Method for synthesizing lithium bisfluorosulfonylimide by recycling fluorosulfonic acid resources

Abstract

The present application relates to a kind of fluorosulfonic acid resource recycling synthesis bifluoride method of sulfurylimide.Lithium fluorosulfonic acid, sulfonamide, sulfurous dichloride, chlorosulfonic acid are used as raw material, overheat steam is used to separate fluorosulfonic acid into sulfuric acid and hydrofluoric acid, sulfonamide is reacted with sulfurous dichloride and chlorosulfonic acid to obtain bis chlorosulfurylimide, and then fluorination and lithiation reaction is carried out, finally, lithium bisfluorosulfurylimide is obtained.Chloride ion can exchange with the cation site (such as the cationic form of bismuth oxide) on the resin as an anion;Chloride ion can also coordinate with the metal center in ferrocene, thereby reducing its concentration;Carboxyl in carboxyl magnesium can react with carbon dioxide to form carboxylate, thereby fixing carbon dioxide;As a Lewis acid, antimony trichloride can interact with the π-electron ligand in ferrocene, and this interaction causes antimony trichloride to be adsorbed on the resin, thereby removing it from the solution;Through the above mechanism, the resin adsorbent containing bismuth oxide, ferrocene and carboxyl magnesium can remove chloride ions, carbon dioxide and antimony trichloride and other impurities;These purified solutions can be used to prepare high-purity lithium bisfluorosulfurylimide;The lithium bisfluorosulfurylimide prepared by the present application has high conversion rate and high selectivity, and can be directly industrialized.

Description

Technical Field

[0001] This invention relates to the field of lithium bisfluorosulfonylimide synthesis technology, and in particular to a method for synthesizing lithium bisfluorosulfonylimide by reusing fluorosulfonic acid resources. Background Technology

[0002] Lithium bisfluorosulfonyl imide (LiFSI) is a novel electrolyte lithium salt used in lithium-ion battery electrolytes. It is environmentally friendly and safe, possessing the basic conditions for industrial application. Compared to the traditional lithium salt lithium hexafluorophosphate (LiPF6), lithium ions in LiFSI dissociate more easily, resulting in higher conductivity. LiFSI has a decomposition temperature above 200℃, exhibiting significantly better thermal stability and safety performance than LiPF6. Furthermore, it demonstrates unique effects in improving high-temperature storage and low-temperature discharge performance, and possesses excellent compatibility with electrodes. Therefore, LiFSI is a promising electrolyte for lithium-ion batteries.

[0003] Chinese patent CN113135555A discloses a method for preparing lithium bis(fluorosulfonyl)imide. This method includes the following steps: lithium nitride and excess sulfuryl fluoride gas are reacted in an organic solvent to obtain a slurry; solid-liquid separation is performed; the resulting liquid is stirred and crystallized under the condition of a solvent to obtain a crystalline slurry; and crystals are separated from the crystalline slurry. This invention's method for preparing lithium bis(fluorosulfonyl)imide uses lithium nitride as the lithium source and reacts it with sulfuryl fluoride gas in an organic solvent system to obtain a lithium bis(fluorosulfonyl)imide solution and lithium fluoride solid. After post-processing, high-purity lithium fluoride is obtained as a byproduct of lithium bis(fluorosulfonyl)imide. This process is simple, environmentally friendly, produces little waste, and has high product yield and purity. However, lithium chloride and chlorosulfonate isocyanate contain chloride ions, and the presence of chloride ions significantly increases the corrosiveness of lithium bis(fluorosulfonyl)imide to the aluminum electrodes commonly used in lithium batteries, seriously affecting the industrial application of lithium bis(fluorosulfonyl)imide.

[0004] Chinese patent CN101747242A describes a process that first reacts sulfonamide with thionyl chloride and chlorosulfonic acid to obtain bischlorosulfonylimide, then reacts it with antimony trifluoride to obtain bisfluorosulfonylimide, followed by reaction with potassium carbonate (rubidium or cesium) to obtain lithium bisfluorosulfonylimide (rubidium or cesium) salt, and finally undergoes a metathesis exchange reaction with lithium perchlorate (or sodium) or lithium tetrafluoroborate (or sodium) in an aprotic polar solvent to obtain lithium bisfluorosulfonylimide (or sodium) salt. This method has the following problems: it involves four chemical reactions and related purification steps, making the process too long; antimony fluoride, lithium perchlorate, or lithium tetrafluoroborate are relatively expensive, resulting in high raw material costs; it consumes a large amount of raw materials and generates a large amount of waste, including antimony trichloride, carbon dioxide, potassium perchlorate, and organic solvents; and the product contains many impurities, making it difficult to purify to meet practical application standards.

[0005] US Patent 8377406B1 describes a method that involves reacting sulfonamide with thionyl chloride and chlorosulfonic acid to obtain bis(chlorosulfonyl)imide, then reacting it with bismuth trifluoride to obtain bis(fluorosulfonyl)imide, and finally reacting it with lithium carbonate (sodium or potassium) to obtain lithium (sodium or potassium) bis(fluorosulfonyl)imide. This method has the following problems: it involves three chemical reactions and related purification steps, resulting in an excessively long process flow; bismuth trifluoride is expensive, and even with chemical recovery methods, the manufacturing cost remains too high; the reaction between bis(fluorosulfonyl)imide and lithium carbonate in aqueous solution produces too many byproducts, and the yield of lithium bis(fluorosulfonyl)imide extracted with ethyl acetate is too low and contains a large amount of impurities.

[0006] Existing methods for synthesizing bischlorosulfonylimide require high purity of the main raw material, hydrofluoric acid, which is expensive. On the other hand, the lithium-ion battery industry is developing rapidly, creating a high market demand for related raw materials. For example, lithium trifluoromethanesulfonate supports the upgrading of secondary batteries, demonstrating significant social and economic benefits. However, the production of lithium trifluoromethanesulfonate generates a large amount of fluorosulfonic acid as a byproduct. Currently, this requires paid recycling by third-party waste disposal companies. Therefore, it is imperative to optimize the existing process for synthesizing bischlorosulfonylimide by utilizing fluorosulfonic acid, improving product yield, reducing manufacturing costs, and achieving battery-grade purity for the manufactured LiFSI. Summary of the Invention

[0007] To address the above problems, this invention provides a method for synthesizing lithium bis(fluorosulfonyl)imide by recycling fluorosulfonic acid resources, the operation steps of which are as follows:

[0008] Steam is continuously passed into a distillation vessel containing fluorosulfonic acid, causing the temperature inside the vessel to rise. After being kept at this temperature for a period of time, the final product remaining in the evaporation vessel is fluorosulfuric acid. The gas produced in the evaporation vessel is cooled to obtain hydrofluoric acid, which is free of sulfuric acid.

[0009] S1: Add 50-60 parts of dichloromethane and 1-5 parts of lithium hydroxide monohydrate to a filter press, cool to 0-5℃, add 10-20 parts of bis(fluorosulfonyl)imide dropwise while stirring, stir for 1-3 hours, then heat to 20-25℃, add 30-40 parts of thionyl chloride dropwise, stir for 10-15 hours, filter, and obtain crude lithium bis(fluorosulfonyl)imide.

[0010] S2: Dissolve crude lithium difluorosulfonylimide in a mixed solvent, add 5-10 parts of dechlorination adsorption resin, stir for 30-60 minutes, filter, evaporate the filtrate under reduced pressure, desolvent and crystallize, wash with dichloroethane, filter, and dry under reduced pressure to obtain lithium difluorosulfonylimide.

[0011] The mixed solvent is 50-60 parts dichloroethane and 5-10 parts diethyl ether.

[0012] The preparation method of the aforementioned difluorosulfonamide is as follows:

[0013] Add 50-70 parts of dichlorosulfonamide and 0.05-0.5 parts of antimony pentachloride to a fluorination reactor, heat the reactor, and slowly introduce 15-20 parts of HF gas while stirring. After the reaction is complete, transfer the material in the reactor to a distillation column for purification to obtain dichlorosulfonamide. The hydrogen chloride generated by the fluorination reaction is washed with water to prepare hydrochloric acid as a byproduct.

[0014] The reaction temperature is 100-130℃ and the time is 15-20h.

[0015] The preparation method of the aforementioned dichlorosulfonamide is as follows:

[0016] Add 60-70 parts by weight of aminosulfonic acid, 100-200 parts by weight of thionyl chloride and 70-90 parts by weight of chlorosulfonic acid to the condensation reaction vessel, heat the mixture, and after the reaction is completed, distill under reduced pressure to obtain dichlorosulfonamide; absorb the gas overflowing from the reaction with alkaline solution.

[0017] The reaction temperature is 100-120℃ and the reaction time is 25-30h.

[0018] The preparation method of the dechlorination adsorption resin is as follows:

[0019] By weight, 100-130 parts of mercapto resin are placed in 500-1000 parts of toluene, and then 0.05-0.5 parts of epoxy nano bismuth oxide, 0.5-2.5 parts of vinyl ferrocene, 3-6 parts of magnesium acrylate, and 4-7 parts of sodium ethoxide are added. The mixture is stirred at 50-60℃ for 40-100 minutes, filtered, washed, and dried to obtain the dechlorination adsorption resin.

[0020] The preparation method of the epoxy-based nano-bismuth oxide is as follows:

[0021] Weigh 2-5 parts of γ-(2,3-epoxypropoxy)propyltriethoxysilane, 100-150 parts of nano-bismuth oxide, and 1000-1300 parts of water and place them in a sealed reaction vessel. Stir at 30-40℃ for 30-60 minutes, filter, and dry to obtain epoxy-based nano-bismuth oxide.

[0022] The thiol resin mentioned is a commercially available product, such as MTS9240 resin or LSC-400 thiol resin.

[0023] The method for preparing the hydrofluoric acid is as follows:

[0024] Under normal pressure, 100°C superheated steam is passed into an 80-90wt% fluorosulfonic acid evaporator for atmospheric distillation. The temperature inside the evaporator is raised to 90-100°C and maintained at 90-100°C for 3-4 hours. The final residue at the bottom of the evaporator is 90-95% sulfuric acid. The gas produced at the top of the evaporator, after cooling, yields hydrofluoric acid with a purity greater than 99%.

[0025] Reaction mechanism

[0026] Thiol resin undergoes an epoxy-thiol reaction with epoxy-based nano-bismuth oxide, a vinyl-thiol reaction with vinyl ferrocene, and an propylene-thiol reaction with magnesium acrylate. The resulting resin adsorbent containing bismuth oxide, ferrocene, and carboxylated magnesium can remove impurities such as chloride ions, carbon dioxide, and antimony trichloride, yielding high-purity lithium difluorosulfonylimide.

[0027] Technical effect

[0028] The present invention provides a method for synthesizing lithium bisfluorosulfonylimide by recycling fluorosulfonic acid resources. Compared with the prior art, the present invention has the following significant advantages:

[0029] 1. This invention uses chlorosulfonic acid, aminosulfonic acid, thionyl chloride, etc. to synthesize lithium difluorosulfonylimide. The process is simple, low-cost, low-consumption, and basically waste-free.

[0030] 2. The lithium difluorosulfonylimide prepared by this formula has high conversion rate and high selectivity, and can be directly applied in industrial applications.

[0031] 3. Chloride ions, as an anion, can exchange with cation sites on the resin (such as the cation form of bismuth oxide); chloride ions can also coordinate with the metal center in ferrocene, thereby reducing its concentration; the carboxyl group in magnesium carboxylate can react with carbon dioxide to form a carboxylate, thereby fixing carbon dioxide; antimony trichloride, as a Lewis acid, can interact with the π-electron ligand in ferrocene, and this interaction leads to the adsorption of antimony trichloride on the resin, thereby removing it from the solution; through the above mechanisms, resin adsorbents containing bismuth oxide, ferrocene, and magnesium carboxylate can remove impurities such as chloride ions, carbon dioxide, and antimony trichloride; these purified solutions can be used to prepare high-purity lithium bis(fluorosulfonyl)imide. Attached Figure Description

[0032] Figure 1 This is a process flow diagram for lithium bis(fluorosulfonyl)imide. Detailed Implementation

[0033] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0034] The testing shall be conducted in accordance with Q / DFD0019-2017.

[0035] Example 1

[0036] A method for synthesizing lithium bisfluorosulfonylimide from chlorosulfonic acid resources, comprising the following steps:

[0037] S1: Add 50g of dichloromethane and 1g of lithium hydroxide monohydrate to a filter press, cool to 0℃, add 10g of bis(fluorosulfonyl)imide dropwise while stirring, stir for 1h, then heat to 20℃, add 30g of thionyl chloride dropwise, stir for 10h, filter, and obtain crude lithium bis(fluorosulfonyl)imide.

[0038] S2: Dissolve crude lithium difluorosulfonylimide in a mixed solvent, add 5g of dechlorination adsorption resin, stir for 30 minutes, filter, evaporate the filtrate under reduced pressure, desolvent and crystallize, wash with dichloroethane, filter, and dry under reduced pressure to obtain lithium difluorosulfonylimide.

[0039] The mixed solvent is 50g of dichloroethane and 5g of diethyl ether.

[0040] The preparation method of the aforementioned difluorosulfonamide is as follows:

[0041] Add 50g of dichlorosulfonamide and 0.05g of antimony pentachloride to a fluorination reactor, heat the reactor, and slowly introduce 15g of HF gas while stirring. After the reaction is complete, transfer the material in the reactor to a distillation column for purification to obtain dichlorosulfonamide. The hydrogen chloride generated by the fluorination reaction is washed with water to prepare hydrochloric acid as a byproduct.

[0042] The reaction temperature was 100℃ and the reaction time was 15 hours.

[0043] The preparation method of the aforementioned dichlorosulfonamide is as follows:

[0044] Add 60g of aminosulfonic acid, 100g of thionyl chloride, and 70g of chlorosulfonic acid to a condensation reaction vessel, heat the mixture, and after the reaction is complete, distill under reduced pressure to obtain dichlorosulfonamide; absorb the overflow gas with alkaline solution.

[0045] The reaction temperature was 100℃ and the reaction time was 25 hours.

[0046] The preparation method of the dechlorination adsorption resin is as follows:

[0047] 100g of mercapto resin was placed in 500g of toluene, and then 0.05g of epoxy nano bismuth oxide, 0.5g of vinyl ferrocene, 3g of magnesium acrylate, and 4g of sodium ethoxide were added. The mixture was stirred at 50℃ for 40 minutes, filtered, washed, and dried to obtain dechlorination adsorption resin.

[0048] The preparation method of the epoxy-based nano-bismuth oxide is as follows:

[0049] Weigh 2g of γ-(2,3-epoxypropoxy)propyltriethoxysilane, 100g of nano-bismuth oxide, and 1000g of water and place them in a sealed reaction vessel. Stir at 30°C for 30 minutes, filter, and dry to obtain epoxy-based nano-bismuth oxide.

[0050] The mercapto resin mentioned is the commercially available product MTS9240 resin.

[0051] The method for preparing the hydrofluoric acid is as follows:

[0052] Under normal pressure, 100°C superheated steam is passed into an 80wt% fluorosulfonic acid evaporator for atmospheric distillation. The temperature inside the evaporator is raised to 90°C and maintained at 90°C for 3 hours. The final residue at the bottom of the evaporator is 90% sulfuric acid. The gas produced at the top of the evaporator, after cooling, yields hydrofluoric acid with a purity greater than 99%.

[0053] Example 2

[0054] A method for synthesizing lithium bisfluorosulfonylimide from chlorosulfonic acid resources, comprising the following steps:

[0055] S1: Add 53g of dichloromethane and 2g of lithium hydroxide monohydrate to a filter press, cool to 0℃, add 13g of difluorosulfonyl imide dropwise while stirring, stir for 2h, then heat to 20℃, add 33g of sulfonyl chloride dropwise, stir for 12h, filter, and obtain crude difluorosulfonyl imide lithium.

[0056] S2: Dissolve crude lithium difluorosulfonylimide in a mixed solvent, add 6g of dechlorination adsorption resin, stir for 40 minutes, filter, evaporate the filtrate under reduced pressure, desolventize and crystallize, wash with dichloroethane, filter, and dry under reduced pressure to obtain lithium difluorosulfonylimide.

[0057] The mixed solvent is 53g of dichloroethane and 6g of diethyl ether.

[0058] The preparation method of the aforementioned difluorosulfonamide is as follows:

[0059] 55g of dichlorosulfonamide and 0.2g of antimony pentachloride were added to a fluorination reactor, and the mixture was heated. 16g of HF gas was slowly introduced while stirring. After the reaction was completed, the material in the reactor was transferred to a distillation column for purification to obtain dichlorosulfonamide. Hydrogen chloride generated by the fluorination reaction was washed with water to prepare hydrochloric acid as a byproduct.

[0060] The reaction temperature was 110℃ and the reaction time was 16h.

[0061] The preparation method of the aforementioned dichlorosulfonamide is as follows:

[0062] Add 63g of aminosulfonic acid, 140g of thionyl chloride, and 75g of chlorosulfonic acid to a condensation reaction vessel, heat the mixture, and after the reaction is complete, distill under reduced pressure to obtain dichlorosulfonamide; absorb the overflow gas with alkaline solution.

[0063] The reaction temperature was 105℃ and the reaction time was 26 hours.

[0064] The preparation method of the dechlorination adsorption resin is as follows:

[0065] 110g of mercapto resin was placed in 600g of toluene, and then 0.2g of epoxy nano bismuth oxide, 1g of vinyl ferrocene, 4g of magnesium acrylate, and 5g of sodium ethoxide were added. The mixture was stirred at 55℃ for 60 minutes, filtered, washed, and dried to obtain dechlorination adsorption resin.

[0066] The preparation method of the epoxy-based nano-bismuth oxide is as follows:

[0067] Weigh 3g of γ-(2,3-epoxypropoxy)propyltriethoxysilane, 110g of nano-bismuth oxide, and 1100g of water and place them in a sealed reaction vessel. Stir at 35°C for 40min, filter, and dry to obtain epoxy-based nano-bismuth oxide.

[0068] The mercapto resin mentioned is the commercially available product MTS9240 resin.

[0069] The method for preparing the hydrofluoric acid is as follows:

[0070] Under normal pressure, 100°C superheated steam is passed into an 85wt% fluorosulfonic acid evaporator for atmospheric distillation. The temperature inside the evaporator is raised to 95°C and maintained at 95°C for 3.5 hours. The final residue at the bottom of the evaporator is 92% sulfuric acid. The gas produced at the top of the evaporator, after cooling, yields hydrofluoric acid with a purity greater than 99%.

[0071] Example 3

[0072] A method for synthesizing lithium bisfluorosulfonylimide from chlorosulfonic acid resources, comprising the following steps:

[0073] S1: Add 58g of dichloromethane and 4g of lithium hydroxide monohydrate to a filter press, cool to 5°C, add 18g of difluorosulfonyl imide dropwise while stirring, stir for 2 hours, then heat to 25°C, add 38g of sulfonyl chloride dropwise, stir for 14 hours, filter, and obtain crude difluorosulfonyl imide lithium.

[0074] S2: Dissolve crude lithium difluorosulfonylimide in a mixed solvent, add 8g of dechlorination adsorption resin, stir for 50 minutes, filter, evaporate the filtrate under reduced pressure, desolvent and crystallize, wash with dichloroethane, filter, and dry under reduced pressure to obtain lithium difluorosulfonylimide.

[0075] The mixed solvent is 58g of dichloroethane and 8g of diethyl ether.

[0076] The preparation method of the aforementioned difluorosulfonamide is as follows:

[0077] 65g of dichlorosulfonamide and 0.4g of antimony pentachloride were added to a fluorination reactor, and the mixture was heated. 18g of HF gas was slowly introduced while stirring. After the reaction was completed, the material in the reactor was transferred to a distillation column for purification to obtain dichlorosulfonamide. Hydrogen chloride generated by the fluorination reaction was washed with water to prepare hydrochloric acid as a byproduct.

[0078] The reaction temperature was 120℃ and the reaction time was 18h.

[0079] The preparation method of the aforementioned dichlorosulfonamide is as follows:

[0080] 68g of aminosulfonic acid, 180g of thionyl chloride, and 85g of chlorosulfonic acid were added to a condensation reaction vessel, and the mixture was heated. After the reaction was completed, the mixture was distilled under reduced pressure to obtain dichlorosulfonamide. The gas overflowing from the reaction was absorbed by an alkaline solution.

[0081] The reaction temperature was 115℃ and the reaction time was 28 hours.

[0082] The preparation method of the dechlorination adsorption resin is as follows:

[0083] 120g of mercapto resin was placed in 800g of toluene, and then 0.4g of epoxy nano bismuth oxide, 2g of vinyl ferrocene, 5g of magnesium acrylate, and 6g of sodium ethoxide were added. The mixture was stirred at 55℃ for 80 minutes, filtered, washed, and dried to obtain dechlorination adsorption resin.

[0084] The preparation method of the epoxy-based nano-bismuth oxide is as follows:

[0085] Weigh 4g of γ-(2,3-epoxypropoxy)propyltriethoxysilane, 140g of nano-bismuth oxide, and 1200g of water and place them in a sealed reaction vessel. Stir at 35°C for 50min, filter, and dry to obtain epoxy-based nano-bismuth oxide.

[0086] The mercapto resin mentioned is the commercially available product LSC-400 mercapto resin.

[0087] The method for preparing the hydrofluoric acid is as follows:

[0088] Under normal pressure, 100°C superheated steam is passed into an 85wt% fluorosulfonic acid evaporator for atmospheric distillation. The temperature inside the evaporator is raised to 95°C and maintained at 95°C for 3.5 hours. The final residue at the bottom of the evaporator is 94% sulfuric acid. The gas produced at the top of the evaporator, after cooling, yields hydrofluoric acid with a purity greater than 99%.

[0089] Example 4

[0090] A method for synthesizing lithium bisfluorosulfonylimide from chlorosulfonic acid resources, comprising the following steps:

[0091] S1: Add 60g of dichloromethane and 5g of lithium hydroxide monohydrate to a filter press, cool to 5°C, add 20g of difluorosulfonyl imide dropwise while stirring, stir for 3h, then heat to 25°C, add 40g of sulfoxide dropwise, stir for 15h, filter, and obtain crude difluorosulfonyl imide lithium.

[0092] S2: Dissolve crude lithium difluorosulfonylimide in a mixed solvent, add 10g of dechlorination adsorption resin, stir for 60 minutes, filter, evaporate the filtrate under reduced pressure, desolvent and crystallize, wash with dichloroethane, filter, and dry under reduced pressure to obtain lithium difluorosulfonylimide.

[0093] The mixed solvent is 60g of dichloroethane and 10g of diethyl ether.

[0094] The preparation method of the aforementioned difluorosulfonamide is as follows:

[0095] 70g of dichlorosulfonamide and 0.5g of antimony pentachloride were added to a fluorination reactor, and the mixture was heated. 20g of HF gas was slowly introduced while stirring. After the reaction was completed, the material in the reactor was transferred to a distillation column for purification to obtain dichlorosulfonamide. Hydrogen chloride generated by the fluorination reaction was washed with water to prepare hydrochloric acid as a byproduct.

[0096] The reaction temperature was 130℃ and the reaction time was 20h.

[0097] The preparation method of the aforementioned dichlorosulfonamide is as follows:

[0098] 70g of aminosulfonic acid, 200g of thionyl chloride, and 90g of chlorosulfonic acid were added to a condensation reaction vessel, and the mixture was heated. After the reaction was completed, the mixture was distilled under reduced pressure to obtain dichlorosulfonamide. The gas that overflowed from the reaction was absorbed by an alkaline solution.

[0099] The reaction temperature was 120℃ and the reaction time was 30 hours.

[0100] The preparation method of the dechlorination adsorption resin is as follows:

[0101] 130g of mercapto resin was placed in 1000g of toluene, and then 0.5g of epoxy nano bismuth oxide, 2.5g of vinyl ferrocene, 6g of magnesium acrylate, and 7g of sodium ethoxide were added. The mixture was stirred at 60℃ for 100 minutes, filtered, washed, and dried to obtain dechlorination adsorption resin.

[0102] The preparation method of the epoxy-based nano-bismuth oxide is as follows:

[0103] Weigh 5g of γ-(2,3-epoxypropoxy)propyltriethoxysilane, 150g of nano-bismuth oxide, and 1300g of water and place them in a sealed reaction vessel. Stir at 40℃ for 60min, filter, and dry to obtain epoxy-based nano-bismuth oxide.

[0104] The mercapto resin mentioned is the commercially available product LSC-400 mercapto resin.

[0105] The method for preparing the hydrofluoric acid is as follows:

[0106] Under normal pressure, 100°C superheated steam is passed into a 90wt% fluorosulfonic acid evaporator for atmospheric distillation. The temperature inside the evaporator is raised to 100°C and maintained at 90-100°C for 4 hours. The final residue at the bottom of the evaporator is 95% sulfuric acid. The gas produced at the top of the evaporator, after cooling, yields hydrofluoric acid with a purity greater than 99%.

[0107] Comparative Example 1

[0108] No dechlorination adsorption resin was added; otherwise, it was the same as in Example 1.

[0109] Comparative Example 2

[0110] Without the addition of epoxy-based nano-bismuth oxide, the rest is the same as in Example 1.

[0111] Comparative Example 3

[0112] Without adding vinyl ferrocene, otherwise the same as in Example 1.

[0113]

[0114]

[0115] Based on the data analysis of the above embodiments and comparative examples, the lithium bis(fluorosulfonyl)imide prepared by the present invention has a high content and low content of impurities such as moisture, chloride, free acid, and insoluble matter.

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for synthesizing lithium bis(fluorosulfonyl)imide from recycled fluorosulfonic acid resources, comprising the following steps, in parts by mass: S1: Add 50-60 parts of dichloromethane and 1-5 parts of lithium hydroxide monohydrate to a filter press, cool to 0-5℃, add 10-20 parts of bis(fluorosulfonyl)imide dropwise while stirring, stir for 1-3 hours, then heat to 20-25℃, add 30-40 parts of thionyl chloride dropwise, stir for 10-15 hours, filter, and obtain crude lithium bis(fluorosulfonyl)imide. S2: Dissolve crude lithium difluorosulfonylimide in a mixed solvent, add 5-10 parts of dechlorination adsorption resin, stir for 30-60 minutes, filter, evaporate the filtrate under reduced pressure, desolvent and crystallize, wash with dichloroethane, filter, and dry under reduced pressure to obtain lithium difluorosulfonylimide. The preparation method of the dechlorination adsorption resin is as follows: By weight, 100-130 parts of mercapto resin are placed in 500-1000 parts of toluene, and then 0.05-0.5 parts of epoxy nano bismuth oxide, 0.5-2.5 parts of vinyl ferrocene, 3-6 parts of magnesium acrylate, and 4-7 parts of sodium ethoxide are added. The mixture is stirred at 50-60℃ for 40-100 minutes, filtered, washed, and dried to obtain dechlorination adsorption resin. The preparation method of the epoxy-based nano-bismuth oxide is as follows: Weigh 2-5 parts of γ-(2,3-epoxypropoxy)propyltriethoxysilane, 100-150 parts of nano-bismuth oxide, and 1000-1300 parts of water and place them in a sealed reaction vessel. Stir at 30-40℃ for 30-60 min, filter, and dry to obtain epoxy-based nano-bismuth oxide. The preparation method of the aforementioned difluorosulfonamide is as follows: Add 50-70 parts of dichlorosulfonamide and 0.05-0.5 parts of antimony pentachloride to a fluorination reactor, heat the reactor, and slowly introduce 15-20 parts of HF gas while stirring. After the reaction is complete, transfer the material in the reactor to a distillation column for purification to obtain dichlorosulfonamide. Hydrogen chloride generated from the fluorination reaction is washed with water to prepare hydrochloric acid as a byproduct. The preparation method of hydrofluoric acid is as follows: Under normal pressure, 100°C superheated steam is passed into an 80-90wt% fluorosulfonic acid evaporator for atmospheric distillation. The temperature inside the evaporator is raised to 90-100°C and maintained at 90-100°C for 3-4 hours. The final residue at the bottom of the evaporator is 90-95% sulfuric acid. The gas produced at the top of the evaporator, after cooling, yields hydrofluoric acid with a purity greater than 99%.

2. The method for synthesizing lithium bisfluorosulfonylimide by recycling fluorosulfonic acid resources according to claim 1, characterized in that: The mixed solvent is 50-60 parts dichloroethane and 5-10 parts diethyl ether.

3. The method for synthesizing lithium bisfluorosulfonylimide by recycling fluorosulfonic acid resources according to claim 1, characterized in that: The reaction temperature for preparing the bis(fluorosulfonyl)imide is 100-130℃, and the reaction time is 15-20h.

4. The method for synthesizing lithium bisfluorosulfonylimide by recycling fluorosulfonic acid resources according to claim 3, characterized in that: The preparation method of the aforementioned dichlorosulfonamide is as follows: Add 60-70 parts by weight of aminosulfonic acid, 100-200 parts by weight of thionyl chloride and 70-90 parts by weight of chlorosulfonic acid to the condensation reaction vessel, heat the mixture, and after the reaction is completed, distill under reduced pressure to obtain dichlorosulfonamide; absorb the gas overflowing from the reaction with alkaline solution.

5. The method for synthesizing lithium bisfluorosulfonylimide by recycling fluorosulfonic acid resources according to claim 4, characterized in that: The heating reaction temperature is 100-120℃, and the time is 25-30h.

Images