Method for preparing bis(fluorosulfonyl)imide acid and salts thereof

Abstract

The invention relates to a method for preparing bis(fluorosulfonyl)imide acid, comprising: the reaction of sulphamic acid or one of the salts thereof with a halogenosulfuric acid and at least one fluorinating agent selected from SOF.sub.2, FSO.sub.2F and SF.sub.4, and the subsequent recovery of bis(fluorosulfonyl)imide acid. The invention also relates to a method for producing salts of bis(fluorosulfonyl)imide from the bis(fluorosulfonyl)imide acid thus produced.

Claims

1. A process for preparing bis(fluorosulfonyl)imide acid of formula FSO.sub.2NHSO.sub.2F, the process comprising the reaction of sulfamic acid or a salt thereof with at least one halosulfuric acid and at least one fluorinating agent selected from the group consisting of SOF.sub.2, FSO.sub.2F and SF.sub.4, then the recovery of the bis(fluorosulfonyl)imide acid.

2. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 1, wherein the halosulfuric acid has the formula XSO.sub.2OH wherein X is a halogen selected from the group consisting of fluorine, chlorine, bromine and iodine.

3. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 1, wherein said reaction is carried out in the presence of an organic solvent.

4. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 1, wherein the halosulfuric acid represents from 1 mol % to 5 molar equivalents expressed relative to the sulfamic acid or salts thereof and the fluorinating agent is FSO.sub.2F.

5. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 4, wherein the halosulfuric acid represents from 5 mol % to 1 molar equivalent expressed relative to the sulfamic acid or salts thereof.

6. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 1, wherein the halosulfuric acid represents from 1 to 5 molar equivalent(s) expressed relative to the sulfamic acid or salts thereof and the fluorinating agent is SOF.sub.2 or SF.sub.4.

7. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 1, wherein said fluorinating agent represents from 1 to 10 molar equivalent(s) expressed relative to the sulfamic acid or salts thereof.

8. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 1, wherein said reaction is performed at a temperature between 0 and 180 C.

9. The process for preparing bis(fluorosulfonyl)imide acid as claimed in claim 1, wherein said bis(fluorosulfonyl)imide acid is recovered by distillation, by sublimation or by extraction.

10. A process for preparing at least one bis(fluorosulfonyl)imide salt, the process comprising preparing the bis(fluorosulfonyl)imide acid according to the process as defined in claim 1, followed by bringing said acid into contact with at least one salification agent.

11. The process for preparing at least one bis(fluorosulfonyl)imide salt as claimed in claim 10, wherein the salification agent is a metal hydroxide, a metal halide, a metal hydride, a metal trifluoroacetate or a metal trifluoromethanesulfonate.

12. The process for preparing at least one bis(fluorosulfonyl)imide salt as claimed in claim 10, wherein said salt has the general formula FSO.sub.2N-M-SO.sub.2F, where M represents an alkali metal, an alkaline-earth metal, a transition metal or a metal selected from lanthanides.

13. The process for preparing at least one bis(fluorosulfonyl)imide salt as claimed in claim 10, wherein said salt is lithium bis(fluorosulfonyl)imide.

14. The process for preparing at least one bis(fluorosulfonyl)imide salt as claimed in claim 10, also comprising a step of purifying said salt.

15. The process for preparing at least one bis(fluorosulfonyl)imide salt as claimed in claim 14, wherein the purification step consists of a recrystallization.

Description

EXAMPLE 1

(1) A solution of sulfamic acid (22.4 g; 230 mmol) in 30 grams of ortho-dichlorobenzene is charged to a 500 ml C276 Hastelloy reactor. Fluorosulfonic acid (1.2 g; 12 mmol) is added and the autoclave is closed. The medium is heated to a temperature of 92 C. The sulfuryl fluoride (47 g; 0.46 mol) is added in such a way as to maintain the pressure below P=37 bar. The addition is carried out over the course of 9 hours.

(2) The temperature is then brought back to ambient temperature and the reactor is decompressed. An analysis of the reaction medium by fluorine 19 NMR shows that the expected bis(fluorosulfonyl)imide acid is formed with a yield of 52%.

EXAMPLE 2

(3) A solution of sulfamic acid (22.4 g; 230 mmol) in 300 grams of dichloroethane is charged to a 500 ml C276 Hastelloy reactor. Fluorosulfonic acid (1.2 g; 12 mmol) is added and the autoclave is closed. The medium is heated to a temperature of 92 C. The sulfuryl fluoride (47 g; 0.46 mol) is added in such a way as to maintain the pressure below P=37 bar. The addition is carried out over the course of 10 hours.

(4) The temperature is then brought back to ambient temperature and the reactor is decompressed. An analysis of the reaction medium by fluorine 19 NMR shows that the expected bis(fluorosulfonyl)imide acid is formed with a yield of 53%.

EXAMPLE 3

(5) 200 g of dichloroethane are charged to a 500 ml C276 Hastelloy reactor, which is then closed and left stirring at ambient temperature and purged with nitrogen. The thionyl fluoride (60 g; 0.34 mol) is then added under pressure to the reactor. The sulfamic acid (22.3 g; 0.23 mol) in solution in dichloroethane (100 g) and then the chlorosulfuric acid (26.8 g; 0.23 mol) are added to the autoclave. The temperature is then maintained at 80 C. for 17 hours. The pressure observed reaches 22 bar at the end of the reaction at this temperature. After returning to ambient temperature, the reactor is decompressed. The analysis of the medium by .sup.19F NMR indicates that the bis(fluorosulfonyl)imide acid is obtained with a yield of 77%.

EXAMPLE 4

(6) The solution obtained in example 3, containing the bis(fluorosulfonyl)imide acid, is concentrated at ambient temperature under reduced pressure while maintaining the temperature of the medium below 80 C.

(7) The residue obtained is distilled under reduced pressure (P=5 mbar) while maintaining the temperature of the boiler below 80 C.

(8) Under an inert atmosphere, the bis(fluorosulfonyl)imide acid thus distilled is slowly added to a suspension of lithium hydride (1.15 g; 0.145 mol) in anhydrous butyl acetate (55 g). The solution is then cooled to 20 C. and the solid obtained is recovered by filtration.

(9) The solid is purified a second time by recrystallization from butyl acetate.

(10) The solid obtained is then rinsed with dichloromethane and dried under vacuum.

(11) The lithium bis(fluorosulfonyl)imide obtained has a purity greater than 90% by weight.