Method for recovering triethylamine in preparation process of bis (fluorosulfonyl) imide triethylamine salt

Abstract

The invention discloses a method for recovering triethylamine in a preparation process of bis (fluorosulfonyl) imide triethylamine salt, which comprises the following steps: (a) taking sulfuryl fluoride, ammonia gas and triethylamine as raw materials, and reacting in an organic solvent to obtain a reaction solution containing bis (fluorosulfonyl) imide triethylamine salt and triethylamine hydrofluoride; (b) adding a phase transfer catalyst and an inorganic alkaline substance, and carrying out heat preservation reaction; (c) filtering to obtain solid fluoride salt and filtrate; and (d) carrying out vacuum evaporation concentration on the filtrate to obtain a concentrate and a triethylamine-containing recovered solvent, and using the triethylamine-containing recovered solvent for the next batch of reaction. According to the method, under the action of the phase transfer catalyst, the added inorganic alkaline substance reacts with the triethylamine hydrofluoride to generate the solid fluoride salt and dissociate the triethylamine, and the triethylamine can be recovered through vacuum evaporation and concentration, so that the method is simple to operate and convenient for industrial implementation, the triethylamine recovery cost is greatly reduced, and the method is suitable for industrial production. Meanwhile, the wastewater treatment difficulty is also reduced.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology and relates to a method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt. Background Technology

[0002] Lithium bisfluorosulfonylimide (LiFSI) is a white, powdery solid with good thermal stability. It is a key material in lithium-ion battery electrolytes and is considered one of the most likely lithium salts to replace lithium hexafluorophosphate. Its electrolyte conductivity is superior to that of lithium hexafluorophosphate, and it exhibits good compatibility with graphite, silicon anodes, and lithium iron phosphate cathodes. It can improve battery cycle and rate performance, enhance discharge performance at low temperatures, and maintain capacity retention at high temperatures. Lithium bisfluorosulfonylimide is prepared by reacting a bisfluorosulfonylimide organic base salt with a lithium source.

[0003] Difluorosulfonyl imide organic base salts can be prepared by reacting thioyl fluoride and ammonia in the presence of an organic base. For example, Chinese patent CN102378755A discloses a method for preparing difluorosulfonyl imide triethylamine salt. This method uses thioyl fluoride and ammonia as raw materials, acetonitrile as a solvent, and reacts in the presence of triethylamine to obtain a target product with a purity exceeding 99%. Chinese patent CN110217764A discloses a method for preparing difluorosulfonyl imide organic base salts. This method involves reacting ammonia with thioyl fluoride in an organic solvent in the presence of an organic base and a fluoride salt to obtain difluorosulfonyl imide organic base salts. The fluoride salts used are sodium fluoride, potassium fluoride, etc., which effectively avoids the formation of dark-colored impurities, improves the purity of the difluorosulfonyl imide salt, and also increases the reaction rate. Chinese patent CN116283601A uses sulfuryl fluoride and ammonium salt as reactants. Under the action of an aprotic polar solvent and an organic basic acid-binding agent, a reaction is carried out in a high-pressure reactor to obtain the organic ammonium salt of bis(fluorosulfonyl)imide. The ammonium salt used is ammonium fluoride, ammonium chloride, ammonium bromide, etc. Chinese patent CN120329199A uses ammonia, sulfuryl fluoride, and liquid organic base as reactants. Without adding solvent or with a small amount of solvent, the reactants are reacted under pressure to generate the organic base salt of bis(fluorosulfonyl)imide, yielding a product with lower color.

[0004] The methods described above for preparing bis(fluorosulfonyl)imide organic base salts are all carried out in the presence of an organic base. The organic base plays two roles: first, it combines with the bis(fluorosulfonyl)imide generated in the reaction to form the target product, the bis(fluorosulfonyl)imide organic base salt; second, it acts as an acid-binding agent, reacting with the byproduct hydrogen fluoride to generate the organic base hydrofluoric acid salt. Since the generation of 1 mole of bis(fluorosulfonyl)imide produces 2 moles of hydrogen fluoride, to ensure the selectivity of the reaction, the generation of 1 mole of the target product, the bis(fluorosulfonyl)imide organic base salt, requires the consumption of 3 moles of organic base, while simultaneously generating 2 moles of organic base hydrofluoric acid salt. The generated organic base hydrofluoric acid salt enters the wastewater during the washing process, increasing the cost of subsequent treatment and recovery. The large consumption of organic base also increases the raw material cost.

[0005] Among all bisfluorosulfonylimide organic base salts, bisfluorosulfonylimide triethylamine salt has the widest range of applications. However, its preparation process also consumes a large amount of triethylamine. Therefore, it is urgent to develop a method for recovering triethylamine during the preparation of bisfluorosulfonylimide triethylamine salt. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt.

[0007] The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt provided by the present invention includes the following steps: (a) using thioyl fluoride, ammonia and triethylamine as raw materials, reacting them in an organic solvent to obtain a reaction solution containing bis(fluorosulfonyl)imide triethylamine salt and triethylamine hydrofluoric acid salt; (b) controlling the temperature not higher than 40°C, adding a phase transfer catalyst and an inorganic alkaline substance to the above reaction solution, and keeping the reaction at this temperature for 0.5 to 10 hours; (c) filtering to obtain a solid fluoride salt and a filtrate; (d) controlling the temperature not higher than 50°C, vacuum evaporating and concentrating the filtrate to obtain a concentrate and a recovered solvent containing triethylamine. The concentrate is washed with water to obtain bis(fluorosulfonyl)imide triethylamine salt, and the recovered solvent containing triethylamine is used for the next batch of reaction.

[0008] According to a preferred embodiment of the present invention, the phase transfer catalyst in step (b) is polyethylene glycol or crown ether, and the weight of the added phase transfer catalyst is 0.002% to 0.1% of the weight of the reaction solution.

[0009] Furthermore, the polyethylene glycol is one or more of polyethylene glycol-400, polyethylene glycol-600, and polyethylene glycol-800, and the crown ether is one or more of 18-crown ether-6 or 15-crown ether-5.

[0010] According to a preferred embodiment of the present invention, the inorganic alkaline substance in step (b) is one or more of calcium hydroxide, calcium oxide, magnesium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, and ammonia, and the molar ratio of the inorganic alkaline substance to the thioyl fluoride in step (a) is 0.5~1.5:1.

[0011] According to a preferred embodiment of the present invention, the filtration in step (c) is one of vacuum filtration, pressure filtration or centrifugal filtration.

[0012] According to a preferred embodiment of the present invention, the temperature of vacuum evaporation concentration in step (d) is 15~50°C and the vacuum degree is -0.1~-0.08MPa.

[0013] According to a preferred embodiment of the present invention, the water washing temperature in step (d) is 5~20°C, the amount of water used is 0.2~1.0 times the weight of the concentrate, the water washing method is multi-stage cross-flow or counter-flow, and the number of water washings is 1~4 times.

[0014] According to a preferred embodiment of the present invention, the triethylamine-containing recovered solvent in step (d) can be used directly in the next batch of reaction without treatment, or it can be used in the next batch of reaction after treatment. The treatment can be one or more of the following: adding a small amount of fresh triethylamine to the recovered solvent to make up for solvent loss, dehydrating the recovered solvent, or further filtering the recovered solvent.

[0015] According to a preferred embodiment of the present invention, the organic solvent is one or more of acetonitrile, tetrahydrofuran, and toluene.

[0016] The advantages of this invention are as follows: Under the action of a phase transfer catalyst, the added inorganic alkaline substance reacts with triethylamine hydrofluoric acid to generate solid fluoride, releasing triethylamine. Triethylamine can be recovered by vacuum evaporation and concentration. The recovered triethylamine can be directly reused in the next batch of reaction without treatment or with only simple treatment, which greatly reduces the consumption of organic base. The operation is simple and easy to implement industrially. Solid-liquid separation can be achieved by simple filtration, which greatly reduces the cost of triethylamine recovery. The solid fluoride can be sold as a by-product. At the same time, the amount of triethylamine hydrofluoric acid in the concentrate is greatly reduced, which reduces the difficulty of subsequent wastewater treatment. Detailed Implementation

[0017] The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt provided by the present invention includes the following steps: (a) using thioyl fluoride, ammonia and triethylamine as raw materials, reacting them in an organic solvent to obtain a reaction solution containing bis(fluorosulfonyl)imide triethylamine salt and triethylamine hydrofluoric acid salt; (b) controlling the temperature not higher than 40°C, adding a phase transfer catalyst and an inorganic alkaline substance to the above reaction solution, and keeping the reaction at this temperature for 0.5 to 10 hours; (c) filtering to obtain a solid fluoride salt and a filtrate; (d) controlling the temperature not higher than 50°C, vacuum evaporating and concentrating the filtrate to obtain a concentrate and a recovered solvent containing triethylamine. The concentrate is washed with water to obtain bis(fluorosulfonyl)imide triethylamine salt, and the recovered solvent containing triethylamine is used for the next batch of reaction.

[0018] The purpose of step (a) is to obtain "difluorosulfonylimide triethylamine salt" with high selectivity. It should be noted that the reaction involved in step (a) is a reaction well known to those skilled in the art, and they can perform the corresponding operations according to methods and parameters in published literature (typically, but not limited to, such as CN102378755A). This invention does not limit these methods. Typically, but not limited to, the reaction temperature in step (a) can be, for example, -20 to 50°C, preferably -10 to 20°C; the molar ratio of triethylamine to ammonia can be 3 to 10:1; the molar ratio of thiosulfonyl fluoride to ammonia can be 1 to 10:1; and the organic solvent used can be one or more of acetonitrile, tetrahydrofuran, and toluene.

[0019] Example 1 (a) Add 200g of fresh acetonitrile to a 500ml reactor, then add 100g (0.99mol) of triethylamine, control the reaction temperature at 10℃, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio (molar ratio) of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), resulting in a reaction solution containing triethylamine salt of difluorosulfonylimide and triethylamine hydrofluoride. (b) Control the reaction temperature at 40°C, add 372 mg of polyethylene glycol-400 and 24.4 g (0.33 mol) of calcium hydroxide to the above reaction solution, and keep the reaction at this temperature for 2 hours; (c) Filter by suction to obtain solid calcium fluoride and filtrate; (d) The temperature was controlled at 40℃ and the vacuum degree was -0.095Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and recovered acetonitrile containing triethylamine. The concentrate was washed twice with 0.2 times the amount of water at 20℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 95.3%. The recovered acetonitrile contained 62g of triethylamine, with a recovery rate of 93%. It was used directly in the next batch of reaction without further treatment.

[0020] Example 2 (a) Add 260g of acetonitrile (containing 62g of triethylamine) recovered in Example 1 to a 500ml reactor, then add 38g of triethylamine (total triethylamine is 0.99mol), control the reaction temperature at 10°C, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), to obtain 370g of reaction solution containing difluorosulfonylimide triethylamine salt and triethylamine hydrofluoride. (b) Control the reaction temperature at 30°C, add 370 mg of polyethylene glycol-400 and 22.4 g (0.4 mol) of calcium oxide to the above reaction solution, and keep the reaction at this temperature for 3 hours; (c) Filter by suction to obtain solid calcium fluoride and filtrate; (d) The temperature was controlled at 50℃ and the vacuum degree was -0.09Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and recovered acetonitrile containing triethylamine. The concentrate was washed twice with 0.2 times the amount of water at 20℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 96.1%. The recovered acetonitrile contained 57g of triethylamine, with a recovery rate of 86%. It was used directly in the next batch of reaction without further treatment.

[0021] Example 3 (a) Add 200g of fresh tetrahydrofuran to a 500ml reactor, then add 100g (0.99mol) of triethylamine, control the reaction temperature at 10℃, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol). 372g of reaction solution containing difluorosulfonylimide triethylamine salt and triethylamine hydrofluoride is obtained. (b) Control the reaction temperature at 40°C, add 372 mg of polyethylene glycol-600 and 23.2 g (0.4 mol) of magnesium hydroxide to the above reaction solution, and keep the reaction at this temperature for 3 hours; (c) Filter by suction to obtain solid magnesium fluoride and filtrate; (d) The temperature was controlled at 30℃ and the vacuum degree was -0.08Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and a recovered tetrahydrofuran containing triethylamine. The concentrate was washed once with 1.0 times the amount of water at 5℃ to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 97.0%. The recovered tetrahydrofuran contained 54g of triethylamine, with a recovery rate of 81%. It was used directly in the next batch of reaction without further treatment.

[0022] Example 4 (a) Add 246g of tetrahydrofuran (containing 54g of triethylamine) recovered in Example 3 to a 500ml reactor, then add 46g of triethylamine (total triethylamine is 0.99mol), control the reaction temperature at 10°C, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), to obtain 364g of reaction solution containing difluorosulfonylimide triethylamine salt and triethylamine hydrofluoride. (b) Control the reaction temperature at 10°C, add 100 mg of polyethylene glycol-800 and 16.8 g (0.7 mol) of lithium hydroxide to the above reaction solution, and keep the reaction at this temperature for 2 hours; (c) Filter by suction to obtain solid lithium fluoride and filtrate; (d) The temperature was controlled at 30℃ and the vacuum degree was -0.08Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and a recovered tetrahydrofuran containing triethylamine. The concentrate was washed three times countercurrently with 0.3 times the amount of water at 5℃ to obtain the target product, triethylamine difluorosulfonylimide, with a yield of 96.7%. The recovered tetrahydrofuran contained 59g of triethylamine, with a recovery rate of 89%. It was used directly in the next batch of reaction without further treatment.

[0023] Example 5 (a) Add 200g of fresh toluene to a 500ml reactor, then add 100g (0.99mol) of triethylamine. Control the reaction temperature at 10℃. While stirring, introduce sulfuryl fluoride and ammonia into the reactor to carry out the reaction. The ratio of sulfuryl fluoride to ammonia is 2:1. The total amount of sulfuryl fluoride introduced is 67.3g (0.66mol). 372g of reaction solution containing difluorosulfonylimide triethylamine salt and triethylamine hydrofluoric acid salt is obtained. (b) Control the reaction temperature at 40°C, add 50 mg of polyethylene glycol-400 and 37 g (0.5 mol) of lithium carbonate to the above reaction solution, and keep the reaction at this temperature for 5 hours; (c) Pressure filtration to obtain solid lithium fluoride and filtrate; (d) The temperature was controlled at 50℃ and the vacuum degree was -0.1Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and a recovered toluene containing triethylamine. The concentrate was washed four times with 0.2 times the amount of water at 10℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 97.6%. The recovered toluene contained 52g of triethylamine, with a recovery rate of 78%. It was used directly in the next batch of reaction without further treatment.

[0024] Example 6 (a) Add 248g of toluene (containing 52g of triethylamine) recovered in Example 5 to a 500ml reactor, then add 48g of triethylamine (total triethylamine is 0.99mol), control the reaction temperature at 10°C, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), to obtain 368g of reaction solution containing difluorosulfonylimide triethylamine salt and triethylamine hydrofluoride. (b) Control the reaction temperature at 25°C, add 100 mg of 15-crown ether-5 and 42.4 g (0.4 mol) of sodium carbonate to the above reaction solution, and keep the reaction at this temperature for 2 hours; (c) Filtration was performed to obtain solid sodium fluoride and filtrate; (d) The temperature was controlled at 50℃ and the vacuum degree was -0.1Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and a recovered toluene containing triethylamine. The concentrate was washed four times with 0.2 times the amount of water at 10℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 94.9%. The recovered toluene contained 55g of triethylamine, with a recovery rate of 82%. It was used directly in the next batch of reaction without further treatment.

[0025] Example 7 (a) Add 200g of fresh acetonitrile to a 500ml reactor, then add 100g (0.99mol) of triethylamine, control the reaction temperature at 10℃, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio (molar ratio) of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), resulting in a reaction solution containing triethylamine salt of difluorosulfonylimide and triethylamine hydrofluoride. (b) Control the reaction temperature at 40°C, add 25 mg of 18-crown ether-8 and 48.3 g (0.35 mol) of potassium carbonate to the above reaction solution, and keep the reaction at this temperature for 10 hours; (c) Centrifuge and filter to obtain solid potassium fluoride and filtrate; (d) The temperature was controlled at 40℃ and the vacuum degree was -0.09Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and recovered acetonitrile containing triethylamine. The concentrate was washed twice with 0.5 times the amount of water at 10℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 95.9%. The recovered acetonitrile contained 51g of triethylamine, with a recovery rate of 76%. It was used directly in the next batch of reaction without further treatment.

[0026] Example 8 (a) Add 249g of acetonitrile (containing 51g of triethylamine) recovered in Example 7 to a 500ml reactor, then add 49g of triethylamine (total triethylamine is 0.99mol), control the reaction temperature at 10°C, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), to obtain 370g of reaction solution containing difluorosulfonylimide triethylamine salt and triethylamine hydrofluoride. (b) Control the reaction temperature at 10°C, add 7.4 mg of polyethylene glycol-400 to the above reaction solution, introduce 16.8 g (0.99 mol) of ammonia gas, and keep the reaction at the temperature for 0.5 hours; (c) Centrifuge and filter to obtain solid ammonium fluoride and filtrate; (d) The temperature was controlled at 15℃ and the vacuum degree was -0.1Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and recovered acetonitrile containing triethylamine. The concentrate was washed four times with 0.2 times the amount of water at 10℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 94.1%. The recovered acetonitrile contained 45g of triethylamine, with a recovery rate of 68%. It was used directly in the next batch of reaction without further treatment.

[0027] Comparative Example 1 (a) Add 200g of fresh acetonitrile to a 500ml reactor, then add 100g (0.99mol) of triethylamine, control the reaction temperature at 10℃, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio (molar ratio) of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), resulting in a reaction solution containing triethylamine salt of difluorosulfonylimide and triethylamine hydrofluoride. (b) Control the reaction temperature at 40°C, add 24.4 g (0.33 mol) of calcium hydroxide to the above reaction solution, and keep the reaction at this temperature for 2 hours; (c) Filter by suction to obtain solid calcium fluoride and filtrate; (d) The temperature was controlled at 40℃ and the vacuum degree was -0.095Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and recovered acetonitrile containing triethylamine. The concentrate was washed twice with 1.0 times the amount of water at 20℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 91.7%. The recovered acetonitrile contained 11g of triethylamine, with a recovery rate of 16%.

[0028] Comparative Example 2 (a) Add 200g of fresh acetonitrile to a 500ml reactor, then add 100g (0.99mol) of triethylamine, control the reaction temperature at 10℃, and introduce sulfuryl fluoride and ammonia into the reactor under stirring to carry out the reaction. The ratio (molar ratio) of sulfuryl fluoride to ammonia is 2:1, and the total amount of sulfuryl fluoride introduced is 67.3g (0.66mol), resulting in a reaction solution containing triethylamine salt of difluorosulfonylimide and triethylamine hydrofluoride. (b) Control the reaction temperature at 40°C, add 372 mg of polyethylene glycol-400 and 26.4 g (0.66 mol) of sodium hydroxide to the above reaction solution, and keep the reaction at this temperature for 2 hours; (c) Filter by suction to obtain solid calcium fluoride and filtrate; (d) The temperature was controlled at 40℃ and the vacuum degree was -0.095Mpa. The filtrate was evaporated and concentrated to obtain a concentrate and recovered acetonitrile containing triethylamine. The concentrate was washed twice with 0.2 times the amount of water at 20℃ in a cross-flow manner to obtain the target product, difluorosulfonylimide triethylamine salt, with a yield of 14.1%. The recovered acetonitrile contained 64g of triethylamine, with a recovery rate of 96%.

[0029] As can be seen from the above comparative examples, without the use of a phase transfer catalyst, the recovery rate of triethylamine is significantly reduced, and effective recovery of triethylamine cannot be achieved; when sodium hydroxide is used as an inorganic alkaline substance, although triethylamine can be recovered, the yield of the target product, difluorosulfonylimide triethylamine salt, is significantly reduced.

[0030] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt, characterized in that, Includes the following steps: (a) Using thiosulfonyl fluoride, ammonia, and triethylamine as raw materials, a reaction is carried out in an organic solvent to obtain a reaction solution containing bis(fluorosulfonyl)imide triethylamine salt and triethylamine hydrofluoric acid salt; (b) Controlling the temperature not to exceed 40°C, a phase transfer catalyst and an inorganic alkaline substance are added to the above reaction solution, and the reaction is maintained at this temperature for 0.5 to 10 hours; (c) Filtration is performed to obtain a solid fluoride salt and a filtrate; (d) Controlling the temperature not to exceed 50°C, the filtrate is vacuum evaporated and concentrated to obtain a concentrate and a recovered solvent containing triethylamine. The concentrate is washed with water to obtain bis(fluorosulfonyl)imide triethylamine salt, and the recovered solvent containing triethylamine is used for the next batch of reaction.

2. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 1, characterized in that, The phase transfer catalyst mentioned in step (b) is polyethylene glycol or crown ether, and the weight of the added phase transfer catalyst is 0.002% to 0.1% of the weight of the reaction solution.

3. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 2, characterized in that, The polyethylene glycol is one or more of polyethylene glycol-400, polyethylene glycol-600, and polyethylene glycol-800, and the crown ether is one or more of 18-crown ether-6 or 15-crown ether-5.

4. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 1, characterized in that, The inorganic alkaline substance mentioned in step (b) is one or more of calcium hydroxide, calcium oxide, magnesium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, and ammonia, and the molar ratio of the inorganic alkaline substance to the sulfuryl fluoride in step (a) is 0.5~1.5:

1.

5. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 1, characterized in that, The filtration described in step (c) is one of vacuum filtration, pressure filtration or centrifugal filtration.

6. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 1, characterized in that, The vacuum evaporation concentration in step (d) is carried out at a temperature of 15~50℃ and a vacuum degree of -0.1~-0.08MPa.

7. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 1, characterized in that, The water washing temperature in step (d) is 5~20℃, the amount of water used is 0.2~1.0 times the weight of the concentrate, the water washing method is multi-stage cross-flow or counter-flow, and the number of water washings is 1~4 times.

8. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 1, characterized in that... The triethylamine-containing recovered solvent described in step (d) is used directly in the next batch of reaction without further treatment.

9. The method for recovering triethylamine during the preparation of bis(fluorosulfonyl)imide triethylamine salt according to claim 1, characterized in that, The organic solvent is one or more of acetonitrile, tetrahydrofuran, and toluene.