Process for preparing lithium bis (fluorosulfonyl) imide salts

Abstract

To provide a method for preparing a lithium bis (fluorosulfonyl) imide salt which is environmentally friendly and / or economically beneficial.SOLUTION: A method for preparing Cl - SO2NHSO2Cl comprising chlorinating sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent, said method resulting in a preferably liquid stream SO2NHSO2Cl comprising Cl - F1 and a gaseous stream F2 comprising HCl and SO2, said method comprising a step a) of treating the gaseous stream F2. The present invention also relates to a process for preparing LiFSI comprising the above process for preparing Cl-SO2NHSO2Cl.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a process for the preparation of lithium salts of imides containing fluorosulfonyl groups. [Background technology]

[0002] Due to their very low basicity, sulfonylimide-type anions are increasingly used in the field of energy storage, either in the form of inorganic salts in batteries or organic salts in supercapacitors, or in the field of ionic liquids. Due to the booming battery market and the need to reduce battery production costs, there is a need for methods for synthesizing this type of anion on a large scale and at low cost.

[0003] In the specific field of Li-ion batteries, the salt currently most widely used is LiPF6, but this salt exhibits a number of drawbacks, such as limited thermal stability, sensitivity to hydrolysis and therefore poor stability of the battery. - New salts with the group have been investigated and have demonstrated numerous advantages, such as better ionic conductivity and resistance to hydrolysis. One of these salts, LiFSI (LiN(FSO2)2), shows very advantageous properties that make it a good candidate to replace LiPF6.

[0004] There are several methods for preparing LiFSI, including chlorination, but these methods result in the release of toxic products that can be released into the atmosphere and therefore have a negative impact on the environment.

[0005] Therefore, there is a further need for a method for the preparation of lithium bis(fluorosulfonyl)imide salts that does not exhibit the above-mentioned drawbacks.

[0006] In particular, there is a need for methods for the preparation of lithium bis(fluorosulfonyl)imide salts that are more environmentally friendly and / or economically advantageous. Summary of the Invention

[0007] The present invention relates to a process for preparing Cl-SO2NHSO2Cl comprising the step of chlorinating sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent, said process resulting in a preferably liquid stream F1 comprising Cl-SO2NHSO2Cl and a gaseous stream F2 comprising HCl and SO2, said process comprising a step a) of treating gaseous stream F2. DETAILED DESCRIPTION OF THE INVENTION

[0008] Process step a) advantageously makes it possible to avoid emitting HCl and SO2 contained in the gaseous stream F2 into the atmosphere.

[0009] This step a) of treating the gas stream F2 preferably comprises a step of contacting said stream F2 with an aqueous alkaline solution, and / or a step of contacting said stream F2 with aqueous hydrogen peroxide, and / or a step of separating the HCl and SO2 contained in stream F2, and / or a step of absorbing the HCl contained in said gas stream F2 in an aqueous solution, and / or a step of absorbing the SO2 contained in said gas stream F2 in a solution of concentrated sulphuric acid.

[0010] According to one embodiment, the gas flow F2 is: more than 20% by weight of HCl, preferably more than 30% by weight of HCl, advantageously more than 40% by weight of HCl; and / or more than 30% by weight of SO2, preferably more than 40% by weight of SO2, advantageously more than 50% by weight of SO2 Includes:

[0011] The gas stream F2 may optionally contain one or more inert gases, such as nitrogen, helium or argon, for example, which may be the inert gases used in the chlorination step described above.

[0012] Stream F1 may optionally comprise a chlorinating agent, such as for example SOCl2, for example in a content of less than 5% by weight, preferentially less than 1% by weight and advantageously less than 0.5% by weight relative to the total weight of said stream F1.

[0013] Stream F1 may optionally comprise a sulfur-containing agent, such as for example H2SO4, for example in a content of less than 5% by weight, preferentially less than 1% by weight and advantageously less than 0.5% by weight, relative to the total weight of said stream F1.

[0014] Stream F1 may optionally comprise chlorinating agents and sulfur-containing agents, such as, for example, SOCl2 and H2SO4, in a total content of, for example, less than 5% by weight, preferentially less than 1% by weight and advantageously less than 0.5% by weight, relative to the total weight of said stream F1.

[0015] Stream F1 may optionally comprise HCl and / or SO2, each in a content preferably less than 5% by weight, preferentially less than 1% by weight and advantageously less than 0.5% by weight relative to the total weight of said stream F1.

[0016] Treatment: Contact with alkaline aqueous solution According to a first embodiment, step a) of treating the gas stream F2 comprises i) contacting the gas stream F2 with an aqueous alkaline solution.

[0017] The alkaline aqueous solution 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.

[0018] Preferably, the alkaline aqueous solution is selected from aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous calcium hydroxide, aqueous magnesium hydroxide, aqueous calcium carbonate, aqueous potassium carbonate, and mixtures thereof.

[0019] The alkaline aqueous solution can be prepared by dissolving at least one alkali metal or alkaline earth metal base in water.

[0020] Preferably, the contacting operation i) is carried out in a neutralization column, in particular operating countercurrently.

[0021] The neutralization column is as follows: at least one packing, for example a random packing and / or a stacked packing, and / or Trays, such as perforated trays, fixed valve trays, movable valve trays, bubble cap trays, or combinations thereof may include:

[0022] According to one embodiment, there are good reasons to control the pH of the aqueous alkaline solution to remain basic during step i) of contacting in the neutralization column.

[0023] According to one embodiment, the gaseous stream F2 is introduced into the bottom of the neutralization column, while the aqueous alkaline solution is introduced into the top of said column.

[0024] According to one embodiment, step i) of contacting the gas stream F2 with an aqueous alkaline solution, in particular in a neutralization column, comprises: a gas stream G1 comprising water and optionally one or more inert gases, preferably recovered at the top of the neutralization column; and - preferably a liquid stream, preferably recovered at the bottom of the neutralization column, water, Cl - Ion and sulfite SO3 2- Ion-containing alkaline flow L1 This allows the formation and recovery of

[0025] The alkaline stream L1 can optionally be sent to a wastewater treatment plant before being discharged to the environment.

[0026] Treatment: Contact with hydrogen peroxide According to a second embodiment, step a) of treating the gas stream F2 comprises ii) contacting the gas stream F2 with aqueous hydrogen peroxide.

[0027] The SO2 contained in the gas stream F2 then reacts with the hydrogen peroxide solution according to the reaction equation: According to TIFF2026016430000001.tif9170, sulfuric acid can be quantitatively formed.

[0028] Preferably, the contacting operation ii) is carried out in a scrub column, in particular operating in countercurrent.

[0029] The hydrogen peroxide solution may be an aqueous solution having a hydrogen peroxide content ranging from 5% to 70% by weight, preferably from 5% to 50% by weight, advantageously from 5% to 35% by weight.

[0030] The hydrogen peroxide / SO2 molar ratio contained in the gas stream F2 may range from 1 to 25, preferably from 1 to 20, and preferentially from 1 to 15.

[0031] The scrub columns are: at least one packing, for example a random packing and / or a stacked packing, and / or Trays, such as perforated trays, fixed valve trays, movable valve trays, bubble cap trays, or combinations thereof may include:

[0032] According to one embodiment, the gas stream F2 is introduced at the bottom of the scrubbing column, while the hydrogen peroxide solution is introduced at the top of said column.

[0033] According to one embodiment, step ii) of contacting the gas stream F2 with aqueous hydrogen peroxide, in particular in a scrubbing column, comprises: a gas stream G2 comprising water and optionally one or more inert gases, preferably recovered at the top of the scrubbing column; and an acid stream L2 comprising water, HCl and H2SO4, preferably a liquid stream, preferably recovered at the bottom of the scrubbing column; This allows the formation and recovery of

[0034] According to one embodiment, at least 90% by weight, preferably at least 95% by weight, preferentially at least 99% by weight and advantageously at least 99.9% by weight of the HCl contained in the gaseous stream F2 is recovered in the acidic stream L2.

[0035] The above step a) may comprise an additional step ii-1) of treating the acidic stream L2, comprising contacting said acidic stream L2 with an aqueous alkaline solution, or an additional step ii-2) of separating the HCl and H2SO4 contained in the acidic stream L2, in order to form and recover a stream F3 comprising HCl and a stream F'3 comprising H2SO4.

[0036] Process ii-1) The alkaline aqueous solution may 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 selected from aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous calcium hydroxide, aqueous magnesium hydroxide, aqueous calcium carbonate, aqueous potassium carbonate, and mixtures thereof.

[0037] Step ii-1) can be carried out in a reactor, preferably a stirred reactor.

[0038] According to one embodiment, step ii-1) comprises the steps of: a gas flow G3 comprising water and optionally one or more inert gases; and - preferably a liquid stream of water, chloride ions and sulfite SO4 2- Ion-containing alkaline flow L3 This allows the formation and recovery of

[0039] The alkaline stream L3 can optionally be sent to a wastewater treatment plant before being discharged to the environment.

[0040] Process ii-2) According to one embodiment, step a) of treating gas stream F2 comprises ii) contacting gas stream F2 with aqueous hydrogen peroxide, followed by step ii-2) of separating the HCl and H2SO4 contained in stream L2 to form and recover a stream F3 comprising HCl and a stream F'3 comprising H2SO4.

[0041] The separation can be by distillation or electrodialysis.

[0042] According to one embodiment, when step ii-2) is a separation by electrodialysis, step ii-2) makes it possible to form and recover a liquid stream F3 comprising HCl and a liquid stream F'3 comprising H2SO4.

[0043] Stream F'3 is preferably a concentrated aqueous H2SO4 solution, preferably containing an H2SO4 content of greater than or equal to 20% by weight, preferably greater than or equal to 50% by weight.

[0044] Flow F3 is as follows: - more than 5% by weight of HCl, preferentially more than 10% by weight of HCl; and - less than 10% by weight, preferentially less than 5% by weight, of H2SO4 Includes:

[0045] Stream F3 can optionally be sent to a wastewater treatment plant before being discharged to the environment.

[0046] The distillation can be carried out in at least one distillation column.

[0047] The separation step advantageously makes it possible to separate the HCl and H2SO4 contained in stream L2.

[0048] According to one embodiment, when step ii-2) is a separation by distillation, step ii-2) preferably makes it possible to form and recover at the top of the distillation column a stream F3 comprising HCl and a liquid stream F'3 comprising H2SO4.

[0049] Stream F3 can be a gas stream or a liquid stream.

[0050] Preferably, stream F3 comprises: - at least 15% by weight, preferably at least 20% by weight, of HCl relative to the total weight of said stream F3; and / or 5000 ppm H2SO4, preferably less than 1000 ppm H2SO4, advantageously less than 500 ppm H2SO4 Includes:

[0051] Stream F'3 is preferably a concentrated aqueous H2SO4 solution, preferably containing an H2SO4 content of greater than or equal to 20% by weight, preferably greater than or equal to 50% by weight.

[0052] Stream F'3 may be subjected to a concentration or dilution step. It can be sold and / or recycled in the process.

[0053] When stream F3 is gaseous, this stream F3 can be sold and / or used as a starting material in another process and / or can be subjected to a step of absorbing the hydrochloric acid contained in said stream F3 in an aqueous solution, preferably demineralized water, allowing the formation and recovery of a hydrochloric acid solution. The weight concentration of HCl in the hydrochloric acid solution can be between 5% and 50% by weight, preferably between 15% and 40% by weight, more particularly between 30% and 35% by weight. The hydrochloric acid solution obtained can advantageously be given commercial economic value.

[0054] When stream F3 is liquid, it can be subjected to a concentration or dilution step to obtain, for example, a 33% by weight hydrochloric acid solution, which can advantageously be given commercial economic value.

[0055] Processing: Gas Separation According to a third embodiment, step a) of treating the gas stream F2 comprises: iii) an optional step of compressing said gas stream F2; iv) Separating the HCl and SO2 contained in said gas stream F2 to obtain a stream G4, preferably a gaseous stream, containing HCl and a stream F4 containing SO2, said stream F4 being capable of being a liquid or gaseous stream. Includes:

[0056] The gas flow G4 may optionally contain one or more inert gases, such as nitrogen.

[0057] The compression step iii) described above may make it possible to compress the gas stream F2 to a pressure of more than 5 bar abs, preferably more than 7 bar abs, preferentially more than 10 bar abs and more advantageously even more than 15 bar abs, for example 20 bar abs.

[0058] The above separation step iv) can be distillation or membrane separation.

[0059] When separation step iv) is a membrane separation, this step advantageously results in a gas stream G4 comprising HCl and a gas stream F4 comprising SO2.

[0060] Membrane separation processes typically involve the use of one or more membranes. When multiple membranes are used, they may be arranged in series or in groups.

[0061] According to one embodiment, step iv) is a membrane separation carried out using one or more membranes.

[0062] The membrane can be inorganic (eg, ceramic or glass), organic (eg, polymeric), or a mixture of the two.

[0063] Preferably, the membrane separation step is carried out using at least one polymer membrane, for example a polymer membrane based on PVDF, polyamide or polyimide, or a mixture thereof.

[0064] When separation step iv) is a membrane separation, this step advantageously comprises the separation of a gas stream G4 containing purified HCl and a gas stream F4 containing purified SO2 (F4g (denoted as ).

[0065] According to a preferred embodiment, step iv) is a distillation carried out in at least one distillation column.

[0066] The distillation column may contain at least 8 theoretical steps, preferably at least 10 theoretical steps, advantageously at least 12 theoretical steps.

[0067] The molar reflux ratio may be at least 1.5, preferably at least 3, advantageously at least 4.

[0068] Separation by distillation is as follows: at a temperature at the bottom of the distillation column ranging from 40°C to 80°C, preferably from 40°C to 60°C, preferentially from 50°C to 60°C, at 10 bar abs; or at a temperature at the bottom of the distillation column ranging from 40°C to 100°C, preferably from 50°C to 90°C, preferentially from 60°C to 80°C, at 14 bar abs This can be done.

[0069] The distillation column comprises: at least one packing, for example a random packing and / or a stacked packing, and / or Trays, such as perforated trays, fixed valve trays, movable valve trays, bubble cap trays, or combinations thereof may include:

[0070] When separation step iv) is a distillation, this step advantageously results in a gaseous stream G4 comprising HCl and a liquid stream F4 comprising SO2. The gaseous stream G4 advantageously contains purified HCl, preferably recovered at the top of the distillation column, and the liquid stream F4 advantageously contains purified SO2, preferably recovered at the bottom of the distillation column.

[0071] The liquid stream F4 obtained at the end of the distillative separation step iv) can optionally be subjected to an additional vaporization step to give a gaseous stream.

[0072] According to one embodiment, step a) of treating the gas stream F2 comprises: iii) an optional step of compressing said gas stream F2; iv) separating the HCl and SO2 contained in said gas stream F2 to obtain a stream G4, preferably a gaseous stream, comprising HCl and a stream F4 comprising SO2, said stream F4 being capable of being a liquid or gaseous stream; and an additional step vi) of treating gas stream G) and / or an additional step vi) of treating stream F4 Includes:

[0073] Flow G4 The gas stream G4 obtained at the end of step iv) advantageously contains less than 100 ppm SO2, preferably less than 80 ppm SO2 and preferentially less than 50 ppm SO2.

[0074] In the context of the present invention, "ppm" means "parts per million" expressed by weight.

[0075] The gas stream G4 obtained at the end of step iv) is advantageously - Directly sold and / or - used as a starting material in another process, and / or - can be subjected to an additional processing step v).

[0076] According to one embodiment, step a) of treating the gas stream F2 comprises: iii) an optional step of compressing said gas stream F2; iv) separating the gas stream F2 to give a stream G4, preferably a gaseous stream, comprising HCl and a stream F4 comprising SO2, said stream F4 being capable of being a liquid or gaseous stream; v) An additional step of treating the gas flow G4, comprising: v-1) an optional step of purifying said gas stream G4, v-2) absorbing the hydrochloric acid contained in the gas stream G4 in an aqueous solution, preferably demineralized water, allowing the formation and recovery of an aqueous hydrochloric acid solution L5, Additional steps, including vi) Optional step of treating stream F4 Includes:

[0077] Step v-1) is preferably a step of absorbing impurities using at least one solid adsorbent, such as activated carbon or alumina, etc. The gas stream G4 obtained at the end of step v-1) can advantageously be sold and / or used as starting material in other ways and / or subjected to step v-2) above.

[0078] Purification step v-1) advantageously makes it possible to reduce the content of residual SO2 in the purified gas stream G4, for example to a content of less than 50 ppm, preferably less than 20 ppm, advantageously less than 10 ppm.

[0079] Step v-2) above advantageously makes it possible to recover an aqueous hydrochloric acid solution L5 and a gas stream G5 comprising water and optionally one or more inert gases.

[0080] The concentration by weight of HCl in the aqueous hydrochloric acid solution L5 may be from 5% to 50% by weight, preferably from 15% to 40% by weight, more particularly from 30% to 35% by weight.

[0081] Solution L5 can advantageously be given commercial economic value.

[0082] Flow F4 Stream F4 advantageously contains less than 100 ppm of HCl, preferably less than 80 ppm and preferentially less than 50 ppm of HCl.

[0083] The liquid or gas stream F4 obtained at the end of step iv) can advantageously be subjected to an additional treatment step vi).

[0084] When stream F4 is a liquid stream, in particular when step iv) is a separation by distillation, treatment step vi) comprises vi-1) contacting said liquid stream F4 with an aqueous alkaline solution.

[0085] The alkaline aqueous solution may 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 selected from aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous calcium hydroxide, aqueous magnesium hydroxide, aqueous calcium carbonate, aqueous potassium carbonate, and mixtures thereof.

[0086] The contacting operation vi-1) can be carried out in a reactor, preferably a stirred reactor.

[0087] The above contacting operation vi-1) can result in a gas stream G6 comprising water and optionally one or more inert gases, and an alkaline stream L6 comprising water, chloride ions and sulfite ions, said stream L6 being preferably a liquid stream.

[0088] The alkaline stream L6 can optionally be sent to a wastewater treatment plant before being discharged to the environment.

[0089] If the stream F4 is a gas stream, in particular when step iv) is a membrane separation or when the liquid stream F4 obtained in the distillation step iv) has been subjected to an evaporation step, the treatment step vi) may be vi-2) contacting said gas stream F4 with an alkaline aqueous solution; or vi-3) contacting the gas flow F4 with aqueous hydrogen peroxide; or vi-4) optionally oxidizing, preferably catalytically or electrochemically, the gas stream F4 in the presence of oxygen to form a stream F5 comprising SO3; followed by a step vi-4-a) of absorbing the SO3 contained in said stream F5 in a concentrated sulfuric acid solution, so as to form and recover a gas stream G9 comprising water and optionally one or more inert gases and oleum L9; followed by an optional step vi-4-b) of diluting oleum L9 in water to form an aqueous solution L10, Oxidizing the gas stream F4 Includes:

[0090] Preferably, the alkaline aqueous solution in 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 selected from aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous calcium hydroxide, aqueous magnesium hydroxide, aqueous calcium carbonate, aqueous potassium carbonate, and mixtures thereof.

[0091] Preferably, the contacting operation vi-2) is carried out in a neutralization column, in particular operating countercurrently.

[0092] The neutralization column is as follows: at least one packing, for example a random packing and / or a stacked packing, and / or Trays, such as perforated trays, fixed valve trays, movable valve trays, bubble cap trays, or combinations thereof may include:

[0093] According to one embodiment, the gaseous stream F4 is introduced at the bottom of the neutralization column, while the aqueous alkaline solution is introduced at the top of said column.

[0094] According to one embodiment, step vi-2) of contacting the gas stream F4 with an aqueous alkaline solution, in particular in a neutralization column, is carried out by: a gas stream G7 comprising water and optionally one or more inert gases, preferably recovered at the top of the neutralization column; and - water, Cl, preferably a liquid stream recovered at the bottom of the neutralization column; - Alkaline flow L7 containing ions and sulfite ions This allows the formation and recovery of

[0095] Stream L7 can optionally be sent to a wastewater treatment plant before being discharged to the environment.

[0096] Preferably, the above step vi-3) is carried out in a scrub column, in particular operating in countercurrent.

[0097] The scrub columns are: at least one packing, for example a random packing and / or a stacked packing, and / or Trays, such as perforated trays, fixed valve trays, movable valve trays, bubble cap trays, or combinations thereof may include:

[0098] According to one embodiment, the gas stream F4 is introduced at the bottom of the scrubbing column, while the hydrogen peroxide solution is introduced at the top of said column.

[0099] The hydrogen peroxide solution may be an aqueous solution having a hydrogen peroxide content ranging from 5% to 70% by weight, preferably from 5% to 50% by weight, advantageously from 5% to 35% by weight.

[0100] The hydrogen peroxide / SO2 molar ratio contained in the gas stream F4 may range from 1 to 25, preferably from 1 to 20, and preferentially from 1 to 15.

[0101] According to one embodiment, step vi-3) of contacting the gas stream F4 with aqueous hydrogen peroxide, in particular in a scrubbing column, is carried out by: a gas stream G8 comprising water and optionally one or more inert gases, preferably recovered at the top of the scrubbing column; and a stream L8 comprising water and H2SO4, preferably a liquid stream, preferably recovered at the bottom of the scrubbing column; This allows the formation and recovery of

[0102] The concentration by weight of H2SO4 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%. Stream L8 may be subjected to a concentration step.

[0103] Stream L8 can advantageously be sold and / or recycled in the chlorination step described above.

[0104] Preferably, the above step vi-4) is carried out in a reactor.

[0105] The concentrated sulfuric acid solution used in step vi-4-a) is preferably a solution having more than 95% by weight of H2SO4.

[0106] The oleum L9 obtained at the end of the above step vi-4-a) can be sold directly and / or subjected to an optional step vi-4-b) of diluting the oleum L9 in water to form an aqueous solution 10. The solution L10, which is advantageously a sulfuric acid solution, can be sold and / or recycled to the above chlorination step and / or step vi-4-a) during the process.

[0107] Treatment: Selective absorption of HCl or SO2 According to a fourth embodiment, step a) of treating the gas stream F2 comprises: vii) absorbing the hydrochloric acid contained in said gas stream F2 in an aqueous solution, said aqueous solution being preferably demineralized water, allowing the formation and recovery of a hydrochloric acid solution L11 and a gas stream G11 comprising SO2, water and optionally one or more inert gases; or x) absorbing the SO2 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 gases, and a stream L12 comprising water, H2SO4 and SO2, said stream L12 being preferably a liquid stream; Includes:

[0108] The absorption step vii) can be carried out in a column, the gas stream G11 being preferably recovered at the top of the column, while the solution L11 is preferably recovered at the bottom of the column.

[0109] The concentration by weight of HCl in the hydrochloric acid solution L11 may be between 5% and 50%, preferably between 15% and 40%, more particularly between 30% and 35%.

[0110] Solution L11 may optionally contain a weight content of SO2 of less than or equal to 100 ppm, preferably less than or equal to 50 ppm and advantageously less than or equal to 20 ppm.

[0111] Step a) of treating the gas stream F2 may preferably comprise, following step vii), a step viii) which comprises purifying the solution L11 by adsorption of the remaining impurities using at least one solid adsorbent, such as activated carbon or silica gel. After such an additional step of adsorption on silica gel or activated carbon, an SO2 content of less than 1 ppm can advantageously be achieved in the HCl solution.

[0112] The optionally purified solution L11 may advantageously be given commercial economic value.

[0113] Step vii) above advantageously makes it possible to recover a hydrochloric acid solution L11 and a gas stream G11 comprising SO2, water and optionally one or more inert gases.

[0114] According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight and preferentially at least 99.9% by weight of the HCl contained in the gas stream F2 is recovered in the liquid stream L11.

[0115] According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight and preferentially at least 99.9% by weight of the SO2 contained in gas stream F2 is recovered in gas stream G11.

[0116] Step a) of treating gas stream F2 may also comprise a step ix) of drying gas stream G11, for example in the presence of calcium sulfate, sodium sulfate, magnesium sulfate, calcium chloride, calcium carbonate, silica gel or molecular sieves.

[0117] The optionally dried gas stream G11 may be subjected to one of steps vi-2), vi-3) or vi-4) above.

[0118] According to one embodiment, step a) of treating the gas stream F2 comprises: x) absorbing the SO2 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 gases, and a stream L12 comprising water, H2SO4 and SO2, said stream L12 being preferably a liquid stream; Includes:

[0119] The concentrated sulfuric acid solution used in step x) is preferably a solution having more than 95% by weight of H2SO4.

[0120] The absorption step x) can be carried out in a column, the gas stream G12 being preferably withdrawn at the top of the column, while the solution L12 is preferably withdrawn at the bottom of the column.

[0121] Gaseous stream G12 comprises more than 50% by weight of HCl, preferably more than 80% by weight, advantageously more than 90% by weight of HCl relative to the total weight of said stream G12.

[0122] Gaseous stream G12 can advantageously be sold directly and / or subjected to an economically valuable process (for example a process similar to step vii) to form a commercial 33% HCl solution.

[0123] According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight and preferentially at least 99.9% by weight of the HCl contained in gas stream F2 is recovered in gas stream G12.

[0124] According to one embodiment, at least 95% by weight, preferably at least 99% by weight, advantageously at least 99.5% by weight and preferentially at least 99.9% by weight of the SO2 contained in gas stream F2 is recovered in stream L12.

[0125] Stream L12 optionally comprises: - may be subjected, at least in part, to a heating step, making it possible to form and recover a gaseous stream G13 comprising SO2 and a stream L13 comprising H2SO4, which can advantageously be recycled to any step of the process involving gaseous SO2, for example to be reused in any of steps vi-2), vi-3) or vi-4) above; and / or It can be subjected at least partly to a step of contacting with aqueous hydrogen peroxide, preferably in a stirred reactor.

[0126] Preferably, the step of contacting the stream L12 with aqueous hydrogen peroxide, in particular in a stirred reactor, comprises the following steps: a gas flow G14 comprising water and optionally one or more inert gases; and a stream L14 comprising water and H2SO4, preferably a liquid stream This allows the formation and recovery of

[0127] The concentration by weight of H2SO4 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%. Stream L14 may be subjected to a concentration step.

[0128] Stream L14 can advantageously be sold and / or recycled in the chlorination step described above.

[0129] Chlorination process The chlorination step according to the present invention comprises: at a temperature between 30°C and 150°C; and / or with a reaction time between 1 hour and 7 days; and / or At pressures between 1bar abs and 20bar abs; This can be done.

[0130] According to the present invention, the sulfur-containing agent may be selected from the group consisting of chlorosulfonic acid (ClSO3H), sulfuric acid, oleum, and mixtures thereof.

[0131] According to the present invention, the chlorinating agent may be selected from the group consisting of thionyl chloride (SOCl), oxalyl chloride (COCl), phosphorus pentachloride (PCl), phosphonyl trichloride (PCl), phosphoryl trichloride (POCl), and mixtures thereof. Preferably, the chlorinating agent is thionyl chloride.

[0132] The chlorination step may be carried out in the presence of a catalyst selected from, for example, a tertiary amine (such as methylamine, triethylamine or diethylmethylamine); pyridine; and 2,6-lutidine.

[0133] The molar ratio between the sulfur-containing acid and the sulfamic acid may be between 0.7 and 5, preferably between 0.9 and 5.

[0134] The molar ratio of chlorinating agent to sulfamic acid may be between 2 and 10, preferably between 2 and 5.

[0135] In particular, when the sulfur-containing agent is chlorosulfonic acid, the molar ratio of the latter to sulfamic acid is between 0.9 and 5, and / or the molar ratio of the chlorinating agent to sulfamic acid is between 2 and 5.

[0136] In particular, when the sulfur-containing agent is sulfuric acid (or oleum), the molar ratio of sulfuric acid (or oleum) to sulfamic acid is between 0.7 and 5.

[0137] In particular, when the sulfur-containing agent is sulfuric acid (or oleum), the molar ratio of sulfuric acid (or oleum) to sulfamic acid is between 0.9 and 5, and / or the molar ratio of the chlorinating agent to sulfamic acid is between 2 and 10.

[0138] Method for preparing LiFSI The present invention also relates to a method for preparing the lithium salt of bis(fluorosulfonyl)imide (LiFSI), comprising the above method for preparing Cl-SO2-NH-SO2-Cl.

[0139] According to one embodiment, the method for preparing the lithium salt of a bis(fluorosulfonyl)imide comprises the steps of: i. A process for preparing bis(chlorosulfonyl)imides from sulfamic acids, as described above; ii. fluorinating the bis(chlorosulfonyl)imide to obtain a bis(fluorosulfonyl)imide; iii. preparing an alkali metal or alkaline earth metal salt of a bis(fluorosulfonyl)imide by neutralizing the bis(fluorosulfonyl)imide using, inter alia, an alkali metal or alkaline earth metal carbonate and an alkali metal or alkaline earth metal hydroxide; iv. optionally, cation exchanging to obtain a lithium bis(fluorosulfonyl)imide salt; and v. Method for Drying and Purifying Lithium Bis(fluorosulfonyl)imide Salts Includes:

[0140] The process for preparing lithium bis(fluorosulfonyl)imide salts according to the invention advantageously makes it possible to avoid the release of HCl and SO into the atmosphere, and thus the process is advantageously less polluting and more environmentally friendly.

[0141] Furthermore, the process for preparing lithium bis(fluorosulfonyl)imide salts according to the invention advantageously makes it possible to economically value certain secondary streams formed during the preparation of said LiFSI, which improves the economic profitability of the process.

[0142] The following examples make it possible to illustrate the invention without limiting it. [Example]

[0143] Example 1: A 100 liter enameled steel reactor equipped with stirring is charged with sulfamic acid (1 equivalent, 257.5 mol, 25 kg) and 95% sulfuric acid (1 equivalent, 257.5 mol, 26.6 kg). Thionyl chloride (4 equivalents, 1030 mol, 122.5 kg) is gradually added to the reactor. The temperature of the reaction medium is gradually increased to 75°C. The reaction is carried out at atmospheric pressure.

[0144] After 60 hours, all is converted to sulfamic acid. A condenser is placed in the vent line of the reactor to condense the vaporized thionyl chloride and reflux it into the reaction medium.

[0145] At the end of the reaction, 67 kg of a liquid containing bis(chlorosulfonyl)imide and unreacted thionyl chloride is obtained.

[0146] The gases produced by the reaction (HCl and SO2) and not condensed in the condenser are sent to a system that makes it possible to absorb them (see examples 2 and 3).

[0147] Example 2: Absorption of HCl and SO2 in H2O2 solution The gas produced by the reaction in Example 1 is sent to a storage tank containing 700 kg of a 5% by weight H2O2 solution. This storage tank is surrounded by a packed column, the top of which is sprayed with the H2O2 solution contained in the storage tank. A pump allows the H2O2 solution to be withdrawn from the storage tank for spraying into the column. The gases produced by the reaction (HCl and SO2) are introduced by a dip pipe into the H2O2 solution contained in the storage tank. HCl and SO2 are absorbed into the H2O2 solution, and SO2 reacts with H2O2 to form H2SO4. The packed column completes the absorption of the gases produced by the reaction, HCl and SO2, and allows the complete conversion of SO2 to H2SO4.

[0148] At the end of the reaction, 797 kg of a solution containing 1% by weight of H2O2, 5% by weight of HCl and 10% by weight of H2SO4 is obtained.

[0149] Example 3: Absorption of HCl in water followed by absorption of SO in H2O2 solution The gases (HCl and SO2) produced by the reaction of Example 1 are sent to an HCl absorption column sprayed with water at the top, where a 33% HCl solution is obtained at the bottom. This column makes it possible to absorb, in particular, gaseous HCl, but not gaseous SO2.

[0150] Gaseous SO2 is collected at the top of the HCl absorption column and sent to a storage tank containing 300 kg of a 10 wt% H2O2 solution. The device for absorbing gaseous SO2 into the H2O2 solution is identical to that described in Example 2. In this configuration, the packed column allows for complete absorption of SO2 and complete conversion of SO2 to H2SO4.

[0151] At the end of the reaction, 130 kg of a 33% HCl solution are obtained on the one hand, and 354 kg of a solution containing less than 1% by weight of H2O2 and 23% by weight of H2SO4 on the other hand.

Claims

1. chlorinating sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent; ２ NHSO ２ A method for preparing Cl, comprising the steps of: ２ NHSO ２ a preferably liquid stream F1 containing Cl, and a stream F2 containing HCl and SO ２ and a gas flow F2 comprising:

2. Step a) of treating the gas stream F2 comprises a step of contacting said stream F2 with an alkaline aqueous solution and / or a step of contacting said stream F2 with a hydrogen peroxide solution and / or a step of treating the HCl and SO 2 contained in said stream F2. ２ and / or absorbing the HCl contained in said gas stream F2 in an aqueous solution and / or absorbing the SO 3 contained in said gas stream F2 in a concentrated sulfuric acid solution. ２ The method of claim 1 , comprising the step of:

3. The gas flow F2 is: more than 20% by weight of HCl, preferably more than 30% by weight 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 SO 4 relative to the total weight of said stream F2 ２ , preferably more than 40 wt.% SO ２ , advantageously more than 50% by weight of SO ２ 3. The method of claim 1 or 2, comprising:

4. Step a) of treating the gas stream F2 consists in i) bringing the gas stream F2 into contact with an aqueous alkaline solution, in particular in a neutralization column, advantageously comprising: a gas stream G1 comprising water and optionally one or more inert gases, preferably recovered at the top of the neutralization column; and - water, Cl, preferably a liquid stream recovered at the bottom of the neutralization column; － ions and sulfite SO ３ ２－ Ion-containing alkaline flow L1 4. The method according to claim 1, comprising contacting the gas stream F2 with an aqueous alkaline solution, which allows the formation and recovery of

5. 4. The method according to claim 1, wherein step a) of treating the gas stream F2 comprises ii) contacting the gas stream F2 with aqueous hydrogen peroxide.

6. Step ii) of contacting the gas stream F2 with aqueous hydrogen peroxide, in particular in a scrubbing column, a gas stream G2 comprising water and optionally one or more inert gases, preferably recovered at the top of the scrubbing column; and - Water, HCl and H, preferably a liquid stream, recovered at the bottom of the scrub column. ２ SO ４ Acidic stream L2 containing 6. The method of claim 5, wherein the method allows for the formation and recovery of

7. an additional step ii-1) of treating stream L2, comprising contacting said stream L2 with an aqueous alkaline solution, or a stream F3 containing HCl and H ２ SO ４ HCl and H contained in stream L2 to form and recover stream F'3 containing ２ SO ４ 7. The method according to claim 6, comprising the additional step ii-2) of separating

8. Step a) of treating the gas stream F2 comprises: iii) an optional step of compressing said gas stream F2; iv) a stream G4, preferably a gaseous stream, containing HCl and SO ２ and a stream F4 containing HCl and SO ２ wherein said stream F4 may be a liquid or gas stream, The separation step iv) is preferably distillation or membrane separation; HCl and SO ２ Separating the 4. The method of claim 1, comprising:

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

10. The step v) is as follows: v-1) an optional step of purifying the gas stream G4; v-2) absorbing the hydrochloric acid contained in said gas stream G4 in an aqueous solution, said aqueous solution being preferably demineralized water, allowing the formation and recovery of an aqueous hydrochloric acid solution L5; 10. The method of claim 9, comprising:

11. when stream F4 is a liquid stream, in particular when step iv) is a separation by distillation, treatment step vi) comprises vi-1) contacting said liquid stream F4 with an aqueous alkaline solution to preferably obtain a gaseous stream G6 comprising water and optionally one or more inert gases, and an alkaline stream L6 comprising water, chloride ions and sulfite ions, said stream L6 being preferably a liquid stream; When stream F4 is a gas stream, process step vi) is vi-2) contacting said gas stream F4 with an alkaline aqueous solution; or vi-3) contacting the gas flow F4 with aqueous hydrogen peroxide; or vi-4) SO ３ oxidizing, preferably catalytically or electrochemically, the gas stream F4 in the presence of oxygen to form a stream F5 comprising: the SO 2 contained in said stream F5 in concentrated sulfuric acid solution so as to make it possible to form and recover a gas stream G9 containing water and optionally one or more inert gases and oleum L9; ３ followed by step vi-4-a) of absorbing; followed by an optional step vi-4-b) of diluting oleum L9 in water to form an aqueous solution L10, Oxidizing the gas stream F4 Including, 11. The method according to claim 9 or 10.

12. Step a) of treating the gas stream F2 comprises: vii) absorbing the hydrochloric acid contained in said gas stream F2 in an aqueous solution, said aqueous solution being preferably demineralized water, a hydrochloric acid solution L11 and SO ２ absorbing the hydrochloric acid, allowing the formation and recovery of a gas stream G11 comprising water and optionally one or more inert gases; or x) SO contained in said gas stream F2 in concentrated sulfuric acid solution ２ a gas flow G12 containing HCl and optionally one or more inert gases, water, H ２ SO ４ and SO ２ and a stream L12 comprising: ２ The process of absorbing 4. The method of claim 1, comprising:

13. Step a) of treating the gas stream F2 comprises: - step viii) followed by a step viii) which preferably comprises purifying the solution L11 by adsorbing the remaining impurities using at least one solid adsorbent, such as activated carbon or silica gel; and an optional step ix) of drying the gas stream G11, carried out for example in the presence of calcium sulfate, sodium sulfate, magnesium sulfate, calcium chloride, calcium carbonate, silica gel or molecular sieves; 13. The method of claim 12, comprising:

14. Flow L12 is: - at least in part, subjected to a heating step and ２ a gas flow G13 containing H ２ SO ４ and a stream L13 comprising: and / or - subjected at least in part to a step of contacting with aqueous hydrogen peroxide, preferably in a stirred reactor; 14. The method according to claim 12 or 13.

15. The chlorination step comprises the following steps: at 30°C and 150°C; and / or with a reaction time between 1 hour and 7 days; and / or at a pressure between 1 bar abs and 20 bar abs; The method according to any one of claims 1 to 14, wherein

16. - the sulfur-containing agent is chlorosulfonic acid (ClSO ３ H), selected from the group consisting of sulfuric acid, oleum, and mixtures thereof; and / or - the chlorinating agent is thionyl chloride (SOCl ２ ), oxalyl chloride (COCl) ２ , phosphorus pentachloride (PCl ５ ), phosphonyl trichloride (PCl ３ ), phosphoryl trichloride (POCl ３ ) and mixtures thereof; 16. The method of any one of claims 1 to 15.

17. The Cl-SO compound according to any one of claims 1 to 16. ２ -NH-SO ２ A method for preparing the lithium salt of a bis(fluorosulfonyl)imide, comprising the step of preparing —Cl.

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