Process for preparing bis(fluorosulfonyl)imides

Abstract

The present invention relates to a process for preparing bis(fluorosulfonyl)imides, comprising the steps of: i) providing a stream A1 comprising HF and a reactor containing a liquid phase A2 comprising a bis(chlorosulfonyl)imide; ii) contacting, in said reactor, said liquid phase A2 with said stream A1 to produce a bis(fluorosulfonyl)imide, characterized in that said stream A1 is injected into said liquid phase A2.

Description

[Technical field]

[0001] The present invention relates to a method for preparing bis(fluorosulfonyl)imides, in particular, to a method for preparing bis(fluorosulfonyl)imides from bis(halosulfonyl)imides. [Background technology]

[0002] Due to their very low basicity, sulfonylimide type anions are increasingly used in the field of energy storage, either in the form of inorganic salts in batteries or organic salts in supercapacitors, or in the field of ionic liquids. Due to the booming battery market and the major challenge of reducing the cost of battery production, large-scale, low-cost synthesis methods for this type of anion are required.

[0003] In the specific field of Li-ion batteries, the salt currently most widely used is LiPF6, but this salt has many drawbacks, such as limited thermal stability and sensitivity to hydrolysis, which reduces the safety of the battery. Recently, FSO2 - New salts with the group have been investigated and have demonstrated a number of advantages, such as better ionic conductivity and resistance to hydrolysis. One of these salts, LiFSI (LiN(FSO2)2), has shown very advantageous properties making it a good candidate to replace LiPF6.

[0004] There are various methods for preparing LiFSI. WO 2009 / 123328 describes in particular the preparation of LiFSI via various steps of preparing intermediate salts, such as zinc bis(fluorosulfonyl)imide salts, followed by ammonium bis(fluorosulfonyl)imide salts, from bis(chlorosulfonyl)imide.

[0005] One of the reaction intermediates to obtain LiFSI is bis(fluorosulfonyl)imide. WO 2015 / 012897 describes the preparation of bis(fluorosulfonyl)imide by fluorination of bis(halosulfonyl)imide in the presence of hydrofluoric acid. The preparation of bis(fluorosulfonyl)imide (HFSI) is obtained under hydrofluoric acid reflux conditions. Carrying out the process under such conditions may promote the formation of undesirable by-products. Moreover, the operating conditions applied in this process require a large energy input that increases the carbon footprint of the process.

[0006] Therefore, there remains a need for a process for preparing bis(fluorosulfonyl)imides that does not have the above-mentioned disadvantages. Summary of the Invention

[0007] According to a first aspect, the present invention provides a process for preparing a bis(fluorosulfonyl)imide, the process comprising: i) providing a stream A1 comprising HF and providing a reactor containing a liquid phase A2 comprising a bis(halosulfonyl)imide; ii) contacting said liquid phase A2 with said stream A1 in said reactor to produce a bis(fluorosulfonyl)imide. wherein said stream A1 is injected into said liquid phase A2.

[0008] Preferably, the reactor comprises means for mechanical stirring of the liquid phase A2. The term "mechanical stirring means" is understood to mean stirring means without the use of magnetic devices within the reactor, for example magnetic stir bars.

[0009] The present invention ensures uniformity of the hydrofluoric acid concentration at any point in the reactor, thereby avoiding zones of the reaction medium with a higher steady-state concentration of HF, which leads to a significant increase in the formation of undesirable by-products and therefore a significant decrease in the yield of bis(fluorosulfonyl)imide.The present invention also ensures uniformity of the temperature at any point in the reaction medium, thereby avoiding the obtaining of hot spots in the reactor, which also promote decomposition reactions.

[0010] To control the stationary concentration of HF, said stream A1 is preferably injected continuously into said liquid phase A2.

[0011] According to a preferred embodiment, step ii) is carried out under pressure and temperature conditions so as to keep the produced bis(halosulfonyl)imides and bis(fluorosulfonyl)imides in liquid form.

[0012] According to a preferred embodiment, during step ii), the temperature of said liquid phase A2 is kept substantially constant.

[0013] According to a preferred embodiment, during step ii) the temperature of said liquid phase A2 varies by at most 5°C absolute, preferably by at most 3°C ​​absolute, by at most 2°C absolute or in particular by at most 1°C absolute.

[0014] According to a preferred embodiment, said reactor also comprises a dip tube through which stream A1 is injected into said liquid phase A2.

[0015] According to a preferred embodiment, said reactor comprises means for mechanical stirring of said liquid phase A2, said stream A1 being injected into said liquid phase A2 close to said mechanical stirring means.

[0016] According to a preferred embodiment, the rate of introduction of hydrofluoric acid contained in stream A1 into liquid phase A2 is at least 1 mol HF / mole bis(halosulfonyl)imide / h and preferably at most 100 mol HF / mole bis(halosulfonyl)imide / h.

[0017] According to a preferred embodiment, step ii) is carried out at a molar ratio of HF / [bis(halosulfonyl)imide] between 2.0 and 3.0.

[0018] According to a preferred embodiment, step ii) is carried out at a temperature above 0°C.

[0019] According to a preferred embodiment, the bis(halosulfonyl)imide compound is a bis(chlorosulfonyl)imide.

[0020] According to another aspect, the present invention provides a method for preparing a lithium bis(fluorosulfonyl)imide salt, the method comprising: a) carrying out the process for preparing a bis(fluorosulfonyl)imide according to the present invention; b) contacting the bis(fluorosulfonyl)imide with a composition comprising at least one lithium salt to form the lithium bis(fluorosulfonyl)imide salt. Includes. [Brief description of the drawings]

[0021] [Figure 1] 1 illustrates a schematic representation of a reactor for carrying out a method for preparing a bis(fluorosulfonyl)imide according to one particular embodiment. [Diagram 2] FIG. 1 illustrates a schematic cross-sectional view of a reactor for carrying out a method for preparing a bis(fluorosulfonyl)imide according to one particular embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] According to a first aspect, the present invention provides a method for preparing a bis(fluorosulfonyl)imide. Preferably, the method comprises: i) providing a stream A1 comprising HF and providing a reactor containing a liquid phase A2 comprising a bis(halosulfonyl)imide; ii) contacting said liquid phase A2 with said stream A1 in said reactor to produce a bis(fluorosulfonyl)imide. Includes.

[0023] In this process, said stream A1 can be a gas or liquid stream, and thus in said stream A1, the hydrofluoric acid can be in gaseous or liquid form.

[0024] According to a particular embodiment, said liquid phase A2 comprises a bis(halosulfonyl)imide but does not comprise an organic solvent, and therefore step ii) of fluorination of the bis(halosulfonyl)imide to the bis(fluorosulfonyl)imide is carried out in the absence of an organic solvent.

[0025] According to another particular embodiment, the liquid phase A2 comprises a bis(halosulfonyl)imide and an organic solvent. The organic solvent SO1 can be selected from esters, nitriles, ethers, aromatic solvents, carbonates, cyclic or heterocyclic solvents and mixtures thereof. Preferably, the organic solvent SO1 is selected from the group consisting of methyl acetate, butyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyronitrile, valeronitrile, benzonitrile, diisopropyl ether, 2-methoxy-2-methylbutane, cyclopentyl methyl ether, benzene, toluene, chlorobenzene, dichlorobenzene, xylene, ethylbenzene, 1,4-dioxane, dimethyl carbonate, ethylene carbonate, sulfolane and mixtures thereof.

[0026] Preferably, the hydrofluoric acid is anhydrous hydrofluoric acid. In the context of the present invention, the term "anhydrous hydrofluoric acid" is understood to mean HF containing less than 500 ppm water, preferably less than 300 ppm water, preferably less than 200 ppm water.

[0027] Preferably, the reactor comprises a mechanical stirring means. Preferably, the mechanical stirring means is a rotary mechanical stirring means. The mechanical stirring means comprises a motor that imparts a rotational motion via a shaft to a stirring element that mixes the liquid phase A2. The stirring element can be of various shapes. For example, the stirring element can be of the propeller type, blade turbine type, or anchor type.

[0028] The stirring element may be of the propeller type and comprises at least two blades, preferably 2, 3, 4, 5, 6, 7 or 8 blades. In this case, the stirring element produces an essentially axial movement with low shear forces. The diameter of the stirring element is for example between 1 / 5 and 2 / 3 of the diameter of said reactor. Such a ratio between the diameter of the stirring element and the diameter of the reactor can promote axial stirring and therefore homogenization and heat transfer. The pitch of the propeller is preferably between 0.5 and 3 times the diameter of the stirring element, in particular the pitch is equal to the diameter of the stirring element. In this specification, pitch refers to the theoretical distance that the propeller travels 360° in one complete revolution. In this configuration, the blades of the stirring element may be arranged perpendicular to the shaft or at an angle to the shaft.

[0029] The stirring element may be of the blade turbine type. In such a configuration, the stirring element comprises a horizontal disk on which two or more blades, in particular 4 to 8 blades, are arranged. In such a configuration, the stirring element induces an essentially radial flow. The diameter of the stirring element is, for example, between 1 / 5 and 2 / 3 of the diameter of the reactor. The blades may be flat or of curved shape. The blades are usually arranged perpendicular to the horizontal disk.

[0030] The stirring element may be of the anchor type, in which case it consists of a flat strip or a U-shaped tube rotating in a diametric plane close to the wall of the reactor.

[0031] The presence of a rotary mechanical stirring means is meant to allow good uniformity of concentration and temperature at any point in the reactor, in particular it promotes heat transfer with the walls of the reactor.

[0032] Preferably, said stream A1 is injected into said liquid phase A2. The term "injected" means that stream A1 is directly introduced into liquid phase A2. Thus, hydrofluoric acid reacts with bis(halosulfonyl)imide to form bis(fluorosulfonyl)imide. Bis(halosulfonyl)imide can be bis(chlorosulfonyl)imide, bis(bromosulfonyl)imide or bis(iodosulfonyl)imide, or a mixture thereof. Preferably, in the present application, bis(halosulfonyl)imide is bis(chlorosulfonyl)imide. In particular, said stream A1 is continuously injected into said liquid phase A2.

[0033] In addition, carrying out step ii) results in the formation of a compound of formula HX, where X is Cl, Br or I. The compound of formula HX formed is preferably in gaseous form under the operating conditions of the method, i.e. under the temperature and pressure conditions used in the method, in particular in step ii). The compound of formula HX can be degassed from the reaction medium, for example by stripping with an inert gas, such as nitrogen, helium or argon. Preferably, the compound HX is continuously removed during carrying out step ii). Preferably, the compound HX is HCl when the bis(halosulfonyl)imide is bis(chlorosulfonyl)imide. The compound HX is HBr when the bis(halosulfonyl)imide is bis(bromosulfonyl)imide. The compound HX is HI when the bis(halosulfonyl)imide is bis(iodosulfonyl)imide.

[0034] Preferably, step ii) is carried out under pressure and temperature conditions which keep the bis(halosulfonyl)imides and bis(fluorosulfonyl)imides produced in liquid form.

[0035] Thus, step ii) may be carried out at atmospheric pressure or at a pressure greater than atmospheric pressure. Preferably, step ii) may be carried out at a pressure less than 10 bara, advantageously less than 9 bara, preferably less than 8 bara, more preferentially less than 7 bara, in particular less than 6 bara.

[0036] Step ii) may be carried out at a temperature above 0°C, advantageously above 5°C, preferably above 10°C and more preferentially above 15°C.

[0037] Preferably, step ii) is carried out at a temperature below 150°C, advantageously below 140°C, preferably below 130°C, more preferentially below 120°C, in particular below 110°C, more particularly below 100°C, preferably below 90°C, advantageously preferably below 80°C, preferentially preferably below 70°C, more preferentially preferably below 60°C and particularly preferably below 50°C.

[0038] Thus, step ii) may be carried out at a temperature above 0°C, advantageously above 5°C, preferably above 10°C, more preferentially above 15°C; and below 150°C, advantageously below 140°C, preferably below 130°C, more preferentially below 120°C, in particular below 110°C, more particularly below 100°C, preferably below 90°C, advantageously and preferably below 80°C, preferentially and preferably below 70°C, more preferentially and preferably below 60°C, in particular and preferably below 50°C.

[0039] Preferably, step ii) may be carried out at a temperature above 0° C., advantageously above 5° C., preferably above 10° C., more preferentially above 15° C.; and below 150° C., advantageously below 140° C., preferably below 130° C., more preferentially below 120° C., in particular below 110° C., more particularly below 100° C., preferably below 90° C., advantageously and preferably below 80° C., preferentially and preferably below 70° C., more preferentially and preferably below 60° C., in particular preferably below 50° C.; and at atmospheric pressure.

[0040] Preferably, step ii) may be carried out at a temperature above 0° C., advantageously above 5° C., preferably above 10° C., more preferentially above 15° C.; and below 150° C., advantageously below 140° C., preferably below 130° C., more preferentially below 120° C., in particular below 110° C., more particularly below 100° C., preferably below 90° C., advantageously preferably below 80° C., preferentially preferably below 70° C., more preferentially preferably below 60° C., in particular preferably below 50° C.; and at a pressure above 1 bara; and below 10 bara, advantageously below 9 bara, preferably below 8 bara, more preferentially below 7 bara, in particular below 6 bara.

[0041] Preferably, during step ii), the temperature of said liquid phase A2 is kept substantially constant. In the present application, the term "substantially constant" is understood to mean a temperature fluctuation of at most 5°C absolute, preferably at most 3°C ​​absolute, more preferentially at most 2°C absolute or in particular at most 1°C absolute.

[0042] Thus, during step ii), the temperature of said liquid phase A2 varies by at most 5°C absolute, preferably by at most 3°C ​​absolute, more preferentially by at most 2°C absolute or in particular by at most 1°C absolute.

[0043] Such small temperature fluctuations can be produced by injecting, preferably continuously, stream A1 directly into liquid phase A2, in particular by injecting said stream A1, preferably continuously, close to the stirring elements as described below, when said stream A1 is injected. Such low temperature gradients in the liquid phase make it possible to minimize or even eliminate secondary reactions that can produce impurities such as FSO3H or FSO2NH2.

[0044] Preferably, in step ii), the rate of introduction of hydrofluoric acid contained in stream A1 into liquid phase A2 is at least 1 mol HF / mole of bis(halosulfonyl)imide / hour, advantageously at least 5 mol HF / mole of bis(halosulfonyl)imide / hour, preferably at least 10 mol HF / mole of bis(halosulfonyl)imide / hour, more preferentially at least 20 mol HF / mole of bis(halosulfonyl)imide / hour, in particular 30 mol HF / mole of bis(halosulfonyl)imide / hour, more particularly at least 40 mol HF / mole of bis(halosulfonyl)imide / hour and suitably at least 50 mol HF / mole of bis(halosulfonyl)imide / hour.

[0045] In particular, in step ii), the rate of introduction of hydrofluoric acid contained in stream A1 into liquid phase A2 is at most 130 mol HF / mole of bis(halosulfonyl)imide / h, advantageously at most 120 mol HF / mole of bis(halosulfonyl)imide / h, preferably at most 110 mol HF / mole of bis(halosulfonyl)imide / h and in particular at most 100 mol HF / mole of bis(halosulfonyl)imide / h.

[0046] Thus, in step ii), the rate of introduction of hydrofluoric acid contained in stream A1 into liquid phase A2 is at least 1 mol HF / mole of bis(halosulfonyl)imide / hour, advantageously at least 5 mol HF / mole of bis(halosulfonyl)imide / hour, preferably at least 10 mol HF / mole of bis(halosulfonyl)imide / hour, more preferentially at least 20 mol HF / mole of bis(halosulfonyl)imide / hour and in particular at least 30 mol HF / mole of bis(halosulfonyl)imide / hour. amide / hour, more particularly at least 40 mol HF / mole of bis(halosulfonyl)imide / hour, preferably at least 50 mol HF / mole of bis(halosulfonyl)imide / hour; and up to 130 mol HF / mole of bis(halosulfonyl)imide / hour, advantageously up to 120 mol HF / mole of bis(halosulfonyl)imide / hour, preferably up to 110 mol HF / mole of bis(halosulfonyl)imide / hour and in particular up to 100 mol HF / mole of bis(halosulfonyl)imide / hour.

[0047] In particular, in step ii), the rate of introduction of hydrofluoric acid contained in stream A1 into liquid phase A2 is at least 1 mol HF / mole of bis(chlorosulfonyl)imide / h, advantageously at least 5 mol HF / mole of bis(chlorosulfonyl)imide / h, preferably at least 10 mol HF / mole of bis(chlorosulfonyl)imide / h, more preferentially at least 20 mol HF / mole of bis(chlorosulfonyl)imide / h, in particular at least 30 mol HF / mole of bis(chlorosulfonyl)imide / h, more particularly at least 40 mol HF / mole of bis(chlorosulfonyl)imide / h and suitably at least 50 mol HF / mole of bis(chlorosulfonyl)imide / h.

[0048] More particularly, in step ii), the rate of introduction of hydrofluoric acid contained in stream A1 into liquid phase A2 is at most 130 mol HF / mole of bis(chlorosulfonyl)imide / h, advantageously at most 120 mol HF / mole of bis(chlorosulfonyl)imide / h, preferably at most 110 mol HF / mole of bis(chlorosulfonyl)imide / h and in particular at most 100 mol HF / mole of bis(chlorosulfonyl)imide / h.

[0049] Thus, in step ii), the rate of introduction of hydrofluoric acid contained in stream A1 into liquid phase A2 is at least 1 mol HF / mole of bis(chlorosulfonyl)imide / h, advantageously at least 5 mol HF / mole of bis(chlorosulfonyl)imide / h, preferably at least 10 mol HF / mole of bis(chlorosulfonyl)imide / h, more preferentially at least 20 mol HF / mole of bis(chlorosulfonyl)imide / h and in particular at least 30 mol HF / mole of bis(chlorosulfonyl)imide / h. HF / mole of bis(chlorosulfonyl)imide / hour, more particularly at least 40 mol HF / mole of bis(chlorosulfonyl)imide / hour, preferably at least 50 mol HF / mole of bis(chlorosulfonyl)imide / hour; and up to 130 mol HF / mole of bis(chlorosulfonyl)imide / hour, preferably up to 120 mol HF / mole of bis(chlorosulfonyl)imide / hour, preferably up to 110 mol HF / mole of bis(chlorosulfonyl)imide / hour and in particular up to 100 mol HF / mole of bis(chlorosulfonyl)imide / hour.

[0050] The above-mentioned introduction rates of hydrofluoric acid make it possible to avoid losses of HF, especially when the hydrofluoric acid is introduced in gaseous form, which therefore makes it possible to improve the overall efficiency of the process.

[0051] In addition, the introduction rate of HF can be controlled to maintain a low steady-state concentration of HF in the reaction medium, i.e., in said liquid phase A2. HF is quickly consumed in the fluorination reaction, and the molar ratio between HF and bis(halosulfonyl)imide is close to stoichiometry. The method makes it possible to limit the use of excess HF. This represents a major economic advantage: the cost of the HF demand will be close to the cost of the theoretical HF requirement required by the stoichiometry of the reaction.

[0052] Thus, according to a preferred embodiment, step ii) is carried out with a molar ratio of HF / [bis(halosulfonyl)imide] of at least 2.0, preferably at least 2.05, in particular at least 2.1.Preferably, step ii) is carried out with a molar ratio of HF / [bis(halosulfonyl)imide] of at most 3.1, preferably at most 3.0, in particular at most 2.9.

[0053] Step ii) is therefore carried out at a molar ratio of HF / [bis(halosulfonyl)imide] of at least 2.0, preferably at least 2.05, in particular at least 2.1; and at most 3.1, preferably at most 3.0, in particular at most 2.9.

[0054] Preferably, step ii) is carried out with a molar ratio of HF / [bis(chlorosulfonyl)imide] of at least 2.0, preferably at least 2.05, in particular at least 2.1. Preferably, step ii) is carried out with a molar ratio of HF / [bis(chlorosulfonyl)imide] of at most 3.1, preferably at most 3.0, in particular at most 2.9.

[0055] Step ii) is therefore carried out with a molar ratio of HF / [bis(chlorosulfonyl)imide] of at least 2.0, preferably at least 2.05, in particular 2.1; and at most 3.1, preferably at most 3.0, in particular at most 2.9.

[0056] According to a preferred embodiment, the reactor comprises a dip tube. This allows the direct injection of the stream A1 into the liquid phase A2. One of the ends E1 of the dip tube is therefore placed in the liquid phase A2. Preferably, the dip tube is positioned close to the mechanical stirring means. The mechanical stirring means, preferably of the rotary type, as defined above, comprises a stirring element. Thus, the dip tube is close to the stirring element. More specifically, the end E1 of the dip tube placed in the liquid phase A2 is positioned close to the mechanical stirring means, preferably close to the stirring element. This allows improving the diffusion of the stream A1 in the liquid phase A2. Such an arrangement between the dip tube and the stirring element ensures a perfect temperature and concentration homogeneity in the liquid phase A2. The maximum dimension of the stirring element passing through its center "C" is therefore denoted "D". According to a particular embodiment, the shortest distance, denoted D1, between the end E1 of the dip tube placed in the liquid phase A2 and the center of the stirring element is less than 2*D. The centre "C" of the stirring element is typically located on the central axis of said shaft of the mechanical stirring means (Figure 2).

[0057] Thus, according to a particular embodiment, the method comprises: i) providing a stream A1 comprising HF and a reactor comprising a liquid phase A2 comprising a bis(halosulfonyl)imide; said reactor comprising a dip tube, one of its ends E1 being located in said liquid phase A2, and a mechanical stirring means comprising a stirring element located in said liquid phase A2; ii) contacting said liquid phase A2 with said stream A1 in said reactor to produce a bis(fluorosulfonyl)imide. wherein a stream A1 is injected into the liquid phase A2 through the submerged tube, and a distance D1 between the end E1 of the submerged tube and a center C of the stirring element is less than 2*D; D represents the maximum dimension of the stirring element passing through its center C.

[0058] Preferably, the reactor may include a jacket, which makes it possible to ensure uniform heating of the reactor and ensure heat exchange with the liquid phase A2.

[0059] Step ii) is preferably carried out in the absence of a catalyst, which makes it possible to obtain very high yields as described below, while avoiding the need for a subsequent step of purification of the bis(fluorosulfonyl)imide to remove all traces of catalyst.

[0060] As defined in the present application, during step ii) hydrofluoric acid reacts with bis(halosulfonyl)imide to form bis(fluorosulfonyl)imide. Thus, during the implementation of the method, said liquid phase A2 will be enriched in bis(fluorosulfonyl)imide. The weight content of bis(fluorosulfonyl)imide in said liquid phase A2 will gradually increase and the weight content of bis(halosulfonyl)imide in said liquid phase A2 will conversely gradually decrease. The method is carried out until the desired conversion or selectivity is obtained.

[0061] The process achieves a conversion of at least 95%, advantageously at least 96%, preferably at least 97%, more preferentially at least 98%, in particular at least 99%, even more particularly at least 99.2%, preferably at least 99.5%, preferentially preferably at least 99.8% and particularly preferably 100%, of the bis(halosulfonyl)imide to the bis(chlorosulfonyl)imide.

[0062] The process makes it possible to obtain a yield of bis(fluorosulfonyl)imide of at least 80%, advantageously at least 85%, preferably at least 90% and more preferentially at least 95%.

[0063] The process may also include a step iii) of degassing the reactor or stripping it in the presence of an inert gas, preferably nitrogen, which makes it possible to remove any HCl that may be dissolved in the liquid phase A2 and to remove any unreacted HF.

[0064] Preferably, the process comprises a step iv) of recovering the bis(fluorosulfonyl)imide and optionally purifying it.

[0065] [Figure 1] shows a schematic diagram of a reactor 1 for carrying out a method for preparing bis(fluorosulfonyl)imide. The reactor 1 includes a jacket 11, a dip tube 7 and a rotary mechanical stirring means 6. The rotary mechanical stirring means 6 includes a motor 10, a shaft 9 and a rotating element 8. The reactor also includes a liquid phase 2, which is introduced into the reactor through a line 2a. The liquid phase 2 is introduced into the reactor before carrying out the fluorination reaction. This liquid phase includes bis(chlorosulfonyl)imide. Hydrofluoric acid 3 is introduced into the reactor through a dip tube 7. As shown in Figure 1, hydrofluoric acid 3 is injected into the liquid phase 2 through a dip tube, one of whose ends is located within the liquid phase 2. In addition, as shown in Figure 2, the end E1 of the dip tube 7, through which HF is injected into the liquid phase, is located near the rotating element 8. The distance D1 between the end E1 of the dip tube 7 and the center C of the stirring element 8 is less than twice the distance D, which represents the maximum dimension passing through the center C of said stirring element 8 (FIG. 2). The hydrochloric acid formed during the reaction is continuously removed via valve 12 and is recovered at 4 for further processing or purification. At the end of the reaction, the reactor 1 can be emptied, whose liquid phase 2 comprises the bis(fluorosulfonyl)imide, which is recovered at 5 for further processing, for example purification or the implementation of the method for preparing lithium bis(fluorosulfonyl)imide salts as described below.

[0066] According to a second aspect, the present invention relates to a method for preparing a lithium bis(fluorosulfonyl)imide salt, preferably comprising: a) carrying out the process for preparing a bis(fluorosulfonyl)imide according to the present invention; b) contacting the bis(fluorosulfonyl)imide with a composition comprising at least one lithium salt to form a composition comprising the lithium bis(fluorosulfonyl)imide salt. Includes.

[0067] According to a preferred embodiment, the composition comprising at least one lithium salt is an aqueous composition, preferably an aqueous suspension or solution.

[0068] According to another preferred embodiment, the composition comprising at least one lithium salt is a solid composition, preferably the composition consists of at least one solid lithium salt.

[0069] In particular, the bis(fluorosulfonyl)imide is added to a vessel containing a composition comprising at least one lithium salt. The vessel may be a reactor and preferably comprises at least one stirring system. The elements allowing the introduction of the composition obtained in step b) are preferably resistant to HF.

[0070] According to one embodiment, the lithium salt is selected from the group consisting of LiOH, LiOH·H2O, LiHCO3, Li2CO3, LiCl, and mixtures thereof. Preferably, the lithium salt is Li2CO3.

[0071] When the composition is an aqueous composition comprising at least one lithium salt, it can be prepared by any conventional means for preparing an alkaline aqueous composition, which can be, for example, dissolving the lithium salt in ultrapure water or deionized water with stirring.

[0072] To determine the amount of lithium salt to be introduced, typically an analysis of the total acidity of the mixture to be neutralized can be carried out.

[0073] According to one embodiment, step c) comprises: the molar ratio of the lithium salt divided by the basicity number of said salt relative to the bis(fluorosulfonyl)imide is greater than or equal to 1, preferably less than 5, preferably less than 3 and preferentially between 1 and 2; and / or the ratio by weight of lithium salt to the weight of water in the aqueous composition is between 0.1 and 2, preferably between 0.2 and 1, preferably between 0.3 and 0.7; It's like that.

[0074] For example, the Li2CO3 salt has a basicity number equal to 2.

[0075] Step b) of the process according to the invention can be carried out at a temperature below 40°C, preferably below 30°C, preferentially below 20°C and in particular below 15°C.

[0076] According to one embodiment, the process according to the invention comprises an additional step of filtering the composition B obtained in step b) to obtain a filtrate F and a cake G. The lithium bis(fluorosulfonyl)imide salt may be contained in the filtrate F and / or in the cake G. The filtrate F may be subjected to at least one step of extraction with an organic solvent S, typically sparingly soluble in water, in order to extract the lithium bis(fluorosulfonyl)imide salt into the organic phase. The extraction step typically results in the separation of an aqueous phase and an organic phase. In the context of the present invention, unless otherwise indicated, the term "spaciously soluble in water" is intended to mean a solvent having a solubility in water of less than 5% by weight. The aforementioned organic solvent S is in particular chosen from esters, nitriles, ethers, chlorinated and aromatic solvents, and mixtures thereof. Preferably, the organic solvent S is chosen from dichloromethane, ethyl acetate, butyl acetate, tetrahydrofuran, diethyl ether and valeronitrile, and mixtures thereof. In particular, the organic solvent S is butyl acetate. For each extraction, the weight of organic solvent used can vary between 1 / 6 and 1 times the weight of the filtrate F. The number of extractions can be between 2 and 10. Preferably, the organic phase obtained from the extraction(s) has a weight content of lithium bis(fluorosulfonyl)imide salt ranging from 5% to 40% by weight. The separated organic phase (obtained at the end of the extraction) can then be concentrated to reach a concentration of lithium bis(fluorosulfonyl)imide salt between 30% and 60% by weight, preferably between 40% and 50% by weight, said concentration being achieved by any evaporation means known to those skilled in the art.

[0077] The above-mentioned cake G may be washed with an organic solvent S' selected from the following families: esters, nitriles, ethers, chlorinated solvents and aromatic solvents, and mixtures thereof. Preferably, the organic solvent S' is selected from dichloromethane, ethyl acetate, butyl acetate, tetrahydrofuran, acetonitrile, diethyl ether and valeronitrile, and mixtures thereof. In particular, the organic solvent S' is butyl acetate. The weight of the organic solvent S' used may range between 1 and 10 times the weight of the cake. The total amount of organic solvent S' intended for washing may be used as a single portion or divided into several portions, in particular with the aim of optimizing the dissolution of the lithium bis(fluorosulfonyl)imide salt. Preferably, the organic phase obtained from the washing (possibly several times) of the cake G has a weight content of lithium bis(fluorosulfonyl)imide salt ranging from 5% to 20% by weight. The separated organic phase resulting from the washing(s) of cake G can then be concentrated to reach a concentration of lithium bis(fluorosulfonyl)imide salt between 30% and 60% by weight, preferably between 40% and 50% by weight, said concentration being achieved by any evaporation means known to the skilled artisan. According to one embodiment, the organic phases resulting from the extraction(s) of filtrate F and the washing(s) of cake G can be pooled before the concentration step. EXAMPLES

[0078] Example 1 394 g of liquid bis(chlorosulfonyl)imide (HCSI) and 19.7 g of liquid 1,4-dioxane are introduced into a stirred 1 liter reactor. The weight ratio between 1,4-dioxane and HCSI is 5%. The mixture is stirred using a turbine with 6 inclined blades and brought to 40 ° C before the introduction of hydrofluoric acid. The reaction is carried out by adjusting the temperature of the reaction medium to 40 ° C and by continuously injecting gaseous HF. The gaseous HF is slowly injected directly into the liquid reaction medium by means of a dip tube. The total amount of HF injected is 110 g, which corresponds to a molar ratio of HF to HCSI of 3. The introduction rate of gaseous HF is adjusted to 37 g / h. The reaction time is 3 hours. The reaction is accompanied by the formation of HCl, which is continuously removed from the reactor. The gases leaving the reactor are sent to a drain. Once all the HF has been introduced, a nitrogen stream with a flow rate of 50 l / h is introduced into the reactor to strip the HF and HCl that may have dissolved in the reaction medium. The stripping is carried out for 5 hours, maintaining the temperature of the medium at 40° C. The stripping gas leaving the reactor is also sent to a drain. After stripping, the reactor contains 336.3 g of crude bis(fluorosulfonyl)imide (HFSI). The composition of this crude HFSI is analyzed by NMR.

[0079] TIFF0007637632000001.tif49170

[0080] 'The conversion of HCSI is complete, reaching 100%. The yield of HFSI is 90.8%.

[0081] Example 2 397 g of liquid bis(chlorosulfonyl)imide (HCSI) and 12 g of liquid 1,4-dioxane are introduced into a stirred 1 liter reactor. The weight ratio between 1,4-dioxane and HCSI is 3%. The mixture is stirred using a turbine with 6 inclined blades and brought to 45 ° C before the introduction of hydrofluoric acid. The reaction is carried out by adjusting the temperature of the reaction medium to 45 ° C and by continuously injecting gaseous HF. The gaseous HF is slowly injected directly into the liquid reaction medium by means of a dip tube. The total amount of HF introduced is 100 g, which corresponds to a molar ratio of HF to HCSI of 2.7. The introduction rate of gaseous HF is adjusted to 38 g / h. The reaction time is 2 hours 40 minutes. The reaction is accompanied by the formation of HCl, which is continuously removed from the reactor. The gases leaving the reactor are sent to a drain. Once all the HF has been introduced, a nitrogen stream with a flow rate of 50 l / h is introduced into the reactor to strip the HF and HCl that may have dissolved in the reaction medium. The stripping is carried out for 5 hours and the temperature of the medium is maintained at 45° C. The stripping gas leaving the reactor is also sent to a drain.

[0082] After stripping, the reactor contains 339.5 g of crude bis(fluorosulfonyl)imide (HFSI), the composition of which is analyzed by NMR.

[0083] TIFF0007637632000002.tif49170

[0084] The conversion of HCSI is complete, reaching 100%, and the yield of HFSI is 93.9%.

Claims

1. 1. A process for preparing a bis(fluorosulfonyl)imide comprising: i) providing a stream A1 comprising HF and providing a reactor containing a liquid phase A2 comprising a bis(halosulfonyl)imide; ii) contacting said liquid phase A2 with said stream A1 in said reactor to produce a bis(fluorosulfonyl)imide; wherein said stream A1 is injected into said liquid phase A2, and wherein the rate of introduction of hydrofluoric acid contained in said stream A1 into said liquid phase A2 is at least 1 mol of HF per mol of bis(halosulfonyl)imide per hour.

2. 2. The process according to claim 1, characterized in that the reactor comprises means for mechanically stirring the liquid phase A2.

3. 3. The process according to claim 1 or 2, characterized in that step ii) is carried out under pressure and temperature conditions so as to keep the bis(halosulfonyl)imides and bis(fluorosulfonyl)imides formed in liquid form.

4. 4. The method according to claim 1, wherein during step ii) the temperature of the liquid phase A2 is kept substantially constant.

5. 5. The method according to claim 1, characterized in that during step ii) the temperature of the liquid phase A2 varies by a maximum of 5°C in absolute value.

6. 6. The process according to claim 1, characterized in that the reactor also comprises a dip tube through which the stream A1 is injected into the liquid phase A2.

7. 7. The process according to claim 1, characterized in that the reactor comprises means for mechanically stirring the liquid phase A2 and that the stream A1 is injected into the liquid phase A2 near the mechanical stirring means.

8. 8. The process according to claim 1, wherein step ii) is carried out at a molar ratio of HF / [bis(halosulfonyl)imide] ≥ 2.0 and ≤ 3.

0.

9. 9. The process according to any one of claims 1 to 8, characterized in that step ii) is carried out at a temperature above 0°C.

10. 10. The method according to claim 1, wherein the bis(halosulfonyl)imide compound is a bis(chlorosulfonyl)imide.

11. 1. A process for preparing a lithium bis(fluorosulfonyl)imide salt comprising: a) carrying out a process for preparing a bis(fluorosulfonyl)imide according to any one of claims 1 to 10; b) contacting the bis(fluorosulfonyl)imide with a composition comprising at least one lithium salt to form the lithium bis(fluorosulfonyl)imide salt. The method includes:

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