Preparation method of fluoroethylene carbonate

Abstract

The invention discloses a preparation method of fluoroethylene carbonate, which comprises the following steps: (1) mixing a fluorinating agent, chloroethylene carbonate, an organic alkali and a solvent, and reacting to generate fluoroethylene carbonate; and (2) adding hydrogen chloride into the reaction system in the step (1), and carrying out quenching reaction to obtain fluoroethylene carbonate. In the quenching reaction stage, accurate control over the quenching reaction is achieved by cooperatively controlling the HCl introduction amount, the temperature and the reaction time of the system. The preparation method of fluoroethylene carbonate has the advantages of few side reactions and high product yield, and is suitable for industrial popularization and application.

Description

Technical Field

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

[0002] Fluoroethylene carbonate is an important electrolyte additive that can form a stable solid electrolyte interface film (SEI film) on the surface of the negative electrode, effectively preventing direct contact between the electrolyte and the negative electrode material, reducing the internal resistance of the battery, inhibiting the growth of lithium dendrites, reducing the risk of battery side reactions and internal short circuits, and extending the cycle life of the battery.

[0003] The traditional synthesis process of fluoroethylene carbonate mainly includes direct fluorination, electrochemical fluorination and solid fluoride halogen exchange, which have many defects. The direct fluorination process and electrochemical fluorination process have high requirements for equipment and process conditions, and the reaction is difficult to control and the cost is high. The halogen exchange method usually uses fluorine-containing alkali metal salts as fluorination agents, which has low reaction efficiency, serious side reactions, and complex post-purification treatment.

[0004] In view of the defects of the conventional process, the existing chemical industry has reported the use of a complex of triethylamine and hydrogen fluoride as a fluorination agent to optimize the preparation process. CN110684007A reported the preparation of fluoroethylene carbonate by co-fluorination of triethylamine trihydrofluoride and triethylamine, but the yield was low and the types of by-products were complex; CN114874179A reported a method for preparing fluoroethylene carbonate using a microchannel reactor, in which an amine dechlorination catalyst was added in excess, and hot water extraction after the reaction was completed may cause the heat-sensitive fluoroethylene carbonate to hydrolyze, and affect the product water content index, and the separation step has defects; CN101774923A reported the use of a nitrogen-containing organic base hydrogen fluoride complex and an acid binding agent to prepare fluoroethylene carbonate, and the reaction process was accelerated by increasing the amount of the acid binding agent added, and the conversion rate was improved, but the excessive acid binding agent would react with the product fluoroethylene carbonate to generate vinylene carbonate. In the above method, an excessive amount of organic base needs to be added to ensure sufficient conversion of the raw material ethylene chlorocarbonate. Excessive organic base is likely to cause side reactions during product refining, resulting in a decrease in yield and an increase in three wastes. Therefore, there is still room for improvement. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing fluoroethylene carbonate. The method has high yield of preparing fluoroethylene carbonate, few by-products and is suitable for industrial promotion and application.

[0006] In order to achieve the above purpose, the following technical solutions are adopted:

[0007] The present invention provides a method for preparing fluoroethylene carbonate, the steps comprising:

[0008] (1) mixing a fluorinating agent, chloroethylene carbonate, an organic base, and a solvent to generate fluoroethylene carbonate;

[0009] (2) adding hydrogen chloride to the reaction system of step (1) to quench the reaction and obtain fluoroethylene carbonate;

[0010] The quenching reaction process satisfies the relationship defined by formula (1):

[0011] In the formula,

[0012] T is the quenching reaction temperature;

[0013] t is the quenching reaction time;

[0014] Y is the molar amount of the basic group in the organic base;

[0015] Z is the molar amount of ethylene chlorocarbonate;

[0016] X is the molar amount of HCl.

[0017] In the method of the present invention, the organic base in the quenching reaction system is quenched. The inventors of the present application have found through experiments that by making the quenching reaction process satisfy the relationship defined by the above formula (1), the organic base in the fluoroethylene carbonate mixture can complete the quenching reaction at a suitable temperature and time, reduce the generation of by-products, and improve the yield.

[0018] In a specific embodiment, in the quenching reaction of step (2), the reaction temperature (T) is controlled to be 20-100°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc.

[0019] In a specific embodiment, the molar ratio (Y) of the basic group in the organic base added in step (1) to the molar ratio (Z) of chloroethylene carbonate is controlled to be Y:Z=1.1 to 1.4:1, for example, 1.1:1, 1.2:1, 1.3:1, 1.4:1, etc.

[0020] In a specific embodiment, the molar amount (X) of HCl added in step (2) is controlled to be 1 to 1.5 times of YZ, for example, 1 time, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, etc., where YZ is the molar amount (Y) of the basic group in the organic base added in step (1) minus the molar amount (Z) of ethylene chlorocarbonate.

[0021] In a specific embodiment, the molar ratio of the chloroethylene carbonate to the fluorinating agent and the solvent in step (1) is 1:(1.05-1.3):(1-10), which can be 1:(e.g., 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, etc.):(e.g., 1, 3, 5, 7, 9, 10, etc.).

[0022] In one embodiment, the fluorinating agent in step (1) is selected from hydrogen fluoride.

[0023] In a specific embodiment, the organic base in step (1) is selected from a combination of one or more of triethylamine, pyridine, diethylamine, N,N-dimethylaniline, and quinoline, preferably triethylamine.

[0024] In a specific embodiment, the solvent in step (1) is selected from one or more combinations of acetonitrile, methyl tert-butyl ether, ethyl acetate, dimethyl carbonate, diethyl carbonate, and tetrahydrofuran, preferably acetonitrile is used as the solvent.

[0025] In a specific embodiment, in the reaction of step (1), the reaction temperature is 20-100°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., preferably 30-70°C, and the reaction time is 1-10h, for example, 1h, 3h, 5h, 7h, 9h, 10h, etc., preferably 2-5h.

[0026] In one embodiment, after the quenching reaction in step (2) is completed, a post-treatment process such as purification is further included to obtain high-purity fluoroethylene carbonate;

[0027] The purification method includes conventional operations in the fields of filtration and vacuum distillation. Specifically, one of the purification methods is to first filter the reaction solution obtained in step (2), and then perform vacuum distillation on the reaction solution at a pressure of 0.5 to 10 kPa, such as 0.5 kPa, 2 kPa, 4 kPa, 6 kPa, 8 kPa, 10 kPa, etc., and a temperature of 80 to 150°C, such as 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., preferably at a pressure of 1 to 5 kPa and a temperature of 90 to 120°C.

[0028] Due to the implementation of the above technical solution, the present invention has the following advantages compared with the prior art:

[0029] The invention provides a method for preparing fluoroethylene carbonate. The method introduces a quenching reaction after a fluorination reaction, adds hydrogen chloride into a fluoroethylene carbonate reaction liquid, consumes excess organic base in the reaction liquid, and generates corresponding hydrochloride with the hydrogen chloride and the organic base, without introducing new solid impurities. The reaction liquid after the quenching reaction is more stably refined, and the yield is significantly improved. The amount of three wastes generated by the side reaction of fluoroethylene carbonate is significantly reduced, and the production process changes little, which is suitable for technical transformation and optimization of existing devices. DETAILED DESCRIPTION

[0030] The following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0031] Unless otherwise specified, the reagents, materials and instruments used in the following examples are conventional reagents, conventional materials and conventional instruments in the art and can be obtained commercially.

[0032] Main raw material source information:

[0033] Ethylene chlorocarbonate: Hubei Wonder Chemical Co., Ltd., product purity is ≥99%.

[0034] Characterization equipment:

[0035] The purity of fluoroethylene carbonate was tested by GC, Agilent 8860, chromatographic column: DB-5.

[0036] Chromatographic conditions:

[0037]

[0038] Standard curves of various components were drawn and the purity analysis of each component was carried out using gas phase area normalization.

[0039] The following is the embodiment content:

[0040] Example 1

[0041] Into a reactor equipped with a thermometer, a feeding port, a sampling port and a stirring system, vinyl chloride: hydrogen fluoride: acetonitrile: triethylamine were fed in a molar ratio of 1:1.1:4:1.2 (Y:Z=1.2:1, Y is the molar amount of the basic group in triethylamine, and Z is the molar amount of vinyl chloride), the fluorination reaction temperature was controlled at 50°C, the reaction residence time was 3.5h, and a fluoroethylene carbonate mixture was obtained.

[0042] 1.25 times (YZ) molar amount of hydrogen chloride was introduced into the fluoroethylene carbonate mixture, and the quenching reaction was carried out at 60°C. The quenching reaction time was calculated to be 23 min according to formula (1). The reaction solution was sampled and analyzed, and the selectivity of fluoroethylene carbonate was 99.3%.

[0043] The reaction product was filtered to obtain a fluoroethylene carbonate reaction liquid, and the fluoroethylene carbonate reaction liquid was distilled and purified under the conditions of a pressure of 1.5 kPa and a temperature of 110° C. The molar yield of fluoroethylene carbonate was 97.5% and the product purity was 99.9%.

[0044] Example 2

[0045] Into a reactor equipped with a thermometer, a feeding port, a sampling port and a stirring system, ethylene chlorocarbonate: hydrogen fluoride: dimethyl carbonate: pyridine is fed in a molar ratio of 1:1.05:7:1.2 (Y:Z=1.2:1, Y is the molar amount of the basic group in pyridine, and Z is the molar amount of ethylene chlorocarbonate), the fluorination reaction temperature is controlled at 25°C, the reaction residence time is 6h, and a fluoroethylene carbonate mixture is obtained.

[0046] 1.05 times (YZ) molar amount of hydrogen chloride was introduced into the fluoroethylene carbonate mixture, and the quenching reaction was carried out at 25°C. The quenching reaction time was calculated to be 71.8 min according to formula (1). The reaction solution was sampled and analyzed, and the selectivity of fluoroethylene carbonate was 99.1%.

[0047] The reaction product was filtered to obtain a fluoroethylene carbonate reaction liquid, and the fluoroethylene carbonate reaction liquid was distilled and purified under the conditions of a pressure of 4 kPa and a temperature of 130° C. The molar yield of fluoroethylene carbonate was 94.3% and the product purity was 99.8%.

[0048] Example 3

[0049] Into a reactor equipped with a thermometer, a feeding port, a sampling port and a stirring system, ethylene carbonate chloride: hydrogen fluoride: ethyl acetate: diethylamine are fed in a molar ratio of 1:1.3:2:1.4 (Y:Z=1.4:1, Y is the molar amount of the basic group in diethylamine, and Z is the molar amount of ethylene carbonate chloride), the fluorination reaction temperature is controlled at 90°C, the reaction residence time is 2h, and a fluoroethylene carbonate mixture is obtained.

[0050] 1.5 times (YZ) molar amount of hydrogen chloride was introduced into the fluoroethylene carbonate mixture, and a quenching reaction was carried out at 90° C. The quenching reaction time was calculated to be 12.9 min according to formula (1). The reaction solution was sampled and analyzed, and the selectivity of fluoroethylene carbonate was 99%.

[0051] The reaction product was filtered to obtain a fluoroethylene carbonate reaction liquid, and the fluoroethylene carbonate reaction liquid was distilled and purified under the conditions of a pressure of 1 kPa and a temperature of 95° C. The molar yield of fluoroethylene carbonate was 93.2% and the product purity was 99.6%.

[0052] Example 4

[0053] Into a reactor equipped with a thermometer, a feeding port, a sampling port and a stirring system, vinyl chloride: hydrogen fluoride: methyl tert-butyl ether: triethylamine are fed in a molar ratio of 1:1.1:2:1.3 (Y:Z=1.3:1, Y is the molar amount of the basic group in triethylamine, and Z is the molar amount of vinyl chloride), the fluorination reaction temperature is controlled at 70°C, the reaction residence time is 3h, and a fluoroethylene carbonate mixture is obtained.

[0054] 1.3 times (YZ) molar amount of hydrogen chloride was introduced into the fluoroethylene carbonate mixture, and the quenching reaction was carried out at 35°C. The quenching reaction time was calculated to be 43.1 min according to formula (1). The reaction solution was sampled and analyzed, and the selectivity of fluoroethylene carbonate was 99.2%.

[0055] The reaction product was filtered to obtain a fluoroethylene carbonate reaction liquid, and the fluoroethylene carbonate reaction liquid was distilled and purified under the conditions of a pressure of 2 kPa and a temperature of 120° C. The molar yield of fluoroethylene carbonate was 94.8% and the product purity was 99.7%.

[0056] Comparative Example 1

[0057] The method of Example 1 was followed, except that the quenching reaction time was adjusted to 5 min (i.e., the quenching reaction was not performed according to the time calculated according to Formula 1), and other operations and conditions remained unchanged. The reaction solution was sampled and analyzed, and the selectivity of fluoroethylene carbonate was 94.3%.

[0058] After purification, the molar yield of fluoroethylene carbonate was 69.2% and the product purity was 99.8%.

[0059] Comparative Example 2

[0060] The method of Example 1 was followed, except that the quenching reaction time was adjusted to 60 min (i.e., the quenching reaction was not performed for the time calculated according to Formula 1), and other operations and conditions remained unchanged. The reaction solution was sampled and analyzed, and the selectivity of fluoroethylene carbonate was 96.2%.

[0061] After purification, the molar yield of fluoroethylene carbonate was 97.3% and the product purity was 99.7%.

[0062] Comparative Example 3

[0063] The method of Example 1 was followed, except that HCl was not introduced to quench the reaction. Other operations and conditions remained unchanged. The reaction solution was sampled and analyzed, and the selectivity of fluoroethylene carbonate was 67.3%.

[0064] After purification, the molar yield of fluoroethylene carbonate was 23.4% and the product purity was 99.4%.

[0065] It can be seen from the embodiments and comparative examples that the problem of side reactions caused by triethylamine during the refining of fluoroethylene carbonate is solved by introducing a quenching reaction unit, and the appropriate quenching time is determined by the empirical formula (1) to carry out the quenching reaction, thereby achieving precise control of the quenching reaction, which provides a new idea for reducing production fluctuations.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing fluoroethylene carbonate, characterized in that the steps include: (1) mixing a fluorinating agent, chloroethylene carbonate, an organic base, and a solvent to generate fluoroethylene carbonate; (2) adding hydrogen chloride to the reaction system of step (1) to quench the reaction and obtain fluoroethylene carbonate; Wherein, the quenching reaction process satisfies the relationship defined by formula (1): T is the quenching reaction temperature; t is the quenching reaction time; Y is the molar amount of the basic group in the organic base; Z is the molar amount of ethylene chlorocarbonate; X is the molar amount of HCl.

2. The preparation method according to claim 1, characterized in that: In step (2), the quenching reaction is carried out at a temperature (T) of 20 to 100°C.

3. The preparation method according to claim 1, characterized in that: The molar ratio (Y) of the basic group in the organic base added in step (1) to the molar ratio (Z) of chloroethylene carbonate is controlled to be Y:Z=1.1-1.4:

1.

4. The preparation method according to claim 1, characterized in that: The molar amount (X) of HCl added in step (2) is controlled to be 1 to 1.5 times of YZ, where YZ is the molar amount (Y) of the basic group in the organic base added in step (1) minus the molar amount (Z) of ethylene chlorocarbonate.

5. The preparation method according to claim 1, characterized in that: The molar ratio of the chloroethylene carbonate to the fluorinating agent and the solvent in step (1) is 1:(1.05-1.3):(1-10).

6. The preparation method according to claim 1, characterized in that: The fluorinating agent in step (1) is selected from hydrogen fluoride.

7. The preparation method according to claim 1, characterized in that: The organic base in step (1) is selected from the group consisting of one or more combinations of triethylamine, pyridine, diethylamine, N,N-dimethylaniline, and quinoline, preferably triethylamine.

8. The preparation method according to claim 1, characterized in that: The solvent in step (1) is selected from one or more combinations of acetonitrile, methyl tert-butyl ether, ethyl acetate, dimethyl carbonate, diethyl carbonate, and tetrahydrofuran, preferably acetonitrile is used as the solvent.

9. The preparation method according to claim 1, characterized in that: The reaction in step (1) is carried out at a temperature of 20 to 100° C., preferably 30 to 70° C., and for a reaction time of 1 to 10 h, preferably 2 to 5 h.

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