A method for preparing sodium bisfluorosulfonimide

Abstract

The application provides a preparation method of sodium bisfluorosulfonimide, comprising the following steps: (1) mixing bischlorosulfonimide and pyridine, stirring to form a complex, then adding pyridine hydrofluoric acid salt, and stirring under insulation to obtain a reaction solution containing HFSI Py; (2) adding acetonitrile to the reaction solution containing HFSI Py, standing for crystallization, centrifugal separation, then adding dichloromethane to the acetonitrile phase, adding isopropyl alcohol for dissolution, and after separation, obtaining an acetonitrile solution containing HFSI Py; (3) mixing sodium salt and acetonitrile to obtain a dispersion liquid, then adding the dispersion liquid into the acetonitrile solution containing HFSI Py, monitoring the pH value of the system on line, reacting, then performing vacuum distillation and vacuum drying to obtain the sodium bisfluorosulfonimide. The application develops a simple, efficient, low-cost, safe and environment-friendly synthesis method of NaFSI, and realizes the goals of safety, high purity and suitability for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical material preparation technology, and relates to a method for preparing sodium difluorosulfonylimide. Background Technology

[0002] Sodium bis(fluorosulfonyl)imide (NaFSI), as a novel electrolyte salt for sodium-ion batteries, shows greater application potential than traditional sodium hexafluorophosphate (NaPF6) due to its high ionic conductivity, excellent thermal and electrochemical stability, and high solubility. However, its industrial-scale preparation still faces many challenges.

[0003] Existing synthetic methods suffer from several significant drawbacks. For instance, methods using anhydrous hydrofluoric acid (HF) as the fluorinating agent are extremely corrosive, toxic, and hazardous, requiring stringent standards for equipment materials and production safety. Routes using ammonia or triethylamine trihydrofluoride as raw materials face challenges in precise gas control and high costs. Palladium-catalyzed hydrogenation processes are cumbersome and economically unfeasible. Furthermore, during salt formation and purification, byproducts such as pyridine hydrochloride (Py·HCl) or residual pyridine are difficult to remove completely, readily reacting with alkali to form impurities like sodium pyridine (Py·NaCl), severely impacting the purity of the final product. Traditional purification methods (such as water washing extraction) may introduce moisture, leading to NaFSI hydrolysis and the formation of byproducts like Na₂FSI. Additionally, using a single high-temperature condition during drying can cause the thermal decomposition of NaFSI.

[0004] Therefore, developing a safe, simple, efficient, and scalable green synthetic route for producing high-purity NaFSI has become an urgent need in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing sodium bis(fluorosulfonyl)imide (NaFSI). Specifically, existing methods for preparing NaFSI generally suffer from poor safety (using highly toxic and corrosive anhydrous HF), high cost (using expensive catalysts), low purity (difficulty in removing persistent pyridine impurities, leading to byproduct formation and excessive residues), and the tendency to trigger side reactions during the process (local over-alkali causing NaFSI hydrolysis, and high-temperature drying causing its thermal decomposition). The present invention aims to solve these problems and develop a simple, efficient, low-cost, safe, and environmentally friendly method for synthesizing NaFSI, achieving the goals of safety, high purity, and suitability for industrial production.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0008] (1) Fluorination reaction:

[0009] Dichlorosulfonamide (HClSI) and pyridine (Py) were mixed and stirred until homogeneous to form a complex. Then, pyridine hydrofluoric acid salt (Py·HF) was added, and the mixture was kept warm and stirred to obtain a reaction solution containing HFSI·Py.

[0010] (2) Purification:

[0011] Add acetonitrile to the reaction solution containing HFSI·Py obtained in step (1), let it stand to crystallize, centrifuge to separate, then add dichloromethane to the acetonitrile phase and add isopropanol to aid dissolution, and after separation, obtain an acetonitrile solution containing HFSI·Py.

[0012] (3) Salt formation and drying:

[0013] Sodium salt and acetonitrile were mixed to obtain a dispersion. The dispersion was then added to the acetonitrile solution containing HFSI·Py obtained in step (2). The pH value of the system was monitored online to avoid local over-alkali reaction. The acetonitrile was removed by a first vacuum distillation and the pyridine was removed by a second vacuum distillation. After vacuum drying, the sodium difluorosulfonamide was obtained, which is a white NaFSI powder with high purity.

[0014] The preparation method provided by this invention involves adding acetonitrile for crystallization, followed by the addition of dichloromethane and isopropanol to form a three-phase system. The isopropanol's bridging effect enriches residual pyridine in the dichloromethane phase, while HFSI·Py remains in the acetonitrile phase. This significantly reduces the residual pyridine content (<50 ppm) and avoids the formation of Py·NaCl as a byproduct during subsequent salt formation. Compared to methods using only water-organic solvent two-phase extraction, this method solves the problem of residual pyridine.

[0015] This invention solves the problem of NaFSI thermal decomposition caused by using a single high-temperature (>100℃) drying method by employing a dual-gradient drying method of reduced pressure and vacuum.

[0016] The method for preparing sodium difluorosulfonylimide of this invention avoids the use of high-temperature reaction conditions (high temperature will aggravate side reactions, and if Py·HF turns into vapor at high temperature, it will be highly toxic and exothermic), difficult-to-control ammonia gas, expensive palladium catalyst, and highly corrosive hydrogen fluoride, which is in line with the principles of green and safe chemistry.

[0017] The preparation method provided by this invention uses an acetonitrile system. The acetonitrile system is significantly superior to the traditional water-based solvent route in terms of reducing the risk of hydrolysis, improving purity, shortening post-processing time, reducing equipment corrosion and environmental impact. It is particularly suitable for the high-purity preparation and industrial scale-up of NaFSI, which is sensitive to moisture.

[0018] Taking sodium hydroxide as an example, the reaction equation for preparing sodium difluorosulfonamide provided by this invention is as follows:

[0019] .

[0020] Preferably, the molar ratio of dichlorosulfonamide (HClSI) to pyridine (Py) in step (1) is 1:(1~2), for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, etc. When the molar ratio of HClSI to Py is less than 1:2, that is, when the amount of Py is too large, after the reaction is completed, the excess pyridine needs to be removed, which increases the difficulty of purification and may also lead to side reactions; when the molar ratio of HClSI to Py is greater than 1:1, that is, when the amount of Py is too small, HClSI cannot completely form a stable complex with Py, and some free HClSI may escape from the system, directly leading to a decrease in reaction yield and product purity.

[0021] Preferably, the stirring temperature during the formation of the complex in step (1) is 20~30℃, for example 20℃, 25℃, 30℃, etc., and the stirring time is 0.5~1h, for example 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, etc. When the stirring temperature is higher than 30℃, the reaction system will undergo thermally induced decomposition and a series of complex side reactions, generating colored impurities. When the stirring temperature is lower than 20℃, the complexation reaction rate decreases, the reaction system will solidify into a solid, stirring cannot proceed, resulting in incomplete subsequent fluorination reaction, which greatly affects the yield and purity of the product.

[0022] Preferably, the molar ratio of dichlorosulfonamide (HClSI) to pyridine hydrofluoric acid (Py·HF) in step (1) is 1:(1.8~2.2), for example, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, etc. When the amount of Py·HF is insufficient, it may lead to incomplete fluorination, generating unnecessary impurities, reducing the purity and yield of the product; when the amount of Py·HF is too large, it will lead to unnecessary waste of raw materials, and the excess Py·HF will also become an impurity, which may trigger side reactions, and at the same time greatly increase the burden and cost of subsequent purification.

[0023] Preferably, when adding pyridine hydrofluoric acid in step (1), the temperature of the system is controlled to be -10~0℃, for example -10℃, -8℃, -6℃, -5℃, -4℃, -2℃, 0℃, etc.

[0024] Preferably, the addition of pyridine hydrofluoric acid in step (1) is done by dripping.

[0025] Preferably, the dropping rate is 0.1~2 mL / min, for example 0.1 mL / min, 0.2 mL / min, 0.3 mL / min, 0.5 mL / min, 0.8 mL / min, 1 mL / min, 1.2 mL / min, 1.4 mL / min, 1.5 mL / min, 1.6 mL / min, 1.8 mL / min, 2 mL / min, etc.

[0026] As a preferred technical solution of the present invention, when adding pyridine hydrofluoric acid, controlling the system temperature at -10~0℃ can effectively inhibit the thermal decomposition of Py·HF reagent and prevent the leakage of highly toxic and volatile HF gas. Adding Py·HF dropwise at 0.1~2 mL / min can control the heat generated by the vigorous substitution reaction, avoiding local overheating that could lead to decomposition and side reactions, while ensuring the selectivity of the fluorination reaction and preventing impurity formation. If the system temperature is above 0℃ and the dropping rate is greater than 2 mL / min, it will lead to excessively high local concentrations, and the cooling system will not be able to dissipate heat in time, causing the overall reaction temperature to spike, triggering a chain of adverse reactions such as accelerated side reactions, decreased product purity, and the generation of corrosive HF. If the temperature is below -10℃ and the dropping rate is below 0.1 mL / min, production efficiency will be significantly reduced.

[0027] Preferably, the temperature for heat preservation and stirring in step (1) is -5~0℃, such as -5℃, -4℃, -3℃, -2℃, 0℃, etc., and the heat preservation and stirring time is 0.5~2h, such as 0.5h, 1h, 1.5h, 2h, etc. If the heat preservation and stirring temperature is too high, it may cause the unreacted Py·HF to decompose due to heat, resulting in incomplete fluorination reaction and possible side reactions; if the heat preservation and stirring temperature is too low, it will lead to a slow reaction rate and residual raw materials. If the heat preservation and stirring time is too long, it will lead to unnecessary energy consumption and potential side reactions; if the heat preservation and stirring time is too short, the reaction will not be complete, affecting the yield and wasting raw materials.

[0028] Preferably, the volume ratio of the HFSI·Py-containing reaction solution to acetonitrile in step (2) is 1:(0.8~1.2), for example, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, etc. The volume ratio of the HFSI·Py-containing reaction solution to acetonitrile is controlled at 1:(0.8~1.2) because at this ratio, Py·HCl can precipitate as completely as possible, while HFSI·Py dissolves in acetonitrile, achieving separation. When the amount of acetonitrile is excessive, impurities such as Py·HCl dissolve in acetonitrile and cannot be separated; insufficient acetonitrile will cause HFSI·Py to reach saturation, also precipitating, reducing the yield and wasting raw materials.

[0029] Preferably, the settling time for crystallization in step (2) is 0.5~1h, for example, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, etc. If the settling time is insufficient, the Py·HCl solid cannot be completely precipitated, introducing impurities; if the settling time is too long, it will not significantly change the amount of impurities precipitated, resulting in unnecessary time costs.

[0030] Preferably, the volume ratio of acetonitrile to dichloromethane in step (2) is 1:(1~2), for example 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, etc.

[0031] Preferably, in step (2), the volume fraction of isopropanol is 1% to 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., based on the total volume of the reaction solution containing HFSI·Py, acetonitrile and dichloromethane as 100%.

[0032] If the amount of dichloromethane and isopropanol is too low, the enrichment effect on Py will be poor, and impurities will still be present in the acetonitrile phase; if the amount of dichloromethane and isopropanol is too high, the enrichment effect on Py will not be significantly improved, resulting in wasted solvent and increased costs.

[0033] Preferably, the sodium salt in step (3) includes any one or a combination of at least two of sodium carbonate, sodium carboxylate, and sodium hydroxide.

[0034] Preferably, the mass ratio of sodium salt to acetonitrile in step (3) is 1:(1~1.5), for example 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1.5, etc.

[0035] Preferably, the molar ratio of sodium salt to HFSI·Py in step (3) is (0.4~1.1):1, for example, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1.1, 1:1, 1.1:1, etc. By precisely controlling this ratio, the preparation efficiency of sodium difluorosulfonylimide can be effectively improved, the production cost reduced, and the quality and performance of the final product ensured.

[0036] Preferably, step (3) of adding the dispersion to the acetonitrile solution containing HFSI·Py obtained in step (2) specifically includes: adding the dispersion to the acetonitrile solution containing HFSI·Py obtained in step (2) under stirring conditions at 0~5℃ (ice bath, e.g., 0℃, 1℃, 2℃, 3℃, 4℃, 5℃, etc.). When adding the dispersion, if the temperature of the system is too high, HFSI·Py will decompose upon heating, leading to side reactions and impurities; if the temperature of the system is too low, the reaction rate will be too slow, the reaction will be incomplete, the yield will be reduced, and raw materials will be wasted.

[0037] Preferably, the pH value in step (3) is 6.8 to 7.2, such as 6.8, 6.9, 7, 7.1, 7.2, etc. Acidic conditions result in the final product being a mixture of NaFSI, unreacted HFSI·Py, and free HFSI acid, introducing impurities; alkaline conditions cause NaFSI to hydrolyze, producing Na2FSI impurities.

[0038] Preferably, the reaction temperature in step (3) is 0~5℃, such as 0℃, 1℃, 2℃, 3℃, 4℃, 5℃, etc., and the reaction time is 6~10h, such as 6h, 7h, 8h, 9h, 10h, etc. A reaction time that is too long will not significantly improve the yield and will lead to unnecessary cost waste; a reaction time that is too short will result in incomplete salt formation and reduce the yield.

[0039] Preferably, the temperature of the first vacuum distillation in step (3) is 30~60℃, for example, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc. If the temperature of the first vacuum distillation is lower than this temperature, acetonitrile impurities cannot be removed; if the temperature of the first vacuum distillation is too high, energy consumption will increase.

[0040] Preferably, the temperature of the second vacuum distillation in step (3) is 60~80℃, for example 60℃, 65℃, 70℃, 75℃, 80℃, etc.

[0041] Preferably, the vacuum drying temperature in step (3) is 50~80℃, for example 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, etc., and the vacuum drying time is 24~48h, for example 24h, 28h, 30h, 36h, 40h, 44h, 48h, etc. If the vacuum drying temperature is too low, it will be impossible to remove the trace amounts of pyridine and possible moisture remaining in the product; if the vacuum drying temperature is too high, it will increase the risk of high-temperature decomposition of NaFSI. If the vacuum drying time is too short, it may be impossible to remove the residual liquid impurities; if the vacuum drying time is too long, it will result in unnecessary energy consumption and cost waste.

[0042] As a preferred embodiment of the present invention, the preparation method includes the following steps:

[0043] (1) Mix dichlorosulfonamide and pyridine in a molar ratio of 1:(1~2), stir at 20~30℃ for 0.5~1h to form a complex, lower the temperature of the system to -10~0℃, and then add pyridine hydrofluoric acid dropwise at a rate of 0.1~2mL / min, and keep warm and stir at -5~0℃ for 0.5~2h to obtain a reaction solution containing HFSI·Py;

[0044] The molar ratio of dichlorosulfonamide to pyridine hydrofluoric acid is 1:(1.8~2.2);

[0045] (2) Add acetonitrile to the reaction solution containing HFSI·Py obtained in step (1), let it stand to crystallize for 0.5~1h, centrifuge to separate, then add dichloromethane to the acetonitrile phase and add isopropanol to aid dissolution, stir and let it stand to separate the liquid, retain the acetonitrile phase, and obtain an acetonitrile solution containing HFSI·Py.

[0046] The volume ratio of the reaction solution containing HFSI·Py to acetonitrile is 1:(0.8~1.2);

[0047] The volume ratio of acetonitrile to dichloromethane is 1:(1~2);

[0048] Based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane as 100%, the volume fraction of isopropanol is 1% to 5%.

[0049] (3) Mix sodium salt and acetonitrile to obtain a dispersion. Then, under stirring conditions at 0~5℃ (ice bath), add the dispersion to the acetonitrile solution containing HFSI·Py obtained in step (2). Control the feeding rate of the dispersion by an online pH meter to maintain the pH value of the system at 6.8~7.2 to avoid local over-alkali. React at 0~5℃ for 6~10h. Then, remove acetonitrile by a first vacuum distillation at 30~60℃, and remove pyridine by a second vacuum distillation at 60~80℃. Finally, vacuum dry at 50~80℃ for 24~48h to obtain the sodium difluorosulfonamide.

[0050] The molar ratio of sodium salt to HFSI·Py is (0.4~1.1):1;

[0051] The mass ratio of sodium salt to acetonitrile is 1:(1~1.5).

[0052] The sodium difluorosulfonamide prepared by the method of the present invention has a yield >95%, such as 95.5%, 96.3%, 96.9%, 98.4%, 98.8%, 99.2%, etc., and a purity ≥98.0%, such as 98.0%, 98.5%, 98.8%, 99.1%, 99.6%, etc.

[0053] This invention achieves efficient and high-purity preparation of sodium bis(fluorosulfonyl)imide through a unique and flexible reaction process, a wide range of raw material ratios and reaction conditions, diverse solvent selection, and optimized purification technology. These key technical aspects ensure its practicality and competitiveness in industrial production.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) The preparation method provided by this invention involves adding acetonitrile for crystallization, followed by the addition of dichloromethane and isopropanol to form a three-phase system. The isopropanol's bridging effect enriches residual pyridine in the dichloromethane phase, while HFSI·Py remains in the acetonitrile phase. This significantly reduces the residual pyridine content (<50 ppm) and avoids the formation of Py·NaCl as a byproduct during subsequent salt formation. Compared to the two-phase extraction method using only water and organic solvents, this method solves the problem of residual pyridine.

[0056] (2) This invention solves the problem of NaFSI thermal decomposition caused by using a single high temperature (>100℃) drying method by using a dual gradient drying method of reduced pressure and vacuum.

[0057] (3) The method for preparing sodium difluorosulfonylimide of the present invention avoids the use of high temperature reaction conditions (high temperature will aggravate side reactions, and if Py·HF turns into vapor at high temperature, it will be highly toxic and exothermic), difficult-to-control ammonia, high-cost palladium catalyst and highly corrosive hydrogen fluoride, which is in line with the principles of green and safe chemistry.

[0058] (4) The acetonitrile system is significantly better than the traditional water-soluble route in terms of reducing hydrolysis risk, improving purity, shortening post-processing time, reducing equipment corrosion and environmental load. It is especially suitable for the high-purity preparation and industrial scale-up of NaFSI that is sensitive to moisture. Detailed Implementation

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0060] Example 1

[0061] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0062] Step 1: Mix dichlorosulfonamide (HClSI) and pyridine (Py) in a molar ratio of 1:1.2, control the reaction temperature at 26℃, and stir for 55 min to form a homogeneous complex solution.

[0063] Step 2: Cool the reaction system to -8℃, and add pyridine hydrofluoric acid salt (Py·HF) dropwise at a rate of 1.3 mL / min under stirring, wherein the molar ratio of HClSI to Py·HF is 1:1.9. After the addition is complete, keep the mixture at -2℃ and continue stirring for 45 min to obtain a reaction solution containing HFSI·Py.

[0064] Step 3: Add 1.15 times the volume of acetonitrile to the reaction solution containing HFSI·Py, and allow it to stand for crystallization for 50 min. After centrifugation, collect the upper acetonitrile phase. Add dichloromethane (acetonitrile:dichloromethane = 1:1.5, volume ratio) and 2 vol% (based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane being 100%) isopropanol to the acetonitrile phase, stir, and allow it to stand for separation, retaining the acetonitrile phase to obtain an acetonitrile solution containing HFSI·Py.

[0065] Step 4: Disperse sodium carboxylate in acetonitrile (sodium carboxylate to acetonitrile mass ratio of 1:1) to obtain a dispersion. Under ice bath stirring, slowly add this dispersion to the above acetonitrile solution containing HFSI·Py (sodium carboxylate to HFSI·Py molar ratio of 1:1.1), controlling the addition rate using an online pH meter to maintain the pH of the reaction system at 7, and the temperature at 0℃ for 9 hours.

[0066] Step 5: The reaction solution was distilled under reduced pressure at 40°C to remove the acetonitrile solvent. The residue was then distilled under reduced pressure at 75°C to remove residual pyridine. Finally, the resulting white solid was dried under vacuum at 75°C for 40 hours to obtain the final product, sodium difluorosulfonamide.

[0067] Example 2

[0068] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0069] Step 1: Mix dichlorosulfonamide (HClSI) and pyridine (Py) in a molar ratio of 1:1.8 and stir at 27°C for 45 min to form a homogeneous complex solution.

[0070] Step 2: Cool the reaction system to -5℃, and add pyridine hydrofluoric acid salt (Py·HF) dropwise at a rate of 1.4 mL / min under stirring, wherein the molar ratio of HClSI to Py·HF is 1:2.1. After the addition is complete, keep the mixture at -4℃ and continue stirring for 1.3 h to obtain a reaction solution containing HFSI·Py.

[0071] Step 3: Add 0.9 times the volume of acetonitrile to the reaction solution containing HFSI·Py, and allow it to stand for crystallization for 50 min. After centrifugation, collect the upper acetonitrile phase. Add dichloromethane (acetonitrile:dichloromethane = 1:1.7, volume ratio) and 4 vol% (based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane being 100%) isopropanol to the acetonitrile phase, stir, and allow it to stand for separation, retaining the acetonitrile phase to obtain an acetonitrile solution containing HFSI·Py.

[0072] Step 4: Disperse sodium carboxylate in acetonitrile (mass ratio of sodium carboxylate to acetonitrile is 1:1.5) to obtain a dispersion. Under ice bath stirring, slowly add this dispersion to the above acetonitrile solution containing HFSI·Py (molar ratio of sodium carboxylate to HFSI·Py is 1:1). Control the addition rate using an online pH meter, maintain the pH of the reaction system at 6.9, control the temperature at 4℃, and react for 7 hours.

[0073] Step 5: The reaction solution was distilled under reduced pressure at 55°C to remove the acetonitrile solvent. The residue was then distilled under reduced pressure at 65°C to remove residual pyridine. Finally, the resulting white solid was dried under vacuum at 65°C for 30 hours to obtain the final product, sodium difluorosulfonamide.

[0074] Example 3

[0075] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0076] Step 1: Mix dichlorosulfonamide (HClSI) and pyridine (Py) in a molar ratio of 1:1.6 and stir at 22°C for 0.6 h to form a homogeneous complex solution.

[0077] Step 2: Cool the reaction system to -4℃, and add pyridine hydrofluoric acid salt (Py·HF) dropwise at a rate of 1.2 mL / min under stirring, wherein the molar ratio of HClSI to Py·HF is 1:1.9. After the addition is complete, keep the mixture at -1℃ and continue stirring for 0.8 h to obtain a reaction solution containing HFSI·Py.

[0078] Step 3: Add 1.1 times the volume of acetonitrile to the reaction solution containing HFSI·Py, and allow it to stand for crystallization for 0.6 h. After centrifugation, collect the upper acetonitrile phase. Add dichloromethane (acetonitrile:dichloromethane = 1:1.5, volume ratio) and 2 vol% (based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane being 100%) isopropanol to the acetonitrile phase, stir, and allow it to stand for separation, retaining the acetonitrile phase to obtain an acetonitrile solution containing HFSI·Py.

[0079] Step 4: Disperse sodium carbonate in acetonitrile (mass ratio of sodium carbonate to acetonitrile is 1:1.3) to obtain a dispersion. Under ice bath stirring, slowly add this dispersion to the above acetonitrile solution containing HFSI·Py (molar ratio of Na2CO3 to HFSI·Py is 0.4:1). Control the addition rate using an online pH meter, maintain the pH of the reaction system at 7.1, control the temperature at 3℃, and react for 7 hours.

[0080] Step 5: The reaction solution was distilled under reduced pressure at 50°C to remove the acetonitrile solvent. The residue was then distilled under reduced pressure at 75°C to remove residual pyridine. Finally, the resulting white solid was dried under vacuum at 70°C for 36 hours to obtain the final product, sodium difluorosulfonamide.

[0081] Example 4

[0082] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0083] Step 1: Mix dichlorosulfonamide (HClSI) and pyridine (Py) in a molar ratio of 1:1.4 and stir at 30°C for 40 min to form a homogeneous complex solution.

[0084] Step 2: Cool the reaction system to -6℃, and add pyridine hydrofluoric acid salt (Py·HF) dropwise at a rate of 2.0 mL / min under stirring, wherein the molar ratio of HClSI to Py·HF is 1:2.2. After the addition is complete, keep the mixture at -3℃ and continue stirring for 1.5 h to obtain a reaction solution containing HFSI·Py.

[0085] Step 3: Add 1.2 volumes of acetonitrile to the reaction solution containing HFSI·Py, and allow it to stand for crystallization for 0.8 h. After centrifugation, collect the upper acetonitrile phase. Add dichloromethane (acetonitrile:dichloromethane = 1:1.6, volume ratio) and 3 vol% (based on the total volume of the HFSI·Py reaction solution, acetonitrile, and dichloromethane being 100%) isopropanol to the acetonitrile phase, stir, and allow it to stand for separation, retaining the acetonitrile phase to obtain an acetonitrile solution containing HFSI·Py.

[0086] Step 4: Disperse sodium carbonate in acetonitrile (mass ratio of sodium carbonate to acetonitrile is 1:1.4) to obtain a dispersion. Under ice bath stirring, slowly add this dispersion to the above acetonitrile solution containing HFSI·Py (molar ratio of Na2CO3 to HFSI·Py is 0.5:1). Control the addition rate using an online pH meter, maintain the pH of the reaction system at 6.8, control the temperature at 2℃, and react for 10 hours.

[0087] Step 5: The reaction solution was distilled under reduced pressure at 60°C to remove the acetonitrile solvent. The residue was then distilled under reduced pressure at 80°C to remove residual pyridine. Finally, the resulting white solid was dried under vacuum at 60°C for 24 hours to obtain the final product, sodium difluorosulfonamide.

[0088] Example 5

[0089] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0090] Step 1: Mix dichlorosulfonamide (HClSI) and pyridine (Py) in a molar ratio of 1:2 and stir at 20°C for 0.5 h to form a homogeneous complex solution.

[0091] Step 2: Cool the reaction system to -10℃, and add pyridine hydrofluoric acid salt (Py·HF) dropwise at a rate of 0.1 mL / min under stirring, wherein the molar ratio of HClSI to Py·HF is 1:1.8. After the addition is complete, keep the mixture at -5℃ and continue stirring for 2 hours to obtain a reaction solution containing HFSI·Py.

[0092] Step 3: Add 0.8 times the volume of acetonitrile to the reaction solution containing HFSI·Py, and allow it to stand for crystallization for 0.5 h. After centrifugation, collect the upper acetonitrile phase. Add dichloromethane (acetonitrile:dichloromethane = 1:2, volume ratio) and 1 vol% (based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane being 100%) isopropanol to the acetonitrile phase, stir, and allow it to stand for separation, retaining the acetonitrile phase to obtain an acetonitrile solution containing HFSI·Py.

[0093] Step 4: Disperse NaOH in acetonitrile (NaOH to acetonitrile mass ratio 1:1.2) to obtain a dispersion. Under ice bath stirring, slowly add this dispersion to the above acetonitrile solution containing HFSI·Py (NaOH to HFSI·Py molar ratio 1:1), controlling the addition rate with an online pH meter to maintain the pH of the reaction system at 7.2, and the temperature at 5℃ for 6 hours.

[0094] Step 5: The reaction solution was distilled under reduced pressure at 30°C to remove the acetonitrile solvent. The residue was then distilled under reduced pressure at 60°C to remove residual pyridine. Finally, the resulting white solid was dried under vacuum at 50°C for 48 hours to obtain the final product, sodium difluorosulfonamide.

[0095] Example 6

[0096] This embodiment provides a method for preparing sodium difluorosulfonamide, the method comprising the following steps:

[0097] Step 1: Mix dichlorosulfonamide (HClSI) and pyridine (Py) in a molar ratio of 1:1 and stir at 25°C for 1 hour to form a homogeneous complex solution.

[0098] Step 2: Cool the reaction system to 0℃, and add pyridine hydrofluoric acid salt (Py·HF) dropwise at a rate of 1.0 mL / min under stirring, wherein the molar ratio of HClSI to Py·HF is 1:2. After the addition is complete, keep the mixture at 0℃ and continue stirring for 1 h to obtain a reaction solution containing HFSI·Py.

[0099] Step 3: Add 1 volume of acetonitrile to the reaction solution containing HFSI·Py, and allow it to stand for 1 hour to crystallize. After centrifugation, collect the upper acetonitrile phase. Add dichloromethane (acetonitrile:dichloromethane = 1:1, volume ratio) and 5 vol% (based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane being 100%) isopropanol to the acetonitrile phase, stir, and allow it to stand for separation. Retain the acetonitrile phase to obtain an acetonitrile solution containing HFSI·Py.

[0100] Step 4: Disperse sodium hydroxide in acetonitrile (sodium hydroxide to acetonitrile mass ratio 1:1) to obtain a dispersion. Under ice bath stirring, slowly add this dispersion to the above acetonitrile solution containing HFSI·Py (NaOH to HFSI·Py molar ratio 1:1), controlling the addition rate with an online pH meter to maintain the pH of the reaction system at 7.0, and the temperature at 0℃ for 8 hours.

[0101] Step 5: The reaction solution was distilled under reduced pressure at 45°C to remove the acetonitrile solvent. The residue was then distilled under reduced pressure at 70°C to remove residual pyridine. Finally, the resulting white solid was dried under vacuum at 80°C for 48 hours to obtain the final product, sodium difluorosulfonamide.

[0102] Example 7

[0103] The only difference between this embodiment and Embodiment 1 is that in step 4, sodium carboxylate is replaced with an equimolar amount of sodium oxalate.

[0104] Example 8

[0105] The only difference between this embodiment and Example 1 is that, in step 4, the molar ratio of sodium carboxylate to HFSI·Py is 0.2:1.

[0106] Example 9

[0107] The only difference between this embodiment and Example 1 is that, in step 4, the molar ratio of sodium carboxylate to HFSI·Py is 1.5:1.

[0108] Example 10

[0109] The only difference between this embodiment and Example 1 is that, in step 4, the pH value of the reaction system is maintained at 6.

[0110] Example 11

[0111] The only difference between this embodiment and Example 1 is that, in step 4, the pH value of the reaction system is maintained at 8.

[0112] Comparative Example 1

[0113] The only difference between this comparative example and Example 1 is that, in step 3, dichloromethane is replaced with an equal volume of acetonitrile.

[0114] Comparative Example 2

[0115] The only difference between this comparative example and Example 1 is that isopropanol is not added in step 3.

[0116] Comparative Example 3

[0117] The only difference between this comparative example and Example 1 is that, in step 3, dichloromethane is replaced with an equal volume of toluene.

[0118] Comparative Example 4

[0119] The only difference between this comparative example and Example 1 is that in step 3, isopropanol is replaced with an equal volume of ethanol.

[0120] Comparative Example 5

[0121] The only difference between this comparative example and Example 1 is that step 5 is different, as follows: the reaction solution is dried at 150°C for 48 hours.

[0122] The performance of the sodium difluorosulfonamide provided in the embodiments and comparative examples of the present invention was tested using the following methods:

[0123] (1) Yield: The formula for calculating yield is: ;

[0124] (2) Purity: The purity of the product was determined by nuclear magnetic resonance fluorine spectroscopy (NMR spectroscopy). 19 The determination was performed using F NMR. In the measured spectrum, F in the product is located at... At that location, F in the impurity is located , The peak areas of the F signal in the above products and impurities are integrated, and the integral values ​​are A and B, respectively. The purity is calculated according to the following formula. .

[0125] The performance test results are shown in Table 1.

[0126] Table 1

[0127]

[0128] As shown in Table 1, the sodium difluorosulfonamide prepared by the methods provided in Examples 1-6 of this invention all have high yields (>95%) and purity (≥98%), indicating that the preparation methods provided by this invention are highly feasible. In Examples 7-11, the yield and purity of sodium difluorosulfonamide decreased significantly because the selection of certain experimental conditions was outside the given range.

[0129] Compared with Example 1, the yield and purity of sodium difluorosulfonamide provided in Comparative Examples 1-5 were significantly reduced. Specifically, in Comparative Examples 1-4, the choice of purification solvent in step 3 was changed, resulting in a large amount of pyridine residue and a large amount of subsequent impurity Py·NaCl, which made it difficult to remove impurities. In Comparative Example 5, a high-temperature drying method was used, which led to the high-temperature decomposition of the final product sodium difluorosulfonamide.

[0130] The applicant declares that the present invention illustrates the preparation method of sodium bis(fluorosulfonyl)imide through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing sodium difluorosulfonamide, characterized in that, The preparation method includes the following steps: (1) Mix dichlorosulfonamide with pyridine, stir to form a complex, then add pyridine hydrofluoric acid salt, keep warm and stir to obtain a reaction solution containing HFSI·Py; (2) Add acetonitrile to the reaction solution containing HFSI·Py obtained in step (1), let it stand to crystallize, centrifuge and separate, then add dichloromethane to the acetonitrile phase and add isopropanol to aid dissolution, and after separation, obtain an acetonitrile solution containing HFSI·Py. (3) Mix sodium salt and acetonitrile to obtain a dispersion, then add the dispersion to the acetonitrile solution containing HFSI·Py obtained in step (2), and monitor the pH value of the system online. After the reaction, remove acetonitrile by the first vacuum distillation, remove pyridine by the second vacuum distillation, and obtain sodium difluorosulfonamide by vacuum drying.

2. The preparation method according to claim 1, characterized in that, The molar ratio of dichlorosulfonamide to pyridine in step (1) is 1:(1~2).

3. The preparation method according to claim 1, characterized in that, The stirring temperature during step (1) when forming the complex is 20~30℃ and the stirring time is 0.5~1h.

4. The preparation method according to claim 1, characterized in that, The molar ratio of dichlorosulfonamide to pyridine hydrofluoric acid in step (1) is 1:(1.8~2.2).

5. The preparation method according to claim 1, characterized in that, When adding pyridine hydrofluoric acid in step (1), the temperature of the system is controlled to be -10~0℃.

6. The preparation method according to claim 1, characterized in that, The method of adding pyridine hydrofluoric acid in step (1) is dropwise addition.

7. The preparation method according to claim 6, characterized in that, The dropping rate is 0.1~2 mL / min.

8. The preparation method according to claim 1, characterized in that, The temperature for heat preservation and stirring in step (1) is -5~0℃, and the heat preservation and stirring time is 0.5~2h.

9. The preparation method according to claim 1, characterized in that, The volume ratio of the HFSI·Py reaction solution to acetonitrile in step (2) is 1:(0.8~1.2).

10. The preparation method according to claim 1, characterized in that, The time for static crystallization in step (2) is 0.5~1h.

11. The preparation method according to claim 1, characterized in that, The volume ratio of acetonitrile to dichloromethane in step (2) is 1:(1~2).

12. The preparation method according to claim 1, characterized in that, In step (2), the volume fraction of isopropanol is 1% to 5%, based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane as 100%.

13. The preparation method according to claim 1, characterized in that, The sodium salt in step (3) includes any one or a combination of at least two of sodium carbonate, sodium carboxylate, and sodium hydroxide.

14. The preparation method according to claim 1, characterized in that, The mass ratio of sodium salt to acetonitrile in step (3) is 1:(1~1.5).

15. The preparation method according to claim 1, characterized in that, The molar ratio of sodium salt to HFSI·Py in step (3) is (0.4~1.1):

1.

16. The preparation method according to claim 1, characterized in that, Step (3) involves adding the dispersion to the acetonitrile solution containing HFSI·Py obtained in step (2), specifically including adding the dispersion to the acetonitrile solution containing HFSI·Py obtained in step (2) at 0~5℃ with stirring.

17. The preparation method according to claim 1, characterized in that, The pH value in step (3) is 6.8~7.

2.

18. The preparation method according to claim 1, characterized in that, The reaction temperature in step (3) is 0~5℃ and the reaction time is 6~10h.

19. The preparation method according to claim 1, characterized in that, The temperature of the first vacuum distillation in step (3) is 30~60℃.

20. The preparation method according to claim 1, characterized in that, The temperature of the second vacuum distillation in step (3) is 60~80℃.

21. The preparation method according to claim 1, characterized in that, The vacuum drying temperature in step (3) is 50~80℃, and the vacuum drying time is 24~48h.

22. A preparation method according to any one of claims 1-21, characterized in that, The preparation method includes the following steps: (1) Mix dichlorosulfonamide and pyridine in a molar ratio of 1:(1~2), stir at 20~30℃ for 0.5~1h to form a complex, lower the temperature of the system to -10~0℃, and then add pyridine hydrofluoric acid dropwise at a rate of 0.1~2mL / min, and keep warm and stir at -5~0℃ for 0.5~2h to obtain a reaction solution containing HFSI·Py; The molar ratio of dichlorosulfonamide to pyridine hydrofluoric acid is 1:(1.8~2.2); (2) Add acetonitrile to the reaction solution containing HFSI·Py obtained in step (1), let it stand to crystallize for 0.5~1h, centrifuge to separate, then add dichloromethane to the acetonitrile phase and add isopropanol to aid dissolution, stir and let it stand to separate the liquid, retain the acetonitrile phase, and obtain an acetonitrile solution containing HFSI·Py. The volume ratio of the reaction solution containing HFSI·Py to acetonitrile is 1:(0.8~1.2); The volume ratio of acetonitrile to dichloromethane is 1:(1~2); Based on the total volume of the reaction solution containing HFSI·Py, acetonitrile, and dichloromethane as 100%, the volume fraction of isopropanol is 1% to 5%. (3) Mix sodium salt and acetonitrile to obtain a dispersion. Then, under stirring conditions at 0~5℃, add the dispersion to the acetonitrile solution containing HFSI·Py obtained in step (2). Control the feeding rate of the dispersion by an online pH meter to maintain the pH value of the system at 6.8~7.2 to avoid local over-alkali. React at 0~5℃ for 6~10h. Then, remove acetonitrile by a first vacuum distillation at 30~60℃, and remove pyridine by a second vacuum distillation at 60~80℃. Then, vacuum dry at 50~80℃ for 24~48h to obtain the sodium difluorosulfonamide. The molar ratio of sodium salt to HFSI·Py is (0.4~1.1):1; The mass ratio of sodium salt to acetonitrile is 1:(1~1.5).

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