Preparation method of high-purity sodium bisfluorosulfonimide

Abstract

The application discloses a preparation method of high-purity sodium bisfluorosulfonimide, and belongs to the technical field of sodium battery electrolyte sodium salt. The method comprises the following steps: preparing bischlorosulfonimide by heating and stirring bisulfamic acid, dichlorosulfoxide and chlorosulfonic acid in a refluxing manner; distilling and purifying the bischlorosulfonimide after fluorination of the bischlorosulfonimide by a fluorination agent to obtain a bisfluorosulfonimide crude product; and drying and recrystallizing the crude product after reaction with a sodium salt to obtain the sodium bisfluorosulfonimide. The preparation method can improve the fluorination conversion rate and yield of the bischlorosulfonimide by adding a cocatalyst containing trimethylammonium chloride, crown ether and phosphonic acid groups, and finally, the high-purity sodium bisfluorosulfonimide is prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium salt for sodium battery electrolytes, and specifically relates to a method for preparing high-purity sodium bis(fluorosulfonyl)imide. Background Art

[0002] Sodium bis(fluorosulfonyl)imide is a common chemical, also known as sodium N-difluorosulfonyl imide, with the chemical formula Na(SO₂F)₂. As a new electrolyte salt for sodium-ion batteries, sodium bis(fluorosulfonyl)imide offers the following advantages: high electrical conductivity, excellent thermal stability, excellent low-temperature resistance, and high hydrolysis resistance.

[0003] CN117361451A discloses a high-efficiency preparation method for sodium bis(fluorosulfonyl)imide. The method comprises three steps for preparing NaFSI: (1) using readily available gases such as sulfuryl fluoride and ammonia as raw materials, the reaction is carried out in an organic solvent environment, triethylamine is added as an acid-binding agent to achieve high product selectivity, and a microchannel reactor is used to achieve high conversion of the gas-liquid phase reaction to generate the intermediate bis(fluorosulfonyl)imide triethylamine salt; (2) due to the presence of by-products in the first step, further separation operations such as evaporation and extraction are required to extract the intermediate product to ensure the purity of the final product; and (3) in the sodiumization process, triethylamine is removed by displacement using highly alkaline sodium hydroxide to obtain the NaFSI product.

[0004] CN117208865A proposes a method for preparing sodium bis(fluorosulfonyl)imide and the resulting product, belonging to the technical field of sodium ion battery additive preparation. The method comprises the following steps: 1) in an anhydrous and oxygen-free environment, dropwise adding an organic solvent containing bis(fluorosulfonyl)imide to an organic solvent containing sodium fluoride for reaction to obtain a mixed solution containing sodium bis(fluorosulfonyl)imide; 2) mixing the mixed solution containing sodium bis(fluorosulfonyl)imide with dichloromethane, followed by crystallization and filtration, resulting in a filtrate as a crude sodium bis(fluorosulfonyl)imide product; 3) dissolving the crude sodium bis(fluorosulfonyl)imide product in an organic solvent and filtering to obtain a filtrate; and 4) adjusting the pH of the filtrate to 7-8 using hexamethyldisilazane to obtain liquid sodium bis(fluorosulfonyl)imide.

[0005] CN116621129A provides a method for preparing sodium bisfluorosulfonyl imide, comprising the following steps: a cation exchange resin column is filled with a strong acid cation exchange resin, and the strong acid cation exchange resin adsorbs sodium ions; an aqueous solution of potassium bisfluorosulfonyl imide is passed through the cation exchange resin column to perform ion exchange, thereby replacing the potassium ions on the potassium bisfluorosulfonyl imide with sodium ions to obtain an aqueous solution containing sodium bisfluorosulfonyl imide; and an organic solution of sodium bisfluorosulfonyl imide or a solid sodium bisfluorosulfonyl imide is prepared.

[0006] In the existing synthesis technology of sodium bis(fluorosulfonyl)imide, the process route is relatively complicated, and the conversion rate and yield of the product are low. Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing high-purity sodium bisfluorosulfonyl imide, thereby improving the yield and purity of the sodium bisfluorosulfonyl imide product.

[0008] Another object of the present invention is to provide sodium bis(fluorosulfonyl)imide prepared by the above method.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] Step 1: Weigh 90-100 parts of sulfamic acid, 290-360 parts of thionyl chloride, and 140-170 parts of chlorosulfonic acid by mass, first add thionyl chloride and sulfamic acid in sequence into a reactor that has been dried and replaced with nitrogen in advance, start stirring, heat until reflux occurs, control the temperature to 90-110°C, keep stirring until the solid sulfamic acid is completely dissolved in the thionyl chloride, then heat to 130-145°C, start adding the pre-weighed chlorosulfonic acid, keep the reaction for 28-32 hours, and collect the crude bischlorosulfonyl imide by vacuum distillation after the reaction is completed, and absorb the tail gas with alkali solution;

[0011] Step 2: Add 200-230 parts of bis(chlorosulfonyl)imide, 0.2-1 parts of fluorination catalyst, and 0.05-0.6 parts of co-catalyst to a tetrafluoroethylene reactor, heating to 80-110°C, slowly introducing 160-240 parts of HF gas under stirring, reacting for 12-18 hours, cooling to room temperature, blowing nitrogen, and purifying by vacuum distillation to obtain bis(fluorosulfonyl)imide;

[0012] Step 3: dissolving 160-200 parts of bis(fluorosulfonyl)imide, 36-48 parts of sodium source in 500-600 parts of non-benign solvent at -40-40°C, reacting at -10-45°C for 24-48 hours after complete dissolution, separating the solid and the liquid after completion of the reaction to obtain a crude solid, washing the solid with 500-600 parts of non-benign solvent, and then drying and recrystallizing to obtain lithium sodium bis(fluorosulfonyl)imide.

[0013] Furthermore, the conditions for the reduced pressure distillation in step 1 are 500-750 Pa and 90-110° C.

[0014] Furthermore, the alkali solution in step 1 is calcium hydroxide, cesium hydroxide, potassium hydroxide or sodium hydroxide.

[0015] Furthermore, the fluorination catalyst described in step 2 is one of SbCl5, TiCl4, SnCl4, and MoCl5.

[0016] Furthermore, the preparation method of the co-catalyst described in step 2 is:

[0017] K1: Add 0.04-0.8 parts of 4'-aminodibenzo-18-crown-6, 15-30 parts of 2,3-epoxypropyltrimethylammonium chloride, 100-160 parts of D418 resin, 1-3 parts of sodium tert-butoxide, and 1000-1200 parts of toluene to a sealed stirred tank, introduce nitrogen, and stir the reaction at 50-60°C for 100-150 minutes. Then, add 0.05-0.7 parts of allyltributyltin, stir the reaction at 50-60°C for 20-60 minutes. After the reaction is completed, filter, and spin dry to obtain a co-catalyst.

[0018] Among them, 4'-aminodibenzo-18-crown-6, CAS: 126531-26-8.

[0019] Furthermore, the D418 resin described in the preparation method of the co-catalyst in step 2 is a chelating resin with a weakly acidic aminophosphonic acid group (-CH2NHCH2PO3-) on a styrene-divinylbenzene copolymer with a special macroporous structure, and its factory form is sodium type.

[0020] Furthermore, the reduced pressure distillation conditions in step 2 are 560-620 Pa and 58-60° C.

[0021] Furthermore, the sodium source in step three is one or more of NaOH, NaCl and NaF.

[0022] Furthermore, the non-benign solvent in step three is one or any combination of dichloromethane, dichloroethane, chloroform, trichloroethane, carbon tetrachloride, n-hexane, cyclohexane, and n-heptane.

[0023] Furthermore, the washing times in step 3 are 3-5 times.

[0024] Furthermore, the drying conditions described in step three are drying by nitrogen purging at room temperature and negative pressure, and the drying time is 10-18 hours.

[0025] The reaction mechanism of this method is:

[0026] Step 1: 1. NH2SO3 H+2SOCl2+ClSO3 H→HN(SO2 Cl)2+2SO2↑+3HCl↑

[0027] Step 2: HN(SO2 Cl)2+2HF→HN(SO2 F)2+2HCl

[0028] Step 3: HN(SO2 F)2+Na + →NaN(SO2F)2+H +.

[0029] The reaction mechanism of the co-catalyst is:

[0030] 4'-Aminodibenzo-18-crown-6 reacts with 2,3-epoxypropyltrimethylammonium chloride; D418 resin reacts with 2,3-epoxypropyltrimethylammonium chloride to produce a cocatalyst containing trimethylammonium chloride, crown ether, and phosphonic acid groups. This can improve the fluorination conversion rate and yield of bischlorosulfonyl imide.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The combined action of trimethylammonium chloride and crown ether shifts the bischlorosulfonyl imide anion from the original reaction phase to a phase more susceptible to fluorination. The phosphonic acid group likely interacts with the fluorinating agent, lowering its activation energy and making it more susceptible to reaction with bischlorosulfonyl imide. This helps prevent side reactions and improves overall yield. This co-catalyst combination effectively increases the conversion and yield of bischlorosulfonyl imide fluorination. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further illustrated below by specific embodiments. Those skilled in the art should understand that the specific embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available conventional commodities.

[0034] Example 1

[0035] Step 1: Weigh 90g of aminosulfonic acid, 290g of thionyl chloride and 140g of chlorosulfonic acid, first add thionyl chloride and aminosulfonic acid in sequence into a reactor that has been dried and replaced with nitrogen in advance, start stirring, heat to reflux, control the temperature to 90°C, keep stirring until the solid aminosulfonic acid is completely dissolved in the thionyl chloride, then heat to 130°C, start adding the pre-weighed chlorosulfonic acid, keep the temperature for reaction for 28h, and collect the crude bischlorosulfonyl imide by vacuum distillation after the reaction is completed, and absorb the tail gas with alkali solution;

[0036] Step 2: Add 200g of bis(chlorosulfonyl)imide, 0.2g of fluorination catalyst, and 0.05g of co-catalyst to a tetrafluoroethylene reactor, heat to 80°C, slowly introduce 160g of HF gas under stirring, react for 12h, cool to room temperature, blow nitrogen, and purify by vacuum distillation to obtain bis(fluorosulfonyl)imide;

[0037] Step 3: Dissolve 160g of bis(fluorosulfonyl)imide and 36g of sodium source in 500g of non-benign solvent at -40°C. After complete dissolution, react at -10°C for 24h. After the reaction is completed, separate the solid and liquid to obtain a crude solid. Wash the solid with 500g of non-benign solvent, then dry and recrystallize to obtain lithium sodium bis(fluorosulfonyl)imide.

[0038] In this embodiment, the conditions for the reduced pressure distillation in step 1 are 500 Pa and 90° C.

[0039] In this embodiment, the alkali solution in step 1 is calcium hydroxide.

[0040] In this embodiment, the fluorination catalyst in step 2 is SbCl5.

[0041] In this embodiment, the preparation method of the co-catalyst described in step 2 is:

[0042] K1: 0.04 g of 4'-aminodibenzo-18-crown-6, 15 g of 2,3-epoxypropyltrimethylammonium chloride, 100 g of D418 resin, 1 g of sodium tert-butoxide, and 1000 g of toluene were added to a sealed stirred tank, nitrogen was introduced, and the mixture was stirred at 50°C for 100 minutes. Then, 0.05 g of allyltributyltin was added, and the mixture was stirred at 50°C for 20 minutes. After the reaction was completed, the mixture was filtered and dried to obtain a co-catalyst.

[0043] 4'-Aminodibenzo-18-crown-6, CAS:126531-26-8

[0044] In this embodiment, the D418 resin described in the preparation method of the co-catalyst in step 2 is a chelate resin with a weakly acidic aminophosphonic acid group (-CH2NHCH2PO3-) on a styrene-divinylbenzene copolymer with a special macroporous structure. Factory form: sodium type.

[0045] In this embodiment, the reduced pressure distillation conditions in step 2 are 560 Pa and 58° C.

[0046] In this embodiment, the sodium source in step 3 is NaOH.

[0047] In this embodiment, the non-benign solvent in step 3 is dichloromethane.

[0048] In this embodiment, the washing times in step 3 are 3 times.

[0049] In this embodiment, the drying conditions described in step 3 are drying by nitrogen purge at room temperature and negative pressure, and the drying time is 10 hours.

[0050] Example 2

[0051] Step 1: Weigh 95g of aminosulfonic acid, 325g of thionyl chloride and 155g of chlorosulfonic acid, first add thionyl chloride and aminosulfonic acid in sequence into a reactor that has been dried and replaced with nitrogen in advance, start stirring, heat to reflux, control the temperature to 100°C, keep stirring until the solid aminosulfonic acid is completely dissolved in the thionyl chloride, then heat to 138°C, start adding the pre-weighed chlorosulfonic acid, keep the temperature for reaction for 30h, and collect the crude bischlorosulfonyl imide by vacuum distillation after the reaction is completed, and absorb the tail gas with alkali solution;

[0052] Step 2: Add 215g of bis(chlorosulfonyl)imide, 0.6g of fluorination catalyst, and 0.3g of co-catalyst to a tetrafluoroethylene reactor, heat to 95°C, slowly introduce 200g of HF gas under stirring, react for 15h, cool to room temperature, blow nitrogen, and purify by vacuum distillation to obtain bis(fluorosulfonyl)imide;

[0053] Step 3: Dissolve 180g of bis(fluorosulfonyl)imide and 30g of a sodium source in 550g of a non-benign solvent at 0°C. After complete dissolution, react at 10°C for 30h. After the reaction is complete, separate the solid and liquid to obtain a crude solid. Wash the solid with 550g of a non-benign solvent, then dry and recrystallize to obtain sodium lithium bis(fluorosulfonyl)imide.

[0054] In this embodiment, the conditions for the reduced pressure distillation in step 1 are 625 Pa and 100° C.

[0055] In this embodiment, the alkali solution in step 1 is or cesium hydroxide.

[0056] In this embodiment, the fluorination catalyst in step 2 is TiCl 4 .

[0057] In this embodiment, the preparation method of the co-catalyst described in step 2 is:

[0058] K1: 0.4 g of 4'-aminodibenzo-18-crown-6, 23 g of 2,3-epoxypropyltrimethylammonium chloride, 130 g of D418 resin, 2 g of sodium tert-butoxide, and 1100 g of toluene were added to a sealed stirred reactor, nitrogen was introduced, and the reaction was stirred at 55°C for 125 minutes. Then 0.4 g of allyltributyltin was added, and the reaction was stirred at 55°C for 40 minutes. After the reaction was completed, the reaction was filtered and dried to obtain a co-catalyst.

[0059] 4'-Aminodibenzo-18-crown-6, CAS:126531-26-8

[0060] In this embodiment, the D418 resin described in the preparation method of the co-catalyst in step 2 is a chelate resin with a weakly acidic aminophosphonic acid group (-CH2NHCH2PO3-) on a styrene-divinylbenzene copolymer with a special macroporous structure. Factory form: sodium type.

[0061] In this embodiment, the reduced pressure distillation conditions in step 2 are 590 Pa and 59° C.

[0062] In this embodiment, the sodium source in step 3 is NaCl.

[0063] In this embodiment, the non-benign solvent in step 3 is dichloroethane.

[0064] In this embodiment, the number of washing times in step 3 is 4 times.

[0065] In this embodiment, the drying conditions described in step 3 are drying by nitrogen purge at room temperature and negative pressure, and the drying time is 14 hours.

[0066] Example 3

[0067] Step 1: Weigh 100g of aminosulfonic acid, 360g of thionyl chloride and 170g of chlorosulfonic acid, first add thionyl chloride and aminosulfonic acid in sequence into a reactor that has been dried and replaced with nitrogen in advance, start stirring, heat to reflux, control the temperature to 110°C, keep stirring until the solid aminosulfonic acid is completely dissolved in the thionyl chloride, then heat to 145°C, start adding the pre-weighed chlorosulfonic acid, keep the reaction for 32h, and collect the crude bischlorosulfonyl imide by vacuum distillation after the reaction is completed, and absorb the tail gas with alkali solution;

[0068] Step 2: Add 230g of bis(chlorosulfonyl)imide, 1 fluorination catalyst, and 0.6g of co-catalyst to a tetrafluoroethylene reactor, heat to 110°C, slowly introduce 240g of HF gas under stirring, react for 18h, cool to room temperature, blow nitrogen, and purify by vacuum distillation to obtain bis(fluorosulfonyl)imide;

[0069] Step 3: Dissolve 200g of bis(fluorosulfonyl)imide, 48g of sodium source in 600g of non-benign solvent at 40°C. After complete dissolution, react at 45°C for 48h. After the reaction is completed, separate the solid and liquid to obtain a crude solid. Wash the solid with 600g of non-benign solvent, then dry and recrystallize to obtain lithium sodium bis(fluorosulfonyl)imide.

[0070] In this embodiment, the conditions for the reduced pressure distillation in step 1 are 750 Pa and 110° C.

[0071] In this embodiment, the alkali solution in step 1 is calcium hydroxide, cesium hydroxide, potassium hydroxide or sodium hydroxide.

[0072] In this embodiment, the fluorination catalyst in step 2 is SnCl 4 .

[0073] In this embodiment, the preparation method of the co-catalyst described in step 2 is:

[0074] K1: 0.8 g of 4'-aminodibenzo-18-crown-6, 30 g of 2,3-epoxypropyltrimethylammonium chloride, 160 g of D418 resin, 3 g of sodium tert-butoxide, and 1200 g of toluene were added to a sealed stirred tank, nitrogen was introduced, and the mixture was stirred at 60°C for 150 minutes. 0.7 g of allyltributyltin was then added and the mixture was stirred at 60°C for 60 minutes. After the reaction was completed, the mixture was filtered and dried to obtain a co-catalyst.

[0075] 4'-Aminodibenzo-18-crown-6, CAS:126531-26-8

[0076] In this embodiment, the D418 resin described in the preparation method of the co-catalyst in Step 2 is a chelating resin with a weakly acidic aminophosphonic acid group (-CH2NHCH2PO3-) on a styrene-divinylbenzene copolymer with a special macroporous structure. Shipping form: sodium form.

[0077] In this embodiment, the reduced pressure distillation conditions in step 2 are 620 Pa and 60° C.

[0078] In this embodiment, the sodium source in step 3 is NaF.

[0079] In this embodiment, the non-benign solvent in step 3 is n-heptane.

[0080] In this embodiment, the number of washing times in step 3 is 5 times.

[0081] In this embodiment, the drying conditions described in step 3 are drying by nitrogen purge at room temperature and negative pressure, and the drying time is 18 hours.

[0082] Comparative Example 1

[0083] No co-catalyst is added in step 2, and the rest of the technical scheme is the same as in Example 1.

[0084] Comparative Example 2

[0085] No 4'-aminodibenzo-18-crown-6 was added to the co-catalyst, and the rest of the technical scheme was the same as in Example 1.

[0086] Comparative Example 3

[0087] No 2,3-epoxypropyltrimethylammonium chloride was added to the co-catalyst, and the rest of the technical scheme was the same as in Example 1.

[0088] Comparative Example 4

[0089] No D418 resin was added to the co-catalyst, and the rest of the technical scheme was the same as in Example 1.

[0090] Evaluation of the embodiment:

[0091] Test method:

[0092] 1. Purity: Purity is tested by ion chromatography.

[0093] 2. Yield: Yield of sodium bisfluorosulfonyl imide = actual amount of sodium bisfluorosulfonyl imide produced / theoretical amount of sodium bisfluorosulfonyl imide produced × 100%.

[0094] Test results:

[0095] Yield (%) purity(%) Example 1 96.9 99.90 Example 2 97.7 99.95 Example 3 98.6 99.99 Comparative Example 1 84.6 88.04 Comparative Example 2 89.4 94.35 Comparative Example 3 90.5 94.64 Comparative Example 4 91.2 94.82

[0096] It can be seen from the above table that compared with the comparative example, the yield and purity of sodium bis(fluorosulfonyl)imide prepared in the example are higher.

[0097] Although the present invention has been described in detail above using general explanations, specific embodiments, and experiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for preparing high-purity sodium bis(fluorosulfonyl)imide, characterized in that: The steps include: Step 1: Weigh 90-100 parts of sulfamic acid, 290-360 parts of thionyl chloride, and 140-170 parts of chlorosulfonic acid by mass, first add thionyl chloride and sulfamic acid in sequence into a reactor that has been dried and replaced with nitrogen in advance, start stirring, heat to reflux, control the temperature to 90-110°C, keep stirring until the solid sulfamic acid is completely dissolved in the thionyl chloride, then heat to 130-145°C, start adding the pre-weighed chlorosulfonic acid, keep the reaction for 28-32 hours, and collect the crude bischlorosulfonimide by vacuum distillation after the reaction is completed, and absorb the tail gas with alkali solution; Step 2: Add 200-230 parts of bis(chlorosulfonyl)imide, 0.2-1 parts of fluorination catalyst, and 0.05-0.6 parts of co-catalyst to a tetrafluoroethylene reactor, heating to 80-110°C, slowly introducing 160-240 parts of HF gas under stirring, reacting for 12-18 hours, cooling to room temperature, blowing nitrogen, and purifying by vacuum distillation to obtain bis(fluorosulfonyl)imide; Step 3: dissolving 160-200 parts of bis(fluorosulfonyl)imide, 36-48 parts of sodium source in 500-600 parts of non-benign solvent at -40-40°C, reacting at -10-45°C for 24-48 hours after complete dissolution, separating the solid and the liquid after completion of the reaction to obtain a crude solid, washing the solid with 500-600 parts of non-benign solvent, and then drying and recrystallizing to obtain sodium bis(fluorosulfonyl)imide; The preparation method of the co-catalyst described in step 2 is: K1: Add 0.04-0.8 parts of 4'-aminodibenzo-18-crown-6, 15-30 parts of 2,3-epoxypropyltrimethylammonium chloride, 100-160 parts of D418 resin, 1-3 parts of sodium tert-butoxide, and 1000-1200 parts of toluene to a sealed stirred tank reactor, introduce nitrogen, and stir the reaction at 50-60°C for 100-150 minutes. Then, add 0.05-0.7 parts of allyltributyltin, stir the reaction at 50-60°C for 20-60 minutes. After the reaction is completed, filter, and spin dry to obtain a co-catalyst.

2. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The conditions of the reduced pressure distillation in step 1 are 500-750 Pa and 90-110° C.

3. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The alkali solution described in step 1 is calcium hydroxide, cesium hydroxide, potassium hydroxide or sodium hydroxide.

4. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The fluorination catalyst described in step 2 is one of SbCl5, TiCl4, SnCl4, and MoCl5.

5. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The D418 resin is a chelating resin with a weakly acidic aminophosphonic acid group on a styrene-divinylbenzene copolymer with a special macroporous structure, and its factory form is sodium type.

6. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The reduced pressure distillation conditions in step 2 are 560-620 Pa, 58-60°C.

7. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The sodium source in step 3 is one or more of NaOH, NaCl and NaF.

8. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The non-benign solvent described in step 3 is one or any combination of dichloromethane, dichloroethane, chloroform, trichloroethane, carbon tetrachloride, n-hexane, cyclohexane, and n-heptane.

9. The method for preparing high-purity sodium bis(fluorosulfonyl)imide according to claim 1, wherein: The washing times in step 3 are 3-5 times, and the drying conditions are drying under normal temperature and negative pressure using nitrogen purge, and the drying time is 10-18 hours.