Preparation method of high-purity potassium bis(fluorosulfonyl)imide

Abstract

The present application relates to a method for preparing high-purity potassium bis(fluorosulfonyl)imide, which comprises the following steps: reacting sulfuryl fluoride, ammonia and triethylamine to obtain a first reaction solution; separating the first reaction solution by washing with water to obtain an aqueous phase α and an organic phase β; adding an aqueous solution of an alkali metal carbonate to the aqueous phase α and the organic phase β respectively, and separating the organic phase β to obtain the aqueous phase α 1 and the organic phase β 1 , the aqueous phase α 1 is separated to obtain the aqueous phase α 2 and the organic phase β 2 ; combining the aqueous phase α 1 and the aqueous phase α 2 to obtain the aqueous phase α 3 , continuously adding an aqueous solution of an alkali metal carbonate, and separating to obtain the aqueous phase α 3 and the organic phase β 3 ; combining the organic phase β 1 , β 2 and β 3 to obtain triethylamine bis(fluorosulfonyl)imide salt, reacting the obtained triethylamine bis(fluorosulfonyl)imide salt with an aqueous solution of potassium hydroxide to obtain a second reaction solution, and after purification treatment, a pure product of potassium bis(fluorosulfonyl)imide is obtained. The present application can safely and efficiently improve the purity and yield of potassium bis(fluorosulfonyl)imide, thereby improving the purity and yield of lithium bis(fluorosulfonyl)imide.

Description

Technical Field

[0001] This application relates to the field of the preparation process of potassium bis(fluorosulfonyl)imide, and particularly to a method for preparing high-purity potassium bis(fluorosulfonyl)imide. Background Art

[0002] With the popularization of the requirements for green and low-carbon, as well as the country's emphasis on and encouragement of the development of new energy, lithium batteries are widely used in new energy vehicles, digital products, energy storage and other fields due to their characteristics such as high working voltage, high energy density, and no memory effect. Among them, lithium bis(fluorosulfonyl)imide (LiFSI) is considered to be the most potential electrolyte lithium salt to replace lithium hexafluorophosphate at present due to its excellent performance.

[0003] The traditional route is to first synthesize LiFSI, and then obtain the target product through purification and drying. However, due to the sensitivity of LiFSI itself to moisture and its easy decomposition during the heating process, the large-scale application of LiFSI and lithium-ion batteries using it is greatly restricted. At present, only low-specification LiFSI can be used as an additive in the electrolyte to make up for some deficiencies of lithium hexafluorophosphate as the main salt. If LiFSI is to play its excellent electrochemical performance as the main salt of the lithium battery electrolyte, it must be a high-purity product. Therefore, it is an urgent technical problem to be solved to prepare LiFSI with a content of more than 99.99%, a water content lower than 20 ppm, and low anion / cation impurity content.

[0004] Potassium bis(fluorosulfonyl)imide (KFSI) is stable in air at room temperature and does not carry bound water. It can be used to prepare anhydrous potassium salts through the neutralization method, and then a series of alkali metal bis(fluorosulfonyl)imides such as lithium bis(fluorosulfonyl)imide and sodium bis(fluorosulfonyl)imide can be prepared from the anhydrous potassium salt. Therefore, it is of great social significance and economic value to develop a new process that directly reacts with pure KFSI as an intermediate to obtain high-quality LiFSI.

[0005] At present, the preparation technologies of potassium bis(fluorosulfonyl)imide can be divided into three routes:

[0006] The first one is to react bis(chlorosulfonyl)imide with fluorinating reagents such as potassium fluoride, zinc fluoride or hydrogen fluoride to generate potassium bis(fluorosulfonyl)imide. Patent CN114436226A first prepares bis(chlorosulfonyl)imide by reacting sulfamic acid, chlorosulfonic acid and thionyl chloride, and then reacts bis(chlorosulfonyl)imide with potassium fluoride in dichloroethane to obtain potassium bis(fluorosulfonyl)imide; a large amount of acidic gases SO2 and HCl will be generated in the first-step reaction of this method, and a large excess of anhydrous potassium fluoride is required in the second-step reaction, with high cost and complex purification.

[0007] The second route is the acid-base neutralization reaction of difluorobisulfonimide with alkaline potassium salts such as potassium hydroxide or potassium carbonate to produce potassium difluorobisulfonimide. Patent CN106006586A proposes that first, dichlorobisulfonimide is obtained by reacting chlorosulfonic acid and chlorosulfonyl isocyanate, then difluorobisulfonimide is obtained by reacting with hydrogen fluoride, and finally potassium difluorobisulfonimide is obtained by reacting difluorobisulfonimide with alkaline potassium compounds. The chlorosulfonyl isocyanate method avoids the generation of gases such as SO 2 and HCl, which is more in line with environmental protection requirements. However, the production capacity of chlorosulfonyl isocyanate is limited, resulting in higher raw material costs and no advantage in industrial-scale production.

[0008] The third route is the metathesis reaction of the organic base salt of difluorobisulfonimide with a potassium source to obtain potassium difluorobisulfonimide. Patent CN116374966A uses a two-step method: sulfuryl fluoride reacts with an ammonium salt to obtain an organic ammonium salt of difluorobisulfonimide, and then the reaction solution containing the organic ammonium salt of difluorobisulfonimide reacts with a potassium reagent through a metathesis reaction to obtain potassium difluorobisulfonimide. However, the problems of this method are as follows: carbon dioxide gas will be generated during the metathesis reaction, which does not conform to the principle of atom economy; using ammonium fluoride, ammonium chloride, ammonium bromide, ammonium bisulfate, etc. as ammonium salts will introduce impurity anions such as Cl - and SO 4 2- , thus reducing the product purity.

[0009] Patent WO2023142028A1 reports a method for recycling raw and auxiliary materials in the production of lithium difluorobisulfonimide. The patent proposes that first, the product mixture generated by the reaction of sulfuryl fluoride, triethylamine, and ammonia is separated into an oil phase containing triethylamine difluorobisulfonimide salt, and an aqueous phase containing triethylamine hydrogen fluoride salt and impurity ions. Then, the oil phase containing triethylamine difluorobisulfonimide salt reacts with an aqueous lithium hydroxide solution to obtain crude lithium difluorobisulfonimide, and the aqueous phase containing triethylamine hydrogen fluoride salt and impurity ions reacts with an alkali metal hydroxide.

[0010] This method can obtain a reaction solution containing lithium difluorobisulfonimide and convert the by-product triethylamine hydrogen fluoride salt into an alkali metal fluoride. Although the utilization of the by-product triethylamine hydrogen fluoride salt and the recovery of triethylamine are realized, the purification and recovery of triethylamine difluorobisulfonimide salt are not involved, and the following problems will occur: 1) There are still impurities such as triethylamine hydrogen fluoride salt in the oil phase. Direct reaction with an aqueous lithium hydroxide solution will increase the amount of lithium hydroxide used, and high-quality lithium difluorobisulfonimide cannot be obtained in an aqueous solution reaction; 2) There is still triethylamine difluorobisulfonimide salt remaining in the aqueous phase, resulting in a low yield of triethylamine difluorobisulfonimide salt, and thus a low yield of lithium difluorobisulfonimide. Summary of the Invention

[0011] In order to safely and efficiently improve the purity and yield of potassium bis(fluorosulfonyl)imide, and thus improve the purity and yield of lithium bis(fluorosulfonyl)imide, the present application provides a method for preparing high-purity potassium bis(fluorosulfonyl)imide.

[0012] The method for preparing high-purity potassium bis(fluorosulfonyl)imide provided by the present application adopts the following technical solution:

[0013] A method for preparing high-purity potassium bis(fluorosulfonyl)imide, comprising the following steps:

[0014] Under the protection of an inert gas, using sulfuryl fluoride, ammonia, and triethylamine as raw materials, a first reaction is carried out in an organic solvent to obtain a first reaction solution containing triethylamine bis(fluorosulfonyl)imide salt;

[0015] The first reaction solution is filtered, concentrated under reduced pressure, washed with water, and then separated into an aqueous phase α and an organic phase β;

[0016] An aqueous solution of an alkali metal carbonate is added to the aqueous phase α and the organic phase β respectively, and the organic phase β is separated into an aqueous phase α 1 and an organic phase β 1 , and the aqueous phase α 1 is separated into an aqueous phase α 2 and an organic phase β 2 ;

[0017] The aqueous phase α 1 is combined with the aqueous phase α 2 to obtain an aqueous phase α 3 , and an aqueous solution of an alkali metal carbonate is continuously added, and then separated into an aqueous phase α 3 and an organic phase β 3 ;

[0018] The organic phase β 1 , β 2 is combined with β 3 to obtain an organic phase β 4 , that is, triethylamine bis(fluorosulfonyl)imide salt. The obtained triethylamine bis(fluorosulfonyl)imide salt and an aqueous solution of potassium hydroxide are subjected to a second reaction to obtain a second reaction solution containing potassium bis(fluorosulfonyl)imide;

[0019] After the second reaction solution is purified, a pure product of potassium bis(fluorosulfonyl)imide is obtained.

[0020] By adopting the above technical solution, under the protection of an inert gas, triethylamine and an organic solvent are mixed and then added to a reaction kettle, then sulfuryl fluoride is introduced, and then ammonia is introduced for reaction to obtain a first reaction solution containing triethylamine bis(fluorosulfonyl)imide salt. The solid insoluble matter in the first reaction solution is removed by filtration, and the organic solvent and triethylamine are removed by concentration under reduced pressure. After washing with water, it is separated into an aqueous phase α and an organic phase β.

[0021] By using an aqueous solution of alkali metal carbonate to wash and separate the aqueous phase and the organic phase multiple times by fractional extraction, the yield and purity of triethylamine bis(fluorosulfonyl)imide can be improved. This is because the basicity order is: triethylamine bis(fluorosulfonyl)imide > alkali metal carbonate > triethylammonium hydrofluoride. The alkali metal carbonate can neutralize and recover triethylammonium hydrofluoride. By adding alkali metal carbonate to the aqueous phase α and the organic phase β respectively, the triethylammonium hydrofluoride in the aqueous phase α and the organic phase β is neutralized and recovered, and the aqueous phase α 1 and the organic phase β 1 are obtained by liquid separation; then, alkali metal carbonate is added to the aqueous phase α 1 to neutralize and recover triethylammonium hydrofluoride, and the aqueous phase α 2 and the organic phase β 2 are obtained by liquid separation; then, the aqueous phase α 1 and the aqueous phase α 2 are combined to obtain the aqueous phase α 3 , and the above operation is repeated to obtain the aqueous phase α 4 and the organic phase β 3 .

[0022] After washing and liquid separation, the triethylammonium hydrofluoride in the organic phase β 1 has been basically removed, and the organic phase β 2 , the organic phase β 3 are all triethylamine bis(fluorosulfonyl)imide recovered from the aqueous phase. Combining the organic phase β 1 , β 2 , β 3 can obtain relatively pure triethylamine bis(fluorosulfonyl)imide, and can also recover the residual triethylamine bis(fluorosulfonyl)imide in the aqueous phase, which not only improves the purity of the prepared potassium bis(fluorosulfonyl)imide, but also improves the yield. And by the above method, the residual triethylammonium hydrofluoride in the organic phase can be neutralized and recovered to improve the utilization recovery rate of the by-product triethylammonium hydrofluoride.

[0023] Since the purity and yield of potassium bis(fluorosulfonyl)imide are improved, high-quality lithium bis(fluorosulfonyl)imide can be directly obtained by reacting with potassium bis(fluorosulfonyl)imide as an intermediate, thereby improving the purity and yield of lithium bis(fluorosulfonyl)imide.

[0024] Moreover, the raw materials used in the above preparation method, such as sulfuryl fluoride, ammonia, organic solvents, and potassium hydroxide, are cheap and easily available. No acidic gases such as sulfur dioxide and hydrogen chloride are generated during the reaction process, and hydrogen fluoride does not need to be used, so it has stronger environmental protection, requires low equipment requirements, reduces production costs, and is suitable for large-scale production.

[0025] Optionally, the molar ratio of ammonia, sulfuryl fluoride, and triethylamine is 1.0:(2.0 - 2.2):(3.0 - 3.5).

[0026] By adopting the above technical solution, sulfuryl fluoride reacts with ammonia to form bis(fluorosulfonyl)imide and hydrogen fluoride, and triethylamine reacts with them to form triethylamine bis(fluorosulfonyl)imide salt and triethylamine hydrogen fluoride salt. However, excessive triethylamine will promote the hydrolysis of sulfuryl fluoride to form by-products such as fluorosulfonic acid. When the molar ratio of ammonia, sulfuryl fluoride and triethylamine is 1.0:(2.0 - 2.2):(3.0 - 3.5), the possibility of by-product generation is small and the yield of the target product is relatively high, that is, the yield of triethylamine bis(fluorosulfonyl)imide salt is good.

[0027] Optionally, the feeding rate of ammonia is 0.3 - 1.0 g / min.

[0028] By adopting the above technical solution, the feeding rate of ammonia has a great influence on the intensity of this reaction. When the feeding rate of ammonia is too fast, the reaction temperature soars and is prone to getting out of control, bringing certain risks; while when the feeding rate of ammonia is too slow, the reaction time is longer, which is not conducive to industrial scale-up production. When the feeding rate of ammonia is controlled at 0.3 - 1.0 g / min, the reaction temperature can be well controlled within the set temperature range, and the reaction pressure ≤ 0.5 MPa throughout the process, and the reaction is safe and efficient.

[0029] Optionally, the reaction temperature of the first reaction is -10 - 25 °C, and the reaction time is 2 - 10 h.

[0030] By adopting the above technical solution, the above reaction temperature and time can make the reaction rate and reaction degree of ammonia, sulfuryl fluoride and triethylamine more appropriate.

[0031] Optionally, the temperature of vacuum concentration is 50 - 90 °C, and a concentrated solution is obtained after vacuum concentration.

[0032] Optionally, the water in the water washing step is deionized water, and the amount of deionized water used is 50% - 200% of the weight of the concentrated solution.

[0033] Optionally, the alkali metal carbonate is potassium carbonate.

[0034] Optionally, the concentration of the alkali metal carbonate aqueous solution is 10 - 50 wt%, and the amount of the alkali metal carbonate aqueous solution used is 20% - 50% of the weight of each aqueous phase or organic phase.

[0035] Optionally, the molar ratio of triethylamine bis(fluorosulfonyl)imide salt to potassium hydroxide is 1:(1 - 1.01).

[0036] By adopting the above technical solution, the above molar ratio of triethylamine bis(fluorosulfonyl)imide salt to potassium hydroxide can make the reaction degree of the second reaction more sufficient, resulting in a higher yield of potassium bis(fluorosulfonyl)imide finally.

[0037] Optionally, the concentration of the aqueous potassium hydroxide solution is 5-50 wt%.

[0038] By adopting the above technical solution, in the acid-base neutralization reaction between triethylamine bis(fluorosulfonyl)imide and potassium hydroxide, it is particularly important to select a suitable reaction solvent. If organic solvents such as acetonitrile and acetone are used for the reaction, it is easy to form a heterogeneous system, reducing the reaction yield. For example, when acetonitrile is used as the reaction solvent, although the raw material triethylamine bis(fluorosulfonyl)imide and the product potassium bis(fluorosulfonyl)imide have high solubility in acetonitrile, the inorganic base KOH is almost insoluble in acetonitrile, forming a heterogeneous reaction system and reducing the reaction efficiency. Using water as the reaction solvent can increase the solubility of the raw materials, promote the progress of the homogeneous reaction, and improve the reaction efficiency; moreover, potassium bis(fluorosulfonyl)imide does not carry bound water and will not affect the subsequent purification.

[0039] Optionally, the reaction temperature of the second reaction is 20-40 °C, and the reaction time is 1-3 h.

[0040] By adopting the above technical solution, the above reaction temperature and time can make the reaction rate and reaction degree between triethylamine bis(fluorosulfonyl)imide and potassium hydroxide more appropriate.

[0041] Optionally, the purification treatment includes the following steps:

[0042] The second reaction solution is filtered, concentrated under reduced pressure, dissolved in a good solvent, and then filtered; concentrated under reduced pressure for the second time, recrystallized with a poor solvent, washed, and dried in vacuo to obtain a pure product of potassium bis(fluorosulfonyl)imide.

[0043] By adopting the above technical solution, in the above purification treatment, first, the solid insoluble substances in the second reaction solution are removed by filtration, and then water and triethylamine are removed by concentration under reduced pressure, i.e., vacuum distillation. By precisely controlling the residual amount of the good solvent; during the recrystallization with the poor solvent, by precisely controlling the addition amount of the poor solvent and the temperature of the system when adding, a potassium bis(fluorosulfonyl)imide with high yield and high purity can be obtained. Compared with the technical route of improving the product purity by multiple recrystallization means and resulting in a low yield, the technical route provided by the present invention has great advantages.

[0044] Optionally, the good solvent is selected from at least one of ethanol, isopropanol, acetonitrile, ethylene glycol dimethyl ether, methyl tert-butyl ether, and ethyl acetate.

[0045] Optionally, the dosage of the good solvent is 0.5-3 times the weight of the theoretical potassium bis(fluorosulfonyl)imide.

[0046] Optionally, the poor solvent is selected from at least one of dichloromethane, dichloroethane, chloroform, and toluene.

[0047] Optionally, the dosage of the poor solvent is 1-10 times the weight of the theoretical potassium bis(fluorosulfonyl)imide.

[0048] Optionally, the temperature of the system when the poor solvent is added is controlled at 40-60°C.

[0049] Optionally, the temperature of the vacuum concentration in the purification treatment is 50-90°C.

[0050] Optionally, the solid content of the concentrated solution obtained after vacuum concentration in the purification treatment is controlled at 90%-100%.

[0051] Optionally, the detergent used in the washing treatment is at least one of toluene, xylene, dichloromethane, dichloroethane, and chloroform.

[0052] Optionally, the dosage of the detergent used in the washing treatment is 2-10 times the weight of the theoretical potassium bis(fluorosulfonyl)imide salt.

[0053] Optionally, the temperature of the vacuum drying is 30-80°C.

[0054] A high-purity potassium bis(fluorosulfonyl)imide provided by the present application adopts the following technical solution:

[0055] A high-purity potassium bis(fluorosulfonyl)imide, including a purity ≥ 99.95%, moisture ≤ 20 ppm, chloride ≤ 5 ppm, free acid ≤ 30 ppm, sodium ion ≤ 5 ppm, and insoluble matter ≤ 50 ppm.

[0056] A use of a high-purity potassium bis(fluorosulfonyl)imide provided by the present application adopts the following technical solution:

[0057] A use of a high-purity potassium bis(fluorosulfonyl)imide, the high-purity potassium bis(fluorosulfonyl)imide can be directly used for synthesizing high-quality lithium bis(fluorosulfonyl)imide.

[0058] In summary, the present application includes at least one of the following beneficial technical effects:

[0059] 1. By controlling the reaction conditions, the process is safe and reliable. The aqueous phase and the organic phase are washed and separated by liquid-liquid extraction multiple times with an aqueous solution of an alkali metal carbonate. On the one hand, the triethylammonium bis(fluorosulfonyl)imide remaining in the aqueous phase can be recovered. On the other hand, the triethylammonium hydrofluoride remaining in the organic phase can be neutralized, and it does not react with the triethylammonium bis(fluorosulfonyl)imide salt, resulting in a higher yield and purity of the triethylammonium bis(fluorosulfonyl)imide salt;

[0060] 2. Reacting triethylammonium bis(fluorosulfonyl)imide with an aqueous solution of potassium hydroxide, and then obtaining a high-purity potassium bis(fluorosulfonyl)imide with a high yield through further purification treatment, which can be directly used for synthesizing high-quality lithium bis(fluorosulfonyl)imide;

[0061] 3. The raw materials used, such as sulfuryl fluoride, ammonia, triethylamine, and potassium hydroxide, are inexpensive and easily available. Acidic gases such as sulfur dioxide and hydrogen chloride are not generated during the reaction process, and hydrogen fluoride does not need to be used, making it more environmentally friendly. The requirements for equipment are not high, reducing production costs and making it suitable for large-scale production. Description of the Drawings

[0062] Figure 1 is the solution of triethylamine bis(fluorosulfonyl)imide in the embodiment of the present invention 19 19F NMR spectrum.

[0063] Figure 2 is the pure product of triethylamine bis(fluorosulfonyl)imide in the embodiment of the present invention 19 19F NMR spectrum.

[0064] Figure 3 is potassium bis(fluorosulfonyl)imide in the embodiment of the present invention 19 19F NMR spectrum. Detailed Embodiments

[0065] The embodiments of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. The specific conditions not specified in the embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not specified as the manufacturer are all conventional products that can be obtained through commercial purchase.

[0066] The technical solution of the present invention is as follows:

[0067] A method for preparing high-purity potassium bis(fluorosulfonyl)imide specifically includes the following steps:

[0068] Under the protection of an inert gas, using sulfuryl fluoride, ammonia, and triethylamine as raw materials, reacting in acetonitrile. The specific reaction formula is shown in the following formula (1) to obtain a first reaction solution containing triethylamine bis(fluorosulfonyl)imide; wherein the reaction temperature is -10 - 25 °C, and the reaction time is 2 - 10 h. Preferably, the reaction temperature is -5 - 5 °C, and the reaction time is 4 - 8 h.

[0069] Filter the above-obtained first reaction solution, concentrate it under reduced pressure, and then separate the layers after washing with water to obtain an aqueous phase α and an organic phase β;

[0070] Among them, the temperature for concentration under reduced pressure is 50 - 90 °C, and a concentrated solution is obtained after concentration under reduced pressure; the water used for washing is deionized water, and the amount of deionized water used is 50 - 200% of the weight of the concentrated solution.

[0071] Add an aqueous solution of an alkali metal carbonate to the aqueous phase α and the organic phase β respectively, and separate the layers of the organic phase β to obtain the aqueous phase α 1With organic phase β 1 and aqueous phase α 1 Liquid separation is carried out to obtain aqueous phase α 2 and organic phase β 2 ; Combine aqueous phase α 1 with aqueous phase α 2 to obtain aqueous phase α 3 ,

[0072] Continue to add an aqueous solution of alkali metal carbonate, and liquid separation is carried out to obtain aqueous phase α 4 and organic phase β 3 ;

[0073] Wherein the aqueous solution of alkali metal carbonate is an aqueous solution of potassium carbonate, the concentration of the aqueous solution of alkali metal carbonate is 10 - 50 wt%, preferably, the concentration of the aqueous solution of alkali metal carbonate is 15 - 30 wt%; the dosage of the aqueous solution of alkali metal carbonate is 20 - 50% of the weight of each stage of aqueous phase or organic phase.

[0074] Combine organic phase β 1 , β 2 with β 3 to obtain organic phase β 4 , that is, triethylamine bis(fluorosulfonyl)imide salt. React the obtained triethylamine bis(fluorosulfonyl)imide salt with an aqueous solution of potassium hydroxide. The specific reaction formula is shown in the following formula (2) to obtain a second reaction solution containing potassium bis(fluorosulfonyl)imide; wherein the concentration of the aqueous solution of potassium hydroxide is 5 - 50 wt%; wherein the reaction temperature is 20 - 40 °C and the reaction time is 1 - 3 h.

[0075]

[0076] The above - obtained second reaction solution is filtered, concentrated under reduced pressure, dissolved in a good solvent, and filtered; concentrated under reduced pressure for the second time, recrystallized with a poor solvent, washed, and dried to obtain a pure product of potassium bis(fluorosulfonyl)imide;

[0077] Wherein the temperature range for concentration under reduced pressure is 50 - 90 °C, and the solid content of the concentrated solution obtained after concentration under reduced pressure is controlled at 90 - 100%; the good solvent is at least one of ethanol, isopropanol, acetonitrile, ethylene glycol dimethyl ether, methyl tert - butyl ether, ethyl acetate; the dosage of the good solvent is 0.5 - 3 times the weight of theoretical potassium bis(fluorosulfonyl)imide, preferably, the dosage of the good solvent is 1 - 2 times the weight of theoretical potassium bis(fluorosulfonyl)imide;

[0078] Wherein the poor solvent is at least one of dichloromethane, dichloroethane, chloroform, toluene, and the temperature of the system is controlled at 40 - 60 °C when the poor solvent is added; the dosage of the poor solvent is 1 - 10 times the weight of theoretical potassium bis(fluorosulfonyl)imide, preferably 3 - 5 times;

[0079] Among them, the detergent used in the washing treatment is at least one of toluene, xylene, dichloromethane, dichloroethane, and chloroform; the dosage of the detergent used in the washing treatment is 2-10 times the weight of the theoretical potassium bis(fluorosulfonyl)imide salt, preferably, the dosage of the detergent used in the washing treatment is 3-6 times the weight of the theoretical potassium bis(fluorosulfonyl)imide salt;

[0080] Among them, the temperature of the vacuum drying is 30-80 °C, preferably, the temperature of the vacuum drying is 40-60 °C.

[0081] I. Examples

[0082] Example 1:

[0083] Step 1:

[0084] Under nitrogen protection, 600 g of acetonitrile and 618 g (6.11 mol) of triethylamine were mixed, added to a 2 L reaction kettle, stirring was started, the temperature of the reaction kettle was controlled at 0-5 °C, then 418.45 g (4.10 mol) of sulfuryl fluoride was added to the reaction kettle, and then 34.06 g (2.00 mol) of ammonia gas was added to the reaction kettle through a mass flowmeter, the feeding rate of ammonia gas was 0.7 g / min, and after the ammonia gas was added, the reaction continued for 3 h; the molar ratio of the above ammonia gas, sulfuryl fluoride and triethylamine was about 1:2:3.

[0085] After the reaction was completed, the first reaction solution containing triethylamine bis(fluorosulfonyl)imide salt was discharged, and the first reaction solution was filtered to remove solid insoluble substances to obtain a triethylamine bis(fluorosulfonyl)imide salt solution.

[0086] Step 2:

[0087] The triethylamine bis(fluorosulfonyl)imide salt solution was concentrated under reduced pressure, and then the concentrated solution was transferred to a 2 L separatory funnel, deionized water with half the mass of the concentrated solution was added, shaken, and allowed to stand for separation to obtain 942 g of aqueous phase α and 648 g of organic phase β.

[0088] 130 g (20% of the weight of organic phase β) of 25% potassium carbonate aqueous solution was added to organic phase β, shaken, and allowed to stand for separation to obtain aqueous phase α 1 and organic phase β1; 188 g (20% of the weight of aqueous phase α) of 25% potassium carbonate aqueous solution was added to aqueous phase α, shaken, and allowed to stand for separation to obtain aqueous phase α 2 and organic phase β 2 ;

[0089] The aqueous phase α 1 and aqueous phase α 2 were combined to obtain 1440 g of aqueous phase α 3 , 288 g (20% of the weight of aqueous phase α 3 ) of 25% potassium carbonate aqueous solution was added, shaken, and allowed to stand for separation to obtain aqueous phase α 4With the organic phase β 3 ;

[0090] Combine the organic phase β 1 , β 2 and β 3 , to obtain the organic phase β 4 , namely triethylamine bis(fluorosulfonyl)imide salt.

[0091] Step 3:

[0092] Transfer the above-obtained triethylamine bis(fluorosulfonyl)imide salt to a 2 L three-necked flask, and add 20% aqueous potassium hydroxide solution dropwise at room temperature (the molar ratio of triethylamine bis(fluorosulfonyl)imide salt to potassium hydroxide is 1:1). Finish the dropping within 2 h, continue stirring for 0.5 h to end the reaction, and obtain a second reaction solution containing potassium bis(fluorosulfonyl)imide.

[0093] The second reaction solution is filtered to remove insoluble substances, and then concentrated under reduced pressure to obtain the crude product of potassium bis(fluorosulfonyl)imide. Add acetonitrile with the same mass as the theoretical potassium bis(fluorosulfonyl)imide, stir to dissolve it fully, then filter, and concentrate under reduced pressure for the second time until the solid content of the solution is 95%;

[0094] When the concentrated solution is cooled to 50 °C, add dichloromethane with twice the mass of the theoretical potassium bis(fluorosulfonyl)imide dropwise to the concentrated solution under stirring, and then let it cool naturally to room temperature. During this process, potassium bis(fluorosulfonyl)imide crystals gradually precipitate. After crystallization at room temperature for 2 h, filter to obtain potassium bis(fluorosulfonyl)imide solid;

[0095] Add dichloromethane with three times the mass of the theoretical potassium bis(fluorosulfonyl)imide to the potassium bis(fluorosulfonyl)imide solid, and stir for 30 min. Repeat the washing operation 1 - 2 times to obtain the wet product of potassium bis(fluorosulfonyl)imide. Dry this wet product in vacuo at 60 °C for 12 h to obtain a white solid product.

[0096] Example 2:

[0097] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: in Step 1, the temperature of the reaction kettle is controlled at -5 - 0 °C.

[0098] Example 3:

[0099] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: 600 g of acetonitrile and 708 g (7.00 mol) of triethylamine are mixed and added to a 2 L reaction kettle. Start stirring, control the temperature of the reaction kettle at 0 - 5 °C, then add 449.06 g (4.40 mol) of sulfuryl fluoride to the reaction kettle, and then add 34.06 g (2.00 mol) of ammonia gas to the reaction kettle through a mass flowmeter. After the ammonia gas is introduced, continue the reaction for 3 h; the molar ratio of the above ammonia gas, sulfuryl fluoride and triethylamine is about 1:2.2:3.5.

[0100] Example 4:

[0101] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: 600 g of acetonitrile and 647.62 g (6.40 mol) of triethylamine are mixed and added to a 2 L reaction kettle. Stirring is started, and the temperature of the reaction kettle is controlled at 0 - 5 °C. Then, 428.65 g (4.20 mol) of sulfuryl fluoride is added to the reaction kettle, and then 34.06 g (2.00 mol) of ammonia gas is added to the reaction kettle through a mass flowmeter. After the ammonia gas is added, the reaction continues for 3 h; the molar ratio of the above ammonia gas, sulfuryl fluoride and triethylamine is about 1:2.1:3.2.

[0102] Examples 5 - 6:

[0103] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 as shown in Table 1.

[0104] Table 1:

[0105]

[0106] Example 7:

[0107] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: the 25% potassium carbonate aqueous solution is replaced with a 15% potassium carbonate aqueous solution.

[0108] Example 8:

[0109] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: the 25% potassium carbonate aqueous solution is replaced with a 30% potassium carbonate aqueous solution.

[0110] Example 9:

[0111] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: in step 3, when the concentrated solution cools down to 50 °C, dichloromethane with a mass 5 times that of the theoretical potassium bis(fluorosulfonyl)imide is added dropwise to the concentrated solution under stirring.

[0112] Example 10:

[0113] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: in step 3, the insoluble substances are filtered off, and then the crude potassium bis(fluorosulfonyl)imide is obtained by vacuum concentration. Acetonitrile with the same mass as the theoretical potassium bis(fluorosulfonyl)imide is added, and the mixture is stirred until it is fully dissolved. Then, it is filtered, and the solution is concentrated by secondary vacuum until the solid content of the solution is 90%.

[0114] Example 11:

[0115] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: in Step 3, the insoluble substances are filtered off, and then concentrated under reduced pressure to obtain the crude potassium bis(fluorosulfonyl)imide. Acetonitrile with the same mass as the theoretical potassium bis(fluorosulfonyl)imide is added, and the mixture is stirred until completely dissolved, and then filtered. The solution is concentrated under reduced pressure for the second time until the solid content of the solution is 100%.

[0116] Example 12:

[0117] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: the feeding rate of ammonia gas is 0.3 g / min.

[0118] Example 13:

[0119] A preparation method of high-purity potassium bis(fluorosulfonyl)imide, which is different from Example 1 in that: the feeding rate of ammonia gas is 1.0 g / min.

[0120] II. Comparative Examples

[0121] Comparative Example 1:

[0122] It is different from Example 1 in that: the organic phase β in Step 2 is directly transferred to a three-necked flask, and a 20% aqueous potassium hydroxide solution (the molar ratio of triethylamine bis(fluorosulfonyl)imide to potassium hydroxide is 1:1) is added dropwise at room temperature, and the addition is completed within 2 h. Stirring is continued for 0.5 h to end the reaction, and a second reaction solution containing potassium bis(fluorosulfonyl)imide is obtained.

[0123] Comparative Example 2:

[0124] It is different from Example 1 in that: under nitrogen protection, 74.4 g of ammonium fluoride is added to a 2 L high-pressure reactor, the temperature is controlled to 10 °C, 480 g of acetonitrile is added, and the mixture is stirred for 0.5 h. Sulfuryl fluoride gas (408 g) is slowly introduced at 10 °C, and the temperature is continuously maintained at 10 °C for 4 h to end the reaction; the reaction solution is distilled under reduced pressure to recover the reaction solvent, and the concentrated solution is washed with water to obtain the organic phase, that is, triethylamine bis(fluorosulfonyl)imide;

[0125] Under nitrogen protection, the obtained triethylamine bis(fluorosulfonyl)imide is added to a three-necked reaction flask, and then a 25% aqueous potassium hydroxide solution (the molar ratio of triethylamine bis(fluorosulfonyl)imide to potassium hydroxide is 1:1) is added. Stir and heat under reflux until no carbon dioxide gas is generated. The insoluble inorganic substances are filtered off, and the reaction solution is distilled under reduced pressure to recover the reaction solvent, and solid potassium bis(fluorosulfonyl)imide is obtained.

[0126] III. Performance Test

[0127] 1) Use a nuclear magnetic resonance hydrogen spectrometer to measure the triethylamine bis(fluorosulfonyl)imide solutions and organic phase β prepared in Examples 1-13 and Comparative Examples 1-2 4The solid product was detected, and the detection results of Example 1 are as follows Figure 1-2 shown;

[0128] 2) The yields of potassium bis(fluorosulfonyl)imide in Examples 1-13 and Comparative Examples 1-2 were calculated. The yield (%) = actual product mass / theoretical product mass × 100%;

[0129] 3) The purity of potassium bis(fluorosulfonyl)imide in Examples 1-13 and Comparative Examples 1-2 was detected using a liquid chromatograph;

[0130] 4) Anion detection method: Potassium bis(fluorosulfonyl)imide in Examples 1-13 and Comparative Examples 1-2 was detected by an ion chromatograph, in ppm;

[0131] 5) Moisture detection method: Potassium bis(fluorosulfonyl)imide in Examples 1-14 and Comparative Examples 1-3 was detected using a Karl Fischer moisture meter from Mettler Toledo, in ppm;

[0132] 6) Free acid detection method: Potassium bis(fluorosulfonyl)imide in Examples 1-13 and Comparative Examples 1-2 was determined by potentiometric titration using a potassium hydroxide-ethanol standard titration solution;

[0133] 7) Trace metal element content test method: The content of each trace metal element in potassium bis(fluorosulfonyl)imide in Examples 1-13 and Comparative Examples 1-2 was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), in ppm.

[0134] 8) DMC insoluble content detection method: The sample was dissolved in dimethyl carbonate (DMC), filtered using a membrane filtration device, and dried at 105°C ± 2°C until the mass was constant.

[0135] The above test results are all shown in Table 2.

[0136] Table 2:

[0137]

[0138]

[0139] Combining Examples 1-13, Comparative Examples 1-2 and Figure 1-3 it can be seen that Figure 1 It indicates that the bis(fluorosulfonyl)imide triethylamine salt solution contains not only bis(fluorosulfonyl)imide triethylamine salt but also a small amount of triethylamine hydrofluoride; and when Figure 2 is compared with Figure 1 it can be found that after decompression compression and fractional washing and liquid separation with an aqueous solution of alkali metal carbonate, the triethylamine hydrofluoride in the organic phase β 4 has been basically removed, and the organic phase β4 In the middle is relatively pure triethylammonium bis(fluorosulfonyl)imide. Finally, from Figure 3 It can be seen that the finally obtained white solid product is relatively pure potassium bis(fluorosulfonyl)imide. The 19 19F NMR spectra of the remaining examples and comparative examples are basically the same as those of Example 1.

[0140] Combined with Examples 1-2 and Table 2, it can be known that the temperatures of the first reaction in Examples 1-2 are different, and the yields of potassium bis(fluorosulfonyl)imide prepared in Examples 1-2 are all ≥87%, the purities are all ≥99.95%, the water contents are all ≤20 ppm, the chlorides are all ≤5 ppm, the free acids are all ≤30 ppm, the sodium ions are all ≤5 ppm, and the insolubles are all ≤50 ppm. It can be seen from the above that the potassium bis(fluorosulfonyl)imide prepared within the temperature range of -5 to 5°C in the first reaction has high yield and purity, and extremely low contents of water, free acid, insolubles and other impurity ions, and can be directly used for synthesizing high-quality lithium bis(fluorosulfonyl)imide.

[0141] Combined with Example 1, Examples 3-4 and Table 2, it can be known that the molar ratios of ammonia, sulfuryl fluoride and triethylamine in Examples 1, 3-4 are all different, and the yields of potassium bis(fluorosulfonyl)imide prepared in Examples 3-4 are all ≥87%, the purities are all ≥99.95%, the water contents are all ≤20 ppm, the chlorides are all ≤5 ppm, the free acids are all ≤30 ppm, the sodium ions are all ≤5 ppm, and the insolubles are all ≤50 ppm; and the yield and purity of Example 4 are relatively better than those of Example 1 and Example 3, and the contents of water, free acid, insolubles and other impurity ions are lower.

[0142] It can be seen from the above that high-purity and high-quality potassium bis(fluorosulfonyl)imide can be prepared by reacting within the molar ratio range of ammonia, sulfuryl fluoride and triethylamine of 1.0:(2.0-2.2):(3.0-3.5), and when the molar ratio of ammonia, sulfuryl fluoride and triethylamine is 1:2.1:3.2, the yield, purity and quality of the prepared potassium bis(fluorosulfonyl)imide are better.

[0143] Combined with Example 1, Examples 5-6 and Table 2, it can be seen that the dosage ratios of the aqueous alkali metal carbonate solution added to each stage of the aqueous phase or the organic phase in Examples 5-6 are different from those in Example 1. The yields of potassium bis(fluorosulfonyl)imide prepared in Examples 5-6 are all ≥87%, the purities are all ≥99.95%, the water contents are all ≤20 ppm, the chlorides are all ≤5 ppm, the free acids are all ≤30 ppm, and the sodium ions are all ≤5 ppm. Moreover, the yield and purity of Example 5 are better than those of Example 1 and Example 6, and the contents of water, free acid, insoluble substances and other impurity ions are lower. From the above, it can be known that when the dosage of the aqueous alkali metal carbonate solution is 20-50% of the weight of each stage of the aqueous phase or the organic phase, potassium bis(fluorosulfonyl)imide with high purity and high quality can be prepared by reaction. And when the dosage of the aqueous alkali metal carbonate solution is 35% of the weight of each stage of the aqueous phase or the organic phase, the yield, purity and quality of the prepared potassium bis(fluorosulfonyl)imide are better.

[0144] Combined with Example 1, Examples 7-8 and Table 2, it can be seen that the mass fractions of the aqueous alkali metal carbonate solution in Example 1 and Examples 7-8 are different. The yields of potassium bis(fluorosulfonyl)imide prepared in Examples 7-8 are all ≥87%, the purities are all ≥99.95%, the water contents are all ≤20 ppm, the chlorides are all ≤5 ppm, the free acids are all ≤30 ppm, the sodium ions are all ≤5 ppm, and the insoluble substances are all ≤50 ppm. It can be seen from this that when the mass fraction of the aqueous alkali metal carbonate solution is within 15-30%, the yield and purity of the prepared potassium bis(fluorosulfonyl)imide are high, and the contents of water, free acid, insoluble substances and other impurity ions are extremely low, and it can be directly used for synthesizing high-quality lithium bis(fluorosulfonyl)imide.

[0145] Combined with Example 1, Example 9 and Table 2, it can be seen that the addition multiples of the poor solvent in Example 1 and Example 9 are different. The yields of potassium bis(fluorosulfonyl)imide prepared in Example 9 are all ≥87%, the purities are all ≥99.95%, the water contents are all ≤20 ppm, the chlorides are all ≤5 ppm, the free acids are all ≤30 ppm, and the sodium ions are all ≤5 ppm. From the above, it can be known that by adding a poor solvent with a mass 3-5 times that of the theoretical potassium bis(fluorosulfonyl)imide to the concentrated solution, the yield and purity of the prepared potassium bis(fluorosulfonyl)imide are high, and the contents of water, free acid, insoluble substances and other impurity ions are extremely low, and it can be directly used for synthesizing high-quality lithium bis(fluorosulfonyl)imide.

[0146] Combined with Example 1, Examples 10-11 and Table 2, it can be seen that the secondary vacuum concentration to the solid content of the solution in Examples 10-11 is different from that in Example 1. The yields of Examples 10-11 are all ≥87%, the purities are all ≥99.95%, the water contents are all ≤20 ppm, the chlorides are all ≤5 ppm, the free acids are all ≤30 ppm, and the sodium ions are all ≤5 ppm. As can be seen from the above, the potassium bis(fluorosulfonyl)imide salt prepared by secondary vacuum concentration to a solid content of the solution within 90-100% has high yield and purity, and extremely low contents of water, free acid, insoluble substances and other impurity ions, and can be directly used for synthesizing high-quality lithium bis(fluorosulfonyl)imide.

[0147] Combined with Example 1, Examples 12-13 and Table 2, it can be seen that the ammonia gas feeding rates in Examples 12-13 are different from that in Example 1. The yields of the potassium bis(fluorosulfonyl)imide salts prepared in Examples 12-13 are all ≥87%, the purities are all ≥99.95%, the water contents are all ≤20 ppm, the chlorides are all ≤5 ppm, the free acids are all ≤30 ppm, and the sodium ions are all ≤5 ppm. It can be seen from this that the potassium bis(fluorosulfonyl)imide salt prepared with an ammonia gas feeding rate within 0.3-1.0 g / min has high yield and purity, and extremely low contents of water, free acid, insoluble substances and other impurity ions, and can be directly used for synthesizing high-quality lithium bis(fluorosulfonyl)imide.

[0148] Combined with Example 1, Comparative Example 1 and Table 2, it can be seen that in Comparative Example 1, the aqueous phase α and the organic phase β were not subjected to fractional washing and liquid separation treatment with an aqueous solution of an alkali metal carbonate. The purity and yield of the potassium bis(fluorosulfonyl)imide salt prepared in Comparative Example 1 are much lower than those in Example 1, the insoluble substance content is much higher than that in Example 1, and the free acid content of the potassium bis(fluorosulfonyl)imide salt prepared in Comparative Example 1 is much higher than 30 ppm, and the chloride and Na ion contents are also significantly higher than those in Example 1. From the above, it can be obtained that after the aqueous phase α and the organic phase β are subjected to fractional washing and liquid separation treatment with an aqueous solution of an alkali metal carbonate, the prepared potassium bis(fluorosulfonyl)imide salt has higher yield and purity, and lower contents of water, free acid, insoluble substances and other impurity ions.

[0149] Combined with Example 1 and Comparative Example 2 and Table 2, it can be seen that in Comparative Example 2, bis(fluorosulfonyl)imide triethylammonium salt was obtained by the reaction of sulfuryl fluoride with ammonium fluoride. As can be seen from Table 2, the purity and yield of the potassium bis(fluorosulfonyl)imide prepared in Comparative Example 2 are much lower than those in Example 1, the insoluble content is much higher than that in Example 1, and the free acid content of the potassium bis(fluorosulfonyl)imide prepared in Comparative Example 2 is much higher than 30 ppm, and the chloride and Na ion contents are also significantly higher than those in Example 1. This is because the direct use of ammonium fluoride in the reaction will introduce many impurity ions. From the above, it can be obtained that the reaction of sulfuryl fluoride with ammonia will generate bis(fluorosulfonyl)imide and hydrogen fluoride, and then triethylamine reacts with them to form bis(fluorosulfonyl)imide triethylammonium salt and triethylamine hydrogen fluoride salt. The bis(fluorosulfonyl)imide triethylammonium salt prepared by this reaction route has higher yield and purity, and lower contents of moisture, free acid, insoluble matter and other impurity ions when producing potassium bis(fluorosulfonyl)imide.

[0150] The above are all the preferred embodiments of this application. The protection scope of this application is not limited by this. Therefore, all equivalent changes made according to the products, methods and principles of this application should be covered within the protection scope of this application.

Claims

1. A preparation method of high-purity potassium bis(fluorosulfonyl)imide, characterized in that, it comprises the following steps: Under the protection of inert gas, using sulfuryl fluoride, ammonia and triethylamine as raw materials, a first reaction is carried out in an organic solvent to obtain a first reaction solution containing triethylamine bis(fluorosulfonyl)imide salt; Filter the first reaction solution, concentrate it under reduced pressure, and then carry out liquid separation after washing with water to obtain aqueous phase α and organic phase β; Add an aqueous solution of alkali metal carbonate to aqueous phase α and organic phase β respectively. The organic phase β is separated to obtain aqueous phase α1 and organic phase β1. The aqueous phase α1 is separated to obtain aqueous phase α2 and organic phase β2; Combine aqueous phase α1 and aqueous phase α2 to obtain aqueous phase α3, continue to add an aqueous solution of alkali metal carbonate, and carry out liquid separation to obtain aqueous phase α4 and organic phase β3; Combine organic phases β1, β2 and β3 to obtain organic phase β4, that is, triethylamine bis(fluorosulfonyl)imide salt. Carry out a second reaction on the obtained triethylamine bis(fluorosulfonyl)imide salt and an aqueous solution of potassium hydroxide to obtain a second reaction solution containing potassium bis(fluorosulfonyl)imide; After subjecting the second reaction solution to purification treatment, a pure product of potassium bis(fluorosulfonyl)imide is obtained; The purification treatment includes the following steps: filtering the second reaction solution, concentrating it under reduced pressure, dissolving it in a good solvent, and filtering; concentrating it under reduced pressure for the second time, recrystallizing it with a poor solvent, washing, and drying it under vacuum to obtain a pure product of potassium bis(fluorosulfonyl)imide; The amount of the poor solvent is 1 - 10 times the theoretical weight of potassium bis(fluorosulfonyl)imide. The temperature of the system when adding the poor solvent is controlled at 40 - 60°C; the good solvent is selected from at least one of ethanol, isopropanol, acetonitrile, ethylene glycol dimethyl ether, methyl tert-butyl ether and ethyl acetate; the poor solvent is selected from at least one of dichloromethane, dichloroethane, chloroform and toluene; The concentration of the aqueous solution of alkali metal carbonate is 10 - 50 wt%, and the amount of the aqueous solution of alkali metal carbonate is 20 - 50% of the weight of each aqueous phase or organic phase; The purity of the pure product of potassium bis(fluorosulfonyl)imide is ≥99.95%, the water content is ≤20 ppm, the chloride content is ≤5 ppm, the free acid content is ≤30 ppm, the sodium ion content is ≤5 ppm, and the insoluble matter content is ≤50 ppm.

2. The preparation method of high-purity potassium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The molar ratio of ammonia, sulfuryl fluoride and triethylamine is 1.0:(2.0 - 2.2):(3.0 - 3.5).

3. The preparation method of high-purity potassium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The feeding rate of ammonia is 0.3 - 1.0 g / min.

4. The preparation method of high-purity potassium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The reaction temperature of the first reaction is -10~25°C, and the reaction time is 2 - 10 h.

5. The preparation method of high-purity potassium bis(fluorosulfonyl)imide according to any one of claims 1 - 4, characterized in that: the molar ratio of triethylamine bis(fluorosulfonyl)imide salt to potassium hydroxide is 1:(1 - 1.01).

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