Preparation method of imidodisulfuryl fluoride and preparation method of imidodisulfuryl fluoride lithium salt

Abstract

The invention provides a preparation method of imidodisulfuryl fluoride and a preparation method of imidodisulfuryl fluoride lithium salt, and the preparation method comprises the following steps: (a) mixing fluorosulfonic acid and urea, heating to 70-90 DEG C, and reacting to obtain a reaction product; the molar ratio of the fluorosulfonic acid to the urea is 2: (1-1.2); (b) transferring the reaction product into an electrolytic bath, and carrying out electrolysis by taking a platinum electrode as an anode, a graphite electrode as a cathode and dilute sulphuric acid as an electrolyte solution so as to treat byproducts contained in the reaction product; and (c) carrying out liquid-liquid extraction on the product of the step (b), and distilling and purifying an organic phase under vacuum to obtain the bis (fluorosulfonyl) imide. An electrolysis technology is introduced to optimize by-product treatment, so that reaction conditions are optimized, the environmental protection effect is improved, and the product purity and yield can be improved.

Description

Technical Field

[0001] The 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] Bis(fluorosulfonyl)imide lithium salt can be used as an electrolyte additive for lithium-ion batteries. It is 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, and reduce the capacity loss of lithium batteries during storage, thereby providing high battery capacity and electrochemical performance of the battery. 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 a 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 lithium reagent in an organic solvent system, 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, which solves 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 material is not easy to obtain, and on the other hand, it will cause great 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 purpose, the present invention provides a method for preparing bisfluorosulfonyl imide, comprising the following steps: (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; (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; (c) subjecting the product of step (b) to liquid-liquid extraction, taking the organic phase and distilling and purifying it under vacuum to obtain bis(fluorosulfonyl)imide.

[0006] Optimally, in step (a), the molar ratio of the fluorosulfonic acid to the urea is 2:1.1.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] Furthermore, in step (c), the liquid-liquid extraction is performed multiple times, and the organic phases after each extraction are combined.

[0011] 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.

[0012] Optimally, in step (c), the vacuum degree of the distillation is 2.0-8.0 kPa and the temperature is 40-60°C.

[0013] 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.

[0014] 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 obtaining the final product by cooling, filtering and drying.

[0015] The preparation method of bisfluorosulfonyl imide of the present invention optimizes the reaction conditions, improves the environmental protection effect, and can improve the purity and yield of the product by changing the reaction steps and the purification method and introducing the electrolysis technology to optimize the by-product treatment; in addition, it further reacts with lithium carbonate to generate a high-purity bisfluorosulfonyl imide lithium salt, thereby avoiding the side reaction caused by the high-temperature reaction and improving the yield. DETAILED DESCRIPTION

[0016] The preparation method of bis(fluorosulfonyl)imide of the present invention comprises the following steps: (a) mixing fluorosulfonic acid and urea, heating to 70-90°C for reaction to obtain a reaction product; the molar ratio of the fluorosulfonic acid to the urea is 2:1-1.2; (b) transferring the reaction product to an electrolytic cell, electrolyzing it with 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; (c) subjecting the product of the step (b) to liquid-liquid extraction, and distilling and purifying the organic phase under vacuum to obtain bis(fluorosulfonyl)imide. By changing the reaction steps and purification method, and introducing electrolysis technology to optimize the by-product treatment, the reaction conditions are optimized, the environmental protection effect is improved, and the product purity and yield can be improved.

[0017] In step (a), the molar ratio of the fluorosulfonic acid to the urea is preferably 2:1.1. In step (b), the voltage of the electrolysis 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. In step (c), an organic solvent is added to the product of step (b) for liquid-liquid extraction, and the organic solvent is ethyl acetate or dichloromethane; specifically, the volume ratio of the organic solvent to the liquid phase in the product of step (b) is 1-2:1. The above liquid-liquid extraction is performed multiple times, and the organic phases after 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; and the desiccant residue is removed by filtration. In step (c), the vacuum degree of the distillation is preferably 2.0-8.0 kPa and the temperature is 40-60°C. This lowers the boiling point, prevents the product from decomposing at high temperatures, and ensures effective 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.

[0018] The present invention also provides a method for preparing a lithium salt of bisfluorosulfonyl imide, which includes the method for preparing the above-mentioned bisfluorosulfonyl imide, and further includes the following steps: mixing the bisfluorosulfonyl imide with lithium carbonate at 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.

[0019] The preferred embodiments of the present invention will be described in detail below.

[0020] Example 1 This embodiment provides a method for preparing bis(fluorosulfonyl)imide, which is as follows: (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); at this time, the molar ratio of fluorosulfonic acid to urea was 2:1.1; (b) transferring the reaction product to an electrolytic cell (the electrolytic cell is made of corrosion-resistant material (polytetrafluoroethylene (PTFE)) and electrolyzing it with 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; 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; (c) adding the product of step (b) into an organic solvent (ethyl acetate, the amount of ethyl acetate used is about 2 times the volume of the aqueous phase of the product), fully mixing the product and the organic solvent in a separatory funnel, and shaking to promote the transfer of impurities into the organic phase); performing liquid-liquid extraction (specifically, separating the organic phase and the aqueous phase after standing, and performing three extractions to ensure that the impurities in the aqueous phase are removed to the maximum extent possible), combining the organic phases after each extraction and performing a drying treatment (using anhydrous sodium sulfate (Na 2 SO 4 ) as a desiccant to remove moisture from the organic phase; the dried organic phase is filtered through filter paper or an appropriate filtering device to remove the desiccant residue).

[0021] The organic phase was distilled and purified under vacuum to obtain bis(fluorosulfonyl)imide. The specific distillation was as follows: a rotary evaporator was used with a condenser and a vacuum pump for distillation, the vacuum degree was maintained at 5 kPa, and the distillation temperature was controlled at 50°C (vacuum degree 2.0-8.0 kPa, distillation temperature 40-60°C, the product can be distilled and purified within this range, and has no effect on the product quality, the same below). Finally, 146.5 g of bis(fluorosulfonyl)imide was obtained (yield of about 80.2%) with a purity of 99.92%.

[0022] This embodiment also provides a method for preparing a lithium salt of bis(fluorosulfonyl)imide, which further comprises: (d) Bis(fluorosulfonyl)imide (146.5 g) and lithium carbonate (62.7 g) (the molar ratio of bis(fluorosulfonyl)imide to lithium carbonate is 1:1.05) were mixed, heated to 100-110° C. for 3 hours, and the final product (120.5 g (yield of about 79.6%), purity of 99.93%) was obtained after cooling, filtering and drying.

[0023] Example 2 This embodiment provides a method for preparing bis(fluorosulfonyl)imide, which is as follows: (a) Fluorosulfonic acid (333 g) and urea (100 g) were mixed and heated to 70-90° C. (this temperature range has little effect on the product quality) to obtain a reaction product (370.5 g); at this time, the molar ratio of fluorosulfonic acid to urea was 2:1.0; (b) transferring the reaction product to an electrolytic cell (the electrolytic cell is made of corrosion-resistant material (polytetrafluoroethylene (PTFE)) and electrolyzing it with 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; 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; (c) adding the product of step (b) into an organic solvent (ethyl acetate, the amount of ethyl acetate used is about 1 times the volume of the aqueous phase of the aforementioned product), fully mixing the product and the organic solvent in a separatory funnel, and shaking to promote the transfer of impurities into the organic phase); performing liquid-liquid extraction (specifically, separating the organic phase and the aqueous phase after standing, and performing three extractions to ensure that impurities in the aqueous phase are removed to the maximum extent possible), combining the organic phases after each extraction and performing a drying treatment (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 filtering device to remove desiccant residues).

[0024] The organic phase was distilled and purified under vacuum to obtain bis(fluorosulfonyl)imide. The specific distillation was as follows: a rotary evaporator was used with a condenser and a vacuum pump for distillation, the vacuum degree was maintained at 5 kPa, and the distillation temperature was controlled at 50°C (vacuum degree 2.0-8.0 kPa, distillation temperature 40-60°C, the product can be distilled and purified within this range, and has no effect on the product quality, the same below). Finally, 140.1 g of bis(fluorosulfonyl)imide was obtained (yield of about 69.7%) with a purity of 99.87%.

[0025] This embodiment also provides a method for preparing a lithium salt of bis(fluorosulfonyl)imide, which further comprises: (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 reaction for 5 hours, and then cooled, filtered and dried to obtain the final product (114.6 g (yield of about 79.2%), purity of 99.89%).

[0026] Example 3 This embodiment provides a method for preparing bis(fluorosulfonyl)imide, which is as follows: (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 the product quality) to obtain a reaction product (326.6 g); at this time, the molar ratio of fluorosulfonic acid to urea was 2:1.2; (b) transferring the reaction product to an electrolytic cell (the electrolytic cell is made of corrosion-resistant material (polytetrafluoroethylene (PTFE)) and electrolyzing it with 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; the electrolysis voltage is 2V, the current is 2A / cm², the temperature is 60°C, and the time is 3h. The concentration of sulfuric acid in the dilute sulfuric acid is 0.5mol / L; (c) adding the product of step (b) into an organic solvent (ethyl acetate, the amount of ethyl acetate used is about 2 times the volume of the aqueous phase of the product), fully mixing the product and the organic solvent in a separatory funnel, and shaking to promote the transfer of impurities into the organic phase); performing liquid-liquid extraction (specifically, separating the organic phase and the aqueous phase after standing, and performing two extractions to ensure that the impurities in the aqueous phase are removed to the maximum extent), combining the organic phases after each extraction and drying (using anhydrous sodium sulfate (Na 2 SO 4 ) as a desiccant to remove moisture from the organic phase; the dried organic phase is filtered through filter paper or an appropriate filtering device to remove the desiccant residue).

[0027] The organic phase was distilled and purified under vacuum to obtain bis(fluorosulfonyl)imide. The specific distillation was as follows: a rotary evaporator was used with a condenser and a vacuum pump for distillation, the vacuum degree was maintained at 5 kPa, and the distillation temperature was controlled at 50°C (vacuum degree 2.0-8.0 kPa, distillation temperature 40-60°C, the product can be distilled and purified within this range, and has no effect on the product quality, the same below). Finally, 122.7 g (yield of about 73.2%) of bis(fluorosulfonyl)imide was obtained with a purity of 99.90%.

[0028] This embodiment also provides a method for preparing a lithium salt of bis(fluorosulfonyl)imide, which further comprises: (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) are mixed in a molar ratio, heated to 100-110° C. for reaction for 2-5 hours, and cooled, filtered and dried to obtain the final product (103 g (yield of about 81.3%), purity of 99.91%).

[0029] Comparative Example 1 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.

[0030] Finally, 130.2 g (yield of about 71.3%) of bis(fluorosulfonyl)imide was obtained with a purity of 95.45%.

[0031] Comparative Example 2 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.

[0032] Finally, 127.0 g (yield of about 69.5%) of bis(fluorosulfonyl)imide was obtained with a purity of 96.83%.

[0033] Comparative Example 3 This example provides a method for preparing bis(fluorosulfonyl)imide, which is basically the same as that in Example 1, except that step (c) is not performed.

[0034] Finally, 134.2 g (yield of about 72.9%) of bis(fluorosulfonyl)imide was obtained with a purity of 86.76%.

[0035] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope 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 2:1-1.2; (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; (c) subjecting the product of step (b) to liquid-liquid extraction, taking the organic phase and distilling and purifying it under vacuum to obtain bis(fluorosulfonyl)imide.

2. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that: In step (a), the molar ratio of the fluorosulfonic acid to the urea is 2:1.

1.

3. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that: 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. The concentration of sulfuric acid in the dilute sulfuric acid is 0.5-2 mol / L.

4. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that: 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.

5. The method for preparing bis(fluorosulfonyl)imide according to claim 4, characterized in that: In step (c), the volume ratio of the organic solvent to the liquid phase in the product of step (b) is 1-2:

1.

6. The method for preparing bis(fluorosulfonyl)imide according to claim 4, characterized in that: In step (c), the liquid-liquid extraction is performed multiple times, and the organic phases after each extraction are combined.

7. The method for preparing bis(fluorosulfonyl)imide according to claim 6, characterized in that: 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.

8. The method for preparing bis(fluorosulfonyl)imide according to claim 1, characterized in that: In step (c), the vacuum degree of the distillation is 2.0-8.0 kPa and the temperature is 40-60°C.

9. 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 8.

10. The method for preparing bis(fluorosulfonyl)imide lithium salt according to claim 9, characterized in that: 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.