Method for preparing lithium bis(fluorosulfonyl)imide salts

Abstract

The present invention relates to a method for preparing Cl-SO2NHSO2Cl, comprising the step of chlorinating sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent, which results in a preferably liquid stream F1 comprising Cl-SO2NHSO2Cl and a gaseous stream F2 comprising HCl and SO2, and which includes a step a) of treating gaseous stream F2. The present invention also relates to a method for preparing Li FSI, which comprises the above-mentioned method for preparing Cl-SO2NHSO2Cl. [Selection diagram] None

Description

Field of the Invention

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

Background Art

[0002] Sulfonylimide type anions are increasingly being 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 their very low basicity. Since the battery market is booming and reducing battery manufacturing costs is a major challenge, there is a need for a method to synthesize this type of anion on a large scale and at low cost.

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

[0004] There are several methods for preparing LiFSI, especially those involving a chlorination step. However, these methods result in the release of toxic products that may be released into the atmosphere and thus have an adverse 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 a method for the preparation of lithium bis(fluorosulfonyl)imide salts that is more environmentally friendly and / or economically beneficial.

Summary of the Invention

[0007] The present invention relates to a method for preparing Cl-SO2NHSO2Cl, comprising the step of chlorinating sulfamic acid using at least one chlorinating agent and at least one sulfur-containing agent, wherein the method yields a preferably liquid flow F1 containing Cl-SO2NHSO2Cl and a gaseous flow F2 containing HCl and SO2, and the method comprises the step a) of treating the gaseous flow F2. [Modes for carrying out the invention]

[0008] Processing step a) advantageously allows for the avoidance of HCl and SO2 contained in the gaseous flow F2 being released into the atmosphere.

[0009] This step a) for processing the gaseous flow F2 preferably includes a step of contacting the flow F2 with an alkaline aqueous solution, and / or a step of contacting the flow F2 with hydrogen peroxide solution, and / or a step of separating HCl and SO2 contained in the flow F2, and / or a step of absorbing HCl contained in the gaseous flow F2 in the aqueous solution, and / or a step of absorbing SO2 contained in the gaseous flow F2 in a concentrated sulfuric acid solution.

[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, and more 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, and advantageously more than 50% by weight of SO2 Includes.

[0011] The gas stream F2 may, in some cases, contain one or more inert gases, such as nitrogen, helium, or argon. For example, it / they may be the inert gases used in the chlorination step described above.

[0012] The flow F1 may, in some cases, contain a chlorinating agent such as SOCl2 in an amount of, for example, 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 the flow F1.

[0013] The flow F1 may, in some cases, contain a sulfur-containing agent such as H2SO4 in a concentration of, for example, 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 the flow F1.

[0014] The flow F1 may, in some cases, contain chlorinating agents and sulfur-containing agents such as SOCl2 and H2SO4, in a total content of, for example, 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 the flow F1.

[0015] The flow F1 may, in some cases, contain HCl and / or SO2, each in a content of 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 the flow F1.

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

[0017] An 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.

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

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

[0020] Preferably, the contact operation i) is carried out in a neutralization column, particularly in a countercurrent.

[0021] The neutralization column is as follows: ·At least one packing, for example, random packing and / or stacked packing, and / or ·A tray, for example, a perforated tray, a fixed valve tray, a movable valve tray, a bubble cap tray or a combination thereof may be included.

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

[0023] 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 the column.

[0024] According to one embodiment, step i) of contacting the gas stream F2, particularly in the neutralization column, with the alkaline aqueous solution is as follows: - A gas stream G1 containing water and optionally one or more inert gases, preferably recovered at the top of the neutralization column; and - An alkaline stream L1, preferably a liquid stream, preferably recovered at the bottom of the neutralization column, containing water, Cl - ions and sulfite SO3 2- ions. It is possible to form and recover.

[0025] The alkaline stream L1 can optionally be sent to a wastewater treatment plant, possibly before discharging it to the environment.

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

[0027] The SO2 contained in the gas stream F2 then reacts with the hydrogen peroxide solution and can quantitatively form sulfuric acid according to the reaction equation:

[0028] ​ Preferably, the contact operation ii) is carried out in a scrub column, particularly in a countercurrent.

[0029] Hydrogen peroxide solution can be an aqueous solution in which the weight content of hydrogen peroxide is in the range of 5% to 70% by weight, preferably 5% to 50% by weight, and advantageously 5% to 35% by weight.

[0030] The molar ratio of hydrogen peroxide / SO2 contained in the gas flow F2 may be in the range of 1 to 25, preferably 1 to 20, and more preferably 1 to 15.

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

[0032] According to one embodiment, the gas flow F2 is introduced to the bottom of the scrub column, while hydrogen peroxide solution is introduced to the top of the column.

[0033] According to one embodiment, step ii) of bringing the gas flow F2 into contact with hydrogen peroxide solution, particularly in a scrub column, is as follows: - Preferably a gas stream G2 containing water and optionally one or more inert gases, recovered at the top of the scrub column; and - Preferably an acidic stream L2 containing water, HCl, and H2SO4, which is a liquid stream recovered at the bottom of the scrub column. This makes it possible to form and recover them.

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

[0035] Step a) above may include an additional step ii-1) of treating the acidic flow L2, which includes contacting the acidic flow L2 with an alkaline aqueous solution, or an additional step ii-2) of separating the HCl and H2SO4 contained in the acidic flow L2 in order to form and recover a flow F3 containing HCl and a flow F'3 containing 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 in a stirred reactor.

[0038] According to one embodiment, step ii-1) is as follows: - A gaseous flow G3 containing water and optionally one or more inert gases; and - Preferably a liquid stream of water, chloride ions, and sulfite SO4 2- Alkaline flow containing ions L3 This makes it possible to form and recover them.

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

[0040] Process ii-2) According to one embodiment, step a) of processing the gaseous flow F2 includes ii) contacting the gaseous flow F2 with hydrogen peroxide solution, and subsequently ii-2) separating the HCl and H2SO4 contained in the flow L2 in order to form and recover a flow F3 containing HCl and a flow F'3 containing H2SO4.

[0041] Separation may be carried out by distillation or electrodialysis.

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

[0043] Flow F'3 is preferably a concentrated H2SO4 aqueous solution containing 20% ​​by weight or more, preferably 50% by weight or more of H2SO4.

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

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

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

[0047] The separation process advantageously allows for the separation of HCl and H2SO4 contained in flow L2.

[0048] According to one embodiment, when step ii-2) is separation by distillation, step ii-2) preferably allows the formation and recovery of a flow F3 containing HCl and a liquid flow F'3 containing H2SO4 at the top of the distillation column.

[0049] Flow F3 can be a gas flow or a liquid flow.

[0050] Preferably, flow F3 is as follows: - At least 15% by weight, preferably at least 20% by weight, of the total weight of the flow F3, HCl; and / or - 5000 ppm H2SO4, preferably less than 1000 ppm H2SO4, advantageously less than 500 ppm H2SO4 Includes.

[0051] Flow F'3 is preferably a concentrated H2SO4 aqueous solution containing 20% ​​by weight or more, preferably 50% by weight or more of H2SO4.

[0052] Flow F'3 may be subjected to a concentration or dilution process. It can then be sold and / or recycled in the manner described above.

[0053] When flow F3 is a gas, this flow F3 can be sold in another process and / or used as a starting material and / or subjected to a process of absorbing the hydrochloric acid contained in the flow F3 in an aqueous solution, the aqueous solution being preferably demineralized water, which enables the formation and recovery of a hydrochloric acid solution. The weight concentration of HCl in the hydrochloric acid solution can be 5% to 50% by weight, preferably 15% to 40% by weight, more specifically 30% to 35% by weight. The resulting hydrochloric acid solution may be advantageously given commercial economic value.

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

[0055] Processing: Gas separation According to the third embodiment, step a) for processing the gas flow F2 is as follows: iii) an optional step of compressing the gas flow F2, iv) A step of separating HCl and SO2 contained in a gaseous flow F2 that results in a flow G4 preferably containing HCl and a flow F4 containing SO2, wherein the flow F4 may be a liquid or gaseous flow. Includes.

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

[0057] The above compression step iii) may enable the gas flow F2 to be compressed to a pressure of more than 5 bar abs, preferably more than 7 bar abs, more preferably more than 10 bar abs, and more advantageously more than 15 bar abs, for example, 20 bar abs.

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

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

[0060] The membrane separation process typically involves the use of one or more membranes. When multiple membranes are used, they may be arranged sequentially or grouped together.

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

[0062] The film may be inorganic (e.g., ceramic or glass), organic (e.g., polymer), 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 membrane separation, this step is advantageously a gas stream G4 containing purified HCl and a gas stream F4 (F4) containing purified SO2. g (This is expressed as) and brings about.

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

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

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

[0068] Separation by distillation is as follows: · At a distillation column bottom temperature in the range of 40°C to 80°C, preferably 40°C to 60°C, and more preferably 50°C to 60°C, at 10 bar abs; or • At a distillation column bottom temperature in the range of 40°C to 100°C, preferably 50°C to 90°C, and more preferably 60°C to 80°C, at 14 bar abs. It is possible.

[0069] The distillation column is as follows: • At least one packing, for example, random packing and / or stacked packing, and / or • Trays, such as perforated trays, fixed valve trays, movable valve trays, bubble cap trays, or combinations thereof. It may include.

[0070] When separation step iv) is distillation, this step advantageously yields a gaseous stream G4 containing HCl and a liquid stream F4 containing 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 separation step iv) by distillation may, in some cases, be subjected to an additional vaporization step to produce a gaseous stream.

[0072] According to one embodiment, step a) for processing the gas flow F2 is as follows: iii) an optional step of compressing the gas flow F2, iv) A step of separating HCl and SO2 contained in a gaseous flow F2 that results in a flow G4 preferably containing HCl and a flow F4 containing SO2, wherein the flow F4 may be a liquid or gaseous flow. and (an additional step of processing the gas flow G) and / or (vi) an additional step of processing the flow F4) Includes.

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

[0074] In the context of this invention, "ppm" means "one part per million" expressed by weight.

[0075] The gas flow G4 obtained at the end of step iv) is advantageously, - Sold directly, and / or - Used as starting material in another process, and / or - Can be subjected to an additional processing step v).

[0076] According to one embodiment, step a) for processing the gas flow F2 is as follows: iii) an optional step of compressing the gas flow F2, iv) A step of separating a gaseous flow F2 that yields a flow G4 preferably containing HCl and a flow F4 containing SO2, wherein the flow F4 may be a liquid or gaseous flow. v) An additional step for processing the gas flow G4, the following: ·v-1) An optional step for purifying the gas flow G4, v-2) A step of absorbing hydrochloric acid contained in the gas flow G4 in an aqueous solution, wherein the aqueous solution is preferably demineralized water, and the step of absorbing hydrochloric acid enables the formation and recovery of the hydrochloric acid aqueous solution L5. Additional steps, including vi) Optional process for processing flow 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. The gaseous stream G4 obtained at the end of step v-1) can be advantageously sold and / or used as a starting material in another way and / or used in step v-2) above.

[0078] The purification step v-1) advantageously allows the content of residual SO2 in the purified gas stream G4 to be reduced to, for example, less than 50 ppm, preferably less than 20 ppm, and advantageously less than 10 ppm.

[0079] The above step v-2) advantageously allows for the recovery of the hydrochloric acid aqueous solution L5 and the gaseous stream G5 containing water and optionally one or more inert gases.

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

[0081] Solution L5 may, to some extent, be given commercial and economic value.

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

[0083] The liquid or gaseous stream F4 obtained at the end of step iv) may, advantageously, be subjected to an additional processing step vi).

[0084] When flow F4 is a liquid flow, and especially when step iv) is separation by distillation, processing step vi) includes vi-1) a step of bringing the liquid flow F4 into contact with an alkaline aqueous 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 contact operation vi-1) can be carried out in a reactor, preferably in a stirred reactor.

[0087] The above contact operation vi-1) can result in a gaseous flow G6 containing water and optionally one or more inert gases, and an alkaline flow L6 containing water, chloride ions and sulfite ions, wherein the flow L6 is preferably a liquid flow.

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

[0089] If the flow F4 is a gaseous flow, especially when step iv) is membrane separation or when the liquid flow F4 obtained in distillation step iv) has been subjected to an evaporation step, then processing step vi) is as follows: vi-2) Contacting the gas flow F4 with an alkaline aqueous solution; or vi-3) Contacting the gas stream F4 with hydrogen peroxide solution; or vi-4) In order to form a flow F5 containing SO3, the gaseous flow F4 is oxidized, preferably catalytically or electrochemically, in the presence of oxygen, and in some cases; The process continues with step vi-4-a) absorbing SO3 contained in the stream F5 in a concentrated sulfuric acid solution so that a gas stream G9 containing water and optionally one or more inert gases and fuming sulfuric acid L9 can be formed and recovered; Subsequently, an optional step vi-4-b) is taken to dilute fuming sulfuric acid L9 in water to form an aqueous solution L10. To oxidize the gas flow F4 Includes.

[0090] Preferably, the alkaline aqueous solution in step vi-2) 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.

[0091] Preferably, the contact operation vi-2) is carried out in a neutralization column, particularly in a countercurrent.

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

[0093] According to one embodiment, the gas flow F4 is introduced to the bottom of the neutralization column, while the alkaline aqueous solution is introduced to the top of the column.

[0094] According to one embodiment, step vi-2), which involves contacting a gas stream F4 with an alkaline aqueous solution, particularly in a neutralization column, is as follows: - Preferably a gas stream G7 containing water and optionally one or more inert gases, recovered at the top of the neutralization column; and - Preferably a liquid stream of water, Cl, recovered at the bottom of the neutralization column. - Alkaline flow L7 containing ions and sulfite ions This makes it possible to form and recover them.

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

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

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

[0098] According to one embodiment, the gas flow F4 is introduced to the bottom of the scrub column, while hydrogen peroxide solution is introduced to the top of the column.

[0099] Hydrogen peroxide solution can be an aqueous solution in which the weight content of hydrogen peroxide is in the range of 5% to 70% by weight, preferably 5% to 50% by weight, and advantageously 5% to 35% by weight.

[0100] The molar ratio of hydrogen peroxide / SO2 contained in the gas flow F4 may be in the range of 1 to 25, preferably 1 to 20, and more preferably 1 to 15.

[0101] According to one embodiment, step vi-3) of bringing the gas flow F4 into contact with hydrogen peroxide solution, particularly in a scrub column, is as follows: - Preferably a gas stream G8 containing water and optionally one or more inert gases, recovered at the top of the scrub column; and - A flow L8 containing water and H2SO4, preferably a liquid flow, preferably recovered at the bottom of the scrub column. This makes it possible to form and recover them.

[0102] The weight concentration of H2SO4 in the aqueous stream L8 may be 5% or more, preferably 10% or more, and advantageously 20% or more. Stream L8 may also be subjected to a concentration process.

[0103] Flow L8 can, advantageously, be sold and / or recycled in the chlorination process described above.

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

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

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

[0107] Treatment: Selective absorption of HCl or SO2 According to the fourth embodiment, step a) for processing the gas flow F2 is as follows: vii) A step of absorbing hydrochloric acid contained in the gas stream F2 in an aqueous solution, wherein the aqueous solution is preferably demineralized water, and the step of absorbing hydrochloric acid enables the formation and recovery of a gas stream G11 containing a hydrochloric acid solution L11, SO2, water, and optionally one or more inert gases; or x) A step of absorbing SO2 contained in the gas stream F2 in a concentrated sulfuric acid solution, wherein it is possible to form and recover a gas stream G12 containing HCl and optionally one or more inert gases, and a stream L12 containing water, H2SO4 and SO2, and the stream L12 is preferably a liquid stream. Includes.

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

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

[0110] Solution L11 may, in some cases, contain SO2 at a weight content of 100 ppm or less, preferably 50 ppm or less, and advantageously 20 ppm or less.

[0111] Step a) for processing the gaseous flow F2 may include, following step vii), step viiii) purifying the solution L11 by adsorbing residual impurities using at least one solid adsorbent, such as activated carbon or silica gel. After such an additional step of adsorption to silica gel or activated carbon, an SO2 content of less than 1 ppm in the HCl solution can be advantageously achieved.

[0112] The selectively purified solution L11 may, at its advantage, be given commercial and economic value.

[0113] Step vii) above advantageously allows for the recovery of the hydrochloric acid solution L11 and the gaseous stream G11 containing 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 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 SO2 contained in the gas stream F2 is recovered in the gas stream G11.

[0116] Step a) of processing the gaseous flow F2 may also include step ix) of drying the gaseous flow G11, which is carried out in the presence of, for example, calcium sulfate, sodium sulfate, magnesium sulfate, calcium chloride, calcium carbonate, silica gel, or molecular sieve.

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

[0118] According to one embodiment, step a) for processing the gas flow F2 is as follows: x) A step of absorbing SO2 contained in the gas stream F2 in a concentrated sulfuric acid solution, wherein it is possible to form and recover a gas stream G12 containing HCl and optionally one or more inert gases, and a stream L12 containing water, H2SO4 and SO2, and the stream L12 is preferably a liquid stream. Includes.

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

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

[0121] The gas flow G12 contains more than 50% by weight of HCl, preferably more than 80% by weight of HCl, and more favorably more than 90% by weight of HCl, based on the total weight of the flow G12.

[0122] The gaseous flow G12 can be advantageously subjected to a process (e.g., a process similar to process vii) that gives it economic value in order to form a 33% HCl solution that is sold directly and / or for commercial use.

[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 HCl contained in the gas stream F2 is recovered in the 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 SO2 contained in the gas flow F2 is recovered in flow L12.

[0125] Flow L12 is optional: - At least partially, it may be subjected to a heating process, making it possible to form and recover a gaseous flow G13 containing SO2 and a flow L13 containing H2SO4. The gaseous flow G13 can advantageously be recycled into any process containing gaseous SO2, for example, it can be reused in any of the above processes vi-2), vi-3), or vi-4); and / or - Preferably, the device can be subjected to a step in which it is brought into contact with hydrogen peroxide solution, at least partially, in a stirred reactor.

[0126] Preferably, the step of bringing flow L12 into contact with hydrogen peroxide solution, particularly in a stirred reactor, is as follows: - A gaseous flow G14 containing water and optionally one or more inert gases; and - Preferably a liquid flow, L14 containing water and H2SO4 This makes it possible to form and recover them.

[0127] The weight concentration of H2SO4 in the aqueous stream L14 may be 5% or more, preferably 10% or more, and advantageously 20% or more. Stream L14 may be subjected to a concentration process.

[0128] Flow L14 can, advantageously, be sold and / or recycled in the chlorination process described above.

[0129] Chlorination process The chlorination process according to the present invention is: • At 30°C and 150°C; and / or • Within a reaction time of 1 hour and 7 days; and / or • At pressures between 1 bar abs and 20 bar abs; It is possible.

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

[0131] According to the present invention, the chlorinating agent can be selected from the group consisting of thionyl chloride (SOCl2), oxalyl chloride (COCl2), phosphorus pentachloride (PCl5), phosphonyl trichloride (PCl3), phosphoryl trichloride (POCl3), 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, tertiary amines (such as methylamine, triethylamine, or diethylmethylamine); pyridine; and 2,6-lutidine.

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

[0134] The molar ratio of the 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 fuming sulfuric acid), the molar ratio of sulfuric acid (or fuming sulfuric acid) to sulfamic acid is between 0.7 and 5.

[0137] In particular, when the sulfur-containing agent is sulfuric acid (or fuming sulfuric acid), the molar ratio of sulfuric acid (or fuming sulfuric acid) 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 lithium salts of bis(fluorosulfonyl)imide (LiFSI), including the above method for preparing Cl-SO2-NH-SO2-Cl.

[0139] According to one embodiment, a method for preparing a lithium salt of bis(fluorosulfonyl)imide is as follows: i. A method for preparing bis(chlorosulfonyl)imide from sulfamic acid as described above; ii. A step of obtaining bis(fluorosulfonyl)imide by fluorinating bis(chlorosulfonyl)imide; iii. A step of preparing an alkali metal or alkaline earth metal salt of bis(fluorosulfonyl)imide by neutralizing bis(fluorosulfonyl)imide, particularly using an alkali metal or alkaline earth metal carbonate and an alkali metal or alkaline earth metal hydroxide; iv. In some cases, a cation exchange step to obtain a lithium bis(fluorosulfonyl)imide salt; and v. Method for drying and purifying lithium bis(fluorosulfonyl)imide salts Includes.

[0140] The method for preparing lithium bis(fluorosulfonyl)imide salt according to the present invention is advantageous in that it allows for the avoidance of releasing HCl and SO2 into the atmosphere. Therefore, this method is advantageous in that it is less polluting and more environmentally friendly.

[0141] Furthermore, the method for preparing lithium bis(fluorosulfonyl)imide salts according to the present invention advantageously allows for the economic value to be given to certain secondary flows formed during the preparation of the LiFSI, which improves the economic profitability of the method.

[0142] The following embodiments will allow for a description of the present invention without limiting it. [Examples]

[0143] Example 1: A 100-liter enameled steel reactor equipped with a stirring valve is filled 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 raised to 75°C. The reaction is carried out at atmospheric pressure.

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

[0145] At the end of the reaction, 67 kg of 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 allows them to be absorbed (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 5% by weight H2O2 solution. This storage tank is surrounded by a packed column with the H2O2 solution contained in the storage tank sprayed onto its top. A pump allows for the intake of H2O2 solution from the storage tank for spraying onto the column. The gases produced by the reaction (HCl and SO2) are introduced into the H2O2 solution contained in the storage tank via a dip pipe. HCl and SO2 are absorbed into the H2O2 solution, and SO2 reacts with H2O2 to form H2SO4. The packed column allows for the absorption of the gases produced by the reaction, HCl and SO2, and the complete conversion of SO2 to H2SO4.

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

[0149] Example 3: Absorption of HCl in water followed by absorption of SO2 in H2O2 solution The gases (HCl and SO2) produced by the reaction in Example 1 are sent to an HCl absorption column with water sprayed at the top. A 33% HCl solution can be obtained at the bottom of this column. This column allows for the absorption of gaseous HCl in particular, 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 10 wt% H2O2 solution. The apparatus for absorbing gaseous SO2 into the H2O2 solution is the same as that described in Example 2. In this configuration, the packed column allows for the completion of SO2 absorption and the complete conversion of SO2 to H2SO4.

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

Claims

1. chlorinating sulfamic acid with at least one chlorinating agent and at least one sulfur-containing agent; ２ NHSO ２ 1. A method for preparing Cl, the method comprising the steps of: ２ NHSO ２ a stream F1 containing Cl and a stream F2 containing HCl and SO ２ and a step a) of treating the gas flow F2, Step a) of treating the gas stream F2 comprises: i) contacting the gas stream F2 with an aqueous alkaline solution in a neutralization column, the aqueous alkaline solution being: a gas stream G1 recovered at the top of the neutralization column, comprising water and optionally one or more inert gases; and - Water, Cl, recovered at the bottom of the neutralization column － ions and sulfite SO ３ ２－ Ion-containing alkaline flow L1 contacting the gas stream F2 with an alkaline aqueous solution, which allows the formation and recovery of Stream F1 contains a chlorinating agent in a content of less than 5% by weight relative to the total weight of said stream F1, method.

2. The gas flow F2 is: more than 20% 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 The method of claim 1 , comprising:

3. The chlorination step comprises the following steps: at a temperature between 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 claim 1 or 2, wherein

4. - 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; 4. The method according to any one of claims 1 to 3.

5. The Cl-SO compound according to any one of claims 1 to 4 ２ -NH-SO ２ A method for preparing the lithium salt of a bis(fluorosulfonyl)imide, comprising the step of preparing —Cl.