A Preparation Method of Bis(fluorosulfonyl)imide and a Preparation Method of Lithium Bis(fluorosulfonyl)imide

Abstract

The present invention provides a method for preparing a bis(fluorosulfonyl)imide and a method for preparing a lithium salt of bis(fluorosulfonyl)imide, comprising the following steps: (a) mixing fluorosulfonic acid and urea, heating the mixture to 70-90°C for reaction to obtain a reaction product; the molar ratio of the fluorosulfonic acid to the urea being 2:1-1.2; (b) transferring the reaction product to an electrolytic cell, and electrolyzing the reaction product using a platinum electrode as an anode, a graphite electrode as a cathode, and dilute sulfuric acid as an electrolyte solution to treat byproducts; and (c) subjecting the product of step (b) to liquid-liquid extraction, extracting the organic phase and distilling and purifying the bis(fluorosulfonyl)imide under vacuum. The introduction of electrolysis technology optimizes byproduct treatment, optimizes reaction conditions, improves environmental performance, and increases product purity and yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical synthesis, and in particular relates to a method for preparing bisfluorosulfonyl imide and a method for preparing bisfluorosulfonyl imide lithium salt. Background Art

[0002] Lithium bis(fluorosulfonyl)imide salt can be used as an electrolyte additive for lithium-ion batteries. When used in the electrolyte of rechargeable lithium batteries, it can effectively reduce the high and low temperature resistance of the SEI layer formed on the surface of the electrode plate at low temperatures, reduce the capacity loss of the lithium battery during storage, thereby providing high battery capacity and electrochemical performance. It can also be used as an electrolyte for primary batteries; it can also be used as a polymerization reaction catalyst and an antistatic agent in the industrial field.

[0003] The Chinese invention patent with application number 202311571100.5 discloses a method for preparing bisfluorosulfonyl imide and lithium bisfluorosulfonyl imide to solve the technical problems of purification of HFSI and residual cations in fluorination. The method for preparing bisfluorosulfonyl imide includes the following steps: reacting thionyl chloride with a fluorinating agent to purify thionyl fluoride; reacting the fluorinating agent with fuming sulfuric acid to purify fluorosulfonic acid; adding thionyl fluoride to aminosulfonic acid and fluorosulfonic acid to react and purify bisfluorosulfonyl imide; the method for preparing lithium bisfluorosulfonyl imide also includes the following steps: reacting bisfluorosulfonyl imide and a lithiating agent in an organic solvent system, and dehydrating and drying. This application pre-fluorination, the resulting fluorosulfonic acid and thionyl fluoride are easier to purify, and the raw materials and selected materials after purification in each step are higher in purity than the prepared bisfluorosulfonyl imide acid, solving the purification problem of bisfluorosulfonyl imide acid. Hydrogen fluoride is used as a fluorinating agent, the reaction efficiency is high, and there is no cation residue in all fluorination processes. However, the application requires the use of thionyl chloride, which will produce a large amount of hydrochloric acid. On the one hand, the raw materials are not easy to obtain, and on the other hand, it will cause significant corrosion to the production equipment. Summary of the Invention

[0004] In order to solve the above technical problems, the object of the present invention is to provide a method for preparing bisfluorosulfonyl imide with high purity and high yield.

[0005] In order to achieve the above technical objectives, the present invention provides a method for preparing bis(fluorosulfonyl)imide, comprising the following steps:

[0006] (a) mixing fluorosulfonic acid and urea, heating to 70-90° C. to react to obtain a reaction product; the molar ratio of the fluorosulfonic acid to the urea is 2:1-1.2;

[0007] (b) transferring the reaction product into an electrolytic cell, and performing electrolysis using a platinum electrode as an anode, a graphite electrode as a cathode, and dilute sulfuric acid as an electrolyte solution to treat the by-products contained therein;

[0008] (c) subjecting the product of step (b) to liquid-liquid extraction, and distilling the organic phase under vacuum to purify the product to obtain bis(fluorosulfonyl)imide.

[0009] Optimally, in step (a), the molar ratio of the fluorosulfonic acid to the urea is 2:1.1.

[0010] Optimally, in step (b), the electrolysis voltage is 2.0-2.5 V, the current is 0.1-2 A / cm², the temperature is 20-60°C, and the time is 1-3 h, and the concentration of sulfuric acid in the dilute sulfuric acid is 0.5-2 mol / L.

[0011] Optimally, in step (c), an organic solvent is added to the product of step (b) to perform liquid-liquid extraction, and the organic solvent is ethyl acetate or dichloromethane.

[0012] Furthermore, in step (c), the volume ratio of the organic solvent to the liquid phase in the product of step (b) is 1-2:1.

[0013] Furthermore, in step (c), the liquid-liquid extraction is performed multiple times, and the organic phases after each extraction are combined.

[0014] Specifically, in step (c), anhydrous sodium sulfate or anhydrous calcium chloride is added to the organic phase as a desiccant to remove moisture from the organic phase; and the desiccant residue is removed by filtration.

[0015] Optimally, in step (c), the vacuum degree of the distillation is 2.0-8.0 kPa and the temperature is 40-60°C.

[0016] Another object of the present invention is to provide a method for preparing a lithium salt of bisfluorosulfonyl imide, which comprises the method for preparing the above-mentioned bisfluorosulfonyl imide.

[0017] Optimally, the process further comprises the following steps: mixing the bis(fluorosulfonyl)imide and lithium carbonate in a molar ratio of 1:1 to 1.1, heating to 100 to 110° C. for reaction for 2 to 5 hours, and cooling, filtering and drying to obtain the final product.

[0018] The preparation method of bisfluorosulfonyl imide of the present invention optimizes reaction conditions, improves environmental protection effects, and can increase product purity and yield by changing the reaction steps and purification method and introducing electrolysis technology to optimize by-product treatment. In addition, the bisfluorosulfonyl imide is further reacted with lithium carbonate to generate a high-purity lithium salt of bisfluorosulfonyl imide, thereby avoiding side reactions caused by high-temperature reaction and improving yield. DETAILED DESCRIPTION

[0019] The present invention provides a method for preparing bis(fluorosulfonyl)imide, comprising the following steps: (a) mixing fluorosulfonic acid and urea, heating them to 70-90°C for reaction to obtain a reaction product; the molar ratio of fluorosulfonic acid to urea is 2:1-1.2; (b) transferring the reaction product to an electrolytic cell, and electrolyzing the reaction product using a platinum electrode as an anode, a graphite electrode as a cathode, and dilute sulfuric acid as an electrolyte to treat byproducts; and (c) subjecting the product of step (b) to liquid-liquid extraction, extracting the organic phase and purifying it by vacuum distillation to obtain bis(fluorosulfonyl)imide. By modifying the reaction steps and purification method, and introducing electrolysis technology to optimize byproduct treatment, the reaction conditions are optimized, environmental performance is enhanced, and product purity and yield are increased.

[0020] In step (a), the molar ratio of fluorosulfonic acid to urea is preferably 2:1.1. In step (b), the electrolysis is performed at a voltage of 2.0-2.5 V, a current of 0.1-2 A / cm², a temperature of 20-60°C, and a duration of 1-3 hours. The concentration of sulfuric acid in the dilute sulfuric acid is 0.5-2 mol / L. In step (c), an organic solvent is added to the product of step (b) to perform liquid-liquid extraction. The organic solvent is ethyl acetate or dichloromethane. Specifically, the volume ratio of the organic solvent to the liquid phase of the product of step (b) is 1-2:1. This liquid-liquid extraction is performed multiple times, and the organic phases from each extraction are combined. In step (c), anhydrous sodium sulfate or anhydrous calcium chloride is added to the organic phase as a desiccant to remove moisture from the organic phase. The desiccant residue is then filtered to remove. In step (c), the vacuum level of the distillation is preferably 2.0-8.0 kPa and the temperature is 40-60°C. This lowers the boiling point, preventing the product from decomposing at high temperatures and ensuring efficient separation and purification at low temperatures. If necessary, multiple distillations can be performed to further increase purity and ensure high quality of the final product.

[0021] The present invention also provides a method for preparing a lithium salt of bis(fluorosulfonyl)imide, comprising the method for preparing the above-mentioned bis(fluorosulfonyl)imide. The method further comprises the following steps: mixing the bis(fluorosulfonyl)imide with lithium carbonate in a molar ratio of 1:1 to 1.1, heating to 100 to 110° C. for reaction for 2 to 5 hours, and cooling, filtering, and drying to obtain a final product.

[0022] The preferred embodiments of the present invention will be described in detail below.

[0023] Example 1

[0024] This embodiment provides a method for preparing bis(fluorosulfonyl)imide, which is as follows:

[0025] (a) Fluorosulfonic acid (302.7 g) and urea (100 g) were mixed and heated to 70-90°C (this temperature range has little effect on product quality) to react to obtain a liquid reaction product (344.6 g); the molar ratio of fluorosulfonic acid to urea was 2:1.1;

[0026] (b) transferring the reaction products to an electrolytic cell (made of corrosion-resistant material (polytetrafluoroethylene (PTFE)) using a platinum electrode as the anode, a graphite electrode as the cathode, and dilute sulfuric acid as the electrolyte solution for electrolysis to treat the by-products contained therein; the electrolysis voltage is 2.2 V, the current is 1 A / cm², the temperature is 40°C, and the time is 2 hours; the concentration of sulfuric acid in the dilute sulfuric acid is 1 mol / L;

[0027] (c) adding the product of step (b) to an organic solvent (ethyl acetate, the amount of ethyl acetate used being approximately twice the volume of the aqueous phase of the product), thoroughly mixing the product and the organic solvent in a separatory funnel, and shaking to facilitate transfer of impurities into the organic phase; performing liquid-liquid extraction (specifically, separating the organic and aqueous phases after standing, and performing three extractions to ensure maximum removal of impurities in the aqueous phase); combining the organic phases after each extraction and drying them (using anhydrous sodium sulfate (Na2SO4) as a desiccant to remove moisture from the organic phase; filtering the dried organic phase through filter paper or an appropriate filtration device to remove desiccant residue).

[0028] The organic phase was distilled under vacuum to purify bis(fluorosulfonyl)imide. The distillation was performed using a rotary evaporator with a condenser and a vacuum pump, maintaining a vacuum of 5 kPa and a distillation temperature of 50°C. (The product can be purified by distillation within a range of 2.0-8.0 kPa and 40-60°C without affecting product quality, the same applies below.) 146.5 g (approximately 80.2% yield) of bis(fluorosulfonyl)imide was obtained with a purity of 99.92%.

[0029] This embodiment also provides a method for preparing a lithium salt of bis(fluorosulfonyl)imide, which further comprises:

[0030] (d) Bis(fluorosulfonyl)imide (146.5 g) and lithium carbonate (62.7 g) (the molar ratio of bis(fluorosulfonyl)imide to lithium carbonate was 1:1.05) were mixed and heated to 100-110° C. for 3 hours. The mixture was cooled, filtered, and dried to obtain the final product (120.5 g (yield: approximately 79.6%), purity: 99.93%).

[0031] Example 2

[0032] This embodiment provides a method for preparing bis(fluorosulfonyl)imide, which is as follows:

[0033] (a) Fluorosulfonic acid (333 g) and urea (100 g) were mixed and heated to 70-90°C (this temperature range has little effect on product quality) to react to obtain a reaction product (370.5 g); at this time, the molar ratio of fluorosulfonic acid to urea was 2:1.0;

[0034] (b) transferring the reaction product to an electrolytic cell (made of corrosion-resistant material (polytetrafluoroethylene (PTFE)) using a platinum electrode as the anode, a graphite electrode as the cathode, and dilute sulfuric acid as the electrolyte solution for electrolysis to treat the by-products contained therein; the electrolysis voltage is 2.5 V, the current is 0.15 A / cm², the temperature is 20°C, and the time is 3 hours; the concentration of sulfuric acid in the dilute sulfuric acid is 1.8 mol / L;

[0035] (c) adding the product of step (b) to an organic solvent (ethyl acetate, the amount of ethyl acetate used being approximately 1 times the volume of the aqueous phase of the product), thoroughly mixing the product and the organic solvent in a separatory funnel, and shaking to facilitate transfer of impurities into the organic phase; performing liquid-liquid extraction (specifically, standing to separate the organic and aqueous phases, and performing three extractions to ensure maximum removal of impurities in the aqueous phase); combining the organic phases after each extraction and drying them (using anhydrous calcium chloride as a desiccant to remove moisture from the organic phase; filtering the dried organic phase through filter paper or an appropriate filtration device to remove desiccant residue).

[0036] The organic phase was distilled under vacuum to purify bis(fluorosulfonyl)imide. The distillation was performed using a rotary evaporator with a condenser and a vacuum pump, maintaining a vacuum of 5 kPa and a distillation temperature of 50°C. (The product can be purified by distillation within a vacuum range of 2.0-8.0 kPa and a distillation temperature of 40-60°C without affecting product quality, the same below.) 140.1 g (approximately 69.7% yield) of bis(fluorosulfonyl)imide was obtained with a purity of 99.87%.

[0037] This embodiment also provides a method for preparing a lithium salt of bis(fluorosulfonyl)imide, which further comprises:

[0038] (d) Bis(fluorosulfonyl)imide (140.1 g) and lithium carbonate (57.1 g) (the molar ratio of bis(fluorosulfonyl)imide to lithium carbonate is 1:1) were mixed in a molar ratio, heated to 100-110° C. for 5 hours, and cooled, filtered, and dried to obtain the final product (114.6 g (yield: approximately 79.2%), purity: 99.89%).

[0039] Example 3

[0040] This embodiment provides a method for preparing bis(fluorosulfonyl)imide, which is as follows:

[0041] (a) Fluorosulfonic acid (277.5 g) and urea (100 g) were mixed and heated to 70-90°C (this temperature range has little effect on product quality) to react to obtain a reaction product (326.6 g); the molar ratio of fluorosulfonic acid to urea was 2:1.2;

[0042] (b) transferring the reaction product to an electrolytic cell (made of corrosion-resistant material (polytetrafluoroethylene (PTFE)) using a platinum electrode as the anode, a graphite electrode as the cathode, and dilute sulfuric acid as the electrolyte solution for electrolysis to treat the by-products contained therein; the electrolysis voltage is 2 V, the current is 2 A / cm², the temperature is 60°C, and the time is 3 hours; the concentration of sulfuric acid in the dilute sulfuric acid is 0.5 mol / L;

[0043] (c) adding the product of step (b) to an organic solvent (ethyl acetate, the amount of ethyl acetate used being approximately twice the volume of the aqueous phase of the product), thoroughly mixing the product and the organic solvent in a separatory funnel, and shaking to facilitate transfer of impurities into the organic phase; performing liquid-liquid extraction (specifically, standing the mixture to separate the organic and aqueous phases, and performing two extractions to ensure maximum removal of impurities in the aqueous phase); combining the organic phases after each extraction and drying them (using anhydrous sodium sulfate (Na2SO4) as a desiccant to remove moisture from the organic phase; filtering the dried organic phase through filter paper or an appropriate filtration device to remove desiccant residue).

[0044] The organic phase was distilled under vacuum to purify the bis(fluorosulfonyl)imide. The distillation was performed using a rotary evaporator with a condenser and a vacuum pump, maintaining a vacuum of 5 kPa and a distillation temperature of 50°C. (The product can be purified by distillation within a vacuum range of 2.0-8.0 kPa and a distillation temperature of 40-60°C without affecting product quality, the same below.) The final yield was 122.7 g (approximately 73.2% yield) of bis(fluorosulfonyl)imide with a purity of 99.90%.

[0045] This embodiment also provides a method for preparing a lithium salt of bis(fluorosulfonyl)imide, which further comprises:

[0046] (d) Bis(fluorosulfonyl)imide (122.7 g) and lithium carbonate (55 g) (the molar ratio of bis(fluorosulfonyl)imide to lithium carbonate is 1:1.1) were mixed in a molar ratio, heated to 100-110° C. for 2-5 hours, and cooled, filtered, and dried to obtain the final product (103 g (yield: approximately 81.3%), purity: 99.91%).

[0047] Comparative Example 1

[0048] This example provides a method for preparing bis(fluorosulfonyl)imide, which is basically the same as that in Example 1, except that: in step (a), the heating temperature of fluorosulfonic acid and urea is 50°C.

[0049] Finally, 130.2 g of bis(fluorosulfonyl)imide was obtained (yield: about 71.3%) with a purity of 95.45%.

[0050] Comparative Example 2

[0051] This example provides a method for preparing bis(fluorosulfonyl)imide, which is basically the same as that in Example 1, except that in step (a), the heating temperature of fluorosulfonic acid and urea is 100°C.

[0052] Finally, 127.0 g of bis(fluorosulfonyl)imide was obtained (yield: about 69.5%) with a purity of 96.83%.

[0053] Comparative Example 3

[0054] This example provides a method for preparing bisfluorosulfonyl imide, which is basically the same as that in Example 1, except that step (c) is not performed.

[0055] Finally, 134.2 g of bis(fluorosulfonyl)imide was obtained (yield: about 72.9%) with a purity of 86.76%.

[0056] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing bis(fluorosulfonyl)imide, characterized in that: The following steps are involved: (a) mixing fluorosulfonic acid and urea, heating to 70-90° C. to react to obtain a reaction product; the molar ratio of the fluorosulfonic acid to the urea is 2:1.1; (b) transferring the reaction product to an electrolytic cell and performing electrolysis using a platinum electrode as an anode, a graphite electrode as a cathode, and dilute sulfuric acid as an electrolyte solution to treat the byproducts contained therein; the electrolysis voltage is 2.0-2.5 V, the current is 0.1-2 A / cm², the temperature is 20-60° C., and the time is 1-3 hours, and the concentration of sulfuric acid in the dilute sulfuric acid is 0.5-2 mol / L; (c) subjecting the product of step (b) to liquid-liquid extraction, and distilling the organic phase under vacuum to purify the product to obtain bis(fluorosulfonyl)imide.

2. The method for preparing bisfluorosulfonyl imide according to claim 1, wherein: In step (c), an organic solvent is added to the product of step (b) to perform liquid-liquid extraction, wherein the organic solvent is ethyl acetate or dichloromethane.

3. The method for preparing bisfluorosulfonyl imide according to claim 2, wherein: In step (c), the volume ratio of the organic solvent to the liquid phase in the product of step (b) is 1-2:

1.

4. The method for preparing bisfluorosulfonyl imide according to claim 2, wherein: In step (c), the liquid-liquid extraction is performed multiple times, and the organic phases after each extraction are combined.

5. The method for preparing bisfluorosulfonyl imide according to claim 4, wherein: In step (c), anhydrous sodium sulfate or anhydrous calcium chloride is added to the organic phase as a desiccant to remove moisture from the organic phase; Filter to remove desiccant residue.

6. The method for preparing bisfluorosulfonyl imide according to claim 1, wherein: In step (c), the vacuum degree of the distillation is 2.0-8.0 kPa and the temperature is 40-60°C.

7. A method for preparing a lithium salt of bis(fluorosulfonyl)imide, characterized in that: It comprises the preparation method of the bisfluorosulfonyl imide according to any one of claims 1 to 6.

8. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 7, wherein: The following steps are also included: The bisfluorosulfonyl imide and lithium carbonate are mixed in a molar ratio of 1:1-1.1, heated to 100-110° C. for reaction for 2-5 hours, and cooled, filtered and dried to obtain a final product.