Gas phase fluorination method of bis (chlorosulfonyl) imidic acid

Abstract

The present invention relates to a process for the production of bis (fluorosulfonyl) imidic acids, which process is economically viable on an industrial scale and provides a high purity product.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from the prior European patent application No. 22305978.3 filed on July 1, 2022, the entire contents of which are hereby incorporated by reference for all purposes. Technical Field

[0003] The present invention relates to a process for producing bis(fluorosulfonyl)imidic acid which is economically viable on an industrial scale and provides a product of high purity. Background Art

[0004] Fluorosulfonyl imide salts, in particular lithium salts of bis(fluorosulfonyl)imide (LiFSI), are useful compounds for battery electrolytes. Different methods, reactants and intermediates for obtaining LiFSI have been described in the patent literature, notably patent CA 2 527 802 (Université de Montréal), which lists several routes for preparing LiFSI, such as a method for preparing LiFSI in a one-step process starting from bis(chlorosulfonyl)imide (HCSI) using anhydrous hydrogen fluoride (HF):

[0005]

[0006] A two-step method for preparing LiFSI is also known in the art, such as involving the use of a fluorinating agent (e.g., anhydrous hydrogen fluoride (HF)) to fluorinate bis(chlorosulfonyl)imide (HCSI) to bis(fluorosulfonyl)imide (HFSI), followed by the use of a lithiating agent to lithiate HFSI to LiFSI. An example of such a method is disclosed in US 9,725,318, in which HCSI is reacted with anhydrous HF in the presence of a solvent. The reaction time to obtain the HFSI conversion is 18 hours.

[0007] Another known two-step method for preparing LiFSI involves using NH4F(HF) as a fluorinating agent. x The first step of fluorinating bis(chlorosulfonyl)imide (HCSI) to ammonium bis(fluorosulfonyl)imide (NH4FSI) is followed by a second step of lithiation of NH4FSI to obtain the LiFSI product. This method is described, for example, in WO 2017 / 090877 A1 (CLS) and EP 3170 789A1 (Nippon Soda).

[0008] Another known two-step method for preparing LiFSI involves using a lithiating agent to lithiate HCSI in a first step to prepare LiCSI as an intermediate product, and then using a fluorinating agent to fluorinate LiCSI to form LiFSI. For example, KR20200049164 (CLS) relates to a method for preparing LIFSI, which includes reacting HCSI with various lithiating agents in (S1) a solvent to produce LiCSI, and then reacting it directly with an anhydrous fluorinating agent without a purification step. A long list of possible solvents is given in the specification, and dimethyl carbonate is used in the example.

[0009] US2017 / 0183230 discloses a method for converting HCSI into HFSI, the method comprising reacting liquid HCSI with anhydrous gaseous HF under conditions of temperature and pressure sufficient to produce gaseous HFSI. Based on the conversion rate of HCSI, the yield of HFSI obtained by this method is about 80%.

[0010] As is known from the patent documents cited above, the production of bis(fluorosulfonyl)imidic acid is carried out in a solvent or with liquid HCSI in order to disperse the reactive entities to allow these entities to react or to allow unreacted materials to be recovered.

[0011] The applicants have recognized that there is still a need in the art for improved methods of making bis(fluorosulfonyl)imidic acid.

[0012] In particular, the applicant is well aware that the processes disclosed in the prior art require long reaction times and achieve low levels of selectivity. Summary of the invention

[0013] In order to overcome the above-mentioned drawbacks, the Applicant faced the problem of providing a continuous production process for the preparation of bis(fluorosulfonyl)imidic acid having a low residence time and a high level of selectivity.

[0014] Additionally, applicants have addressed the environmental aspects of the route to prepare bis(fluorosulfonyl)imidic acid, thereby providing a process that does not require the use of hazardous solvents, which will minimize the amount of solid / salt waste, and will provide opportunities for by-product valorization.

[0015] Thus, in a first aspect, the present application relates to a process for producing bis(fluorosulfonyl)imidic acid (HFSI), the process comprising the step of contacting gaseous bis(chlorosulfonyl)imidic acid (HCSI) with gaseous anhydrous hydrogen fluoride (HF), wherein the process is carried out in the absence of a solvent.

[0016] The process of the present invention for making bis(fluorosulfonyl)imidic acid (HFSI) is characterized by high conversion and high levels of selectivity, thereby providing HFSI that is particularly suitable for many applications, notably as an intermediate for the preparation of LiFSI for use in battery applications.

[0017] Advantageously, the process of the invention is carried out in the all-gas phase. In other words, the process of the invention is a solvent-free process, which means that no solvent is added to the reaction mixture during the reaction. This is advantageous because, firstly, the step of removing the solvent is avoided, thereby reducing the complexity of the industrial process and its overall cost; secondly, the preliminary step of treating the solvent to reduce its water content is also avoided. In addition, side reactions between HCSI and / or HFSI and the organic solvent are avoided or at least significantly reduced, thereby increasing the overall yield. DETAILED DESCRIPTION

[0018] According to the process of the present invention, gaseous HCSI is reacted with gas-phase anhydrous HF.

[0019] Gas phase HCSI can be prepared by heating solid or molten HCSI to a temperature above the boiling point (Tb) of HCSI. HCSI ) temperature and / or obtained from solid or molten HCSI by reduced pressure vaporization of HCSI.

[0020] Heating the HCSI at any pressure (superatmospheric pressure; about atmospheric pressure; or reduced pressure) can be accompanied by the use of a carrier gas, such as nitrogen. In this way, the partial pressure of the HCSI will be reduced and the vaporization is advantageously more efficient.

[0021] As mentioned above, the boiling point of HCSI (Tb HCSI ) depends on the pressure: boiling point of HCSI or Tb HCSI It is hereby used to specify that the vapor pressure of the HCSI is equal to the pressure surrounding the liquid / molten HCSI and the temperature at which the liquid / molten HCSI becomes vapor.

[0022] Solid or molten HCSI is commercially available or can be produced by any known method, such as:

[0023] - by reacting chlorosulfonyl isocyanate (ClSO2NCO) with chlorosulfonic acid (ClSO2OH) (CSI route);

[0024] - by reacting cyanogen chloride (CNCl) with sulfuric anhydride (SO3) and with chlorosulfonic acid (ClSO2OH); or

[0025] - By reacting aminosulfonic acid (NH2SO2OH) with thionyl chloride (SOCl2) and with chlorosulfonic acid (ClSO2OH) (SFA route).

[0026] When solid HCSI is used as the starting material, the solid HCSI is melted to a temperature above its melting temperature (Tm HCSI ) to obtain HCSI in a molten state (also called liquid state), followed by heating the HCSI to a temperature above its boiling point (Tb) in step b). HCSI ) temperature.

[0027] Preferably, step a) is carried out at a temperature (Ta) suitable for melting the HCSI and maintaining the HCSI in a molten state while minimizing its thermal degradation.

[0028] Step a) at or above the melting point (Tm) of HCSI HCSI ) is carried out at a temperature (Ta). In this case, Ta ≥ Tm HCSI For example, Ta may be equal to or higher than the melting point (Tm) of HCSI. HCSI ) plus 5°C. In this case, Ta ≥ Tm HCSI As another example, Ta may be equal to or higher than the melting point (Tm) of HCSI. HCSI ) plus 10°C. In this case, Ta ≥ Tm HCSI +10.

[0029] It will be appreciated that the melting point of HCSI is affected by the presence and amount of impurities.

[0030] Preferably, step a) is carried out at a temperature (Ta) equal to or higher than 30° C., such as equal to or higher than 37° C., such as equal to or higher than 38° C., equal to or higher than 40° C., equal to or higher than 45° C. or even equal to or higher than 50° C. The temperature Ta is preferably lower than 150° C., more preferably equal to or lower than 100° C. In any case, step a) is carried out at a temperature (Ta) lower than the degradation temperature of the HCSI.

[0031] The liquid HCSI is then further heated to a temperature above its boiling point (Tb) in step b). HCSI ) temperature.

[0032] The liquid HCSI may be suitably vaporized into gaseous HCSI by any means known to those skilled in the art.

[0033] As described, each of step a) and / or step b) can be carried out at above atmospheric pressure, at atmospheric pressure or under reduced pressure. For example, step a) can be carried out at atmospheric pressure, and step b) can be carried out under vacuum at a pressure between 10 and 100000 Pa, preferably between 1000 and 10000 Pa.

[0034] Preferably, in step b) the gaseous HCSI is obtained under reduced pressure under conditions of reducing the HCSI partial pressure, such as by heating in a closed container at an appropriate constant temperature and / or using a carrier gas.

[0035] The container will be selected by one of ordinary skill in the art, with appropriate selection of materials of construction that are resistant to and compatible with the chemicals involved, which are particularly aggressive due to their acidic nature.

[0036] The loading of the liquid HCSI into the closed container can be suitably carried out with a carrier gas through a cannula so as to avoid any contact with moisture in the air. The expression "cannula" is not particularly limited and is intended to cover means of carrier gas-assisted transfer of the operating HCSI into the reactor. Pumping or other transfer means can be advantageously used, such as the use of a temperature-controlled pipe (with settings for maintaining the HCSI in the liquid state). The liquid HCSI is also maintained in a water-free atmosphere in the container. Suitable carrier gases for the cannula are nitrogen or argon.

[0037] The gas phase HCSI can then be charged into a closed reactor for contact with gaseous anhydrous HF.

[0038] The gas-phase HCSI can be charged as is into the closed reactor.

[0039] Alternatively, the gaseous HCSI can be charged into the closed reactor as a mixture with a carrier gas [mixture (M1)], wherein the mixture (M1) can be obtained by bubbling a carrier gas into the gaseous HCSI and maintained at a temperature above its boiling point. The carrier gas to be bubbled into the closed container can be the same gas used for the cannula, or can be a different gas.

[0040] The term "carrier gas" as used in the method of the present invention is intended to mean any chemically stable and dry gas, wherein the moisture content is not higher than 100 ppm.

[0041] The mixture (M1) can also be obtained by purging the headspace above the liquid HCSI with a carrier gas. In such a mixture (M1), the partial pressure of the HCSI vapor will be lower than the vapor tension of HCSI at the temperature of the mixture (M1): in other words, under the pressure conditions of the mixture (M1), the HCSI in the mixture will be at a temperature above its boiling point (Tb). HCSI ) at a temperature of .

[0042] The carrier gas used for preparing the mixture (M1) is preferably nitrogen.

[0043] The gaseous HCSI or the mixture (M1) containing the gaseous HCSI may be added to a closed reactor to be contacted with the gaseous HF gradually or all at once.

[0044] It is to be understood that the gaseous HCSI may contain impurities generated during heating steps a) or b), or impurities already present in the solid or molten HCSI starting material, without these impurities impairing its properties.

[0045] The gas-phase HCSI has a purity of at least 95%, preferably at least 98%, more preferably at least 99.5%.

[0046] Gaseous anhydrous hydrogen fluoride (HF) may suitably be introduced into the closed reactor by injection.

[0047] At atmospheric pressure, the boiling point of HF is 19.5° C. Therefore, in order to obtain anhydrous HF in the gas phase, liquid anhydrous HF may be preheated in a suitable apparatus that maintains the anhydrous HF in the gas phase and is connected to the reactor via a suitable injection system that is suitably thermostated to maintain the anhydrous HF in the gas phase.

[0048] HF may be provided to the reactor at a temperature ranging from 19.5°C to 200°C, preferably at a temperature of 19.5°C to 150°C.

[0049] The addition of gaseous anhydrous HF can be carried out continuously or semi-continuously.

[0050] Typically, gaseous anhydrous HF is added continuously at a substantially constant rate or in a controlled manner throughout the reaction time.

[0051] Gaseous anhydrous HF may be supplied to the reactor as it is. Alternatively, gaseous anhydrous HF may be diluted with a carrier gas and supplied to the reactor in a gas phase mixed with the carrier gas [mixture (M2)].

[0052] The carrier gas used for preparing the mixture (M2) is preferably nitrogen; usually anhydrous nitrogen is used.

[0053] According to a preferred embodiment of the invention, the reaction between HCSI and gaseous anhydrous HF is therefore carried out in a closed reactor in the presence of a carrier gas from the mixture (M1) and / or from the mixture (M2).

[0054] Additional carrier gas may be fed directly into the reactor.

[0055] A purge gas may optionally be used to flush the reactor without introducing any of the aforementioned streams. The purge gas may be the same gas a used for step b) and for the carrier gas used in preparing the mixture (M2).

[0056] The molar ratio between HCSI and anhydrous HF is preferably between 1:1 and 1:3, preferably between 1:1 and 1:2.5. However, good results have been obtained using a more significant excess of HF; molar ratios of 1:1 to 1:30 are effective, and ratios of 1:10 to 1:25 offer advantages. The preferred molar ratio will be selected by one of ordinary skill in the art taking into account various parameters, including the need to recycle excess HF, and the kinetics / yields dependent on the HCSI:HFSI ratio.

[0057] Similarly, without being exhaustive, the molar ratio between HCSI and the total amount of carrier gas in the reactor mixture may preferably be between 1:3 and 1:30, preferably between 1:3 and 1:15.

[0058] The reaction between HCSI in the vapor phase and anhydrous HF is typically conducted in a closed reactor under temperature and pressure conditions suitable to maintain all reactants and carrier gas in the vapor phase.

[0059] Typically, the reaction is carried out in a closed reactor at a temperature of 100 to 300 °C, more preferably 160 to 220 °C, still more preferably 160 to 180 °C.

[0060] The residence time of the reactants in the closed reactor is preferably between 10 seconds and 3 hours.

[0061] Reaction conditions are maintained such that the generated HFSI is removed from the reaction mixture as a gas.

[0062] The generated HFSI may be mixed with another gas (eg, unreacted HF, a carrier gas, unreacted HCSI, etc., which is generally referred to as a gaseous reaction mixture) for extraction.

[0063] At the end of the reaction, HFSI is separated from the gaseous reaction mixture by condensation, while other gaseous products (such as HCl and HF) remain in the gas phase, thereby making it easy to purify HFSI.

[0064] According to certain embodiments, these excess gaseous products (such as unreacted HF and HCl) can be separated by any method known in the art (such as distillation or stripping).HF can be advantageously recovered for reuse in the fluorination of HCSI.

[0065] The described embodiments allow for direct conversion of HCSI to HFSI with anhydrous HF in a high atom efficiency process that enables continuous fluorination with good to excellent yields and reduced environmental impact (primarily value-added gaseous effluents).

[0066] The process according to the invention advantageously provides a high conversion of HSCI to HFSI, with a yield higher than 90%, preferably higher than 95% and more preferably higher than 99%.

[0067] The HFSI separated after the reaction is completed may include some impurities, such as fluorosulfuric acid. The amount of such fluorosulfuric acid may range from 0 to 10% by mole. In a preferred embodiment of the present invention, the amount of impurities in the HFSI is less than 1% by mole.

[0068] Furthermore, the process according to the invention advantageously provides HFSI with high levels of conversion and selectivity in molar yields up to >90%, and even above 99%, which makes it particularly suitable for many applications, notably as an intermediate for the preparation of LiFSI for use in battery applications.

[0069] An additional advantage of the present invention is that the above-mentioned high levels of conversion and high levels of selectivity are obtained without the need for the addition of one or more catalysts, thereby reducing the operating costs and expenses of the process.

[0070] Thus, the present invention provides a process for producing bis(fluorosulfonyl)imidic acid (HFSI), comprising the step of contacting gaseous bis(chlorosulfonyl)imidic acid (HCSI) with gaseous anhydrous hydrogen fluoride (HF), wherein the process is carried out in the absence of solvent and in the absence of added catalysts such as cobalt oxide, nickel oxide, molybdenum oxide and mixtures thereof, which may or may not be supported on, for example, silica, alumina or activated carbon. This results in a more sustainable and economically viable process.

[0071] In another object, the present invention therefore provides bis(fluorosulfonyl)imidic acid (HFSI) obtainable by a process as defined above.

[0072] All raw materials (including reactants) used in the process according to the invention may preferably show very high purity standards. Preferably, their content of metal components such as Na, K, Ca, Mg, Fe, Cu, Cr, Ni, Zn is less than 10ppm, more preferably less than 5ppm, or less than 2ppm.

[0073] The bis(fluorosulfonyl)imidic acid (HFSI) obtained at the end of the process of the invention can advantageously be used as such for other reactions, or alternatively be further purified by any means known to the skilled person, including distillation, crystallization, etc.

[0074] The HFSI obtained by the process of the present invention can also be salified by subjecting it to a cation exchange step so as to obtain an alkali metal salt, an alkaline earth metal salt or a quaternary ammonium cation salt suitable for secondary batteries.

[0075] Consistently, the present invention further relates to a method for making an alkali metal salt, an alkaline earth metal salt or a quaternary ammonium cation salt of HFSI, the method comprising:

[0076] a. producing bis(fluorosulfonyl)imidic acid (HFSI) by a process comprising the steps of contacting gaseous bis(chlorosulfonyl)imidic acid (HCSI) with gaseous anhydrous hydrogen fluoride (HF), wherein the process is carried out in the absence of a solvent, and

[0077] b. salifying the HFSI thus obtained.

[0078] According to a preferred embodiment, HFSI is salified using a lithium salt according to methods known to those skilled in the art to provide direct lithiation of HFSI to lithium bis(fluorosulfonyl)imide (LiFSI).

[0079] Advantageously, lithium bis(fluorosulfonyl)imide (LiFSI) prepared according to the method of the present invention can be used in an electrolyte composition of an electrochemical cell.

[0080] In a further aspect, the present invention relates to an electrolyte composition comprising LiFSI obtained by the method of the present invention. Advantageously, the electrolyte composition is a non-aqueous electrolyte composition.

[0081] Some or all of the steps of the process according to the invention are advantageously carried out in equipment capable of withstanding the corrosion of the reactants, the reaction medium and the products.

[0082] For this purpose, for the parts in contact with the reaction medium, corrosion-resistant materials are selected, such as alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon and tungsten (in the order of or alloys of nickel, chromium, iron and manganese to which copper and / or molybdenum are added (known as or Monel TM The invention relates to a polymeric compound resistant to corrosion by the reaction medium, and more particularly ...

[0083] The present invention will now be described with reference to the following examples, which are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0084] Experimental Section

[0085] raw material

[0086] Bis(chlorosulfonyl)imidic acid (HCSI) was synthesized via the CSI or SFA route.

[0087] Anhydrous HF, commercially available from Solvay.

[0088] The HCSI was melted and then charged into the autoclave through an argon cannula to avoid any contact with moisture in the air. The autoclave was placed in an oven to maintain the temperature at 155° C. In a second oven before the reactor, the temperature was fixed at 155° C. In the autoclave, a nitrogen flow of 3.2 l / h was bubbled in the liquid allowing a gas phase containing a mixture of nitrogen and HCSI to be brought into the reactor.

[0089] At the same time, anhydrous HF was injected into the reactor in gas phase. To obtain this gas phase, a bottle of anhydrous HF was placed in a first oven at 54° C. A second oven containing a nozzle and a valve was heated at 72° C. The gas phase mixture containing HCSI and anhydrous HF was diluted by a co-feed of nitrogen just before the inlet of the reactor. The reactor was placed in a closed box and heated with an electric jacket.

[0090] At the outlet, the product is neutralized with aqueous KOH solution. 19 The product obtained by the reaction was analyzed by F NMR.

[0091] The results of tests conducted at different temperatures ranging from 160°C to 220°C using 4.5 g of HCSI in the following molar ratios: HCSI / HF / N2: 1 / 11 / 15 are reported in Table 1.

[0092] Table 1

[0093]

Claims

1. A method for producing bis(fluorosulfonyl)imidic acid (HFSI), The method comprises the steps of contacting gaseous bis(chlorosulfonyl)imidic acid (HCSI) with gaseous anhydrous hydrogen fluoride (HF), Wherein the process is carried out in the absence of a solvent.

2. The method according to claim 1, wherein: Gaseous HCSI is prepared by heating solid or molten HCSI to a temperature above the boiling point (Tb HCSI ) temperature and / or obtained from solid or molten HCSI by vaporizing HCSI under reduced pressure.

3. The method according to claim 1, wherein: Gaseous HCSI is obtained from liquid HCSI by a two-step process, which includes: a) Melt solid HCSI to a temperature above its melting temperature (Tm) HCSI ) temperature; and b) further heated to above its boiling point (Tb HCSI ) temperature.

4. A method according to any one of the preceding claims, wherein: Gaseous HCSI is charged into a closed reactor for contact with gaseous anhydrous HF mixed with a carrier gas [mixture (M1)].

5. A method according to any one of the preceding claims, wherein: Gaseous anhydrous HF is charged into the closed reactor for contact with gaseous HCSI mixed with a carrier gas [mixture (M2)].

6. The method according to any one of claims 4 or 5, wherein: The carrier gas was nitrogen.

7. A method according to any one of the preceding claims, wherein: The molar ratio between HCSI and the anhydrous HF is between 1:1 and 1:3, preferably between 1:1 and 1:2.

5.

8. A method according to any one of the preceding claims, wherein: The ratio between HCSI and the total amount of carrier gas in the reactor mixture is preferably between 1:3 and 1:30, preferably between 1:3 and 1:

15.

9. A method according to any one of the preceding claims, wherein: The step of contacting gaseous HCSI with gaseous anhydrous HF is carried out in a closed reactor at a temperature of 100 to 300°C, more preferably 160 to 220°C, still more preferably 160 to 180°C.

10. A method according to any one of the preceding claims, wherein: The residence time of the reactants in the closed reactor is between 10 seconds and 3 hours.

11. A method for producing an alkali metal salt, an alkaline earth metal salt or a quaternary ammonium cation salt of HFSI, the method comprising: a. producing bis(fluorosulfonyl)imidic acid (HFSI) by a process comprising the steps of contacting gaseous bis(chlorosulfonyl)imidic acid (HCSI) with gaseous anhydrous hydrogen fluoride (HF), wherein the process is carried out in the absence of a solvent, and b. salifying the HFSI thus obtained.

12. The method according to claim 11, wherein: The salt-forming step of HFSI is carried out using a lithium salt to provide lithium bis(fluorosulfonyl)imide (LiFSI).

13. Bis(fluorosulfonyl)imidic acid (HFSI) obtainable by the process according to any one of claims 1 to 10.

14. Lithium bis(fluorosulfonyl)imide (LiFSI), obtainable by the method according to claim 11 or 12.

15. Use of lithium bis(fluorosulfonyl)imide (LiFSI) according to claim 14 in a non-aqueous electrolyte for a battery. 16 . An electrolyte composition comprising the lithium bis(fluorosulfonyl)imide (LiFSI) according to claim 15 .

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