Method for removing one or more target impurities from crude fluorosulfonylimide compounds

Abstract

The present invention relates to a method for removing one or more target impurities, which are chlorides, from a crude bisfluorosulfonylimide mixture containing a hydrogen (bisfluorosulfonyl)imide compound, and to forming a purified mixture by reacting the crude mixture in the molten phase with water or an aqueous solution of an inorganic acid to remove the one or more target impurities.

Description

[Technical Field]

[0001] Cross-reference of related patent applications This invention claims priority under European Patent Application No. 23305878.3, filed in Europe on 2 June 2023, the entire contents of which application are incorporated herein by reference for all purposes.

[0002] The present invention relates to a method for removing one or more target impurities, which are chlorides, from a crude bisfluorosulfonylimide mixture containing a hydrogen (bisfluorosulfonyl)imide compound and one or more target impurities, thereby forming a purified mixture. [Background technology]

[0003] Bis(fluorosulfonyl)imides and their salts, particularly lithium bis(fluorosulfonyl)imides (LiFSIs), are useful compounds in various technological fields. Bis(fluorosulfonyl)imide salts are especially useful in battery electrolytes.

[0004] Bis(fluorosulfonyl)imide (HFSI, formula HN(SO2F)2) is a well-known intermediate in the production of second-generation battery salts (e.g., LiFSI or NaFSI), and various synthetic routes for preparing HFSI have been proposed. Several synthetic routes involve chloride intermediates, and in particular, HFSI can be fluorinated with various fluorinating agents, especially nucleophilic fluorinating agents, such as HF and AsF. 3、 It can be produced by fluorination of bis(chlorosulfonyl)imide (HCSI) using BiF3 and SbF3 (see Formulas 1 and 2 below): 3HN(SO2Cl)2+2M'F3→3HN(SO2F)2+2M'CI3(M'=As,Sb,Bi) Formula 1 or HN(SO2Cl)2+2HF→HN(SO2F)2+2HCI Formula 2

[0005] Regardless of the manufacturing method, the production of HFSI involves the presence of multiple impurities, which may remain in the final product (either as is or converted in downstream processes) and adversely affect the performance of FSI salts in battery applications. Impurities that are chlorides containing a -SO2Cl moiety, such as bis(chlorosulfonyl)imide, (chlorosulfonylfluorosulfonyl)imide, sulfamoyl chloride (NH2SO2Cl), and chloride sulfonyliimide oligomers (F-SO2-NH-SO2-NH-SO2-Cl and chlorosulfonic acid, etc.), are particularly serious impurities because they are precursors to chloride ion species.

[0006] Bis(chlorosulfonyl)imide (HCSI) has a significantly higher boiling point than bis(fluorosulfonyl)imide (HFSI), while fluoro / chloro mixed analogs have intermediate boiling points, and chlorosulfonic acid has a boiling point of 152°C. Therefore, although purification by fractional distillation is a widely known technique, it can be complex and may require many theoretical plates (i.e., high CAPEX for industrialization), particularly as mentioned in International Publication No. 2019 / 229357.

[0007] Alternative methods for purifying HFSI have been proposed.

[0008] U.S. Patent No. 10,734,664 of SES Holdings Pte. Ltd. discloses a method for removing impurities from crude HFSI, which involves crystallizing pure HFSI from an organic anhydrous solvent, but impurities such as HF, FSO3H, HCl, and H2SO4 remain in the solution phase. The described method introduces an organic solvent into the system, which is generally undesirable as it can introduce complexity. Furthermore, its applicability / effectiveness remains questionable as no information is provided regarding the purification efficiency for, for example, ClSO3H, HCSI, and other chlorine-containing molecules.

[0009] Furthermore, Honeywell's U.S. Patent No. 11267707 proposes a method for producing purified bis(fluorosulfonyl)imide, which involves preparing a liquid mixture containing bis(fluorosulfonyl)imide and fluorosulfonic acid, and then contacting this liquid mixture with ammonia gas to produce ammonium salts of specific acidic impurities. However, compounds with chlorosulfonic acid groups -SO2Cl having lower pKas (e.g., CSA or HCFSI) may not be selectively removed by this process. In addition, this method requires the use of toxic, corrosive, and flammable ammonia gas.

[0010] Chinese Patent No. 113912028 of SHENZHEN XINCHEN NEW ENERGY TECH CO LTD. discloses a method for purifying HFSI that is said to reduce the chlorine impurity content, and this method comprises (1) adding an acid or a salt thereof to the crude HFSI product under nitrogen protection and heating the reaction while stirring, and (2) distillation / rectification under pressure to obtain HFSI with a low chloride content. The acid may be an inorganic acid (e.g., concentrated sulfuric acid, sulfamic acid, etc.) or an organic acid (e.g., oxalic acid, citric acid, tartaric acid, etc.). However, in this document, water is disclosed as an undesirable compound that should be limited and should not exceed 3% in the organic acid. Also, in this document, organic acids and inorganic acids are not distinguished.

[0011] Therefore, in the art, there is a lack of improved, efficient, and economically viable methods for removing impurities, specifically chlorides, from HFSI that can supply high-purity HFSI for use as a raw material in the production of lithium bis(fluorosulfonyl)imide without using toxic, hazardous, or harmful solvents / reactants. [Overview of the project]

[0012] One objective of the present invention is (i) Formula (I) F-SO2-NH-SO2-R 1 (I) Compound (wherein R1 represents F or Cl, preferably R 1 (is F) (ii) One or more target impurities which are chlorides having at least one -SO2Cl moiety, A method for forming a purified HFSI mixture [purified mixture (P-HFSI)] by at least partially removing one or more target impurities, which are chlorides having at least one -SO2Cl moiety, from a crude bis(fluorosulfonyl)imide (HFSI) mixture [crude mixture (C-HFSI)] containing, Step (a) - A step of melting the crude mixture (C-HFSI) at a temperature exceeding the melting point of the compound of formula (I) to obtain a molten mixture [molten mixture (M-FSI)]; Step (b) - The crude mixture (M-HFSI) is brought into contact with (b1) water, or (b2) an acidic aqueous solution containing water and at least one inorganic acid (the amount of water is a maximum of 50 equivalents relative to the total equivalent amount of target impurities present in the crude mixture (C-HFSI)). A step of at least partially hydrolyzing the target impurity which is the chloride; and Step (c) - A step of removing at least partially the target impurity, which is the hydrolyzed chloride, to obtain a purified mixture [purified mixture (P-HFSI)]; Regarding methods including

[0013] Surprisingly, the applicant found that the method detailed above has the following advantages: - A high-purity compound of formula (I), such as HFSI, is provided, thereby simplifying the downstream purification process in the production of FSI salts. - No solvents are used (sustainability, HSE, and quality of the final product). - Only hydrogen chloride and sulfuric acid derivatives, which can be easily separated (e.g., by distillation), are produced as by-products. - High purification rate of chlorosulfonyl derivatives. - Liquid-phase process (no need to manage solids). - Inorganic acids containing water are inexpensive, easy to supply to the reactor (liquid), and used in small quantities. - React under mild conditions (room temperature, atmospheric pressure). - Potential metal contaminants are removed by subsequent distillation. - An aqueous solution is added in a fed-batch manner to control the exothermic hydrolysis reaction.

Mode for Carrying Out the Invention

[0014] In the present disclosure: - Expressions such as “… to … included in” and “in the range of … to …” should be understood to include the limits; - Any description, even if described in relation to a specific embodiment, is applicable to other embodiments of the present invention and is interchangeable with them, - When an element or component is said to be included in and / or selected from a list of listed elements or components, in the relevant embodiments explicitly contemplated herein, the element or component can be any one of the individual listed elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components, and it should be understood that any element or component listed in the list of elements or components can be omitted from such a list, - Any enumeration in this specification of numerical ranges by endpoints includes all numbers included within the enumerated range and the endpoints of the range and equivalents.

[0015] Step (a) of the method according to the present invention consists of melting the crude compound of formula (I), preferably melting bis(fluorosulfonyl)imide, and bis(fluorosulfonyl)imide, that is, HFSI, can be used as a raw material. This can be represented by the formula: F-SO2-NH-SO2-F.

[0016] As described above, the crude mixture (C-HFSI) contains one or more target impurities, which are chlorides having at least one -SO2Cl moiety. Impurities that are chlorides having -SO2Cl moieties and are advantageous to be removed at least partially by the method of the present invention include, in particular, bis(chlorosulfonyl)imide, (chlorosulfonylfluorosulfonyl)imide, sulfamoyl chloride (NH2SO2Cl), chloride sulfonylimide oligomers (such as F-SO2-NH-SO2-NH-SO2-Cl), and chlorosulfonic acid.

[0017] The content of the target impurity, which is chloride, in the crude mixture (C-HFSI) is not particularly limited. The method of the present invention is effective in removing at least partially a variable amount of the target impurity. However, it is generally understood that the crude mixture (C-HFSI) may contain the target impurity, which is chloride, in an amount of at least 500 ppm, preferably at least 1000 ppm, and more preferably at least 1500 ppm. Although there is no particular upper limit, it is practical that the crude mixture (C-HFSI) may contain the target impurity, which is chloride, in an amount of up to 10000 ppm, preferably up to 8000 ppm, and more preferably up to 5000 ppm.

[0018] According to the present invention, in step (a), a crude mixture (C-HFSI) containing the compound of formula (I) and one or more target impurities which are chlorides is melted by raising the temperature to a temperature above the melting point of compound (I). The melting point of HFSI is approximately 17°C, which means that in step (a), if compound (I) is HFSI, it is heated to a temperature above approximately 17°C.

[0019] The choice of temperature is not particularly important, as long as an appropriate melt viscosity is obtained to supply the molten crude mixture (C-HFSI) in process (b).

[0020] Typically, the temperature in step (a) is in the range of 17°C to 120°C, preferably 20°C to 80°C, and more preferably 25°C to 50°C.

[0021] Typically, the crude mixture (C-HFSI) is melted in a protective atmosphere, particularly in a substantially moisture-free atmosphere. The moisture content in step (a) is usually maintained at less than 5,000 ppm, more preferably less than 1,000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, and even more preferably less than 50 ppm relative to the compound of formula (I).

[0022] As mentioned above, step (b) is typically carried out in a substantially diluent-free state. This means that no diluent is added, or if any residual diluent is present, its amount is less than 1% by weight of the total weight of the molten mixture (M-HFSI).

[0023] As previously stated, step (b) of the present invention is substantially a diluent-free step. In other words, during the reaction of step (b), the mixture (M-HFSI) contains either no solvent / diluent at all, or only a very small amount of diluent (also called solvent). It is particularly advantageous to carry out step (b) without adding additional diluent. In fact, using a diluent during such a step would mean that the solvent would need to be removed after the reaction in order to obtain the purest possible product that can be used for battery applications. The step of removing the diluent increases the complexity of the industrial process and the overall cost. It is possible to avoid potentially harmful reactions between HFSI, its impurities, or hydrogen chloride, which is a by-product formed in step (b), and any diluent that may be used. In addition, because step (b) does not require a step of removing the diluent, the present invention provides a simpler purification process as a whole, significantly reducing the complexity of the industrial process and the overall cost.

[0024] Preferably, the amount of diluent is less than 0.5% by weight, less than 0.1% by weight, less than 0.01% by weight, or less than 0.001% by weight, based on the total weight of the crude mixture (M-HFSI).

[0025] Diluents that are usually avoided include, for example, polar aprotic solvents, which can be selected from the following group: - Cyclic and acyclic carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, - Cyclic and acyclic esters, e.g., gamma-butyrolactone, gamma-valerolactone, methyl formate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, isopropyl acetate, propyl propionate, butyl acetate, - Cyclic and acyclic ethers, e.g., diethyl ether, diisopropyl ether, methyl-t-butyl ether, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, - Amide compounds, e.g., N,N-dimethylformamide, N-methyloxazolidinone, - Sulfoxide and sulfone compounds, such as sulfolane, 3-methylsulfolane, dimethyl sulfoxide, - Cyano, nitro, chloro, or alkyl-substituted alkanes or aromatic hydrocarbons, such as acetonitrile, valeronitrile, adiponitrile, benzonitrile, nitromethane, and nitrobenzene.

[0026] As described above, in step (b), the molten mixture (M-HFSI) is brought into contact with (b1) water, or (b2) an acidic aqueous solution containing water and at least one inorganic acid.

[0027] Step (b) can be carried out in any type of reaction vessel in which the molten mixture (M-HFSI) can be brought into contact with (b1) or (b2). Typically, a stirring vessel particularly suitable for ensuring sufficient contact between the molten HFSI and (b1) or (b2) can be used. Furthermore, the vessel does not need to be equipped with stirring means, but it may be equipped with other means to ensure such sufficient contact in the molten mixture (M-HFSI), such as means for circulating the molten mixture (M-HFSI). Thus, the vessel can have any suitable three-dimensional shape, including cylindrical or tubular. The parts of the vessel intended to come into contact with the molten mixture (M-HFSI) can be made of corrosion-resistant materials such as alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon, and tungsten, sold under the Hastelloy® brand, or nickel, chromium, iron, and manganese alloys with added copper and / or molybdenum, sold under the names Inconel® or Monel®, more specifically Hastelloy C276 or Inconel 600, 625, or 718 alloys. Stainless steels such as austenitic steel, more specifically austenitic chromium-nickel stainless steel containing an intentional amount of molybdenum, can also be selected, which enhances general corrosion resistance and particularly improves pitting corrosion resistance to chloride ion solutions, and is called SS316, or its SS316L version, which is an ultra-low carbon version of SS316 that minimizes harmful carbide deposition during welding. Steels having a nickel content of up to 22% by weight, preferably 6% to 20%, and more preferably 8% to 14%, can be used. 304 and 304L steels have a nickel content that varies from 8% to 12%, and 316 and 316L steels have a nickel content that varies from 10% to 14%. Containers made of or coated with polymer compounds resistant to corrosion of the molten mixture (M-HFSI) may also be used. Examples of such materials include PTFE (polytetrafluoroethylene) or PFA (perfluoroalkyl resin). Glassware may also be used.Using homogeneous materials would not be outside the scope of this invention. Other materials that may be suitable for contact with the molten mixture (M-HFSI) include graphite derivatives and ceramic materials.

[0028] While not bound by this theory, the applicant believes that during step (b), the water added as (b1) or (b2) causes selective hydrolysis of the -SO2Cl groups contained in the target impurity, which is a chloride present in the molten mixture (M-HFSI), according to the following reaction pathway. a. ClSO3H + H2O → H2SO4 + HCl b.ClSO2-NH-SO2Cl+H2O→HO-SO2-NH2+H2SO4+HCl c.ClSO2-NH-SO2F+H2O→HO-SO2-NH-SO2F+HCl

[0029] Because the -SO2F group is very unsensitive to hydrolysis, hydrolysis occurs selectively and does not substantially affect the compound of formula (I), especially HFSI. Furthermore, all hydrolysis products formed have volatility / boiling points that are significantly different from the compound of formula (I), especially HFSI, thus facilitating further purification steps.

[0030] As mentioned above, water can be added as is, i.e., according to embodiment (b1), or, in some cases, it may be beneficial to add water as an aqueous solution of an inorganic acid, according to embodiment (b2). In this embodiment, since water is added essentially diluted with the inorganic acid, the basicity of the water itself decreases, and as a result, the hydrolysis reaction becomes kinetically and thermodynamically unfavorable. This method reduces the exothermic nature of the reaction, which is advantageous in reducing by-decomposition reactions.

[0031] The inorganic acid is preferably selected from the group consisting of (i) hydrogen acids of formula HX (where X is a halogen selected from Cl, F, Br, and I), (ii) sulfuric acid, (iii) phosphoric acid and polyphosphoric acid, (iv) nitric acid, and (v) boric acid.

[0032] Preferably, the inorganic acid can be selected from the group consisting of (i) hydrogen acids of formula HX (where X is a halogen selected from Cl, F, Br, and I) and (ii) sulfuric acid.

[0033] In case (b2), a concentrated inorganic acid solution is usually used. In the case of hydrochloric acid, which is the preferred acid of formula HX, a concentration of at least 15% by weight, preferably at least 20% by weight, and more preferably at least 30% by weight in water is advantageously used. Fuming hydrochloric acid at a concentration of up to 38% by weight in water can be used. In the case of sulfuric acid, a high-concentration solution containing up to 98% by weight of sulfuric acid in water can be used. Although aqueous sulfuric acid solutions having a concentration of about 96% by weight in water have been found to yield advantageous results, lower concentrations of sulfuric acid solutions may also be effective and can advantageously limit the total amount of undiluted sulfuric acid used to supply water in step (b).

[0034] Water (b1) or a mixture (b2) is typically supplied to the reaction vessel in step (b) in liquid form. Conventional means for supplying liquid reactants to a liquid (molten) reaction mass can be advantageously used.

[0035] As mentioned above, during step (b), gaseous byproducts such as HCl may be generated by hydrolysis (regardless of whether (b1) or (b2) is used). HCl can be removed from the molten mixture (M-HFSI) by evacuating the reaction vessel while step (b) is being performed. According to this embodiment, an inert gas stream, such as anhydrous nitrogen or anhydrous air, can be used to facilitate the removal of HCl from the molten mixture (M-HFSI). Alternatively, the removal of HCl can be facilitated by operating under reduced pressure, i.e., at a pressure lower than the ambient pressure (1 bar). This can be achieved by connecting the vessel containing the molten mixture (M-HFSI) to a suction device.

[0036] Although the amount of HCl produced by the hydrolysis of the target impurity, which is a chloride, is relatively limited, it can be recovered by methods known in the art for its effective utilization.

[0037] Step (b) is typically carried out at a temperature ranging from about 17°C, which is the melting point of compound (I), preferably the melting point of HFSI, to 100°C, preferably 20°C to 50°C, and more preferably 20°C to 30°C.

[0038] As mentioned above, the amount of water (via (b1) or (b2)) needs to be controlled. In fact, compounds of formula (I), such as HFSI, are susceptible to hydrolysis, albeit at a slow reaction rate, so the stoichiometric amount of water (via (b1) or (b2)) is important.

[0039] Excess water (after (b1) or (b2)) may be advantageous for promoting hydrolysis. Consistently, the amount of water may be up to 50 equivalents, preferably up to 25 equivalents, and more preferably up to 10 equivalents, based on the total equivalent amount of target impurities present in the crude mixture (C-HFSI). However, to avoid undesirable hydrolysis reactions of the compounds of formula (I), particularly hydrogen bis(fluorosulfonyl)imide, an amount of up to 5 equivalents, preferably up to 4 equivalents, and more preferably up to 3 equivalents, based on the total equivalent amount of target impurities present in the crude mixture (C-HFSI), is preferred.

[0040] At least equimolar amounts must be used. However, since water may be consumed by other hydrolysis reactions that may affect other hydrolyzable impurities that may be present in the crude mixture (C-HFSI), preferably the amount is at least 1.2 equivalents and at least 1.5 equivalents based on the total equivalent amount of target impurities present in the crude mixture (C-HFSI). Very good results were obtained when the amount of water was adjusted to a range of 1.0 to 3.0 equivalents, preferably 1.5 to 2.5 equivalents, based on the total equivalent amount of target impurities present in the crude mixture (C-HFSI).

[0041] The reaction in step (b) can be carried out in a batch, semi-batch, or continuous manner. In the batch process, the crude mixture (C-HFSI) is placed in a container, melted to obtain a molten mixture (M-HFSI), and then (b1) and / or (b2) are added to the molten mixture (M-HFSI), and the reaction can be carried out until the reaction is complete (for example, until the generation of HCl is no longer detected). In the semi-batch process, the crude mixture (C-HFSI) is placed in a container, and after performing the melting step (a) on it, it is gradually reacted with (b1) or (b2) that is added stepwise, little by little, or continuously by continuous addition, and the molten mixture (M-HFSI) can be reacted until the addition of (b1) and / or (b2) is complete. Furthermore, instead, the molten mixture (M-HFSI) and (b1) and / or (b2) can be continuously fed into the reaction vessel simultaneously.

[0042] Step (c) includes at least partially removing the hydrolyzed compound formed in step (b) to obtain a purified mixture [purified mixture (P-HFSI)]. The purified mixture (P-HFSI) is usually obtained as a liquid phase.

[0043] The step (c) of removing the hydrolyzed compound can be carried out according to standard techniques.

[0044] Step (c) can include a preliminary step (c0) of contacting the mixture obtained in step (b) with at least one salt (S) of the formula M p X p or M p 2(SO4) p where M p is a metal cation of valence p or an ammonium cation of valence p = 1, X is a halide, preferably a halide selected from Cl and Br, and the amount of the salt (S) is 0.9 to 10 equivalents per equivalent of the target impurity which is chloride present in the crude mixture (C-HFSI).

[0045] In fact, since the water added as (b1) and / or (b2) is thought to selectively hydrolyze the -SO2Cl group to the sulfonic acid group as described above, step (c0) may be useful to convert the acid compound into a salt (formula -SO3). p M p Their volatility can be significantly reduced by converting them to the corresponding sulfonates that have the group.

[0046] As mentioned above, the salt (S) used in step (c0) can be a halide or a sulfate. However, although sulfates are effective, halides can produce hydrogen acids as reaction products that can be easily removed / separated, so halides are sometimes preferred.

[0047] M p This is the equation NH4 for p=1. + It can be an ammonium cation. However, to improve thermal stability, it is preferably an alkali metal cation or an alkaline earth metal cation. p It is more preferable that M is selected from alkali metal cations. p It is most preferably Li, Na, and K, and more preferably Na and K.

[0048] Sulfates such as Na2SO4, K2SO4, NaHSO4, and KHSO4 can be used as needed.

[0049] The halide may be any halide, including I and Br, but Cl and F are preferred.

[0050] formula M p X p The salts (S) are favorably NH4Cl, LiCl, LiF, KCl, KF, NaCl, NaF, RbCl2, RbF 2、A selection is made from the group consisting of CaCl2, CaF2, CsCl2, and CsF2, and as mentioned above, alkali metal salts are preferred. Therefore, in these preferred embodiments, LiCl, LiF, KCl, KF, NaCl, and NaF are used, and KCl, KF, NaCl, and NaF are more preferably used.

[0051] In step (c0), the salt (S) is typically brought into contact with the solid molten mixture (M-HFSI) obtained in step (b).

[0052] The salt (S) is usually supplied to the reaction vessel of process (c0) in powder form. The powdered salt (S) can be supplied to the reaction vessel of process (c0) via a powder conveyor, which may be a pneumatic conveying means including both pressurized and vacuum pneumatic means, which may be a screw conveying means, such as an auger conveying means, a helix conveying means, a worm conveying means, or a flexible screw conveying means; a belt conveying means may be used; a vibrating conveying means may be used; or other means configured to distribute the powdered salt (S) into the vessel (c0). Alternatively, (S) can be supplied as a slurry, such as Na2SO4 + NaHSO4 in anhydrous H2SO4.

[0053] When the salt (S) is supplied to process (b) in powder form, it is advantageous that it has an average particle size of less than 1000 μm.

[0054] Typically, step (c) may include, in addition to step (c0), a distillation step to obtain a purified mixture (P-HFSI), the distillation step may be performed directly on the product obtained from step (b), or after step (c0), and / or after completing a preliminary separation step, such as any solid / liquid separation, if the product from step (b) and / or (c0) contains suspended solids.

[0055] The fractional distillation step is preferably carried out in step (c), and the product obtained from the previous step is distilled at a temperature of 20 to 170°C, preferably 25 to 100°C, and more preferably 25 to 80°C.

[0056] Distillation, particularly fractional distillation, may be carried out at atmospheric pressure or under reduced pressure, and the distillation temperature will be adjusted by those skilled in the art according to the applied pressure.

[0057] Fractional distillation may be carried out continuously or in batches.

[0058] When fractional distillation is performed in a batch process, heating the products obtained from the previous step in a boiler allows for the initial evaporation and separation of light fractions, such as those containing HCl (if present). By increasing the boiler temperature, distillation of the purified mixture (P-HFSI) containing HFSI is then achieved. Because the hydrolysis products have low volatility, they are usually removed as residues in the boiler.

[0059] When fractional distillation is performed continuously, a distillation column is usually used; the purified mixture (P-HFSI) containing the compound of formula (I), for example HFSI, is usually recovered from the top of the column; the light fraction, for example, containing HCl (if present), can be discharged from the top, while the hydrolyzed compound is removed from the bottom of the column as a bottom product.

[0060] As mentioned above, the content of the target impurity, which is chloride, in the purified mixture (P-HFSI) is lower than in the crude mixture (C-HFSI). Preferably, the target impurity, which is chloride, is present in the purified mixture (P-HFSI) in an amount of less than 1000 ppm, preferably less than 500 ppm, and more preferably less than 150 ppm.

[0061] If any disclosure of a patent, patent application, or publication incorporated herein by reference conflicts with any description in this application to such an extent that it obscures certain terms, the description herein shall prevail.

[0062] The present invention will be further described in the following examples, which are provided for illustrative purposes only and are not intended to limit the scope of this specification or the claims in any way. [Examples]

[0063] The HFSI was supplied by PROVISCO CS.

[0064] ClSO3H was supplied by SIGMA-ALDRICH (product ID 571024, batch #BCCF1678).

[0065] 96.4% of the H2SO4 was supplied from VWR (product ID 20700.298, batch #18C064006).

[0066] The target impurities, which are chlorides, were determined as chloride anions after hydrolysis was complete by IC using a Dionex ICS-3000 system equipped with a conductivity detector having the following components: - Columns: AS20 4*250mm Analytical and AG20 4*50mm Guard - Suppressor: ASRS300-4mm, external water refill type.

[0067] Cl in HFSI - The amount was quantitatively measured after calibration using a commercially available standard solution.

[0068] Example: Selective removal of ClSO3H from HFSI 100.1 g of HFSI, specifically containing 0.557 g of ClSO3H, was placed in a 100 mL glass Schott bottle under a dry argon atmosphere. The container was fitted with a PTFE three-neck cap and a PTFE magnetic stirrer. Dry argon was supplied to the reactor, and the gas outlet was connected to a KOH aqueous solution scrubber. The chloride concentration, measured by ion chromatography, was found to be 1004 ppm.

[0069] Stirring was started at 600 rpm, and then 4.45 g of 96.4% H2SO4 was gradually added over 10 minutes using a syringe and a cannula connected to a syringe pump. After that, 19 A sample of the medium was taken for 1F NMR analysis. The chloride concentration was found to have decreased to 149 pm.

Claims

1. (i) Formula (I) F-SO ２ -NH-SO ２ -R １ Compound (I) (wherein R １ represents F or Cl, preferably R １ (is F) (ii) at least one -SO ２ One or more target impurities that are chlorides having a Cl moiety, From a crude bis(fluorosulfonyl)imide (HFSI) mixture containing [crude mixture (C-HFSI)], at least one -SO ２ A method for forming a purified HFSI mixture [purified mixture (P-HFSI)] by at least partially removing one or more target impurities that are chlorides having a Cl moiety, Step (a) - A step of melting the crude mixture (C-HFSI) at a temperature exceeding the melting point of the compound of formula (I) to obtain a molten mixture [molten mixture (M-FSI)]; Step (b) - The crude mixture (M-HFSI) is brought into contact with (b1) water, or (b2) an acidic aqueous solution containing water and at least one inorganic acid (the amount of water is a maximum of 50 equivalents relative to the total equivalent amount of target impurities present in the crude mixture (C-HFSI)). A step of at least partially hydrolyzing the target impurity which is the chloride; and Step (c) – A step of removing at least partially the target impurity, which is the hydrolyzed chloride, to obtain a purified mixture [purified mixture (P-HFSI)]; A method that includes this.

2. - The inorganic acid is favorably selected from the group consisting of (i) a hydrogen acid of formula HX (where X is a halogen selected from Cl, F, Br, and I), (ii) sulfuric acid, (iii) phosphoric acid and polyphosphoric acid, (iv) nitric acid, and (v) boric acid, preferably the inorganic acid is selected from the group consisting of (i) a hydrogen acid of formula HX (where X is a halogen selected from Cl, F, Br, and I), and (ii) sulfuric acid; and / or --SO ２ The target impurity, which is the chloride having a Cl moiety, is selected from the group consisting of bis(chlorosulfonyl)imide, (chlorosulfonylfluorosulfonyl)imide, sulfamoyl chloride (NH ２ SO ２ Cl), F-SO ２ -NH-SO ２ -NH-SO ２ -Cl and other sulfonyl chloride imide oligomers, and chlorosulfonic acid; The method according to claim 1.

3. In step (a), the crude mixture (C-HFSI) is melted by raising the temperature to a level above the melting point of compound (I); compound (I) is of formula: F-SO ２ -NH-SO ２ The method according to claim 1 or 2, wherein if it is an HFSI of -F, it is melted at a temperature above 18°C; and / or the crude mixture (C-HFSI) is melted in a protective atmosphere, particularly in a substantially moisture-free atmosphere; and the moisture content in step (a) is maintained to typically less than 5,000 ppm, more preferably less than 1,000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, and even more preferably less than 50 ppm with respect to the compound of formula (I).

4. The method according to any one of claims 1 to 3, wherein step (b) is carried out in substantially the absence of a diluent, and no diluent is added, or if a diluent is present, the amount is less than 1% by weight based on the total weight of the molten mixture (M-HFSI).

5. During step (b), HCl is generated and removed from the molten mixture (M-HFSI) by evacuating the reaction vessel, and step (b) is preferably, - An inert gas stream is used to facilitate the removal of HCl from the molten mixture (M-HFSI); and / or - The removal of HCl is facilitated by operating under reduced pressure. The method according to any one of claims 1 to 4.

6. The method according to any one of claims 1 to 5, wherein step (b) is carried out at a temperature from the melting point of compound (I), more specifically at about 17°C and / or up to 100°C if compound (I) is an HFSI, preferably at 20°C to 50°C, and more preferably at 20°C to 30°C.

7. The method according to any one of claims 1 to 6, wherein the amount of water added as (b1) and / or (b2) is a maximum of 25 equivalents, more preferably a maximum of 10 equivalents, based on the total equivalent amount of target impurities present in the crude mixture (C-HFSI); and / or the amount of water is a maximum of 5 equivalents, preferably a maximum of 4 equivalents, more preferably a maximum of 3 equivalents, based on the total equivalent amount of target impurities present in the crude mixture (C-HFSI).

8. The reaction in step (b) - A batch process in which the crude mixture (C-HFSI) is placed in a container, melted to obtain the molten mixture (M-HFSI), and then (b1) and / or (b2) are added to the molten mixture (M-HFSI) and the reaction is carried out until the reaction is complete; or - A semi-batch method in which the crude mixture (C-HFSI) is placed in a container, a melting step (a) is performed thereon, and then (b1) or (b2) is gradually added stepwise, little by little, or continuously, and the molten mixture (M-HFSI) is reacted until the addition of (b1) and / or (b2) is complete; or - In a continuous process, the molten mixture (M-HFSI) and (b1) and / or (b2) are simultaneously and continuously supplied to the reaction vessel; The method according to any one of claims 1 to 7.

9. Step (c) is the mixture obtained in step (b), which is given formula M ｐ X ｐ or M ｐ ２ (SO ４ ) ｐ The process includes a preliminary step (c0) of contacting at least one salt (S) of M in the formula ｐ The method according to any one of claims 1 to 8, wherein is a metal cation with valency p or an ammonium cation with valency p=1, X is a halide, preferably selected from Cl and Br, and the amount of salt (S) is 0.9 to 10 equivalents for each equivalent of the target impurity, which is a chloride present in the crude mixture (C-HFSI).

10. M in salt (S) ｐ However, formula NH ４ ＋ The ammonium cation (p=1), alkali metal cation, or alkaline earth metal cation is preferred, and is preferably M ｐ It is selected from alkali metal cations, most preferably M ｐ The method according to claim 10, wherein is any of Li, Na, and K, and more preferably Na and K.

11. Formula M ｐ X ｐ The aforementioned salt (S) is NH ４ Cl, LiCl, LiF, KCl, KF, NaCl, NaF, RbCl ２ , RbF ２、 CaCl ２ CaF ２ , CsCl ２ , CsF ２ The method according to claim 10, wherein the method is selected from the group consisting of; preferably selected from the group consisting of LiCl, LiF, KCl, KF, NaCl, and NaF; most preferably selected from the group consisting of KCl, KF, NaCl, and NaF.

12. Step (c), in some cases, includes, in addition to step (c0), a distillation step, preferably a fractional distillation step, to obtain a purified mixture (P-HFSI). - The product obtained from the previous step is distilled at a temperature of 20 to 170°C, preferably 25 to 100°C, more preferably 25 to 80°C, and / or - The distillation is carried out under atmospheric pressure or reduced pressure. The method according to any one of claims 1 to 11.

13. The method according to claim 12, wherein step (c) is a fractional distillation step carried out continuously, a distillation column is used, a purified mixture (P-HFSI) containing the compound of formula (I) is recovered from the top of the column, and the hydrolyzed compound is removed from the bottom of the column as a bottom product.

14. The method according to any one of claims 1 to 13, wherein the content of the target impurity, which is a chloride, in the purified mixture (P-HFSI) is less than 1000 ppm, preferably less than 500 ppm, and more preferably less than 150 ppm.

15. The method according to any one of claims 1 to 14, wherein step (b) is carried out in a stirring vessel that ensures sufficient contact between the molten HFSI and (b1) and / or (b2).

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