Purification method of bis (fluorosulfonyl) imide

Abstract

The invention discloses a purification method of bis (fluorosulfonyl) imide, which specifically comprises the following steps: mixing a bis (fluorosulfonyl) imide crude product with perfluorosulfonate, and carrying out ion exchange reaction; after the reaction, rectifying and separating to obtain purified bis (fluorosulfonyl) imide; the bis (fluorosulfonyl) imide crude product contains 1 ppm to 30 wt% of fluorosulfonic acid, preferably 10 ppm to 5 wt% of fluorosulfonic acid, and more preferably 0.01 to 1 wt% of fluorosulfonic acid. The method comprises the following steps: adding perfluorosulfonate, carrying out an ion exchange reaction on a difluorosulfonyl imide crude product containing fluorosulfonic acid to obtain a mixture of difluorosulfonyl imide, fluorosulfonate and high-boiling-point perfluorosulfonic acid, and carrying out rectification separation to obtain a difluorosulfonyl imide pure product.

Description

Technical Field

[0001] The present invention relates to a purification method, and particularly to a purification method of bis(fluorosulfonyl)imide. Background Art

[0002] Power batteries have attracted public attention due to the development of new energy vehicles and energy storage. As a key link in the manufacture of power batteries, synthesizing new electrolytes with high electron mobility is also an important method to improve the performance of power batteries. Currently, the mainstream power battery electrolyte in the market is lithium hexafluorophosphate LiPF6. Compared with LiPF6, the new power battery electrolyte bis(fluorosulfonyl)imide salt has higher chemical stability and better conductivity, and has good competitiveness and market prospects in the field of power batteries.

[0003] Bis(fluorosulfonyl)imide salt is generally synthesized by reacting bis(fluorosulfonyl)imide with an alkali metal salt, and there are many reports in the known technologies, such as CN109562941B, 112645294B, CN114873571A, etc. As a raw material for synthesizing the new power battery electrolyte bis(fluorosulfonyl)imide salt, the purity of bis(fluorosulfonyl)imide is crucial for maintaining excellent battery performance.

[0004] However, another report "Z. anorg. allg. Chem., 2005, 631(1): 55 - 59" pointed out that in the process of preparing bis(chlorosulfonyl)imide using sulfamic acid and chlorosulfonyl isocyanate as raw materials, both raw materials contain chlorosulfonic acid. And in the process of fluorinating bis(chlorosulfonyl)imide to form bis(fluorosulfonyl)imide, chlorosulfonic acid further forms fluorosulfonic acid, resulting in a high content of fluorosulfonic acid impurities in bis(fluorosulfonyl)imide. Since their boiling points are close, it is difficult to separate and purify them by conventional distillation.

[0005] Chinese patent application CN116924357A discloses a crystallization method of bis(fluorosulfonyl)imide, which separates light component impurities by melt crystallization, but the production efficiency of melt crystallization is low and it is not suitable for industrial production. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention proposes a purification method of bis(fluorosulfonyl)imide. By adding a perfluorosulfonate and performing an ion exchange reaction on the crude bis(fluorosulfonyl)imide containing fluorosulfonic acid, a mixture of bis(fluorosulfonyl)imide, fluorosulfonate, and high-boiling perfluorosulfonic acid can be obtained. After separation by distillation, pure bis(fluorosulfonyl)imide can be obtained. This method is simple to operate and has wide industrial applicability.

[0007] A purification method of bis(fluorosulfonyl)imide, specifically, mixing the crude bis(fluorosulfonyl)imide with a perfluorosulfonate and performing an ion exchange reaction; after the reaction, separating by distillation to obtain purified bis(fluorosulfonyl)imide;

[0008] The crude bis(fluorosulfonyl)imide contains 1 ppm to 30 wt% of fluorosulfonic acid, preferably 10 ppm to 5 wt% of fluorosulfonic acid, and more preferably 0.01 - 1 wt% of fluorosulfonic acid.

[0009] As a preferred embodiment of the present invention, the addition amount of the perfluorosulfonate is 1 - 10 times, preferably 1 - 5 times, and more preferably 1 - 2 times the molar amount of fluorosulfonic acid in the crude bis(fluorosulfonyl)imide.

[0010] As a preferred embodiment of the present invention, the perfluorosulfonate is selected from one or more of potassium perfluorobutanesulfonate, sodium perfluorobutanesulfonate, lithium perfluorobutanesulfonate, potassium perfluoropentanesulfonate, sodium perfluoropentanesulfonate, lithium perfluoropentanesulfonate, potassium perfluorohexanesulfonate, sodium perfluorohexanesulfonate, and lithium perfluorohexanesulfonate.

[0011] As a preferred embodiment of the present invention, the reaction temperature of the ion exchange reaction is 20 - 250 °C, preferably 50 - 150 °C.

[0012] As a preferred embodiment of the present invention, after the reaction, the first rectification separation is carried out under the following conditions to obtain purified bis(fluorosulfonyl)imide:

[0013] The operating temperature of the bottom of the rectification column is 60 - 120 °C, the operating pressure inside the column is 0.2 - 30 kPaA, and bis(fluorosulfonyl)imide is taken out from the top of the column.

[0014] As a preferred embodiment of the present invention, the bottom mixed liquid taken out from the first rectification separation is subjected to a second rectification separation under the following conditions:

[0015] The operating temperature of the bottom of the rectification column is 120 - 350 °C, the operating pressure inside the column is 0.2 - 100 kPaA, and the high - value - added product perfluorosulfonate is taken out from the bottom of the column; the overhead product includes perfluorosulfonic acid with a relatively high boiling point under normal pressure and residual bis(fluorosulfonyl)imide, and the perfluorosulfonic acid can be reused to prepare perfluorosulfonate with an alkali metal salt and recycled.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) Adding perfluorosulfonate to react with fluorosulfonic acid to convert the fluorosulfonic acid in bis(fluorosulfonyl)imide into a high - boiling - point salt; then using rectification separation to obtain high - purity bis(fluorosulfonyl)imide.

[0018] 2) The obtained perfluorosulfonate is recovered by the second rectification separation and can be used as a high - value - added product; moreover, the perfluorosulfonic acid taken out can be reused to prepare perfluorosulfonate with an alkali metal salt and recycled, which has good economic efficiency in industrial applications.

[0019] 3) The present invention realizes the purification of key substances and obtains high - value - added by - products, has high industrial efficiency, and is suitable for large - scale popularization and application. Detailed implementation mode

[0020] The present invention will be further described below through specific embodiments. The embodiments described in the present invention are only for the purpose of explaining the present invention and do not limit the scope of the present invention.

[0021] The main raw material information used in the following embodiments of the present invention is as follows:

[0022] Potassium perfluorobutanesulfonate (CAS: 29420-49-3), purchased from Beijing Innochem Science & Technology Co., Ltd.;

[0023] Lithium perfluorobutanesulfonate (CAS: 131651-65-5), purchased from Beijing Innochem Science & Technology Co., Ltd.;

[0024] Potassium perfluoropentanesulfonate (CAS: 3872-25-1), purchased from Beijing J&K Scientific Ltd.);

[0025] Sodium perfluoropentanesulfonate (CAS: 630402-22-1), purchased from Shanghai Wentong Technology Co., Ltd.;

[0026] Potassium perfluorohexanesulfonate (CAS: 3871-99-6), purchased from Beijing J&K Scientific Ltd.

[0027] The main detection / analysis means involved in the present invention are as follows:

[0028] Substance content test: The components are quantitatively analyzed by external standard method using Thermo Fisher ion chromatography HPIC, and the chromatographic column is an anion analytical column.

[0029]

Example 1

[0030] Take 500 g of bis(fluorosulfonyl)imide crude product (containing 100 ppm of fluorosulfonic acid), add potassium perfluorobutanesulfonate according to 1 times the molar amount of fluorosulfonic acid, react at 50 °C for 2 h in a reaction kettle, and then transfer the reaction solution to a two-stage rectification column.

[0031] The bottom operating temperature of the first-stage rectification column is 100 °C, the rectification column operating pressure is 5 kPaA, high-purity bis(fluorosulfonyl)imide (fluorosulfonic acid content is 13 ppm) is taken from the top of the column, the product yield is 99.0%, and the bottom liquid mixture enters the second-stage rectification column.

[0032] The bottom operating temperature of the second-stage rectification column is 150 °C, the rectification column operating pressure is 2 kPaA, perfluorobutanesulfonic acid is taken from the top of the column, and potassium fluorosulfonate is separated from the bottom of the column.

[0033]

Example 2

[0034] Take 500 g of crude bis(fluorosulfonyl)imide (containing 10 ppm of fluorosulfonic acid), add lithium perfluorobutanesulfonate in an amount 10 times the molar amount of fluorosulfonic acid, and react at 250 °C for 2 h in a reaction kettle. Subsequently, transfer the reaction solution to a two-stage distillation column.

[0035] The bottom operating temperature of the first-stage distillation column is 60 °C, the operating pressure of the distillation column is 0.2 kPaA, high-purity bis(fluorosulfonyl)imide (with a fluorosulfonic acid content of 2 ppm) is withdrawn from the top of the column, the product yield is 99.1%, and the bottom mixture enters the second-stage distillation column.

[0036] The bottom operating temperature of the second-stage distillation column is 120 °C, the operating pressure of the distillation column is 20 kPaA, perfluorobutanesulfonic acid is withdrawn from the top of the column, and lithium fluorosulfonate is separated from the bottom.

[0037]

Example 3

[0038] Take 500 g of crude bis(fluorosulfonyl)imide (containing 30 wt% of fluorosulfonic acid), add potassium perfluoropentanesulfonate in an amount 1.5 times the molar amount of fluorosulfonic acid, and react at 80 °C for 2 h in a reaction kettle. Subsequently, transfer the reaction solution to a two-stage distillation column.

[0039] The bottom operating temperature of the first-stage distillation column is 120 °C, the operating pressure of the distillation column is 4 kPaA, high-purity bis(fluorosulfonyl)imide (with a fluorosulfonic acid content of 7 ppm) is withdrawn from the top of the column, the product yield is 96.2%, and the bottom mixture enters the second-stage distillation column.

[0040] The bottom operating temperature of the second-stage distillation column is 200 °C, the operating pressure of the distillation column is 0.5 kPaA, perfluoropentanesulfonic acid is withdrawn from the top of the column, and potassium fluorosulfonate is separated from the bottom.

[0041]

Example 4

[0042] Take 500 g of crude bis(fluorosulfonyl)imide (containing 0.5 wt% of fluorosulfonic acid), add lithium perfluorobutanesulfonate in an amount 1.05 times the molar amount of fluorosulfonic acid, and react at 100 °C for 2 h in a reaction kettle. Subsequently, transfer the reaction solution to a two-stage distillation column.

[0043] The bottom operating temperature of the first-stage distillation column is 120 °C, the operating pressure of the distillation column is 10 kPaA, high-purity bis(fluorosulfonyl)imide (with a fluorosulfonic acid content of 6 ppm) is withdrawn from the top of the column, the product yield is 99.7%, and the bottom mixture enters the second-stage distillation column.

[0044] The bottom operating temperature of the second-stage distillation column is 180 °C, the operating pressure of the distillation column is 50 kPaA, perfluorobutanesulfonic acid is withdrawn from the top of the column, and lithium fluorosulfonate is separated from the bottom.

[0045]

Example 5

[0046] Take 500 g of crude bis(fluorosulfonyl)imide (containing 5 wt% fluorosulfonic acid), add sodium perfluoropentanesulfonate according to 1.05 times the molar amount of fluorosulfonic acid, react at 20 °C for 2 h in a reaction kettle, and then transfer the reaction solution to a two-stage distillation column.

[0047] The bottom operating temperature of the first-stage distillation column is 80 °C, the operating pressure of the distillation column is 5 kPaA, high-purity bis(fluorosulfonyl)imide (fluorosulfonic acid content is 10 ppm) is taken from the top of the column, the product yield is 99.3%, and the bottom mixture enters the second-stage distillation column.

[0048] The bottom operating temperature of the second-stage distillation column is 250 °C, the operating pressure of the distillation column is 100 kPaA, perfluoropentanesulfonic acid is taken from the top of the column, and sodium fluorosulfonate is separated from the bottom.

[0049]

Example 6

[0050] Take 500 g of crude bis(fluorosulfonyl)imide (containing 1 wt% fluorosulfonic acid), add potassium perfluorohexanesulfonate according to 1.1 times the molar amount of fluorosulfonic acid, react at 250 °C for 2 h in a reaction kettle, and then transfer the reaction solution to a two-stage distillation column.

[0051] The bottom operating temperature of the first-stage distillation column is 80 °C, the operating pressure of the distillation column is 20 kPaA, high-purity bis(fluorosulfonyl)imide (fluorosulfonic acid content is 9 ppm) is taken from the top of the column, the product yield is 99.0%, and the bottom mixture enters the second-stage distillation column.

[0052] The bottom operating temperature of the second-stage distillation column is 300 °C, the operating pressure of the distillation column is 50 kPaA, perfluorohexanesulfonic acid is taken from the top of the column, and potassium fluorosulfonate is separated from the bottom.

[0053]

Example 7

[0054] Take 500 g of crude bis(fluorosulfonyl)imide (containing 10 wt% fluorosulfonic acid), add potassium perfluorohexanesulfonate according to 1.1 times the molar amount of fluorosulfonic acid, react at 70 °C for 2 h in a reaction kettle, and then transfer the reaction solution to a two-stage distillation column.

[0055] The bottom operating temperature of the first-stage distillation column is 120 °C, the operating pressure of the distillation column is 30 kPaA, high-purity bis(fluorosulfonyl)imide (fluorosulfonic acid content is 8 ppm) is taken from the top of the column, the product yield is 98.5%, and the bottom mixture enters the second-stage distillation column.

[0056] The bottom operating temperature of the second-stage distillation column is 350 °C, the operating pressure of the distillation column is 10 kPaA, perfluorohexanesulfonic acid is taken from the top of the column, and potassium fluorosulfonate is separated from the bottom.

[0057]

Example 8

[0058] Take 500 g of crude bis(fluorosulfonyl)imide (containing 20 wt% fluorosulfonic acid), add lithium perfluorobutanesulfonate in an amount 1.1 times the molar amount of fluorosulfonic acid, react at 90 °C for 2 h in a reaction kettle, and then transfer the reaction solution to a two-stage distillation column.

[0059] The bottom operating temperature of the first-stage distillation column is 100 °C, the operating pressure of the distillation column is 20 kPaA, high-purity bis(fluorosulfonyl)imide (fluorosulfonic acid content is 5 ppm) is taken from the top of the column, the product yield is 97.8%, and the bottom mixture enters the second-stage distillation column.

[0060] The bottom operating temperature of the second-stage distillation column is 130 °C, the operating pressure of the distillation column is 0.2 kPaA, perfluorobutanesulfonic acid is taken from the top of the column, and lithium fluorosulfonate is separated from the bottom of the column.

[0061]

Example 9

[0062] Take 500 g of crude bis(fluorosulfonyl)imide (containing 0.01 wt% fluorosulfonic acid), add potassium perfluorobutanesulfonate in an amount 1.1 times the molar amount of fluorosulfonic acid, react at 130 °C for 2 h in a reaction kettle, and then transfer the reaction solution to a two-stage distillation column.

[0063] The bottom operating temperature of the first-stage distillation column is 100 °C, the operating pressure of the distillation column is 30 kPaA, high-purity bis(fluorosulfonyl)imide (fluorosulfonic acid content is 8 ppm) is taken from the top of the column, the product yield is 99.7%, and the bottom mixture enters the second-stage distillation column.

[0064] The bottom operating temperature of the second-stage distillation column is 130 °C, the operating pressure of the distillation column is 0.2 kPaA, perfluorobutanesulfonic acid is taken from the top of the column, and potassium fluorosulfonate is separated from the bottom of the column.

[0065] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the method of the present invention, several improvements and supplements can be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A purification method of difluoromethanesulfonimide, characterized in that, Mix the crude bis(fluorosulfonyl)imide and the perfluorosulfonate, and carry out an ion exchange reaction; after the reaction, perform rectification separation to obtain purified bis(fluorosulfonyl)imide; The crude bis(fluorosulfonyl)imide contains 1 ppm to 30 wt% of fluorosulfonic acid, preferably 10 ppm to 5 wt% of fluorosulfonic acid, and more preferably 0.01 - 1 wt% of fluorosulfonic acid.

2. The purification method of difluoromethanesulfonimide according to claim 1, characterized in that, The addition amount of the perfluorosulfonate is 1 - 10 times the molar amount of fluorosulfonic acid in the crude bis(fluorosulfonyl)imide, preferably 1 - 5 times, and more preferably 1 - 2 times.

3. The purification method of difluoromethanesulfonimide according to claim 1 or 2, characterized in that, The perfluorosulfonate is selected from one or more of potassium perfluorobutanesulfonate, sodium perfluorobutanesulfonate, lithium perfluorobutanesulfonate, potassium perfluoropentanesulfonate, sodium perfluoropentanesulfonate, lithium perfluoropentanesulfonate, potassium perfluorohexanesulfonate, sodium perfluorohexanesulfonate, and lithium perfluorohexanesulfonate.

4. The purification method of difluoromethanesulfonimide according to any one of claims 1-3, characterized in that, The reaction temperature of the ion exchange reaction is 20 - 250 °C, preferably 50 - 150 °C.

5. The purification method of difluoromethanesulfonimide according to any one of claims 1-4, characterized in that, After the reaction, perform the first rectification separation under the following conditions to obtain purified bis(fluorosulfonyl)imide: The operating temperature of the bottom of the rectification column is 60 - 120 °C, the operating pressure inside the column is 0.2 - 30 kPaA, and bis(fluorosulfonyl)imide is taken out from the top of the column.

6. The purification method of bis(fluorosulfonyl)imide according to claim 5, characterized in that, The bottom liquid mixture taken out from the first rectification separation is subjected to the second rectification separation under the following conditions: The operating temperature of the bottom of the rectification column is 120 - 350 °C, the operating pressure inside the column is 0.2 - 100 kPaA, and the high - value - added product fluorosulfonate is taken out from the bottom of the column.