxide solvent. After the reaction, 2,2-difluoroethyl acetate is obtained by distillation. The reaction temperature is 120°C, higher than the boiling point of 2-chloro-1,1-difluoroethane. This means that R142 participates in the reaction in a gaseous state, which can easily lead to raw material leakage. Furthermore, the method requires high airtightness and pressure resistance of the reaction apparatus, hindering large-scale application.

[0007] Chinese invention patent application CN119591498A, published on March 11, 2025, discloses a method for synthesizing 2,2-difluoroethyl acetate. In this method, 2-chloro-1,1-difluoroethane, an alkali metal acetate, and a solvent undergo a continuous reaction at a temperature of 140–200°C under the catalysis of a reaction catalyst. The crude product is then subjected to solid-liquid separation and distillation to obtain 2,2-difluoroethyl acetate. This synthesis method is simple and easy to operate, and produces 2,2-difluoroethyl acetate with high purity. However, it requires the addition of a special catalyst and involves a relatively high reaction temperature, increasing the energy consumption, reaction steps, and production cost of the synthesis process. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing 2,2-difluoroethyl acetate, and to provide a method for obtaining high-purity 2,2-difluoroethyl acetate.

[0009] To achieve the above objectives, the technical solution adopted in the preparation method of 2,2-difluoroethyl acetate in this invention is as follows: A method for preparing 2,2-difluoroethyl acetate includes the following steps: (1) 2,2-Difluoro-1-chloroethane and an alkali metal acetate react in dimethyl sulfoxide under an inert gas atmosphere; (2) Separate the solid and liquid phases of the reaction liquid completed in step (1). Extract the liquid with an organic solvent and water. Detect whether the organic phase contains dimethyl sulfoxide. If there is no dimethyl sulfoxide residue, distill the organic phase to obtain 2,2-difluoroethyl acetate. If the organic phase contains dimethyl sulfoxide, distill off part of the organic solvent in the organic phase and add water for extraction again. Distill the obtained organic phase to obtain 2,2-difluoroethyl acetate. The dimethyl sulfoxide is not miscible with the organic solvent. The organic solvent is a good solvent for 2,2-difluoroethyl acetate and is not miscible with water.

[0010] The beneficial effects of the above scheme are as follows: The method for preparing 2,2-difluoroethyl acetate of the present invention is a pioneering invention. The present invention uses metal acetate and 2,2-difluoro-1-chloroethane as reactants to prepare 2,2-difluoroethyl acetate in dimethyl sulfoxide. The subsequent post-treatment process of extraction followed by distillation of the reaction solution effectively avoids the problem of interaction between dimethyl sulfoxide and the product, which makes distillation difficult. It also avoids the problems of reduced product purity due to the decomposition of dimethyl sulfoxide during high-temperature distillation and the combination of decomposition products with the product. Furthermore, the reaction conditions of the present invention are mild, the operation is simple, no complex catalytic system is required, and it does not rely on specific reaction equipment, thus possessing good prospects for large-scale industrial production.

[0011] As a further improvement, the organic solvent is methyl tert-butyl ether or n-hexane.

[0012] As a further improvement, the volume ratio of organic solvent to water in step (2) is 1:(1~1.2).

[0013] As a further improvement, the volume ratio of dimethyl sulfoxide to organic solvent in step (1) is 1:(2~2.5).

[0014] As a further improvement, the partial distillation is 1 / 2 to 2 / 3 of the original volume of the distilled organic solvent; the volume ratio of the added water to the dimethyl sulfoxide in step (1) is (0.8-1):1.

[0015] As a further improvement, in step (1), 5 to 7 mL of dimethyl sulfoxide is used for each gram of the 2,2-difluoro-1-chloroethane.

[0016] As a further improvement, the alkali metal acetate mentioned in step (1) is one of sodium acetate, potassium acetate, and lithium acetate.

[0017] As a further improvement, the molar ratio of the 2,2-difluoro-1-chloroethane to the alkali metal acetate is 1:(1.1~2).

[0018] As a further improvement, the reaction in step (1) is carried out at a temperature of 100-120°C for 4-8 hours. Attached Figure Description

[0019] Figure 1 This is the NMR spectrum of the colorless and transparent liquid obtained in Example 5 of the present invention. Detailed Implementation

[0020] Lithium-ion batteries are currently the most common energy storage devices, offering higher capacity and more stable performance compared to traditional batteries. The key factors influencing lithium-ion battery performance lie in the various properties of the organic electrolyte. 2,2-Difluoroethyl acetate (FEA) is an important fluorine-containing compound. In battery manufacturing, electrolyte additives containing FEA are added to the electrolyte to increase the hydrogen ion concentration, thereby reducing losses during energy conversion.

[0021] Currently, the method for preparing 2,2-difluoroethyl acetate via acylation of 2,2-difluoroethanol and acetyl chloride as reactants under the action of an acid scavenger is complex and the reactants are easily hydrolyzed in water, making it unsuitable for industrial production. The method using 2,2-difluoroethyl acetate and alkali metal acetates as reactants requires high airtightness and pressure resistance of the reaction apparatus and relies on specially prepared catalysts, increasing production costs and hindering large-scale application. Furthermore, preliminary research revealed that existing technologies directly distill the reaction solution after the reaction, but numerous experiments have shown that high temperatures introduce new impurities, leading to a decrease in the purity of the final 2,2-difluoroethyl acetate.

[0022] Based on this, the present invention provides a method for preparing 2,2-difluoroethyl acetate, using 2,2-difluoro-1-chloroethane and an alkali metal acetate as reactants, reacting them in dimethyl sulfoxide to prepare 2,2-difluoroethyl acetate; then, using an organic solvent that is immiscible with dimethyl sulfoxide but has good solubility in 2,2-difluoroethyl acetate and water, the reaction solution is first extracted, during which 2,2-difluoroethyl acetate is extracted into the organic phase by the organic solvent, while dimethyl sulfoxide dissolves in water to form an aqueous phase; finally, the extracted organic phase is distilled to obtain 2,2-difluoroethyl acetate with high purity.

[0023] The organic solvent is methyl tert-butyl ether or n-hexane; preferably, the organic solvent is methyl tert-butyl ether.

[0024] The alkali metal acetate is one of sodium acetate, potassium acetate, and lithium acetate; to improve the conversion rate of the reactants and the yield of the products, it is further preferred that the alkali metal acetate is potassium acetate.

[0025] The molar ratio of 2,2-difluoro-1-chloroethane to the alkali metal acetate is 1:(1.1~2); to improve the conversion rate of the reactants and the yield of the products, more preferably, the molar ratio of 2,2-difluoro-1-chloroethane to the alkali metal acetate is 1:1.5.

[0026] The reaction temperature is 100-120℃ and the reaction time is 4-8h; to improve the conversion rate of reactants and the yield of products, the reaction temperature is more preferably 110℃ and the reaction time is 6h.

[0027] The present invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the equipment and reagents used in the embodiments, experimental examples and comparative examples are all commercially available.

[0028] Specific embodiments of the preparation method of 2,2-difluoroethyl acetate according to the present invention: Example 1 The preparation method of 2,2-difluoroethyl acetate in this embodiment is as follows: Under nitrogen protection, 25 mL of dry dimethyl sulfoxide and 6.38 g of potassium acetate were rapidly added to a 100 mL three-necked flask. The reaction system was sealed and stirred. The low-temperature circulating bath was turned on, and when the temperature rose to 110 °C, 5 g of R142 was slowly added dropwise using a constant pressure dropping funnel. The reaction was then maintained at 110 °C with stirring. After the reaction was complete (6 h), heating was stopped, and the sample was taken after cooling. After the reaction was completed, stirring was stopped, and the reaction solution was filtered. The filtrate was extracted with 50 mL of methyl tert-butyl ether and 50 mL of deionized water. If no residual dimethyl sulfoxide was found in the NMR spectrum of the organic phase, the organic phase was purified by distillation at 65 °C and atmospheric pressure. If the NMR spectrum of the organic phase contains residual dimethyl sulfoxide solvent, after distilling 2 / 3 methyl tert-butyl, the product is extracted again with 20 mL of deionized water to obtain a yellow organic phase liquid. The yellow liquid is then distilled again at 120 °C and atmospheric pressure to obtain a colorless and transparent liquid, namely pure 2,2-difluoroethyl acetate (FEA), with a yield of 63.9% and a purity of 99.8%.

[0029] Example 2 The preparation method of 2,2-difluoroethyl acetate in this embodiment is as follows: Under nitrogen protection, 100 mL of dry dimethyl sulfoxide and 29.44 g of potassium acetate were rapidly added to a 250 mL three-necked flask. The reaction system was sealed and stirred. The low-temperature circulating bath was turned on, and when the temperature rose to 110 °C, 20 g of R142 was slowly added dropwise using a constant pressure dropping funnel. The reaction was then maintained at 110 °C with stirring. After the reaction was complete (6 h), heating was stopped, and the sample was taken after cooling. After the reaction was completed, stirring was stopped, and the reaction solution was filtered. The filtrate was extracted with 200 mL of methyl tert-butyl ether and 200 mL of deionized water. If no residual dimethyl sulfoxide was found in the NMR spectrum of the organic phase, the organic phase was purified by distillation at 65 °C and atmospheric pressure. If the NMR spectrum of the organic phase contains residual dimethyl sulfoxide solvent, after distillation of 2 / 3 methyl tert-butyl ether, the product is extracted again with 80 mL of deionized water to obtain a yellow liquid organic phase. The yellow liquid is then distilled again at 120 °C and atmospheric pressure to obtain a colorless and transparent liquid, namely pure 2,2-difluoroethyl acetate (FEA), with a yield of 79.77% and a purity of 99.5%.

[0030] Example 3 The preparation method of 2,2-difluoroethyl acetate in this embodiment is as follows: Under nitrogen protection, 25 mL of dry dimethyl sulfoxide and 6.15 g of sodium acetate were rapidly added to a 100 mL three-necked flask. The reaction system was sealed and stirred. The low-temperature circulating bath was turned on, and when the temperature rose to 110 °C, 5 g of R142 was slowly added dropwise using a constant-pressure dropping funnel. The reaction was then maintained at 110 °C with stirring. After the reaction was complete (6 h), heating was stopped, and the mixture was cooled and sampled. After the reaction was completed, stirring was stopped, and the reaction solution was filtered. The purification process was the same as described in Example 1, yielding a colorless and transparent liquid, namely pure 2,2-difluoroethyl acetate (FEA), with a yield of 65.32% and a purity of 99.7%.

[0031] Example 4 The preparation method of 2,2-difluoroethyl acetate in this embodiment is as follows: Under nitrogen protection, 200 mL of dry dimethyl sulfoxide and 58.6 g of sodium acetate were rapidly added to a 500 mL three-necked flask. The reaction system was sealed and stirred. The low-temperature circulating bath was turned on, and when the temperature rose to 110 °C, 40 g of R142 was slowly added dropwise using a constant-pressure dropping funnel. The reaction was then maintained at 110 °C with stirring. After the reaction was complete (6 h), heating was stopped, and the sample was taken after cooling. After the reaction was completed, stirring was stopped, and the reaction solution was filtered. The filtrate was extracted with 400 mL of methyl tert-butyl ether and 400 mL of deionized water. If no residual dimethyl sulfoxide was found in the NMR spectrum of the organic phase, the organic phase was purified by distillation at 65 °C and atmospheric pressure. If the NMR spectrum of the organic phase contains residual dimethyl sulfoxide, after distillation of 2 / 3 methyl tert-butyl ether, the product is extracted again with 160 mL of deionized water to obtain a yellow liquid organic phase. The yellow liquid is then distilled again at 120 °C and atmospheric pressure to obtain a colorless and transparent liquid, namely pure 2,2-difluoroethyl acetate (FEA), with a yield of 72.8% and a purity of 99.6%.

[0032] Example 5 The preparation method of 2,2-difluoroethyl acetate in this embodiment is as follows: Under nitrogen protection, 500 mL of dry dimethyl sulfoxide (DMSO) and 147 g of sodium acetate were rapidly added to a 1 L three-necked flask. The reaction system was sealed and stirred. A low-temperature circulating bath was turned on, and when the temperature rose to 110 °C, 100 g of R142 was slowly added dropwise using a constant-pressure dropping funnel. The reaction was then maintained at 110 °C with stirring. After the reaction was complete (6 h), heating was stopped, and the mixture was cooled and sampled. After the reaction was finished, stirring was stopped, and the reaction solution was filtered. The filtrate was extracted with 1 L of methyl tert-butyl ether and 1 L of deionized water. If no residual DMSO was found in the NMR spectrum of the organic phase, the organic phase was purified by distillation at 65 °C and atmospheric pressure. If residual DMSO was found in the NMR spectrum of the organic phase, the product was extracted again with 400 mL of deionized water after the distillation of 2 / 3 of the DMSO, yielding a yellow liquid. The yellow liquid was then decolorized by distillation at 120 °C and atmospheric pressure to obtain a colorless and transparent liquid, which is pure 2,2-difluoroethyl acetate (FEA).

[0033] The obtained colorless and transparent liquid was analyzed by 1H NMR spectroscopy, and the results are as follows: Figure 1 As shown. Figure 1 The NMR spectrum of the colorless and transparent liquid obtained in Example 5 of this invention is shown. Calculations based on the NMR data indicate a yield of 79.3% and a purity of 99%.

[0034] Comparative Example 1 The only difference between this comparative example and Example 5 is that the reaction solution after the reaction was completed was filtered, and the filtrate was directly distilled at atmospheric pressure to obtain a product with a purity of 93.815%. The atmospheric pressure distillation oil bath temperature was 170°C. Distilling and purifying the product in the presence of a large amount of dimethyl sulfoxide (DMSO) results in the product interacting with DMSO, making it difficult to obtain a high-purity product.

[0035] Comparative Example 2 The only difference between this comparative example and Example 5 is that the reaction solution after the reaction was completed was filtered, and the filtrate was directly subjected to vacuum distillation to obtain a product with a purity of 65.37%. The atmospheric distillation temperature was 110°C and the pressure was 40 psi. Distillation purification of the product in the presence of a large amount of dimethyl sulfoxide (DMSO) results in the product interacting with DMSO, making it difficult to obtain a high-purity product.

[0036] Comparative Example 3 The only difference between this comparative example and Example 5 is that the reaction solution after the reaction was completed was filtered, and the filtrate was directly extracted with petroleum ether as the extractant. It was found that the petroleum ether phase contained a small amount of this product, while the dimethyl sulfoxide phase contained a large amount of this product. The extractant petroleum ether has low solubility for this product.

[0037] Comparative Example 4 The only difference between this comparative example and Example 2 is that acetonitrile was used as the reaction solvent (instead of dimethyl sulfoxide). After the reaction was completed, it was found that the raw material R142 was still present and no product was generated.

[0038] Comparative Example 5 The only difference between this comparative example and Example 2 is that acetone was used as the reaction solvent (instead of dimethyl sulfoxide). After the reaction was completed, it was found that the raw material R142 was still present and no product was generated.

[0039] Comparative Example 6 The only difference between this comparative example and Example 3 is that N,N-dimethylformamide was used as the reaction solvent (instead of dimethyl sulfoxide). After the reaction, the results showed that while products were formed, the reactants were not completely reacted. Extending the reaction time to 8 hours did not result in complete reaction of the reactants; the reaction almost reached equilibrium, leading to a loss of reactants.

[0040] Comparative Example 7 The only difference between this comparative example and Example 3 is that N,N-dimethylacetamide was used as the reaction solvent (instead of dimethyl sulfoxide). After the reaction, the results showed that while products were formed, the reactants were not completely reacted. Extending the reaction time to 8 hours did not result in complete reaction of the reactants; the reaction almost reached equilibrium, leading to a loss of reactants.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing 2,2-difluoroethyl acetate, characterized in that: Includes the following steps: (1) 2,2-Difluoro-1-chloroethane and an alkali metal acetate react in dimethyl sulfoxide under an inert gas atmosphere; (2) Separate the solid and liquid phases of the reaction liquid completed in step (1). Extract the liquid with an organic solvent and water. Detect whether the organic phase contains dimethyl sulfoxide. If there is no dimethyl sulfoxide residue, distill the organic phase to obtain 2,2-difluoroethyl acetate. If the organic phase contains dimethyl sulfoxide, distill off part of the organic solvent in the organic phase and add water for extraction again. Distill the obtained organic phase to obtain 2,2-difluoroethyl acetate. The dimethyl sulfoxide is not miscible with the organic solvent. The organic solvent is a good solvent for 2,2-difluoroethyl acetate and is not miscible with water.

2. The method for preparing 2,2-difluoroethyl acetate according to claim 1, characterized in that: The organic solvent is methyl tert-butyl ether or n-hexane.

3. The method for preparing 2,2-difluoroethyl acetate according to claim 1 or 2, characterized in that: In step (2), the volume ratio of organic solvent to water is 1:(1~1.2).

4. The method for preparing 2,2-difluoroethyl acetate according to claim 3, characterized in that: The volume ratio of dimethyl sulfoxide to organic solvent in step (1) is 1:(2~2.5).

5. The method for preparing 2,2-difluoroethyl acetate according to claim 1 or 2, characterized in that: The partial distillation is 1 / 2 to 2 / 3 of the original volume of the distilled organic solvent; the volume ratio of the added water to the dimethyl sulfoxide in step (1) is (0.8-1):

1.

6. The method for preparing 2,2-difluoroethyl acetate according to claim 1 or 2, characterized in that: In step (1), each gram of the 2,2-difluoro-1-chloroethane corresponds to 5-7 mL of dimethyl sulfoxide.

7. The method for preparing 2,2-difluoroethyl acetate according to claim 1 or 2, characterized in that: The alkali metal acetate mentioned in step (1) is one of sodium acetate, potassium acetate, and lithium acetate.

8. The method for preparing 2,2-difluoroethyl acetate according to claim 7, characterized in that: The molar ratio of 2,2-difluoro-1-chloroethane to alkali metal acetate is 1:(1.1~2).

9. The method for preparing 2,2-difluoroethyl acetate according to claim 1 or 2, characterized in that: The reaction in step (1) is carried out at a temperature of 100-120℃ for 4-8 hours.

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