Process for purifying bis(fluorosulfonyl)imide salts

Abstract

The present invention relates to a process for purifying a solution of a bis(fluorosulfonyl)imide salt.

Description

[Technical Field]

[0001] Cross-reference to related patent applications This application claims priority to European Patent Application No. 22306894.1, filed December 15, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a process for purifying a solution of a bis(fluorosulfonyl)imide salt. [Background technology]

[0003] Bis(fluorosulfonyl)imide (FSI) and its salts, particularly the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are useful compounds in a variety of technical fields, including for the production of battery electrolytes.

[0004] Several methods for preparing FSI and its salts have been described in the art. Among the various techniques described, most of the preparation methods involve a fluorination reaction in which a fluorinating agent is reacted with a suitable compound in a solvent.

[0005] Much effort has been made in the art to improve the processes for producing FSI salts and their intermediate compounds, particularly with respect to the purity and yield of the intermediates and final compounds, as well as reducing the cost of the overall production process.

[0006] FSI salts are also known to be affected by water and can react to form unwanted species that significantly degrade the quality and electrochemical properties of the FSI salt.

[0007] EP 3494085 (in the name of Arkema) discloses a method for drying and purifying LiFSI salts in an organic solvent (S1) and compositions containing LiFSI and water in an amount of 5 to 45 ppm by weight. The method specifically comprises the steps of: a) adding deionized water to extract LiFSI and form an aqueous solution of the salt; a') optionally concentrating such an aqueous solution; b) extracting LiFSI from the aqueous solution with an organic solvent (S2) and forming an azeotrope with water; c) concentrating the LiFSI by evaporating the organic solvent; and d) optionally crystallizing the LiFSI. Summary of the Invention

[0008] Applicant recognizes that despite all attempts in the art, there remains a need for a process for purifying salts of bis(fluorosulfonyl)imides (salts-FSI), particularly for removing water, that is efficient and can be easily scaled up from laboratory scale to pilot scale and industrial scale.

[0009] More specifically, the Applicant faced the problem of providing a process that makes it possible to purify salt-FSI without its degradation and with a high recovery yield, even when applied on an industrial scale.

[0010] Surprisingly, the applicant has developed a new process for purifying salts of FSI that meets the above criteria and needs and that can be easily scaled up from laboratory scale to pilot plants and industrial plants.

[0011] An advantage of the process of the present invention is that the total purification time is very short: for example, even if the process lasts for 5 or 10 hours or even longer, no degradation of the starting salt-FSI occurs and the entire process can last for less than an additional hour.

[0012] Another advantage of the process of the present invention is that the solvent and water obtained as waste can be further recycled. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 depicts a schematic diagram of the laboratory setup used in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] In this application: - Numerical ranges are inclusive unless otherwise stated. - any description, even if made in relation to a particular embodiment, is applicable to and interchangeable with other embodiments of the invention; - when an element or component is said to be included in and / or selected from a list of enumerated elements or components, it is to be understood that in the relevant embodiments expressly contemplated herein, the element or component may be any one of the individually enumerated elements or components, or may be selected from a group consisting of any two or more of the explicitly enumerated elements or components, and that any element or component enumerated in a list of elements or components may be omitted from such list; - The term "ppm" (or "parts per million") refers to weight fraction relative to the total weight of the composition, unless otherwise specified.

[0015] The present invention relates to a method for purifying a composition comprising a salt of a bis(fluorosulfonyl)imide [salt-FSI], said composition being in the form of a solution, said method comprising: (I) A composition [composition (COMP)], at least one solvent [solvent (S1)], - water in an amount of at least 100 ppm; - at least one salt of bis(fluorosulfonyl)imide [Salt-FSI] in a first concentration (Salt-FSI 1); providing a composition [composition (COMP)] comprising: (II) filling the composition (COMP) into a container; (III) subjecting the composition (COMP) to distillation; (IV) A composition [composition (COMP-F)], at least one organic solvent [solvent (S1)], - water in an amount less than 100 ppm; - at least one salt-FSI in a second concentration (salt-FSI 2), said second concentration (salt-FSI 2) being higher than said first concentration (salt-FSI 1) in the composition (COMP); and recovering a composition comprising the compound [composition (COMP-F)]. Includes.

[0016] Preferably, the at least one salt-FSI is a salt of bis(fluorosulfonyl)imide with one of lithium, sodium, potassium, zinc or magnesium, with lithium, sodium and potassium being more preferred.

[0017] The term "charging" or "charging" as used herein means that a composition described herein is placed in a suitable container (also called a receiver or apparatus) for carrying out a subsequent distillation step. In the context of the present invention, "charging a composition into a container" is equivalent to "adding" or "feeding" or "injecting" a composition into a container.

[0018] The term "recovering" as used herein means that the composition (COMP-F) is removed or taken from a container in which a previous step is carried out.

[0019] The term "vessel" as used herein means a vessel that is highly suitable for the process of the present invention, i.e., a vessel that is adapted to withstand the pressures and temperatures used in the process of the present invention and the potentially corrosive nature of the reactants and products involved in the process.

[0020] According to a preferred embodiment, steps (II) and (III) are carried out simultaneously.

[0021] More preferably, steps (II), (III) and (IV) are carried out simultaneously.

[0022] Even more preferably, steps (I) to (IV) are carried out simultaneously.

[0023] The configuration of the apparatus for carrying out the method of the present invention is not limited. The apparatus can advantageously be configured as a batch, semi-batch or continuous distillation system.

[0024] Preferably, for carrying out the process of the present invention, such a vessel is preferably a vessel such as a distillation column or a boiler equipped with a distillation column.

[0025] Preferably, the composition (COMP) comprises salt-FSI at a concentration of about 0.1 to about 35 wt %, more preferably about 0.5 to 30 wt %, and even more preferably 1 to 20 wt %, based on the total weight of the composition (COMP).

[0026] Preferably, said composition (COMP) comprises water in an amount of at least 120 ppm, more preferably at least 150 ppm, and even more preferably at least 500 ppm, based on the total weight of the composition (COMP).

[0027] The maximum amount of water in the composition (COMP) is not limited, as long as the water content of the composition (COMP) is compatible with the method according to the present invention. However, the composition (COMP) preferably contains water in an amount of up to 5,000 ppm, more preferably up to 30,000 ppm, based on the total weight of the composition (COMP).

[0028] Preferably, said at least one solvent (S1) is selected from the group consisting of optionally fluorinated carbonate solvents such as ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, lactones such as γ-butyrolactone, γ-valerolactone, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxane, The solvents selected from the group comprising ethers such as methyl formate, methyl acetate, ethyl acetate, methyl propionate, isopropyl acetate, n-butyl acetate, n-propyl propionate, 2,2-difluoroethyl acetate, optionally fluorinated esters such as sulfolane, 3-methylsulfolane, dimethyl sulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, nitromethane and nitrobenzene.

[0029] More preferably, said solvent (S1) is chosen from optionally fluorinated carbonate solvents and esters.

[0030] Even more preferred solvents (S1) are selected from dimethyl carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, ethyl acetate, isopropyl acetate and n-butyl acetate.

[0031] According to a more preferred embodiment, said solvent (S1) is chosen from ethyl methyl carbonate (EMC), dimethyl carbonate and n-butyl acetate.

[0032] The amount of said at least one solvent (S1) in the composition (COMP) is such that it amounts to 100% by weight of the composition (COMP).

[0033] According to a preferred embodiment, the solvent (S1) is an electronic grade solvent.

[0034] The composition (COMP) may be prepared according to any method known in the art.

[0035] Preferably, the composition (COMP) is obtained in the form of a solution from the manufacturing process and is used as such in step (I) of the process of the invention.

[0036] Alternatively, a predetermined amount of salt-FSI in solid form is dissolved in a suitable organic solvent, which is preferably the solvent (S1) defined above.

[0037] Preferably, step (II) is carried out by pump or gravity.

[0038] In step (II), the composition (COMP) is filled into a container by means of a suitable tool, preferably a nozzle or an injector.

[0039] In step (II), the composition (COMP) can be charged sequentially either semi-continuously or continuously.

[0040] Preferably, the composition (COMP) is continuously filled into the container.

[0041] Alternatively, the composition (COMP) may be semi-continuously filled into the container, e.g., the composition (COMP) may be filled into the container over a period of time, e.g., 30 to 120 seconds, preferably about 60 seconds, and then the filling is stopped for another period of time that may be equal to, shorter than, or longer than the filling time.

[0042] Preferably, step (III) is carried out via a distillation column.

[0043] Preferably, a reflux ratio of water to solvent (S1) of about 0.1 to about 100 or even more is maintained in the upper part of the distillation column.

[0044] Preferably, step (III) is carried out at a pressure of less than 500 mbar abs (0.05 MPa), more preferably less than 300 mbar abs (0.03 MPa), even more preferably less than 150 mbar abs (0.015 MPa) or less than 50 mbar abs (0.005 MPa).

[0045] In step (IV), the composition (COMP-F) is continuously recovered.

[0046] Preferably, step (IV) is carried out by pump or gravity.

[0047] Preferably, the composition (COMP-F) contains salt-FSI at a concentration of about 0.2 to about 70 wt %, more preferably about 1.0 to 60 wt %, and even more preferably 2 to 40 wt %, based on the total weight of the composition (COMP-F).

[0048] Preferably, said composition (COMP-F) comprises water at a concentration of less than 150 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, based on the total weight of the composition (COMP-F).

[0049] Preferably, steps (II) and (III) are carried out simultaneously, and step (IV) is initiated after steps (II) and (III).

[0050] At the end of step (IV) or while step (IV) is in progress, water, optionally mixed with solvent (S1), is obtained as a distillation product, which can advantageously be recycled in a separate method or process.

[0051] Preferably, the composition (COMP-F) comprises at least one other substance. The at least one other substance is preferably: - fluoride (F) in an amount preferably less than 100 ppm, as determined by ion chromatography (IC) - ), and / or - Chloride (Cl) in an amount preferably less than 100 ppm, as measured by IC - ), and / or - Sulfates (SO4) preferably in an amount less than 1,000 ppm as measured by IC 2- ), and / or - Sulfamate (NH2SO3 - ), and / or - Fluorosulfonates (FSO3 - ) is selected from.

[0052] Preferably, the amount of said at least one other substance in the composition (COMP-F) is preferably as follows: - Fluoride (F) in an amount of up to 50 ppm, e.g., less than 40 ppm, less than 30 ppm, less than 25 ppm - ), Chloride (Cl) in an amount of maximum 50 ppm, for example less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm or even less than 8 ppm - ), - Sulfates (SO4 2- ) and different acidic substances. The amount is measured by ion chromatography (IC).

[0053] Preferably, sulfate (SO4 2- ) The acidic substance different from NH2SO 3 - and / or FSO3 - is selected from.

[0054] Preferably, (SO4 2- ) the acidic substance is different from the above in the amount of: - Less than 50 ppm, e.g., less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm or even less than 5 ppm of sulfamate (NH2SO3- ), and / or - Less than 50 ppm, e.g., less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm or even less than 5 ppm of fluorosulfonates (FSO3 - ) is.

[0055] To the extent that the disclosure of any patents, patent applications, and publications incorporated herein by reference contradicts the statements of this application to the extent that a term may be unclear, the statements of this application shall control.

[0056] The present invention will now be described in more detail with reference to the following examples, the purpose of which is illustrative only and is not intended to limit the scope of the present disclosure. [Example]

[0057] Example 1 – Continuous Process A composition in the form of a solution containing LiFSI (10% by weight) in EMC and water in an amount of 2500 ppm relative to the total weight of the composition was continuously fed from a storage vessel through an inlet into a distillation column (1.8 meters high, 5 cm diameter equivalent, packed with structural packing, and containing approximately 20 theoretical plates) preset at 20 mbar abs (0.002 MPa) and 20°C at the distillation column head from a storage vessel through an inlet for 6 hours. The feed was carried out by operating continuously under vacuum at 20 mbar abs (0.002 MPa). At the top of the distillation column, a reflux ratio between water and EMC of approximately 1-2 was used.

[0058] As the distillation proceeded, the solution of LiFSI in EMC was continuously removed from the bottom of the distillation column and EMC / H2O was continuously removed from the top of the distillation column.

[0059] The process was continued for 6 hours, and when steady-state operation was reached, a composition was obtained containing water in the form of a solution of LiFSI (26.3 wt%) in EMC in an amount of less than 20 ppm relative to the total weight of the mixture, as determined by Karl Fischer titration in EMC.

[0060] Example 2 - Batch Process 623 g of a composition in the form of a solution containing LiFSI in EMC (30 wt %) and 1372 g of EMC / HO (3381 ppm water) was fed to a distillation column as described above in Example 1. A total of 1995 g of LiFSI (9.4 wt %) containing water in an amount of 2300 ppm based on the total weight of the composition was fed to the same distillation column.

[0061] The temperature steadily increased from 20 to 27 °C as the process progressed, and distillation was initiated by applying 20 mbar abs (0.002 MPa). Approximately 900 g of a mixture of EMC / HO was distilled with a decreasing water concentration over time, as measured by Karl Fischer titration, until a range of 1100 to 600 ppm was obtained.

[0062] Then, 432 g of EMC containing 25 ppm water was added. Distillation was continued at 20 mbar abs (0.002 MPa) and the temperature increased from 20 to 27 °C until approximately 600 g of a mixture of EMC / HO was distilled, with a water content of 600 to 300 ppm as determined by Karl Fischer titration on the EMC.

[0063] The LiFSI solution obtained at the bottom of the distillation column contained 52 ppm water by KF titration and about 28 wt % LiFSI as determined by NMR.

Claims

1. 1. A method for purifying a composition comprising a salt of bis(fluorosulfonyl)imide [salt-FSI], wherein the composition is in the form of a solution, the method comprising: (I) A composition [composition (COMP)] comprising: at least one solvent [solvent (S1)], water in an amount of at least 100 ppm, - at least one salt of bis(fluorosulfonyl)imide [Salt-FSI] in a first concentration (Salt-FSI 1); providing a composition [composition (COMP)] comprising: (II) filling the composition (COMP) into a container; (III) subjecting the composition (COMP) to distillation; (IV) A composition [composition (COMP-F)], at least one organic solvent [solvent (S1)], water in an amount of less than 100 ppm, - said at least one salt-FSI in a second concentration (Salt-FSI 2), said second concentration (Salt-FSI 2) being higher than said first concentration (Salt-FSI 1) in composition (COMP); and and recovering a composition [composition (COMP-F)] comprising the A method comprising:

2. 2. The method of claim 1, wherein the salt-FSI is a salt of bis(fluorosulfonyl)imide with one of lithium, sodium, potassium, zinc, or magnesium.

3. at least steps (II) and (III) are carried out simultaneously, and / or - The method according to claim 1 or 2, wherein at least steps (II), (III) and (IV) are carried out simultaneously.

4. 4. The method according to any one of claims 1 to 3, wherein said composition (COMP) comprises said salt-FSI in a concentration of 0.1 to 35 wt. %, more preferably 0.5 to 30 wt. %, even more preferably 1 to 20 wt. %, based on the total weight of said composition (COMP).

5. 5. The method according to any one of claims 1 to 4, wherein said composition (COMP) comprises water in an amount of at least 120 ppm, more preferably at least 150 ppm, and even more preferably at least 500 ppm, based on the total weight of composition (COMP).

6. 6. The method according to any one of claims 1 to 5, wherein said composition (COMP) comprises water in an amount of up to 30,000 ppm based on the total weight of the composition (COMP).

7. The solvent (S1) may be selected from the group consisting of optionally fluorinated carbonate solvents such as ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate (EMC), and diethyl carbonate; lactones such as γ-butyrolactone and γ-valerolactone; ethers such as dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, and 4-methyl-1,3-dioxolane; and methyl formate.

7. The process according to any one of claims 1 to 6, wherein the solvent is selected in the group comprising optionally fluorinated esters such as methyl acetate, ethyl acetate, methyl propionate, isopropyl acetate, n-butyl acetate, n-propyl propionate, 2,2-difluoroethyl acetate, and polar aprotic solvents such as sulfolane, 3-methylsulfolane, dimethyl sulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, nitromethane and nitrobenzene.

8. Step (III) is through a distillation column, preferably maintaining a reflux ratio at the top of said column of between 0.1 and 100; and / or 8. The process according to any one of claims 1 to 7, carried out at a pressure of less than 500 mbar abs (0.05 MPa).

9. 9. The method according to any one of claims 1 to 8, wherein the composition (COMP-F) comprises the salt-FSI at a concentration of about 0.2 to about 70 wt. %, more preferably about 1.0 to 60 wt. %, and even more preferably 2 to 40 wt. %, based on the total weight of the composition (COMP-F).

10. The method according to any one of claims 1 to 9, wherein the (COMP-F) comprises water in an amount of less than 150 ppm, preferably less than 100 ppm, more preferably less than 50 ppm, based on the total weight of the composition (COMP-F).

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