Process for preparing the lithium salt of bis (fluorosulfonyl) imide

FIELD OF THE INVENTION

The present invention relates to a process for preparing a lithium salt of imides containing a fluorosulfonyl group.

TECHNICAL BACKGROUND

Sulfonylimide type anions, due to their very low basicity, are increasingly used in the field of energy storage in the form of inorganic salts in batteries, or organic salts in supercapacitors or in the field of liquids. ionic. As the battery market is booming and the reduction of battery manufacturing costs is becoming a major issue, a large-scale, low-cost synthesis process for this type of anions is necessary.

In the specific field of Li-ion batteries, the salt currently most used is LiPF 6 but this salt shows many disadvantages such as limited thermal stability, sensitivity to hydrolysis and therefore lower battery safety. . Recently, new salts possessing the FS0 2 group have been studied and have demonstrated many advantages such as better ionic conductivity and resistance to hydrolysis. One of these salts, LiFSI (LiN (FS0 2 ) 2 ) has shown very interesting properties which make it a good candidate to replace LiPF 6 .

There are several processes for preparing LiFSI, comprising in particular a chlorination step. However, these processes lead to the release of toxic products, which could be released into the atmosphere and therefore have a negative impact on the environment.

There is therefore still a need for a process for preparing a lithium salt of bis (fluorosulfonyl) imide which does not have the aforementioned drawbacks.

In particular, there is a need for a process for preparing bis (fluorosulfonyl) imide lithium salt which is more environmentally friendly, and / or which is economically viable.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for the preparation of Ci-S0 2 NHS0 2 CI comprising a step of chlorination of sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent, said process leading to a flow F1, preferably liquid. , comprising CI-SO2NHSO2CI and a gas stream F2 comprising HCl and S0 2 , said method comprising a step a) of treating the gas stream F2.

Treatment step a) advantageously makes it possible to avoid the rejection of HCl and S0 2 , contained in the gas stream F2, into the atmosphere.

Step a) of treatment of gas stream F2 preferably comprises a step of bringing said stream F2 into contact with an alkaline aqueous solution, and / or a step of bringing said stream F2 into contact with a solution of hydrogen peroxide, and / or a step of separation of HCl and S0 2 contained in said stream F2, and / or a step of absorption of HCl contained in said gas stream F2 in an aqueous solution, and / or a step of absorption of S0 2 contained in said gas stream F2 in a concentrated sulfuric acid solution.

According to one embodiment, the gas flow F2 comprises:

- more than 20% by weight of HCl, preferably more than 30% by weight of HCl, and advantageously more than 40% by weight of HCl; and or

- more than 30% by weight of S0 2 , preferably more than 40% by weight of S0 2 , and advantageously more than 50% by weight of S0 2 .

The gas stream F2 may optionally comprise one or more inert gas (s), such as, for example, nitrogen, helium or argon. It may, for example, be the inert gas (s) used in the aforementioned chlorination step.

The stream F1 can optionally comprise the chlorinating agent, such as for example SOCI 2 , for example in a mass content of less than 5% by weight, preferably less than 1% by weight, and advantageously less than 0.5% by weight per relative to the total weight of said stream F1.

The stream F1 may optionally comprise the sulfur-containing agent, such as for example H 2 S0 4 , for example in a mass content of less than 5% by weight, preferably less than 1% by weight, and advantageously less than 0.5% by weight. weight relative to the total weight of said stream F1.

The stream F1 can optionally comprise the chlorinating agent and the sulfur-containing agent, such as for example SOCI 2 , and H 2 S0 4, for example in a total mass content of less than 5% by weight, preferably less than 1% by weight, and advantageously less than 0.5% by weight relative to the total weight of said stream F1.

The stream F1 can optionally comprise HCl and / or S0 2 , each in a content preferably less than 5% by weight, preferably less than 1% by weight, and advantageously less than 0.5% by weight relative to the total weight of said F1 flow.

Treatment: contact with an alkaline solution

According to a first embodiment, step a) of treating the gas stream F2 comprises i) bringing the gas stream F2 into contact with an alkaline aqueous solution.

The alkaline aqueous solution can be an aqueous solution of an alkali or alkaline earth metal hydroxide, or an aqueous solution of an alkali or alkaline earth metal carbonate.

Preferably, the alkaline aqueous solution is chosen from an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, potassium carbonate, and mixtures thereof. .

The alkaline aqueous solution can be prepared by dissolving at least one alkaline or alkaline earth base in water.

Preferably, the contacting i) is carried out in a neutralization column, in particular operating against the current.

The neutralization column can include:

o at least one packing such as for example a loose packing and / or a structured packing,

and or

o trays such as, for example, perforated trays, fixed valve trays, movable valve trays, domed trays, or combinations thereof.

According to one embodiment, it is necessary to control the pH of the alkaline aqueous solution, so that it remains basic during step i) of contacting in the neutralization column.

According to one embodiment, the gas stream F2 is introduced at the bottom of the neutralization column, while the alkaline aqueous solution is introduced at the top of said column.

According to one embodiment, step i) of bringing the gas stream F2 into contact, in particular in a neutralization column, with an alkaline aqueous solution makes it possible to form and recover:

a gas stream G1 comprising water and optionally one or more inert gas (s), preferably recovered at the top of the neutralization column; and

an alkaline stream L1 comprising water, Cl ions and sulphite ions S0 3 2 , preferably recovered at the bottom of the neutralization column, L1 preferably being liquid.

The alkaline stream L1 can optionally be directed to a wastewater treatment plant, before possible release into the environment.

Treatment: contact with a solution of hydrogen peroxide

According to a second embodiment, step a) of treating the gas stream F2 comprises ii) bringing the gas stream F2 into contact with a solution of hydrogen peroxide.

The S0 2 contained in the gas stream F2 can then react with hydrogen peroxide to quantitatively form sulfuric acid according to the reaction equation:

SO2 + H2O2 -► H2SO4

Preferably, the contacting ii) is carried out in a washing column, in particular operating against the current.

The hydrogen peroxide solution can be an aqueous solution in which the mass content of hydrogen peroxide ranges from 5 to 70% by weight, preferably from 5% to 50% by weight, and advantageously from 5% to 35% by weight. weight.

The hydrogen peroxide / S0 2 molar ratio contained in the gas stream F2 can range from 1 to 25, preferably from 1 to 20, and preferably from 1 to 15.

The washing column can include:

o at least one packing such as for example a loose packing and / or a structured packing,

and or

o trays such as, for example, perforated trays, fixed valve trays, movable valve trays, domed trays, or combinations thereof.

According to one embodiment, the gas stream F2 is introduced at the bottom of the washing column, while the hydrogen peroxide solution is introduced at the top of said column.

According to one embodiment, step ii) of bringing the gas stream F2 into contact, in particular in a washing column, with a solution of hydrogen peroxide makes it possible to form and recover:

a gas stream G2 comprising water and optionally one or more inert gas (s), preferably recovered at the head of the washing column; and

an acid stream L2 comprising water, HCl and H 2 S0 4 , preferably recovered at the bottom of the washing column, said stream L2 preferably being liquid.

According to one embodiment, at least 90% by weight, preferably at least 95% by weight, preferably at least 99% by weight, and advantageously at least 99.9% by weight of HCl contained in the gas stream F2 are recovered in the acid stream L2.

The above-mentioned step a) can comprise an additional step ii-1) of treatment of the acid stream L2 comprising contacting said acid stream L2 with an aqueous alkaline solution, or an additional step ii-2) of separation of HCl and of H 2 S0 contained in the acid stream L2 to form and recover a stream F3 comprising HCl and a stream F'3 comprising H 2 S0.

Step ii-1)

The alkaline aqueous solution can be an aqueous solution of an alkali or alkaline earth metal hydroxide, or an aqueous solution of an alkali or alkaline earth metal carbonate. Preferably, the alkaline aqueous solution is chosen from an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, potassium carbonate, and mixtures thereof. .

Step ii-1) can be carried out in a reactor, and preferably in a stirred reactor.

According to one embodiment, step ii-1) makes it possible to form and recover:

- a gas flow G3 comprising water and optionally one or more inert gas (s), and

an alkaline stream L3 comprising water, chloride ions and sulfate ions S0 2 , said stream L3 preferably being liquid.

The alkaline stream L3 can optionally be directed to a wastewater treatment plant, before possible release into the environment.

Step ii-2)

According to one embodiment, step a) of treating the gas stream F2 comprises ii) bringing the gas stream F2 into contact with a solution of hydrogen peroxide, followed by a step ii-2) of separating HCl and of H 2 S0 contained in the stream L2 to form and recover a stream F3 comprising HCl and a stream F'3 comprising H 2 S0 4 .

The separation can be a separation by distillation or by electrodialysis.

According to one embodiment, when step ii-2) is a separation by electrodialysis, it makes it possible to form and recover a liquid F3 stream comprising HCl, and a liquid F'3 stream comprising H 2 S0.

The flow F'3 is preferably a concentrated aqueous solution of H2SO4, preferably comprising a mass content of H 2 S0 4 greater than or equal to 20%, preferably greater than or equal to 50%.

The F3 flow includes:

- more than 5% by weight of HCl, preferably more than 10% by weight of HCl; and

- Less than 10% by weight of H 2 S0 4, preferably less than 5% by weight.

The flow F3 can optionally be directed to a wastewater treatment plant, before possible release into the environment.

The distillation can be carried out in at least one distillation column.

The separation step advantageously makes it possible to separate HCl and H 2 S0 4 contained in the stream L2.

According to one embodiment, when step ii-2) is a separation by distillation, it makes it possible to form and recover a stream F3 comprising HCl, preferably at the top of the distillation column, and a liquid stream F'3 comprising H 2 S0 4 .

The flow F3 can be a gas flow or a liquid flow.

Preferably, the flow F3 comprises:

- at least 15% by weight of HCl, preferably at least 20% by weight relative to the total weight of said stream F3; and or

- less than 5000 ppm of H 2 S0 4 , preferably less than 1000 ppm of H 2 S0 4 , and advantageously less than 500 ppm of H 2 S0 4 .

The stream F'3 is preferably a concentrated aqueous solution of H 2 S0 4 , preferably comprising a mass content of H 2 S0 4 greater than or equal to 20%, preferably greater than or equal to 50%.

The flow F'3 can optionally be subjected to a concentration or dilution step. It can be marketed, and / or recycled in said process.

When the stream F3 is gaseous, it can be marketed, and / or used as a raw material in another process, and / or subjected to a step of absorption of the hydrochloric acid contained in said stream F3 in an aqueous solution, said aqueous solution preferably being demineralized water, making it possible to form and recover a hydrochloric acid solution. The mass concentration of HCl in the hydrochloric acid solution can be 5 to 50%, preferably 15 to 40%, and more particularly 30 to 35% by weight. The hydrochloric acid solution obtained can advantageously be used commercially.

When the stream F3 is liquid, it can be subjected to a concentration or dilution step, for example to obtain a hydrochloric acid solution at 33% by weight, which can advantageously be developed commercially.

Treatment: Sé
des qaz

According to a third embodiment, step a) of treating the gas stream F2 comprises:

iii) a possible step of compressing said gas stream F2,

iv) a step of separating HCl and S0 2 contained in said gas stream F2 leading to a flow G4, preferably gaseous, comprising HCl, and to a stream F4 comprising S0 2, said stream F4 possibly being liquid or gaseous.

The gas stream G4 may optionally comprise one or more inert gas (s), such as, for example, nitrogen.

The aforementioned compression step iii) can make it possible to compress the gas stream F2 to a pressure greater than 5 bar abs, preferably greater than 7 bar abs, and preferably greater than 10 bar abs, and even more advantageously greater than 15 bar abs. , for example greater than 20 bars abs.

The above-mentioned separation step iv) can be a distillation or a membrane separation.

When the separation step iv) is a membrane separation, it advantageously leads to a gas stream G4 comprising HCl, and to a gas stream F4 comprising S0 2 .

A membrane separation step typically comprises the use of one or more membranes. When several membranes are used, they can be arranged in series or in a cluster.

According to one embodiment, step iv) is a membrane separation carried out with one or more membrane (s).

The membrane (s) can be inorganic (eg ceramic or glass), organic (s) (eg polymeric) or a mixture of both.

Preferably, the membrane separation step is carried out with at least one polymeric membrane, for example based on PVDF, polyamide, polyimide, or their mixtures.

When the separation step iv) is a membrane separation, it advantageously leads to a gas stream G4 comprising purified HCl, and to a gas stream F4 (denoted F 4 g ) comprising purified S0 2 .

According to a preferred embodiment, step iv) is a distillation carried out in at least one distillation column.

The distillation column can comprise at least 8 theoretical stages, preferably at least 10 theoretical stages, advantageously at least 12 theoretical stages.

The molar reflux rate can be at least 1.5, preferably at least 3, and advantageously at least 4.

Separation by distillation can be carried out:

o at a temperature at the bottom of the distillation column ranging from 40 ° C to 80 ° C, preferably from 40 ° C to 60 ° C, and preferably from 50 ° C to 60 ° C, at a pressure of 10 bar abs; or

o at a temperature at the bottom of the distillation column ranging from 40 ° C to 100 ° C, preferably from 50 ° C to 90 ° C, and preferably from 60 ° C to 80 ° C, at a pressure of 14 bar abs.

The distillation column can include:

o at least one packing such as for example a loose packing and / or a structured packing,

and or

o trays such as, for example, perforated trays, fixed valve trays, movable valve trays, domed trays, or combinations thereof.

When the separation step iv) is a distillation, it advantageously leads to a gas stream G4 comprising HCl, and to a liquid stream F4 comprising S0 2 . The gas stream G4 advantageously comprises purified HCl, preferably recovered at the top of the distillation column, and the liquid stream F4 advantageously comprises purified S0 2 , preferably recovered at the bottom of the distillation column.

The liquid stream F4 obtained at the end of the separation step iv) by distillation may optionally be subjected to an additional vaporization step to lead to a gas stream.

According to one embodiment, step a) of treating the gas stream F2 comprises: iii) a possible step of compressing said gas stream F2,

iv) a step of separating HCl and S0 2 contained in said gas stream F2 leading to a flow G4, preferably gaseous, comprising HCl, and to a stream F4 comprising S0 2, said stream F4 possibly being liquid or gaseous; and

an additional step v) for treating the gas stream G4, and / or an additional step vi) for treating the stream F4.

G4 flow

The gas stream G4 obtained at the end of step iv) advantageously comprises less than 100 ppm of S0 2 , preferably less than 80 ppm of S0 2 , and preferably less than 50 ppm of S0 2 .

In the context of the invention, “ppm” are “parts per million” expressed by weight.

The gas stream G4 obtained at the end of step iv) can advantageously be:

- directly marketed, and / or

- used as a raw material in another process; and or

- subject to an additional processing step v).

According to one embodiment, step a) of treating the gas stream F2 comprises: iii) a possible step of compressing said gas stream F2,

iv) a step of separating the gas stream F2 leading to a stream G4, preferably gaseous, comprising HCl, and to a stream F4 comprising S0 2, said stream F4 possibly being liquid or gaseous;

v) an additional step of treating the gas stream G4, said step v) comprising:

o v-1) an optional step of purifying said gas stream G4;

o v-2) a step of absorbing the hydrochloric acid contained in said gas stream G4 in an aqueous solution, said aqueous solution preferably being demineralized water, making it possible to form and recover an aqueous solution of hydrochloric acid L5;

vi) a possible step of processing the stream F4.

Step v-1) is preferably an impurity adsorption step with at least one solid adsorber, such as, for example, activated carbon or alumina. The gas flow G4 obtained at the end of step v-1) can advantageously be marketed, and / or used as a raw material in another process, and / or subjected to step v-2) above.

The purification step v-1) advantageously makes it possible to reduce the residual SO 2 content, for example to a content of less than 50 ppm, preferably less than 20 ppm, and advantageously less than 10 ppm, in the purified gas stream G4 .

The above-mentioned step v-2) advantageously makes it possible to collect an aqueous solution of hydrochloric acid L5, and a gas stream G5 comprising water and optionally one or more inert gas (s).

The mass concentration of HCl in the aqueous solution of hydrochloric acid L5 may be 5 to 50%, preferably 15 to 40%, and more particularly 30 to 35% by weight.

The L5 solution can advantageously be developed commercially.

Flow F 4

Stream F4 advantageously comprises less than 100 ppm of HCl, preferably less than 80 ppm, and preferably less than 50 ppm of HCl.

The stream F4, liquid or gaseous, obtained at the end of step iv), can advantageously be subjected to an additional treatment step vi).

In the case where the stream F4 is liquid, in particular when step iv) is a separation by distillation, the treatment step vi) comprises vi-1) bringing said liquid stream F4 into contact with an alkaline aqueous solution.

The alkaline aqueous solution can be an aqueous solution of an alkali or alkaline earth metal hydroxide, or an aqueous solution of an alkali or alkaline earth metal carbonate. Preferably, the alkaline aqueous solution is chosen from an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, potassium carbonate, and mixtures thereof. .

The contacting vi-1) can be carried out in a reactor, and preferably in a stirred reactor.

The aforementioned contacting vi-1) can lead to a gas flow G6 comprising water and optionally one or more inert gas (s), and to an alkaline flow L6 comprising water, chloride ions and ions sulphites, said stream L6 preferably being liquid.

The alkaline stream L6 can optionally be directed to a wastewater treatment plant, before possible release into the environment.

In the case where the stream F4 is gaseous, in particular when step iv) is a membrane separation or when the liquid stream F4 obtained in distillation step iv) has been subjected to a vaporization step, the treatment step vi) includes:

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 solution of hydrogen peroxide; or

vi-4) oxidation, preferably catalytic or electrochemical, of the gas stream F4 in the presence of oxygen to form a stream F5 comprising S0 3 , followed optionally;

o a step vi-4-a) of absorption of S0 3 contained in said stream F5 in a concentrated sulfuric acid solution, making it possible to form and recover a gas stream G9 comprising water and optionally one or more inert gas (s), and an L9 oleum;

o then optionally a step vi-4-b) of diluting the oleum L9 in water, to form an aqueous solution L10.

Preferably, the alkaline aqueous solution of step vi-2) can be an aqueous solution of an alkali metal or alkaline earth metal hydroxide, or an aqueous solution of an alkali metal or alkaline earth metal carbonate. Preferably, the alkaline aqueous solution is chosen from an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, potassium carbonate, and mixtures thereof. .

Preferably, the contacting vi-2) is carried out in a neutralization column, in particular operating against the current.

The neutralization column can include:

o at least one packing such as for example a loose packing and / or a structured packing,

and or

o trays such as, for example, perforated trays, fixed valve trays, movable valve trays, domed trays, or combinations thereof.

According to one embodiment, the gas stream F4 is introduced at the bottom of the neutralization column, while the alkaline aqueous solution is introduced at the top of said column.

According to one embodiment, step vi-2) of bringing the gas stream F4 into contact, in particular in a neutralization column, with an alkaline aqueous solution makes it possible to form and recover:

a gas stream G7 comprising water and optionally one or more inert gas (s), preferably recovered at the top of the neutralization column; and

an alkaline stream L7 comprising water, Cl ions and sulphite ions, preferably recovered at the bottom of the neutralization column, said stream L8 preferably being liquid.

The L7 flow can optionally be directed to a wastewater treatment plant, before any discharge into the environment.

Preferably, step vi-3) mentioned above is carried out in a washing column, in particular operating against the current.

The washing column can include:

o at least one packing such as for example a loose packing and / or a structured packing,

and or

o trays such as, for example, perforated trays, fixed valve trays, movable valve trays, domed trays, or combinations thereof.

According to one embodiment, the gas stream F4 is introduced at the bottom of the washing column, while the hydrogen peroxide solution is introduced at the top of said column.

The hydrogen peroxide solution can be an aqueous solution in which the mass content of hydrogen peroxide ranges from 5% to 70% by weight, preferably from 5% to 50% by weight, and advantageously from 5% to 35%. in weight.

The hydrogen peroxide / S0 2 molar ratio contained in the gas stream F4 can range from 1 to 25, preferably from 1 to 20, and preferably from 1 to 15.

According to one embodiment, step vi-3) of bringing the gas stream F4 into contact, in particular in a washing column, with a solution of hydrogen peroxide makes it possible to form and recover:

a gas stream G8 comprising water and optionally one or more inert gas (s), preferably recovered at the head of the washing column; and

a stream L8 comprising water and H 2 S0, preferably recovered at the bottom of the washing column, said stream L8 preferably being liquid.

The mass concentration of H 2 S0 4 in the aqueous stream L8 may be greater than or equal to 5%, preferably greater than or equal to 10%, and advantageously greater than or equal to 20%. The L8 flow can optionally be subjected to a concentration step.

The L8 stream can advantageously be marketed, and / or recycled in the aforementioned chlorination step.

Preferably, the above-mentioned step vi-4) is carried out in a reactor.

The concentrated sulfuric acid solution used in step vi-4-a) is preferably a solution containing more than 95% by weight of H 2 S0.

The L9 oleum obtained at the end of the above-mentioned step vi-4-a) can be directly marketed, and / or subjected to an optional step vi-4-b) of dilution of the L9 oleum in water, to form an aqueous solution L10. Solution L10 is advantageously a sulfuric acid solution which can be marketed, and / or recycled in the process, for example to the above-mentioned chlorination step and / or to step vi-4-a).

Treatment: selective absorption of HCl or S0 2

According to a fourth embodiment, step a) of treating the gas stream F2 comprises:

vii) a step of absorbing the hydrochloric acid contained in said gas stream F2 in an aqueous solution, said aqueous solution preferably being demineralized water, making it possible to form and recover a solution of hydrochloric acid L1 1, and a gas stream G1 1 comprising SO2, water and optionally one or more inert gases;

or

x) a step of absorption of S0 2 contained in said gas stream F2 in a concentrated sulfuric acid solution, making it possible to form and recover a gas stream G12 comprising HCl optionally one or more inert gas (s), and a stream L12 comprising water, H 2 S0 4 and S0 2, said stream L12 preferably being liquid.

The absorption step vii) can be carried out in a column, the gas stream G1 1 preferably being recovered at the top of the column, while the solution L1 1 preferably being recovered at the bottom of the column.

The mass concentration of HCl in the hydrochloric acid solution L1 1 can be 5 to 50%, preferably 15 to 40%, and more particularly 30 to 35%.

The solution L1 1 can optionally comprise S0 2 in a mass content of less than or equal to 100 ppm, preferably less than or equal to 50 ppm, advantageously less than or equal to 20 ppm.

Step a) of treatment of the gas stream F2 can comprise a step viii), subsequent to step vii), comprising the purification of the solution L1 1, preferably by adsorption of residual impurities with at least one solid adsorber, such as, for example, activated carbon or silica gel. After this additional adsorption step on silica gel or activated carbon, it is advantageously possible to reach S0 2 contents of less than 1 ppm in the HCl solution.

The solution L1 1, optionally purified, can advantageously be developed commercially.

The above-mentioned step vii) advantageously makes it possible to collect a hydrochloric acid solution L1 1, and a gas stream G1 1 comprising S0 2 , water, and optionally one or more inert gas (s).

According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight, and preferably at least 99.9% by weight of HCl contained in the gas stream F2 are recovered in the liquid flow L1 1.

According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight, and preferably at least 99.9% by weight of S0 2 contained in the gas stream F2 are recovered in the gas stream G1 1.

Step a) of treatment of the gas stream F2 can also comprise a step ix), of drying of the gas stream G1 1, for example carried out in the presence of calcium sulfate, sodium sulfate, magnesium sulfate, sodium chloride. calcium, calcium carbonate, silica gel or molecular sieve.

The gas stream G1 1, optionally dried, can be subjected to one of stages vi-2), vi-3) or vi-4) as defined above.

According to one embodiment, step a) of treating the gas stream F2 comprises: x) a step of absorbing S0 2 contained in said gas stream F2 in a concentrated sulfuric acid solution, making it possible to form and recover a gas stream G12 comprising HCl and optionally one or more inert gas (s), and a stream L12 comprising water, H 2 S0 4 and S0 2, said stream L12 preferably being liquid.

The concentrated sulfuric acid solution used in step x) is preferably a solution containing more than 95% by weight of H 2 S0 4 .

The absorption step x) can be carried out in a column, the gas stream G12 preferably being recovered at the top of the column, while the solution L12 is preferably recovered at the bottom of the column.

The gas stream G12 comprises more than 50% by weight of HCl, preferably more than 80% by weight of HCl, and advantageously more than 90% by weight of HCl relative to the total weight of said stream G12.

The gas stream G12 can advantageously be marketed directly, and / or be subjected to an upgrading step to form a commercial 33% HCl solution (it can for example be a step similar to step vii) below. above).

According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight, and preferably at least 99.9% by weight of HCl contained in the gas stream F2 are recovered in the gas stream G12.

According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight, and preferably at least 99.9% by weight of S0 2 contained in the gas stream F2 are recovered in stream L12.

The L12 flow can optionally:

- Be subjected at least partially to a heating step, making it possible to form and recover a gas stream G13 comprising S0 2 , and a stream L13 comprising H 2 S0 4 . The gas stream G13 can advantageously be recycled to any step of the process comprising gaseous SO 2 , for example reused in any one of steps vi-2), vi-3) or vi-4) mentioned above;

and or

be subjected at least partially to a step of bringing into contact with a solution of hydrogen peroxide, preferably in a stirred reactor.

Preferably, the step of bringing the stream L12 into contact, in particular in a stirred reactor, with a solution of hydrogen peroxide makes it possible to form and recover:

- a gas stream G14 comprising water and optionally one or more inert gas (s); and

- A stream L14 comprising water and H 2 S0 4 , said stream L14 preferably being liquid.

The mass concentration of H 2 S0 in the aqueous stream L14 may be greater than or equal to 5%, preferably greater than or equal to 10%, and advantageously greater than or equal to 20%. The L14 stream can optionally be subjected to a concentration step.

The L14 stream can advantageously be marketed, and / or recycled in the aforementioned chlorination step.

Chlorination step

The chlorination step according to the invention can be carried out:

o at a temperature between 30 ° C and 150 ° C; é ^ or

o with a reaction time of between 1 hour and 7 days; and or

o at a pressure between 1 bar abs and 20 bar abs.

According to the invention, the sulfur-containing agent can be chosen from the group consisting of chlorosulfonic acid (CIS0 3 H), sulfuric acid, oleum, and mixtures thereof.

According to the invention, the chlorinating agent can be chosen from the group consisting of thionyl chloride (SOCI 2 ), oxalyl chloride (COCI) 2 , phosphorus pentachloride (PCI 5 ), phosphonyl trichloride (PCI 3 ), phosphoryl trichloride (POCI 3 ), and mixtures thereof. Preferably, the chlorinating agent is thionyl chloride.

The chlorination step can be carried out in the presence of a catalyst, such as for example chosen from a tertiary amine (such as methylamine, triethylamine, or diethylmethylamine); pyridine; and 2,6-lutidine.

The molar ratio between sulfur acid and sulfamic acid can be between 0.7 and 5, preferably between 0.9 and 5.

The molar ratio between the chlorinating agent and the sulfamic acid can be between 2 and 10, preferably between 2 and 5.

In particular, when the sulfur-containing agent is chlorosulfonic acid, the molar ratio between the latter and the sulfamic acid is between 0.9 and 5, and / or the molar ratio between the chlorinating agent and the acid. sulfamic is between 2 and 5.

In particular, when the sulfur-containing agent is sulfuric acid (or oleum), the molar ratio between sulfuric acid (or oleum) and sulfamic acid is between 0.7 and 5.

In particular, when the sulfur-containing agent is sulfuric acid (or oleum), the molar ratio between sulfuric acid (or oleum) and sulfamic acid is between 0.9 and 5, and / or the molar ratio between the chlorinating agent and the sulfamic acid is between 2 and 10.

LiFSI pre process

The present invention also relates to a process for preparing the lithium salt of bis (fluorosulfonyl) imide (LiFSI) comprising the process for preparing CI-SO2-NH-SO2-Cl mentioned above.

According to one embodiment, the process for preparing the lithium salt of bis (fluorosulfonyl) imide comprises the following steps:

i. process for preparing bis (chlorosulfonyl) imide from sulfamic acid as described above;

ii. fluorination of bis (chlorosulfonyl) imide to bis (fluorosulfonyl) imide,

iii. preparation of the alkaline or alkaline-earth salt of bis (fluorosulfonyl) imide by neutralization of the bis (fluorosulfonyl) imide, in particular using an aqueous solution of a base chosen from carbonates of alkali or alkaline-earth metals, and alkali or alkaline earth metal hydroxides, iv. optionally cation exchange to obtain a lithium salt of bis (fluorosulfonyl) imide; and

v. method of drying and purifying the lithium salt of bis (fluorosulfonyl) imide.

The process for preparing the lithium salt of bis (fluorosulfonyl) imide according to the invention advantageously makes it possible to avoid the rejection of HCl and S0 2 into the atmosphere. The process is therefore advantageously less polluting and more respectful of the environment.

In addition, the process for preparing the lithium salt of bis (fluorosulfonyl) imide according to the invention advantageously allows the upgrading of certain secondary streams formed during the preparation of said LiFSI, which generates better economic profitability of the process.

The following examples make it possible to illustrate the present invention without, however, limiting it.

EXAMPLES

Example 1:

A 100-liter enamelled steel reactor equipped with stirring is charged with sulfamic acid (1 eq, 257.5 moles, 25 kg) and sulfuric acid 95% (1 eq, 257.5 moles, 26.6 kg). Thionyl chloride (4 eq, 1030 moles, 122.5 kg) is added gradually to the reactor. The temperature of the reaction medium is gradually increased to 75 ° C. The reaction is carried out at atmospheric pressure.

Total conversion to sulfamic acid is obtained after 60 hours. A condenser is placed 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 are obtained containing bis (chlorosulfonyl) imide and unreacted thionyl chloride.

The gases generated by the reaction (HCl and S0 2 ) and not condensed by the condenser are directed to a system allowing them to be absorbed (see examples 2 and 3).

Example 2: HCl and S0 2 in a solution of H 2 0 2

The gases generated by the reaction of Example 1 are sent to a storage containing 700 kg of a solution of H 2 0 2 5% by weight. This storage is surmounted by a packed column sprayed at the top with the H 2 O 2 solution contained in said storage. A pump is used to withdraw the H 2 0 2 solution from the storage to water the column. The gases generated by the reaction (HCl and S0 2 ) are introduced into the H 2 O 2 solution contained in the storage by means of a dip tube. The HCl and the S0 2 are absorbed in the solution of H 2 0 2 and the S02 reacts with H 2 0 2 to form H 2 S0 4 . The packed column makes it possible to finalize the absorption of the gases generated by the HCl and S0 2 reaction and to completely convert the S0 2 into H 2 S0 4 .

At the end of the reaction, a solution of 797 kg is obtained comprising 1% by weight of H 2 0 2 , 5% by weight of HCl and 10% by weight of H 2 S0.

Example 3: HCl absorption in water followed by S0 2 absorption in a solution of HpQp

The gases generated by the reaction of Example 1 (HCl and S0 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 the gaseous HCl, while the gaseous S0 2 is not absorbed.

The gaseous S0 2 is recovered at the top of the HCl absorption column and is directed to a storage containing 300 kg of a solution of a 10% by weight H 2 0 2 solution . The device for absorbing the gaseous S0 2 in a solution of H 2 0 2 is identical to that described in Example 2. In this configuration, the packed column makes it possible to finalize the absorption of the S0 2 and to completely convert the S0 2 to H 2 S0 4 .

At the end of the reaction, 130 kg of a 33% HCl solution are obtained on the one hand and a 354 kg solution comprising less than 1% by weight of H 2 0 2 and 23% by weight of H 2 S0 on the other hand. 4 .

CLAIMS

1. Process for preparing Cl-S0 2 NHS0 2 CI comprising a step of chlorinating the sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent, said process leading to a flow F1, preferably liquid, comprising Cl - S0 2 NHS0 2 CI and a gas stream F2 comprising HCl and S0 2 , said method comprising a step a) of treatment of the gas stream F2.

2. Method according to claim 1, wherein step a) of treating the gas stream F2 comprises a step of bringing said stream F2 into contact with an alkaline aqueous solution, and / or a step of bringing said stream F2 into contact with a solution of hydrogen peroxide, and / or a step of separating HCl and S0 2 contained in said stream F2, and / or a step of absorbing HCl contained in said gas stream F2 in an aqueous solution, and / or a step of absorbing S0 2 contained in said gas stream F2 in a concentrated sulfuric acid solution.

3. Method according to any one of claims 1 or 2, wherein the gas stream F2 comprises:

- more than 20% by weight of HCl, preferably more than 30% by weight of HCl, and advantageously more than 40% by weight of HCl, relative to the total weight of said stream F2; and or

- more than 30% by weight of S0 2 , preferably more than 40% by weight of S0 2 , and advantageously more than 50% by weight of S0 2, relative to the total weight of said stream F2.

4. Method according to any one of claims 1 to 3, in which step a) of treatment of the gas stream F2 comprises i) bringing the gas stream F2 into contact with an alkaline aqueous solution, in particular in a neutralization column. , advantageously making it possible to train and recover:

a gas stream G1 comprising water and optionally one or more inert gas (s), preferably recovered at the top of the neutralization column; and

an alkaline stream L1 comprising water, Cl ions and sulphite ions S0 3 2 , preferably recovered at the bottom of the neutralization column, L1 preferably being liquid.

5. Method according to any one of claims 1 to 3, wherein step a) of treating the gas stream F2 comprises ii) bringing the gas stream F2 into contact with a solution of hydrogen peroxide.

6. The method of claim 5, wherein step ii) of bringing the gas stream F2 into contact, in particular in a washing column, with a solution of hydrogen peroxide makes it possible to form and recover:

a gas stream G2 comprising water and optionally one or more inert gas (s), preferably recovered at the head of the washing column; and

an acid stream L2 comprising water, HCl and H 2 S0 4 , preferably recovered at the bottom of the washing column, said stream L2 preferably being liquid.

7. The method of claim 6, comprising an additional step ii-1) of treatment of the stream L2 comprising contacting said stream L2 with an alkaline aqueous solution, or an additional step ii-2) of separation of HCl and H2SO4. contained in the stream L2 to form and recover a stream F3 comprising HCl and a stream F'3 comprising H 2 S0 4, said separation preferably being a distillation or an electrodialysis.

8. Method according to any one of claims 1 to 3, wherein step a) of treating the gas stream F2 comprises:

iii) a possible step of compressing said gas stream F2,

iv) a step of separating HCl and S0 2 contained in said gas stream F2 leading to a flow G4, preferably gaseous, comprising HCl, and to a stream F4 comprising S0 2, said stream F4 possibly being liquid or gaseous;

the separation step iv) preferably being a distillation or a membrane separation.

9. The method of claim 8, wherein step a) comprises an additional step v) of treatment of the gas stream G4, and / or an additional step vi) of treatment of the stream F4.

10. The method of claim 9, wherein said step v) comprises:

o v-1) an optional step of purifying said gas stream G4;

o v-2) a step of absorption of the hydrochloric acid contained in said gas stream G4 in an aqueous solution, said aqueous solution being

preferably demineralized water, making it possible to form and recover an aqueous solution of hydrochloric acid L5.

1 1. A method according to any one of claims 9 or 10, wherein:

when the stream F4 is liquid, in particular when step iv) is a separation by distillation, the treatment step vi) comprises vi-1) bringing said liquid stream F4 into contact with an alkaline aqueous solution, preferably resulting in a gas stream G6 comprising water and optionally one or more inert gas (s), and an alkaline stream L6 comprising water, chloride ions and sulphite ions, said stream L6 preferably being liquid;

when the stream F4 is gaseous, the treatment step 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 solution of hydrogen peroxide;

or

vi-4) oxidation, preferably catalytic or electrochemical, of the gas stream F4 in the presence of oxygen to form a stream F5 comprising S0 3 , followed optionally;

o a step vi-4-a) of absorption of S0 3 contained in said stream F5 in a concentrated sulfuric acid solution, making it possible to form and recover a gas stream G9 comprising water and optionally one or more inert gas (s), and an L9 oleum;

o then optionally a step vi-4-b) of diluting the oleum L9 in water, to form an aqueous solution L10.

12. Method according to any one of claims 1 to 3, wherein step a) of treating the gas stream F2 comprises:

vii) a step of absorbing the hydrochloric acid contained in said gas stream F2 in an aqueous solution, said aqueous solution preferably being demineralized water, making it possible to form and recover a solution of hydrochloric acid L1 1, and a gas stream G1 1 comprising S0 2 , water and optionally one or more inert gases;

or

x) a step of absorption of S0 2 contained in said gas stream F2 in a concentrated sulfuric acid solution, making it possible to form and recover a gas stream G12 comprising HCl optionally one or more inert gas (s), and a stream L12 comprising water, H 2 S0 and S0 2, said stream L12 preferably being liquid.

13. The method of claim 12, in step a) of treating the gas stream F2 comprises:

- a step viii), subsequent to step vii), comprising the purification of the solution L1 1, preferably by adsorption of residual impurities with at least one solid adsorber, such as for example activated carbon or a silica gel ; and

- a possible step ix), of drying the gas stream G1 1, for example carried out in the presence of calcium sulphate, sodium sulphate, magnesium sulphate, calcium chloride, calcium carbonate, silica gel or molecular sieve.

14. A method according to any one of claims 12 or 13, wherein flow L12 is:

- At least partially subjected to a heating step, making it possible to form and recover a gas stream G13 comprising S0 2 , and a stream L13 comprising H 2 S0 4 ;

and or

- At least partially subjected to a step of bringing into contact with a solution of hydrogen peroxide, preferably in a stirred reactor.

15. A method according to any one of claims 1 to 14, wherein the chlorination step is carried out:

o at a temperature between 30 ° C and 150 ° C; é ^ or

o with a reaction time of between 1 hour and 7 days; and or

o at a pressure between 1 bar abs and 20 bar abs.

16. A method according to any one of claims 1 to 15, wherein:

the sulfur-containing agent is chosen from the group consisting of chlorosulfonic acid (CISO 3 H), sulfuric acid, oleum, and mixtures thereof; and or

- the chlorinating agent is chosen from the group consisting of thionyl chloride (SOCI 2 ), oxalyl chloride (COCI) 2 , phosphorus pentachloride (PCI 5 ), phosphonyl trichloride (PCI 3 ), trichloride phosphoryl (POCI 3 ), and mixtures thereof; the chlorinating agent preferably being thionyl chloride.

17. Process for preparing the lithium salt of bis (fluorosulfonyl) imide comprising the process for preparing Cl-S0 2 -NH-S0 2 -Cl as defined according to any one of claims 1 to 16.