Gas-phase fluorination method of hydrogen bis(chlorosulfonyl)imide

Abstract

The present invention relates to a method for producing bis(fluorosulfonyl)imide acid, which can be economically realized on an industrial scale and from which a high-purity product can be obtained.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority based on European Patent Application No. 22305978.3, filed earlier on July 1, 2022, and the entire content of this application is incorporated herein by reference for all purposes.

[0002] The present invention relates to a method for producing bis(fluorosulfonyl)imide acid, which can be economically realized on an industrial scale and from which a high - purity product can be obtained.

Background Art

[0003] Fluorosulfonylimide salts, especially the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are useful compounds for battery electrolytes. Various processes, reactants, and intermediates leading to LiFSI are described in the patent literature, especially in Canadian Patent No. 2527802 (Universite de Montreal), which describes several routes for preparing LiFSI, for example, a process for preparing LiFSI in one step starting from bis(chlorosulfonyl)imide (HCSI) using anhydrous hydrogen fluoride (HF):

Chemical Formula

[0004] In the art, two - step processes for preparing LiFSI are also known, such as a method that includes fluorinating bis(chlorosulfonyl)imide (HCSI) to bis(fluorosulfonyl)imide (HFSI) using a fluorinating agent, for example, anhydrous hydrogen fluoride (HF), and then lithiating HFSI to LiFSI using a lithiating agent. An example of such a process is disclosed in U.S. Patent No. 9,725,318, which reacts HCSI with anhydrous HF in the presence of a solvent. The reaction time for conversion to HFSI is 18 hours.

[0005] Another known two-step process for preparing LiFSI uses NH4F(HF) as the fluorinating agent x and includes a first step of fluorination of bis(chlorosulfonyl)imide (HCSI) to ammonium bis(fluorosulfonyl)imide (NH4FSI) using NH4F(HF) as the fluorinating agent, followed by a second step of lithiation of NH4FSI that results in the LiFSI product. Such processes are described, for example, in International Publication No. WO 2017 / 090877A1 (CLS) and European Patent Application Publication No. EP 3170789A1 (Nippon Soda Co., Ltd.).

[0006] Another known two-step process for preparing LiFSI involves lithiation of HCSI in a first step using a lithiating agent to prepare LiCSI as an intermediate product, and subsequent fluorination of LiCSI to LiFSI using a fluorinating agent. For example, Republic of Korea Patent No. 10-2020-0049164 (CLS) relates to a method for preparing LIFSI, which includes reacting HCSI with various lithiating reagents in a (SI) solvent to produce LiCSI and then reacting it directly with an anhydrous fluorinating reagent without purification. A long list of possible solvents is shown in the same specification, and dimethyl carbonate is used in the examples.

[0007] U.S. Patent Application Publication No. 2017 / 0183230 discloses a process for converting HCSI to HFSI, which includes reacting liquid HCSI with anhydrous gaseous HF under conditions of temperature and pressure sufficient to produce gaseous HFSI. The yield of HFSI achieved by this method is about 80% based on the conversion of HCSI.

[0008] As can be seen from the above patent documents, the production of bis(fluorosulfonyl)imide acid is carried out using HCSI in a solvent or in the liquid phase to disperse the reactants and react them or to enable the recovery of unreacted species.

[0009] The applicant has recognized that there is still a need in the art to improve the process for manufacturing bis(fluorosulfonyl)imide acid.

[0010] In particular, the applicant is fully aware that the processes disclosed in the prior art require long reaction times and only low levels of selectivity can be obtained. SUMMARY OF THE INVENTION

[0011] For the purpose of overcoming the above drawbacks, the applicant has addressed the problem of providing a continuous manufacturing process for preparing bis(fluorosulfonyl)imide acid that has a short residence time and a high level of selectivity.

[0012] Furthermore, the applicant has provided a process that addresses the environmental aspects of the route to bis(fluorosulfonyl)imide acid, does not require the use of dangerous solvents, minimizes the amount of solid / salt waste, and provides opportunities for the effective utilization of by-products.

[0013] Accordingly, in a first aspect, the present application relates to a method for manufacturing bis(fluorosulfonyl)imide acid (HFSI) carried out without a solvent, which includes a step of contacting gaseous bis(chlorosulfonyl)imide acid (HCSI) with gaseous hydrogen fluoride (HF).

[0014] The method for manufacturing bis(fluorosulfonyl)imide acid (HFSI) of the present invention is characterized by a high conversion yield and a high level of selectivity, and provides HFSI that is particularly suitable as an intermediate for preparing LiFSI used in many applications, especially battery applications.

[0015] Advantageously, the method of the present invention is carried out entirely in the gas phase. In other words, the method of the present invention is a solvent-free method, which means that no solvent is added to the reaction mixture during the reaction. This is advantageous, firstly, because the step of removing the solvent is avoided, resulting in a reduction in the complexity and overall cost of the industrial process, and secondly, because the preliminary step of treating the solvent to reduce the 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, increasing the overall yield.

DETAILED DESCRIPTION OF THE INVENTION

[0016] According to the method of the present invention, gaseous HCSI reacts with anhydrous HF in the gas phase.

[0017] Gaseous HCSI can be obtained by heating solid or molten HCSI to a temperature above the boiling point (Tb HCSI ) of HCSI and / or by vaporizing HCSI under reduced pressure.

[0018] Heating of HCSI can be carried out by using a carrier gas such as nitrogen at any pressure (above atmospheric pressure, approximately atmospheric pressure, or reduced pressure). In such a method, the partial pressure of HCSI is reduced, and advantageously, vaporization becomes more effective.

[0019] The boiling point (Tb HCSI ) of HCSI mentioned above is known to be pressure-dependent: the boiling point or Tb HCSI of HCSI is used herein to represent the temperature at which the vapor pressure of HCSI is equal to the pressure surrounding the liquid / melted HCSI and the liquid / melted HCSI changes to vapor.

[0020] Solid or molten HCSI is commercially available or can be prepared by any known method, for example, - by reacting chlorosulfonyl isocyanate (ClSO2NCO) with chlorosulfonic acid (ClSO2OH) (CSI route); - By reacting cyanogen chloride (CNCl) with sulfur trioxide (SO3) and chlorosulfonic acid (ClSO2OH); or - By reacting sulfamic acid (NH2SO2OH) with thionyl chloride (SOCl2) and chlorosulfonic acid (ClSO2OH) (SFA route); It can be produced.

[0021] When solid HCSI is used as the starting material, before heating HCSI to a temperature above its boiling point (Tb HCSI ) in step b), a preliminary step a) is performed to melt solid HCSI to a temperature above its melting point (Tm HCSI ) to obtain molten HCSI (also called the liquid state).

[0022] Preferably, step a) is carried out at a temperature (Ta) suitable for melting HCSI and maintaining HCSI in the molten state while minimizing its thermal decomposition.

[0023] Step a) is carried out at a temperature (Ta) above the melting point (Tm HCSI ) of HCSI. In this case, Ta ≥ Tm HCSI . For example, Ta can be the melting point (Tm HCSI ) of HCSI plus 5°C or more. In this case, Ta ≥ Tm HCSI +5. As another example, Ta can be the melting point (Tm HCSI ) of HCSI plus 10°C or more. In this case, Ta ≥ Tm HCSI +10.

[0024] It will be understood that the melting point of HCSI is affected by the presence and amount of impurities.

[0025] Preferably, the temperature (Ta) at which step a) is carried out is 30°C or more, for example 37°C or more, for example 38°C or more, 40°C or more, 45°C or more, and further 50°C or more. The temperature Ta is preferably less than 150°C, more preferably 100°C or less. In any case, the temperature (Ta) at which step a) is carried out is less than the decomposition temperature of HCSI.

[0026] The liquid-state HCSI is then further heated to a temperature exceeding its boiling point (Tb HCSI ) in step b).

[0027] The liquid-state HCSI can be appropriately vaporized into the gas-phase HCSI by any means known to those skilled in the art.

[0028] As described above, each of step a) and / or step b) can be carried out above atmospheric pressure, or 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 in the range of 10 to 100,000 Pa, preferably 1000 to 10,000 Pa.

[0029] Preferably, the gas-phase HCSI is obtained in step b) under reduced pressure under conditions that lower the partial pressure of HCSI, for example, by heating in a sealed container in a properly thermostatically controlled state and / or using a carrier gas.

[0030] The container will be selected by those skilled in the art who appropriately select a construction material having corrosion resistance and being compatible with the relevant chemicals that are particularly aggressive due to their acidity.

[0031] The filling of the liquid-state HCSI into the sealed container can be appropriately carried out by cannulation with a carrier gas to avoid contact with moisture in the air. The expression "cannulation" is not particularly limited and is intended to include means for transferring the HCSI assisted by a carrier gas to the reactor. For example, pumps or other transfer means can be advantageously used, such as using a temperature-controlled pipeline (configured to maintain the HCSI in a liquid state). The liquid-state HCSI is also kept in an anhydrous atmosphere inside the container. Carrier gases suitable for cannulation are nitrogen or argon.

[0032] The gas-phase HCSI can be filled into a sealed reactor for subsequent contact with anhydrous HF gas.

[0033] The gaseous HCSI can be directly filled into the closed reactor.

[0034] Alternatively, the gaseous HCSI may be filled into the closed reactor as a mixture with a carrier gas [mixture (M1)]. The mixture (M1) can be obtained by blowing the carrier gas into the gaseous HCSI and maintaining the temperature above its boiling point. The carrier gas blown into the closed container may be the same gas or a different gas used for cannulation.

[0035] The term "carrier gas" used in the method of the present invention is intended to mean a chemically stable, dry gas with a water content of 100 ppm or less.

[0036] The mixture (M1) can also be obtained by sweeping the headspace above the liquid HCSI with the carrier gas. In such a mixture (M1), the partial pressure of the HCSI vapor is lower than the vapor pressure of HCSI at the temperature of the mixture (M1). In other words, the HCSI in the mixture is at a temperature higher than its boiling point (Tb HCSI ) under the pressure conditions of the mixture (M1).

[0037] The carrier gas used for the preparation of the mixture (M1) is preferably nitrogen.

[0038] The gaseous HCSI or the mixture (M1) containing gaseous HCSI can be added to the closed reactor to be contacted with the gaseous HF gradually or at once.

[0039] The gaseous HCSI may contain impurities generated during the heating step a) or b), or impurities already present in the solid or molten HCSI starting material, but these are understood not to impair the properties of HCSI.

[0040] The gaseous HCSI has a purity of at least 95%, preferably at least 98%, more preferably at least 99.5%.

[0041] Gaseous anhydrous hydrogen fluoride (HF) can be suitably introduced into the sealed reactor by injection.

[0042] At atmospheric pressure, the boiling point of HF is 19.5 °C. Therefore, in order to obtain anhydrous HF in the gas phase, the liquid anhydrous HF may be preheated in a suitable device for holding anhydrous HF in the gas phase, which is connected to the reactor via a suitable injection system that is appropriately temperature-controlled to hold the anhydrous HF in the gas phase.

[0043] HF can be supplied to the reactor at a temperature in the range of 19.5 °C to 200 °C, preferably at a temperature of 19.5 °C to 150 °C.

[0044] The addition of gaseous anhydrous HF can be carried out continuously or semi - continuously.

[0045] Typically, gaseous anhydrous HF is added continuously or in a controlled manner at a substantially constant rate throughout the reaction time.

[0046] Gaseous anhydrous HF can be supplied directly to the reactor. Alternatively, gaseous anhydrous HF can be diluted with a carrier gas and supplied to the reactor in the gas phase as a mixture with the carrier gas [mixture (M2)].

[0047] The carrier gas used for the preparation of the mixture (M2) is preferably nitrogen, and usually anhydrous nitrogen is used.

[0048] Therefore, according to a preferred embodiment of the present invention, the reaction between HCSI and gaseous anhydrous HF is carried out in a sealed reactor in the presence of a carrier gas derived from the mixture (M1) and / or the mixture (M2).

[0049] Additional carrier gas may be supplied directly to the reactor.

[0050] Optionally, a purge gas may be used to flash the reactor without introducing the aforementioned flow. This can be the same gas as the gas in step b) and the same gas as the carrier gas used in the preparation of the mixture (M2).

[0051] The molar ratio between HCSI and anhydrous HF is preferably from 1:1 to 1:3, preferably from 1:1 to 1:2.5. Furthermore, good results have been obtained using a more significantly excessive HF, a molar ratio of 1:1 to 1:30 is effective, and a ratio of 1:10 to 1:25 gives an advantage. The selection of the preferred molar ratio is made by those skilled in the art considering various parameters such as the need to recycle the excessive HF and the dependence of the reaction rate / yield on the HCSI:HFSI ratio.

[0052] Similarly, although not exhaustive, the molar ratio of HCSI to the total amount of carrier gas in the reactor mixture may preferably be from 1:3 to 1:30, preferably from 1:3 to 1:15.

[0053] The gas-phase reaction between HCSI and anhydrous HF is usually carried out in a closed reactor under temperature and pressure conditions suitable for maintaining all reactants and carrier gas in the gas phase.

[0054] Typically, the reaction is carried out in a closed reactor at a temperature of 100 to 300 °C, more preferably 160 to 220 °C, and even more preferably 160 to 180 °C.

[0055] The residence time of the reactants in the closed reactor is preferably from 10 seconds to 3 hours.

[0056] The reaction conditions are maintained such that the generated HFSI is removed as a gas from the reaction mixture.

[0057] The generated HFSI may be withdrawn as a mixture with another gas, for example, a mixture with unreacted HF, carrier gas, unreacted HCSI, etc., which is usually called the gas reaction mixture.

[0058] At the end of the reaction, while HFSI is separated from the gaseous reaction mixture by condensation, other gaseous products such as HCl and HF remain in the gas phase, thereby facilitating the purification of HFSI.

[0059] According to certain embodiments, 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 advantageously be recovered for reuse in the fluorination of HCSI.

[0060] The described embodiments enable the direct conversion of HCSI to HFSI using anhydrous HF in a highly atom-efficient approach, thereby enabling continuous fluorination with good to excellent yields and reduced environmental impact (mainly valuable gas emissions).

[0061] The method according to the present invention advantageously provides a high conversion rate from HSCI to HFSI in a yield of more than 90%, preferably more than 95%, more preferably more than 99%.

[0062] The HFSI isolated after the reaction may contain some impurities such as fluorosulfonic acid. Such fluorosulfuric acid can be in an amount in the range of 0 to 10 mol%. In a preferred embodiment of the present invention, the amount of impurities in HFSI is less than 1 mol%.

[0063] Furthermore, in the method according to the present invention, advantageously, HFSI can be obtained with a high molar yield that can exceed 90%, and even exceed 99%, with a high conversion rate and selectivity, and therefore it is particularly suitable as an intermediate for preparing LiFSI used in many applications, especially battery applications.

[0064] A further advantage of the present invention is that the above-mentioned high level of conversion rate and high level of selectivity can be obtained without the need to add a catalyst, thereby reducing the execution cost and expense of the process.

[0065] Accordingly, the present invention provides a process for producing bis(fluorosulfonyl)imide acid (HFSI) which comprises contacting gaseous bis(chlorosulfonyl)imide acid (HCSI) with gaseous hydrogen fluoride (HF), said process being carried out without the addition of a solvent and without the addition of a catalyst such as cobalt oxide, nickel oxide, molybdenum oxide, and mixtures thereof, which may or may not be supported on, for example, silica, alumina, activated carbon, etc. Thereby, a more sustainable and economically viable process is realized.

[0066] Accordingly, for another object, the present invention provides bis(fluorosulfonyl)imide acid (HFSI) obtainable by the process defined above.

[0067] All starting materials used in the process according to the invention, such as reactants, may preferably exhibit very high purity standards. Preferably, their contents of metal components such as Na, K, Ca, Mg, Fe, Cu, Cr, Ni, Zn, etc. are less than 10 ppm, more preferably less than 5 ppm, or less than 2 ppm.

[0068] The bis(fluorosulfonyl)imide acid (HFSI) obtained at the end of the process of the present invention can be advantageously used as such in other reactions, or may optionally be further purified by any means known to those skilled in the art including distillation, crystallization, etc.

[0069] The HFSI obtained by the process of the present invention may be converted into salt form by passing through a cation exchange step in order to obtain an alkali metal salt, alkaline earth metal salt, or quaternary ammonium cation salt suitable for use in secondary batteries.

[0070] Consistently, the present invention further provides a process for producing an alkali metal salt, alkaline earth metal salt, or quaternary ammonium cation salt of HFSI, a. Producing bis(fluorosulfonyl)imide acid (HFSI) by a solvent-free method including a step of contacting gaseous bis(chlorosulfonyl)imide acid (HCSI) with gaseous hydrogen fluoride (HF), and b. Converting the thus obtained HFSI into a salt form, relates to a method including these steps.

[0071] According to a preferred embodiment, HFSI is converted into a salt form using a lithium salt in order to directly lithiate HFSI to lithium bis(fluorosulfonyl)imide (LiFSI) according to methods known to those skilled in the art.

[0072] Advantageously, lithium bis(fluorosulfonyl)imide (LiFSI) prepared according to the method of the present invention can be used in an electrolyte composition for an electrochemical cell.

[0073] In a further aspect, the present invention relates to an electrolyte composition containing LiFSI obtained by the method of the present invention. Advantageously, the electrolyte composition is a non-aqueous electrolyte composition.

[0074] Some or all of the steps of the method according to the present invention are advantageously carried out in an apparatus capable of withstanding corrosion of reactants, reaction media, and products.

[0075] For this purpose, an alloy based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon and tungsten, sold under the Hastelloy® brand, or the name Inconel® or Monel TMNickel, chromium, iron, and manganese alloys to which copper and / or molybdenum are added and which are sold under the name, more particularly corrosion-resistant materials such as Hastelloy C276 or Inconel 600, 625, or 718 alloys, are selected for parts that come into contact with the reaction medium. Apparatus made of or coated with a polymeric compound that is resistant to corrosion of the reaction medium may also be used. In particular, materials such as PTFE (polytetrafluoroethylene, i.e., Teflon) or PFA (perfluoroalkyl resin) may be mentioned. Glass and glass-lined as well as enamelled apparatus may also be used. Furthermore, corrosion-resistant silicon carbide (or SiC) materials can also be advantageously used. The use of equivalent materials (such as tungsten carbide) would not be outside the scope of the present invention.

[0076] Here, the present invention will be described in connection with the following examples, which are illustrative only and are not intended to limit the scope of the present invention.

Examples

[0077] Raw materials Bis(chlorosulfonyl)imide acid (HCSI) synthesized via the CSI or SFA route. Anhydrous HF commercially available from Solvay.

[0078] HCSI was melted and then charged into an autoclave with an argon cannulation to avoid contact with moisture in the air. The autoclave was placed in an oven and maintained at a temperature of 155°C. In a second oven in front of the reactor, the temperature was fixed at 155°C. In the autoclave, a gas phase containing a mixture of nitrogen and HCSI can be carried to the reactor by blowing nitrogen into the liquid at a flow rate of 3.2 l / h.

[0079] In parallel, anhydrous HF was injected into the reactor in the gas phase. To obtain this gas phase, the 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 simultaneously supplying nitrogen immediately before the inlet of the reactor. The reactor was placed in a sealed cabinet and heated with an electric jacket.

[0080] At the outlet, the product was neutralized with an aqueous solution of KOH. The product obtained from the reaction was analyzed by 19F NMR.

[0081] The results of tests carried out at different temperatures in the range of 160 °C to 220 °C with a molar ratio of HCSI / HF / N2: 1 / 11 / 15 using 4.5 g of HCSI are reported in Table 1.

[0082]

Table 1

Claims

1. A method for producing bis(fluorosulfonyl)imide acid (HFSI), The process includes contacting gaseous bis(chlorosulfonyl)imide acid (HCl) with gaseous anhydrous hydrogen fluoride (HF), A method performed without solvents.

2. Gaseous HCSI boils solid or molten HCSI at the boiling point (Tb) of HCSI. ＨＣＳＩ The method according to claim 1, obtained by heating to a temperature exceeding ) and / or by reduced-pressure vaporization of HCSI.

3. Gaseous HCSI, a) Solid HCSI, its melting temperature (Tm ＨＣＳＩ To melt it to a temperature exceeding ); and b) Its boiling point (Tb ＨＣＳＩ To further heat to a temperature exceeding ) The method according to claim 1, obtained from liquid HCSI by a two-step procedure including the following.

4. The method according to claim 1, wherein gaseous HCSI is placed in a sealed reactor to contact gaseous anhydrous HF as a mixture with a carrier gas [mixture (M1)].

5. The method according to claim 1, wherein anhydrous gaseous HF is placed in a sealed reactor to contact gaseous HCSI as a mixture with a carrier gas [mixture (M2)].

6. The method according to claim 4 or 5, wherein the carrier gas is nitrogen.

7. The method according to claim 1, wherein the molar ratio of HCSI to anhydrous HF is 1:1 to 1:3, preferably 1:1 to 1:2.

5.

8. The method according to claim 1, wherein the ratio of the total amount of HCSI to carrier gas in the reactor mixture is preferably 1:3 to 1:30, and preferably 1:3 to 1:

15.

9. The method according to claim 1, wherein the step of contacting gaseous HCSI with gaseous anhydrous HF is carried out in a sealed reactor at a temperature of 100 to 300°C, more preferably 160 to 220°C, and even more preferably 160 to 180°C.

10. The method according to claim 1, wherein the residence time of the reactants in the sealed reactor is 10 seconds to 3 hours.

11. A method for producing alkali metal salts, alkaline earth metal salts, or quaternary ammonium cation salts of HFSI, a. Producing bis(fluorosulfonyl)imide acid (HFSI) by a solvent-free method that includes contacting gaseous bis(chlorosulfonyl)imide acid (HCSI) with gaseous anhydrous hydrogen fluoride (HF), and b. Converting the HFSI obtained in this way into a salt form. A method that includes this.

12. The method according to claim 11, wherein the step of converting HFSI into a salt is performed using a lithium salt to obtain lithium bis(fluorosulfonyl)imide (LiFSI).

13. A bis(fluorosulfonyl)imide acid (HFSI) obtained by the method described in claim 1.

14. Lithium bis(fluorosulfonyl)imide (LiFSI) obtained by the method described in claim 11.

15. Use of lithium bis(fluorosulfonyl)imide (LiFSI) according to claim 14 in a non-aqueous electrolyte for batteries.

16. An electrolyte composition comprising lithium bis(fluorosulfonyl)imide (LiFSI) as described in claim 15.