Method for preparing lithium bis(fluorosulphonyl)imide salt

Abstract

A method for preparing Cl—SO.sub.2NHSO.sub.2Cl including a step of chlorinating sulphamic acid with at least one chlorinating agent and at least one sulphur-containing agent, the method resulting in a flow F1, preferably liquid, including Cl—SO.sub.2NHSO.sub.2Cl and a gas stream F2 including HCl and SO.sub.2, the method including a step a) of treating the gas stream F2. Also, a method for preparing LiFSl including the abovementioned method for preparing Cl—SO.sub.2NHSO.sub.2Cl.

Claims

1. A process for the preparation of Cl—SO.sub.2NHSO.sub.2Cl comprising a stage of chlorination of sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent, said process resulting in a stream F1 comprising Cl—SO.sub.2NHSO.sub.2Cl and a gas stream F2 comprising HCl and SO.sub.2, said process comprising a stage a) of treatment of the gas stream F2.

2. The process as claimed in claim 1, in which stage a) of treatment of the gas stream F2 comprises a stage of bringing said stream F2 into contact with an alkaline aqueous solution, and/or a stage of bringing said stream F2 into contact with a hydrogen peroxide solution, and/or a stage of separation of HCl and SO.sub.2 contained in said stream F2, and/or a stage of absorption of HCl contained in said gas stream F2 in an aqueous solution, and/or a stage of absorption of SO.sub.2 contained in said gas stream F2 in a concentrated sulfuric acid solution.

3. The process as claimed in claim 1, in which the gas stream F2 comprises: more than 20% by weight of HCl, with respect to the total weight of said stream F2; and/or more than 30% by weight of SO.sub.2, with respect to the total weight of said stream F2.

4. The process as claimed in claim 1, in which stage a) of treatment of the gas stream F2 comprises i) bringing the gas stream F2 into contact with an alkaline aqueous solution.

5. The process as claimed in claim 1, in which stage a) of treatment of the gas stream F2 comprises ii) bringing the gas stream F2 into contact with a hydrogen peroxide solution.

6. The process as claimed in claim 5, in which stage ii) of bringing the gas stream F2 into contact with a hydrogen peroxide solution makes it possible to form and to recover: a gas stream G2 comprising water and optionally one or more inert gas(es); and an acid stream L2 comprising water, HCl and H.sub.2SO.sub.4.

7. The process as claimed in claim 6, comprising an additional stage ii-1) of treatment of the stream L2 which comprises bringing said stream L2 into contact with an alkaline aqueous solution, or an additional stage ii-2) of separation of HCl and of H.sub.2SO.sub.4 contained in the stream L2 in order to form and to recover a stream F3 comprising HCl and a stream F′3 comprising H.sub.2SO.sub.4.

8. The process as claimed in claim 1, in which stage a) of treatment of the gas stream F2 comprises: iii) an optional stage of compression of said gas stream F2, iv) a stage of separation of HCl and SO.sub.2 contained in said gas stream F2 resulting in a stream G4 comprising HCl and in a stream F4 comprising SO.sub.2, it being possible for said stream F4 to be a liquid or gas stream.

9. The process as claimed in claim 8, in which stage a) comprises an additional stage v) of treatment of the gas stream G4, and/or an additional stage vi) of treatment of the stream F4.

10. The process as claimed in claim 9, in which said stage v) comprises: v-1) an optional stage of purification of said gas stream G4, v-2) a stage of absorption of the hydrochloric acid contained in said gas stream G4 in an aqueous solution, making it possible to form and to recover an aqueous hydrochloric acid solution L5.

11. The process as claimed in claim 9, in which: when the stream F4 is a liquid stream, in particular when stage iv) is a separation by distillation, the treatment stage vi) comprises vi-1) bringing said liquid stream F4 into contact with an alkaline aqueous solution, resulting in a gas stream G6 comprising water and optionally one or more inert gas(es) and in an alkaline stream L6 comprising water, chloride ions and sulfite ions; when the stream F4 is a gas stream, the treatment stage vi) comprises: vi-2) bringing said gas stream F4 into contact with an alkaline aqueous solution; or vi-3) bringing the gas stream F4 into contact with a hydrogen peroxide solution; or vi-4) the oxidation of the gas stream F4 in the presence of oxygen in order to form a stream F5 comprising SO.sub.3, optionally followed; by a stage vi-4-a) of absorption of SO.sub.3 contained in said stream F5 in a concentrated sulfuric acid solution, making it possible to form and to recover a gas stream G9, comprising water and optionally one or more inert gas(es), and an oleum L9; then optionally a stage vi-4-b) of dilution of the oleum L9 in water, in order to form an aqueous solution L10.

12. The process as claimed in claim 1, in which stage a) of treatment of the gas stream F2 comprises: vii) a stage of absorption of the hydrochloric acid contained in said gas stream F2 in an aqueous solution, making it possible to form and to recover a hydrochloric acid solution L11 and a gas stream G11 comprising SO.sub.2, water and optionally one or more inert gases; or x) a stage of absorption of SO.sub.2 contained in said gas stream F2 in a concentrated sulfuric acid solution, making it possible to form and to recover a gas stream G12 comprising HCl and optionally one or more inert gas(es) and a stream L12 comprising water, H.sub.2SO.sub.4 and SO.sub.2.

13. The process as claimed in claim 12, in stage a) of treatment of the gas stream F2 comprises: a stage viii), subsequent to stage vii), comprising the purification of the solution L11; and an optional stage ix) of drying the gas stream G11, for example carried out in the presence of calcium sulfate, sodium sulfate, magnesium sulfate, calcium chloride, calcium carbonate, silica gel or molecular sieve.

14. The process as claimed in claim 12, in which stream L12 is: subjected, at least partially, to a heating stage, making it possible to form and to recover a gas stream G13 comprising SO.sub.2 and a stream L13 comprising H.sub.2SO.sub.4; and/or subjected, at least partially, to a stage of bringing into contact with a hydrogen peroxide solution.

15. The process as claimed in claim 1, in which the chlorination stage is carried out: at a temperature of between 30° C. and 150° C.; and/or with a reaction time of between 1 hour and 7 days; and/or at a pressure of between 1 bar abs and 20 bar abs.

16. The process as claimed in claim 1, in which: the sulfur-containing agent is chosen from the group consisting of chlorosulfonic acid (ClSO.sub.3H), sulfuric acid, oleum and their mixtures; and/or the chlorinating agent is chosen from the group consisting of thionyl chloride (SOCl.sub.2), oxalyl chloride (COCl).sub.2, phosphorus pentachloride (PCl.sub.5), phosphonyl trichloride (PCl.sub.3), phosphoryl trichloride (POCl.sub.3) and their mixtures.

17. A process for the preparation of the lithium salt of bis(fluorosulfonyl)imide comprising the process for the preparation of Cl—SO.sub.2—NH—SO.sub.2—Cl as defined according to claim 1.

Description

EXAMPLES

Example 1

(1) A 100-liter enamelled steel reactor equipped with a stirrer is charged with sulfamic acid (1 eq, 257.5 mol, 25 kg) and 95% sulfuric acid (1 eq, 257.5 mol, 26.6 kg). Thionyl chloride (4 eq, 1030 mol, 122.5 kg) is gradually added to the reactor. The temperature of the reaction medium is gradually increased up to 75° C. The reaction is carried out at atmospheric pressure.
Total conversion to sulfamic acid is obtained after 60 hours. A condenser is positioned on the vent line of the reactor so as to condense the vaporized thionyl chloride and to reflux it into the reaction medium.
At the end of the reaction, 67 kg of liquid containing bis(chlorosulfonyl)imide and unreacted thionyl chloride is obtained.
The gases generated by the reaction (HCl and SO.sub.2) and not condensed by the condenser are directed to a system which makes it possible to absorb them (cf. examples 2 and 3).

Example 2

HCl and SO.SUB.2 .Absorption in an H.SUB.2.O.SUB.2 .Solution

(2) The gases generated by the reaction of example 1 are sent to a storage tank containing 700 kg of a 5% by weight H.sub.2O.sub.2 solution. This storage tank is surmounted by a packed column sprayed at the top with the H.sub.2O.sub.2 solution contained in said storage tank. A pump makes it possible to withdraw the H.sub.2O.sub.2 solution from the storage tank in order to spray the column. The gases generated by the reaction (HCl and SO.sub.2) are introduced the H.sub.2O.sub.2 solution contained in the storage tank by means of a dip pipe. The HCl and the SO.sub.2 are absorbed in the H.sub.2O.sub.2 solution and the SO.sub.2 reacts with H.sub.2O.sub.2 to form H.sub.2SO.sub.4. The packed column makes it possible to finalize the absorption of the gases generated by the reaction, HCl and SO.sub.2, and to completely convert the SO.sub.2 into H.sub.2SO.sub.4.
At the end of the reaction, a solution of 797 kg is obtained comprising 1% by weight of H.sub.2O.sub.2, 5% by weight of HCl and 10% by weight of H.sub.2SO.sub.4.

Example 3

HCl Absorption in Water Followed by SO.SUB.2 .Absorption in an H.SUB.2.O.SUB.2 .Solution

(3) The gases generated by the reaction of example 1 (HCl and SO.sub.2) are directed to an HCl absorption column sprayed with water at the top. This column makes it possible to obtain a 33% HCl solution at the bottom. This column makes it possible to specifically absorb gaseous HCl, while gaseous SO.sub.2 is not absorbed.
The gaseous SO.sub.2 is recovered at the top of the HCl absorption column and is directed to a storage tank containing 300 kg of a 10% by weight H.sub.2O.sub.2 solution of a solution. The device for absorption of gaseous SO.sub.2 in an H.sub.2O.sub.2 solution is identical to that described in example 2. In this configuration, the packed column makes it possible to finalize the absorption of SO.sub.2 and to completely convert the SO.sub.2 into H.sub.2SO.sub.4.
At the end of the reaction, 130 kg of a 33% HCl solution, on the one hand, and a solution of 354 kg comprising less than 1% by weight of H.sub.2O.sub.2 and 23% by weight of H.sub.2SO.sub.4, on the other hand, are obtained.