Process for producing phosphorus pentafluoride

Abstract

The present invention relates to a method for producing phosphorus pentafluoride and lithium hexafluorophosphate.

Description

[Technical field]

[0001] The present invention relates to the technical field of chemical process engineering, in particular industrial synthesis, especially the production of starting materials for electrolytes. In particular, the present invention relates to a method for producing phosphorus pentafluoride, and further, the present invention relates to a method for producing lithium hexafluorophosphate. [Background technology]

[0002] Lithium hexafluorophosphate (LiPF6) is the lithium salt of hexafluorophosphoric acid (HPF6) and is the lithium salt usually used to produce electrolytes for lithium-ion batteries and accumulators. Hexafluorophosphoric acid is unstable but can be obtained in aqueous form by reacting phosphoric acid with hydrofluoric acid or fluorspar (calcium fluoride, CaF2) in the presence of sulfuric acid. However, anhydrous salts of hexafluorophosphoric acid, especially lithium hexafluorophosphate, cannot be prepared in this way or are very difficult to prepare. However, for the production of electrolytes, especially for lithium-ion batteries and accumulators, the raw materials used must be completely anhydrous in order to avoid undesired side reactions. An important starting product for the production of anhydrous lithium hexafluorophosphate is phosphorus pentafluoride (PF5), which is obtained industrially by chemically reacting phosphorus pentachloride (PCl5) with it in hydrogen fluoride (HF). Here, phosphorus pentafluoride is obtained in a multi-step synthesis from elemental phosphorus. First, elemental phosphorus is reacted with elemental chlorine to give phosphorus trichloride (PCl3), which is then selectively oxidized in a further step by elemental chlorine to phosphorus pentachloride (PCl5). Then, by reaction in HF, chloride is exchanged for fluoride, so that phosphorus pentafluoride and HCl are produced as a by-product. Thus, in the end, at least three reaction steps are required to obtain phosphorus pentafluoride. [ka] [ka] [ka]

[0003] A further drawback of this synthesis is the need to dispose of the HCl that is produced. Moreover, the use of the intermediate phosphorus pentachloride is disadvantageous for further reasons: for example, chlorinated compounds, especially the reaction products, but also the by-products, are generally environmentally problematic and require laborious disposal. Moreover, phosphorus pentachloride is highly hygroscopic and decomposes quickly, even after the exclusion of water, into the more stable phosphorus trichloride and elemental chlorine. Due to the described properties, PCl5 can only be transported in small containers under protective gas, therefore industrial use for the production of phosphorus pentafluoride is only possible if the production of phosphorus pentafluoride is carried out immediately after the production of phosphorus pentachloride. Phosphorus pentafluoride is usually chemically reacted with lithium fluoride (LiF) in solution to give lithium hexafluorophosphate.

[0004] [ka]

[0005] Here, various solvents can be used, such as, for example, hydrogen fluoride, liquid sulfur dioxide, or acetonitrile. Additionally, a method is known in which phosphorus pentafluoride is chemically reacted with a lithium salt in liquid hydrogen fluoride to give lithium hexafluorophosphate. Furthermore, DE 19614503 A1 describes a process for the preparation of lithium hexafluorophosphate, in which calcium fluoride is first chemically reacted with phosphorus pentachloride in an autoclave to give phosphorus pentafluoride, which is then chemically reacted with a lithium salt in hydrogen fluoride to give lithium hexafluorophosphate.

[0006] However, the use of autoclaves is both equipment- and energy-intensive and, moreover, one starts here again from chlorinated starting products, which therefore requires a laborious purification of the phosphorus pentafluoride obtained, since lithium hexafluorophosphate must not only be anhydrous but also chloride-free, especially for use in lithium-ion batteries and accumulators. The prior art therefore still lacks a method for producing phosphorus pentafluoride or lithium hexafluorophosphate that is industrially easy to implement, requires a minimum number of reaction steps and starts from inexpensive, well-available and stable reactants. Furthermore, the prior art still lacks a method for producing phosphorus pentafluoride or lithium hexafluorophosphate that does not require the use of chlorinated starting materials. Summary of the Invention

[0007] It is therefore an object of the present invention to avoid, or at least mitigate, the above-mentioned disadvantages associated with the prior art. In particular, it is an object of the present invention to provide a process for the preparation of phosphorus pentafluoride and lithium hexafluorophosphate which is industrially simple to carry out, in particular starting from inexpensive and commonly available starting materials. It is yet a further object of the present invention to provide a process for the preparation of phosphorus pentafluoride and lithium hexafluorophosphate which does not require chlorinated reactants or intermediate products. The subject of the invention according to a first aspect is therefore a method for producing phosphorus pentafluoride as defined in claim 1, further advantageous configurations of this aspect of the invention being the subject of the corresponding dependent claims. A further subject of the invention according to its second aspect is a method for producing lithium hexafluorophosphate as claimed in claim 19, further advantageous configurations of this aspect of the invention being the subject of the dependent claims relating thereto. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] It is self-evident that the specific configurations, in particular the specific embodiments, etc. mentioned below are only described in relation to certain inventive aspects and apply correspondingly to other inventive aspects, without the need for this to be explicitly mentioned. Furthermore, it should be noted that in all the quantitative information given below, either relative or percentage, in particular mass-related, these quantitative information are selected by the skilled person within the scope of the present invention such that the total of the contents, additives or auxiliary substances etc. always amounts to 100% or 100% by mass, however this is self-evident to the skilled person. Furthermore, it can be said that all of the parameter information etc. listed below can, in principle, be determined or identified by standardized or explicitly specified determination methods, or by determination methods that are common to those skilled in the art. With this in mind, the subject matter of the present invention will now be explained in more detail.

[0009] [First aspect] According to a first aspect of the invention, the subject of the invention is a method for producing phosphorus pentafluoride (PF5), which comprises chemically reacting phosphoric acid (H3PO4) with hydrogen fluoride (HF). Phosphorus pentafluoride is formed or obtained by chemically reacting phosphoric acid with hydrogen fluoride. In particular, by means of the process according to the invention it is possible to obtain anhydrous phosphorus pentafluoride which is eminently suitable for the preparation of lithium hexafluorophosphate. A particular advantage of the present invention is found in the use of phosphoric acid as reactant, i.e., the available material is cheap and industrially available, so that within the scope of the present invention, the laborious synthesis of unstable phosphorus pentachloride can be omitted. Furthermore, in general, within the scope of the present invention, the use of chlorine and chlorinated substances can be omitted, which is, on the one hand, favorable from the viewpoint of environmental protection, and on the other hand, also allows a significantly easier processing of the obtained products, since they do not have to be separated from chlorinated by-products in a time-consuming manner. As mentioned above, phosphorus pentafluoride is produced by chemical reaction of phosphoric acid with hydrogen fluoride (also called hydrogen fluoride). Water is formed as a further product of the reaction, which is in particular chemically bound by unreacted or excess hydrogen fluoride. In the reaction of phosphoric acid and hydrogen fluoride, the equilibrium between reactants and products is quickly adjusted, although with appropriate reaction operation it is possible to make the reaction proceed quantitatively with respect to the phosphoric acid used. To do this, the equilibrium of the reaction must be:

[0010] [ka] Since it is entirely on the product side, i.e. on the right side, it is preferable to work with an excess of hydrogen fluoride. Phosphorus pentafluoride has a boiling point of -84.6°C, whereas pure hydrogen fluoride has a boiling point of 19.5°C, so that it is easily possible to separate the formed phosphorus pentafluoride from the reaction mixture by distillation, which is a further advantage of the method according to the invention. Hydrogen fluoride, which may be mixed in during the separation of phosphorus pentafluoride, can then be suitably physically separated from phosphorus pentafluoride, for example by distillation. In order to achieve the most complete chemical reaction of the phosphoric acid, it is advantageous to keep the water content as low as possible throughout the reaction, i.e. not only do the reactants have as low a water content as possible, but the amount of water formed during the chemical reaction is small compared to the hydrogen fluoride (hydrogen fluoride) used.

[0011] In the scope of the present invention, it has proven to be particularly useful if the reaction mixture has a water content of less than 10% by weight, in particular less than 5% by weight, preferably less than 3% by weight, based on the reaction mixture. These water contents are maintained, if possible, throughout all process steps for producing phosphorus pentafluoride, i.e. are not exceeded at any process step. An excess, if any, should occur only after removal of phosphorus pentafluoride from the reaction mixture. In the scope of the present invention, particularly good results are obtained when the hydrogen fluoride used has a water content of less than 5 kg / t, in particular less than 2 kg / t, suitably less than 1 kg / t, preferably less than 500 g / t, the content being related to the total amount of hydrogen fluoride and water, i.e. hydrogen fluoride contaminated with water, respectively. Particularly preferably, the hydrogen fluoride used is anhydrous. In the context of the present invention, anhydrous hydrogen fluoride is understood to mean less than 100 g / t of hydrogen fluoride, based on the mass of hydrogen fluoride which may contain water.

[0012] The aforementioned water contents of hydrogen fluoride give very good results and indicate the range in which hydrogen fluoride should preferably be introduced into the process. When hydrogen fluoride is used multiple or repeatedly, for example in batchwise but also in continuous process operation, it is also possible to operate with higher water contents in subsequent process cycles, as will be further described below.

[0013] Within the scope of the present invention, it is generally intended that hydrogen fluoride be used in liquid form. Furthermore, within the scope of the present invention, it is also intended that hydrogen fluoride is preferably used in excess. Within the scope of the present invention, hydrogen fluoride is preferably used both as reactant and as solvent. As already mentioned above, a large excess of hydrogen fluoride can completely or almost completely shift the reaction equilibrium to the product side, so that the phosphoric acid used is chemically reacted, if possible quantitatively, to phosphorus pentafluoride. Here, the excess of hydrogen fluoride is preferably so large that it does not exceed the above-mentioned water content of the reaction mixture. As already mentioned above, within the scope of the present invention it is preferred that the reactants used have as low a water content as possible. In the context of the present invention, as far as phosphoric acid is concerned, it can be understood that phosphoric acid may contain water, i.e., based on the mixture of H3PO4 and water, has a water content of at most 20% by weight, in particular at most 15% by weight, suitably at most 10% by weight, preferably at most 5% by weight, particularly preferably at most 2% by weight, very particularly preferably at most 1% by weight.Therefore, also with respect to phosphoric acid, it is of course preferred that phosphoric acid has as low a proportion of water as possible.

[0014] However, within the scope of the present invention, it is also easily possible to use commercially available 85% phosphoric acid as a reactant. This too can be chemically reacted with a large excess of hydrogen fluoride to give anhydrous phosphorus pentafluoride, which can be removed without problems from the reaction mixture. However, due to the high hydration enthalpy of hydrogen fluoride, it is preferred that the reactant is as low in water as possible or even anhydrous, since otherwise it would be necessary to cool the reaction mixture significantly to prevent uncontrolled off-gassing of phosphorus pentafluoride and / or hydrogen fluoride from the reaction mixture. In the scope of the present invention, it is particularly preferred that the phosphoric acid is anhydrous. Phosphoric anhydride is a solid and can be used as a fine powder. The best results are obtained when using phosphoric anhydride. According to a preferred embodiment of the present invention, it is intended to add phosphoric acid in a finely dispersed and / or small amount to hydrogen fluoride. The introduction of phosphoric acid in a finely dispersed and / or small amount to hydrogen fluoride, especially to a large excess of hydrogen fluoride, has the advantage that the reaction heat is quickly dissipated and the reaction proceeds completely to give phosphorus pentafluoride.

[0015] Likewise, it is contemplated within the scope of the present invention that the phosphoric acid is preferably added to the hydrogen fluoride with mixing. Additionally, it is preferred that mixing of the reaction mixture continue throughout the reaction period. In the context of the present invention, mixing is understood in particular to mean stirring the reaction mixture, in particular constant stirring of the reaction mixture, or injection of phosphoric acid into hydrogen fluoride. Side reactions can be avoided by preferably vigorous constant mixing of the reaction mixture, especially when phosphoric acid is added to hydrogen fluoride in finely dispersed or small amounts. Among the side reactions observed are, in particular, oligomerization or polymerization of phosphoric acid, which occurs when the water absorption effect of hydrogen fluoride is stronger than the accumulation of fluoride in phosphoric acid. However, this side reaction can be effectively countered by vigorous stirring or vigorous mixing of the reaction mixture. If the phosphoric acid introduced is immediately finely dispersed in a large excess of hydrogen fluoride, a complete chemical reaction to phosphorus pentafluoride is observed. In contrast, if the phosphoric acid is not dispersed quickly enough, especially if the reaction mixture is not well mixed, the described polymerization reaction is observed. These side reactions and their products do not prevent further reaction proceeding, but they do reduce the yield, since polymerized phosphorus compounds remain in the reaction mixture.

[0016] Moreover, in the case of unfavorable reaction procedures, the reaction may not proceed completely to phosphorus pentafluoride, but only to phosphorus oxide trifluoride (POF3). However, even here, a large excess of hydrogen fluoride can prevent the formation of POF3. A high excess of hydrogen fluoride and a low water content promote the chemical reaction to PF5. And yet, POF3 does not hinder the reaction procedure, but only reduces the yield. Since POF3 has a boiling point of -39.7°C, which is significantly higher than the boiling point of PF5 -84.6°C, it is likewise possible to control the selective removal of only PF5 from the reaction mixture by selecting the exhaust gas conditions or distillation conditions. Here, as far as the temperature at which the chemical reaction is carried out is concerned, this is usually carried out at a temperature below the boiling point of hydrogen fluoride, i.e. below 19.5°C. It has proven useful to carry out the chemical reaction at a temperature below 15°C, in particular below 10°C, preferably below 5°C. Therefore, within the scope of the present invention, it is preferred that the reaction conditions, in particular the reaction temperature, remain below the boiling point of pure hydrogen fluoride. However, it is entirely possible to choose a higher temperature when the reaction is carried out under pressure. Within the scope of the present invention, it is generally intended to remove the phosphorus pentafluoride formed from the reaction mixture following the chemical reaction of phosphoric acid with hydrogen fluoride.

[0017] In this connection, it has proven to be advantageous if phosphorus pentafluoride is removed from the reaction mixture via the gas phase. As already mentioned above, phosphorus pentafluoride has a boiling point of -84.6°C, whereas hydrogen fluoride has a boiling point of 19.5°C, so that separation by distillation, i.e. via the gas phase, is easily possible. During the chemical reaction with phosphoric acid, especially when an aqueous solution of phosphoric acid, in particular 85% phosphoric acid, is used, the boiling point of hydrogen fluoride is still significantly higher than that of pure hydrogen fluoride, due to the water concentration in hydrogen fluoride. However, phosphorus pentafluoride forms hydrogen bridge bonds together with hydrogen fluoride, so that in order for phosphorus pentafluoride to be removable from the reaction mixture, in particular to pass into the gas phase, it is necessary to provide a certain amount of energy to isolate phosphorus pentafluoride. According to the invention, it has proven to be useful if phosphorus pentafluoride is removed from the reaction mixture at a temperature below 25°C, in particular below 22°C, preferably below 20°C.

[0018] Likewise, within the scope of the present invention it is contemplated that phosphorus pentafluoride is removed from the reaction mixture at a temperature in the range from -30°C to 25°C, in particular from -20°C to 22°C, suitably from -15°C to 20°C, preferably from -10°C to 19.5°C. Thus, the reaction mixture can be heated to reach or even slightly above the boiling point of pure hydrogen fluoride. As mentioned above, the boiling point of pure hydrogen fluoride is 19.5° C. at normal pressure, i.e., at normal pressure, the reaction mixture can be heated to 19.5° C. or slightly above in order to remove phosphorus pentafluoride from the reaction mixture. However, it is also possible to work at elevated pressure and elevated temperatures. Furthermore, in the scope of the present invention, it has proven useful if phosphorus pentafluoride is removed from the reaction mixture in a method step subsequent to the chemical reaction of phosphoric acid with hydrogen fluoride, in particular in the second method step (b). In principle, due to the large difference in boiling points between phosphorus pentafluoride and hydrogen fluoride, it is also possible to remove phosphorus pentafluoride from the reaction mixture immediately after its formation, in particular by converting it into the gas phase, but in this case it is very difficult to set reproducible controlled conditions. Therefore, preferably, the removal of phosphorus pentafluoride from the reaction mixture is carried out in a method step subsequent to the chemical reaction.

[0019] According to a preferred embodiment of the present invention, (a) in a first method step, chemically reacting phosphoric acid (H3PO4) with hydrogen fluoride (HF) to form phosphorus pentafluoride; (b) in a second process step subsequent to the first process step (a), removing the phosphorus pentafluoride formed in process step (a) from the reaction mixture. is the intention.

[0020] For this particularly preferred embodiment of the invention, all the features, particularities and advantages described above in relation to the further embodiments apply correspondingly. In the scope of the present invention, it has further proved useful if the process, in particular process step (a), is carried out continuously or discontinuously, preferably continuously.The process according to the invention can be carried out discontinuously, i.e. batchwise, for example, by charging liquid hydrogen fluoride into a reactor and adding phosphoric acid with vigorous stirring.After the reaction is over, the reaction mixture is heated, whereby phosphorus pentafluoride is selectively transferred into the gas phase and removed from the reaction mixture. However, within the scope of the present invention, it is preferred that the process operations, in particular the chemical reaction of phosphoric acid with hydrogen fluoride, proceed continuously, for example in a tubular reactor, with the chemical reaction of phosphoric acid and hydrogen fluoride first being carried out with mixing and then the phosphorus pentafluoride formed being removed from the reaction mixture, preferably in a further continuous process, for example in a further section of the tubular reactor or in a further tubular reactor.

[0021] Within the scope of the present invention, it is advantageously envisaged that following the removal of phosphorus pentafluoride, the hydrogen fluoride containing water is further used or processed, in particular in the third process step (c). In the scope of the present invention, it is preferably intended that the hydrogen fluoride used, which may be contaminated with water and phosphorus compounds after carrying out the reaction, is further used for further chemical reaction, especially with phosphoric acid.Here, possible contamination with phosphorus compounds is not an obstacle, but water content is important. For example, hydrogen fluoride should have water of 2% by weight or less, in particular 1% by weight or less, preferably 0.5% by weight or less, based on the total amount of water and hydrogen fluoride. If the water proportion is higher, it becomes particularly difficult to achieve a complete chemical reaction of phosphoric acid to phosphorus pentafluoride. If the water content becomes too high, after removal of phosphorus pentafluoride from the remaining reaction mixture, the so-called sump, anhydrous hydrogen fluoride can be distilled off without problems and then used again to produce phosphorus pentafluoride. Aqueous hydrofluoric acid remains, which can be used for various commercial purposes, optionally after removal of phosphorus-containing impurities.

[0022] Therefore, within the scope of the present invention, preferably (a) in a first method step, chemically reacting phosphoric acid (H3PO4) with hydrogen fluoride (HF) to form phosphorus pentafluoride; (b) in a second process step subsequent to the first process step (a), removing the phosphorus pentafluoride formed in process step (a) from the reaction mixture; (c1) optionally returning the hydrogen fluoride obtained in process step (b) to process step (a), in particular until the hydrogen fluoride has a water content of at most 2% by weight, suitably at most 1% by weight, preferably at most 0.5% by weight, based on aqueous hydrogen fluoride, or (c2) optionally treating the aqueous hydrogen fluoride obtained in process step (b); is the intention.

[0023] The hydrogen fluoride treated in process step (c2) can then be used again in process step (a) or can also be used elsewhere. In the context of the present invention, recycling in process step (a) is understood in particular to mean, in a batchwise manner, the addition of further phosphoric acid to the hydrogen fluoride still present in the reactor after removal of phosphorus pentafluoride.In the case of a continuous process operation, recycling in process step (a) is understood in particular to mean that the aqueous hydrogen fluoride remaining after removal of phosphorus pentafluoride is reacted again with phosphoric acid, in particular by reintroducing it into the reactor to produce phosphorus pentafluoride by chemical reaction with phosphoric acid.

[0024] [Second aspect] The phosphorus pentafluoride obtained within the scope of the present invention is anhydrous and does not contain any chlorine-containing impurities, so it is excellently suitable for the preparation of lithium hexafluorophosphate.Suitable methods for the preparation of lithium hexafluorophosphate are known in the prior art.In particular, it is possible to obtain lithium hexafluorophosphate by chemically reacting a lithium salt, in particular lithium fluoride, with phosphorus pentafluoride in liquid hydrogen fluoride. According to a second aspect of the invention, a further subject of the invention is a method for producing lithium hexafluorophosphate (LiPF6), comprising chemically reacting phosphorus pentafluoride obtained by the method described above with a lithium salt. Within the scope of the present invention, it is preferred that the lithium salt is selected from lithium carbonate, lithium sulfate, lithium fluoride and mixtures thereof. Preferably, the lithium salt is lithium fluoride. In the scope of the present invention, it is preferably intended that the chemical reaction of phosphorus pentafluoride with the lithium salt is carried out in solution, in particular in a solvent. In this connection, particularly good results are obtained when the solvent is selected from the group of hydrogen fluoride, sulfur dioxide, acetonitrile and mixtures thereof, in particular when it is hydrogen fluoride, preferably liquid hydrogen fluoride.

[0025] According to a preferred embodiment of the present invention, (A) in a first method step, chemically reacting phosphoric acid (H3PO4) with hydrogen fluoride (HF) to form phosphorus pentafluoride; (B) in a second process step subsequent to the first process step (A), removing the phosphorus pentafluoride formed in process step (A) from the reaction mixture; and (C) chemically reacting the phosphorus pentafluoride obtained in process step (B) with a lithium salt, in particular in liquid hydrogen fluoride, thereby forming lithium hexafluorophosphate. is the intention. For this particular embodiment of the invention, all the advantages, features and particularities mentioned above in connection with the further embodiments apply correspondingly.

[0026] In a further preferred embodiment of the present invention, I) forming phosphorus pentafluoride in a first method section; (a) in a first method step, chemically reacting phosphoric acid (H3PO4) with hydrogen fluoride (HF) to form phosphorus pentafluoride; (b) in a second process step subsequent to the first process step (a), removing the phosphorus pentafluoride formed in process step (a) from the reaction mixture; (c1) optionally returning the hydrogen fluoride obtained in process step (b) to process step (a), in particular until the hydrogen fluoride has a water content of at most 2% by weight, suitably at most 1% by weight, preferably at most 0.5% by weight, based on aqueous hydrogen fluoride, or (c2) optionally treating the aqueous hydrogen fluoride obtained following process step (b); II) In a subsequent process section, the phosphorus pentafluoride obtained in process step (b) of process section I is chemically reacted with a lithium salt, in particular lithium fluoride, preferably in liquid hydrogen fluoride, thereby obtaining lithium hexafluorophosphate. is the intention. All of the advantages, features and special features discussed above in relation to the further embodiments apply to this particular embodiment. For further details of this aspect of the invention, reference can be made to the above description of the process according to the invention for producing phosphorus pentafluoride, which also applies correspondingly with respect to the process for producing lithium hexafluorophosphate.

Claims

1. Phosphorus pentafluoride (PF 5 ), comprising the steps of: Phosphate (H 3 P.O. 4 ) with hydrogen fluoride (HF).

2. 2. The process according to claim 1, characterized in that the reaction mixture has a water content of less than 10% by weight, in particular less than 5% by weight, preferably less than 3% by weight, based on the reaction mixture.

3. 3. The process according to claim 1 or 2, characterized in that the hydrogen fluoride used has a water content of less than 5 kg / t, in particular less than 2 kg / t, advantageously less than 1 kg / t, preferably less than 500 g / t.

4. 4. The method according to claim 1, wherein the hydrogen fluoride is used in liquid form.

5. The method according to any one of claims 1 to 4, characterized in that the hydrogen fluoride is used in excess.

6. 6. The method according to claim 1, wherein the phosphoric acid has a water content of at most 20% by weight, in particular at most 15% by weight, preferably at most 10% by weight, preferably at most 5% by weight, particularly preferably at most 2% by weight, very particularly preferably at most 1% by weight.

7. 7. The method of claim 6, wherein the phosphoric acid is anhydrous.

8. The method according to any one of claims 1 to 7, characterized in that the phosphoric acid is finely dispersed and / or added in small amounts to the hydrogen fluoride.

9. 9. The method according to claim 1, wherein the phosphoric acid is added to the hydrogen fluoride with mixing.

10. The process according to any one of claims 1 to 9, characterized in that the chemical reaction is carried out at a temperature below 15°C, in particular below 10°C, preferably below 5°C.

11. A method according to any one of claims 1 to 10, characterized in that following the chemical reaction, the phosphorus pentafluoride formed is removed from the reaction mixture.

12. 12. The method of claim 11, wherein the phosphorus pentafluoride is removed from the reaction mixture via the vapor phase.

13. 13. The method according to claim 11 or 12, characterized in that the phosphorus pentafluoride is removed from the reaction mixture at a temperature below 25°C, in particular below 22°C, preferably below 20°C.

14. 14. A method according to any one of claims 11 to 13, characterized in that the phosphorus pentafluoride is removed from the reaction mixture in a method step subsequent to the chemical reaction of the phosphoric acid with the hydrogen fluoride.

15. (a) In a first method step, phosphoric acid (H 3 P.O. 4 chemically reacting the fluoride (C) with hydrogen fluoride (HF) to form phosphorus pentafluoride; (b) in a second process step subsequent to the first process step (a), removing the phosphorus pentafluoride formed in process step (a) from the reaction mixture. The method according to any one of claims 1 to 14, characterized in that

16. The method according to any one of the preceding claims, characterized in that the method, in particular method step (a), is carried out continuously or discontinuously, preferably continuously.

17. 17. The method according to claim 1, characterized in that following the removal of the phosphorus pentafluoride, the hydrogen fluoride containing water is further used or processed, in particular in the third method step (c).

18. (a) In a first method step, phosphoric acid (H 3 P.O. 4 chemically reacting said fluoride with hydrogen fluoride (HF) to form phosphorus pentafluoride; (b) in a second process step subsequent to said first process step (a), removing said phosphorus pentafluoride formed in process step (a) from said reaction mixture; (c1) optionally returning the hydrogen fluoride obtained in process step (b) to process step (a), in particular until the hydrogen fluoride produced in process step (a) has a water content of at most 5% by weight, in particular at most 2% by weight, preferably at most 1% by weight, preferably at most 0.5% by weight, based on aqueous hydrogen fluoride, or (c2) optionally treating said aqueous hydrogen fluoride obtained in process step (b). The method according to any one of claims 1 to 17, characterized in that

19. Lithium hexafluorophosphate (LiPF 6 19. A process for the preparation of phosphorus pentafluoride, characterized in that the phosphorus pentafluoride obtainable by the process according to any one of claims 1 to 18 is chemically reacted with a lithium salt.

20. 20. The method according to claim 19, characterized in that the lithium salt is selected from lithium carbonate, lithium sulfate, lithium fluoride and mixtures thereof, preferably lithium fluoride.

21. 21. A method according to claim 19 or 20, characterized in that the chemical reaction of phosphorus pentafluoride with the lithium salt is carried out in solution, in particular in a solvent.

22. 22. The method according to claim 21, characterized in that the solvent is selected from the group of hydrogen fluoride, sulfur dioxide, acetonitrile and mixtures thereof, in particular hydrogen fluoride, preferably liquid hydrogen fluoride.

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