Preparation method of hexafluorophosphoric acid
By controlling the reaction conditions under high temperature and high pressure, combined with nitrogen replacement and condensation treatment, the problem of low yield of hexafluorophosphoric acid was solved, achieving efficient and low-cost preparation of hexafluorophosphoric acid, and improving product yield and purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIUJIANG TINCI ADVANCED MATERIALS CO LTD
- Filing Date
- 2024-11-05
- Publication Date
- 2026-05-08
AI Technical Summary
Existing methods for preparing hexafluorophosphate have low yields and are prone to decomposition at high temperatures, resulting in high energy consumption and increased costs.
Under conditions of 65–100°C and a pressure not lower than 0.4 MPa, oxygen-containing phosphorus compounds are mixed and reacted with anhydrous hydrogen fluoride. By controlling the pressure and temperature, the mass transfer effect is improved, side reactions are suppressed, and the yield of hexafluorophosphoric acid is increased. Unreacted hydrogen fluoride is recovered by nitrogen replacement and condensation, thereby reducing energy consumption.
It significantly improved the yield of hexafluorophosphate, reduced energy consumption, decreased the occurrence of side reactions, reduced production costs, and improved product purity.
Smart Images
Figure SMS_6
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery material preparation technology, specifically relating to a method for preparing hexafluorophosphate. Background Technology
[0002] Electrolyte, as one of the four key materials in rechargeable batteries, has a significant impact on the battery's electrochemical performance and is often referred to as the "blood" of a rechargeable battery. Among them, electrolyte salts are an important component of electrolytes, and hexafluorophosphates are widely used in current commercial rechargeable batteries because they can improve battery energy density and electrochemical performance, as well as have excellent chemical and thermal stability.
[0003] There are many existing methods for preparing hexafluorophosphate, the most common being the reaction of anoxic phosphoric acid compounds with anhydrous hydrogen fluoride. However, this method has a low yield. Therefore, it is necessary to investigate a method for preparing hexafluorophosphate with a high yield. Summary of the Invention
[0004] To address the aforementioned deficiencies, this invention provides a method for preparing hexafluorophosphate, which can significantly improve the yield of hexafluorophosphate.
[0005] This invention provides a method for preparing hexafluorophosphate, comprising the following steps:
[0006] Oxygen-containing phosphorus compounds are mixed with anhydrous hydrogen fluoride and reacted at a temperature of 65–100 °C and a pressure of not less than 0.4 MPa to obtain hexafluorophosphoric acid.
[0007] Furthermore, the reaction temperature is 65–85°C, and / or the reaction time is 0.5–2 h.
[0008] Furthermore, the pressure in the reaction is 0.4–1.5 MPa.
[0009] Furthermore, the oxygen-containing phosphorus compound includes at least one of polyphosphoric acid, anhydrous phosphoric acid, and phosphorus pentoxide.
[0010] Furthermore, the molar ratio of the polyphosphoric acid to the anhydrous hydrogen fluoride is 1:(26.4 to 48.0).
[0011] Furthermore, the molar ratio of the anhydrous phosphoric acid to the anhydrous hydrogen fluoride is 1:(6.6 to 12.0).
[0012] Furthermore, the molar ratio of phosphorus pentoxide to anhydrous hydrogen fluoride is 1:(13.2~24.0).
[0013] Furthermore, the oxygen-containing phosphorus compound is polyphosphoric acid;
[0014] The molar ratio of the polyphosphoric acid to the anhydrous hydrogen fluoride is 1:(26.4 to 36.0).
[0015] Furthermore, after the reaction is complete, the reaction system is cooled to -10 to 20°C and replaced with nitrogen to obtain hexafluorophosphoric acid.
[0016] Furthermore, the mixture obtained by displacement is condensed, and the product at -20 to 5°C is collected to obtain recovered hydrogen fluoride.
[0017] The method for preparing hexafluorophosphate in this invention involves mixing an oxygen-containing phosphorus compound with anhydrous hydrogen fluoride and reacting the mixture at a temperature of 65–100°C and a pressure of not less than 0.4 MPa. This reduces the viscosity of the oxygen-containing phosphorus compound, which facilitates sufficient contact between the compound and the anhydrous hydrogen fluoride, improves mass transfer, and thus increases the yield of hexafluorophosphate. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0019] Currently, to prevent hexafluorophosphate from decomposing at high temperatures and producing phosphorus pentafluoride and phosphorus trifluoride (reaction formulas are shown in Equations 1 and 2), the reaction rate is generally controlled by lowering the temperature during the reaction process, thereby inhibiting the decomposition of hexafluorophosphate. However, the oxyphosphorus compounds used as raw materials for the preparation of hexafluorophosphate are mostly viscous liquids at low temperatures, resulting in poor mass transfer and low yields of hexafluorophosphate. Moreover, this reaction is exothermic, and maintaining low temperatures requires cooling operations, which consumes a large amount of energy. Therefore, simply controlling the reaction temperature cannot achieve a high yield.
[0020] Formula 1;
[0021] Formula 2.
[0022] In view of this, the present invention provides a method for preparing hexafluorophosphate, comprising the following steps:
[0023] Oxygen-containing phosphorus compounds are mixed with anhydrous hydrogen fluoride and reacted at a temperature of 65–100 °C and a pressure of not less than 0.4 MPa to obtain hexafluorophosphoric acid.
[0024] This invention, while increasing the reaction temperature, also controls the pressure during the reaction process, ensuring it is not lower than 0.4 MPa. This not only effectively reduces the viscosity of the oxyphosphorus compound and improves the mass transfer between anhydrous hydrogen fluoride and the oxyphosphorus compound, allowing for sufficient contact and reaction between the two, significantly increasing the conversion rate of the oxyphosphorus compound and thus improving the yield of hexafluorophosphoric acid; it also effectively suppresses the side reactions of hexafluorophosphoric acid at high temperatures, further increasing the yield of hexafluorophosphoric acid. Simultaneously, it liquefies the anhydrous hydrogen fluoride, which is originally in gaseous form, further improving the mass transfer between the anhydrous hydrogen fluoride and the oxyphosphorus compound, allowing for better reaction and further increasing the yield of hexafluorophosphoric acid. Furthermore, this process eliminates the need for cooling operations, effectively reducing reaction energy consumption and costs.
[0025] For example, the reaction temperature is 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C.
[0026] The present invention does not specify the mixing order of the oxygen-containing phosphorus compound and anhydrous hydrogen fluoride. It can be that the oxygen-containing phosphorus compound is added to the anhydrous hydrogen fluoride, or that the anhydrous hydrogen fluoride is added to the oxygen-containing phosphorus compound.
[0027] The present invention does not specify the mixing method of oxygen-containing phosphorus compounds and anhydrous hydrogen fluoride, as long as the oxygen-containing phosphorus compounds and anhydrous hydrogen fluoride are mixed evenly, for example, by using magnetic stirring or mechanical stirring.
[0028] In one specific embodiment, the reaction temperature is 65–85°C. Exemplarily, the reaction temperature is 65°C, 70°C, 75°C, 80°C, or 85°C. Within this range, the oxygen-containing phosphorus compound and anhydrous hydrogen fluoride can react more effectively, further increasing the yield of hexafluorophosphoric acid; at the same time, energy consumption can be reduced, and the occurrence of side reactions can be minimized.
[0029] In one specific embodiment, the reaction time is 0.5–2 hours. Exemplarily, the reaction time is 0.5 hours, 0.8 hours, 1.1 hours, 1.4 hours, 1.7 hours, or 2.0 hours. When the reaction time is within this range, the degree of reaction between the oxyphosphorus compound and anhydrous hydrogen fluoride can be further enhanced, resulting in a higher conversion rate of the oxyphosphorus compound and thus increasing the yield of hexafluorophosphoric acid; simultaneously, it also helps to reduce energy consumption and save costs.
[0030] In one specific embodiment, the pressure during the reaction is 0.4–1.5 MPa. Exemplarily, the pressure during the reaction is 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, or 1.5 MPa. Within this range, not only can the inhibition of side reactions be guaranteed, but operational safety can also be improved and costs reduced.
[0031] In one specific embodiment, the oxygen-containing phosphorus compound includes at least one of polyphosphoric acid, anhydrous phosphoric acid, and phosphorus pentoxide.
[0032] When the aforementioned compound is a mixture of multiple specific compounds, the present invention does not impose excessive restrictions on the proportions between the various specific compounds.
[0033] When the oxygen-containing phosphorus compound is polyphosphoric acid, anhydrous phosphoric acid, or phosphorus pentoxide, the reaction principle is shown in Equations 3, 4, and 5.
[0034] Formula 3;
[0035] Equation 4;
[0036] Formula 5.
[0037] In one specific embodiment, the molar ratio of polyphosphoric acid to anhydrous hydrogen fluoride is 1:(26.4–48). Within this range, an excess of anhydrous hydrogen fluoride ensures that the polyphosphoric acid is fully reacted, further improving the conversion rate of the polyphosphoric acid.
[0038] For example, the molar ratio of polyphosphoric acid to anhydrous hydrogen fluoride is 1:26.4, 1:28.0, 1:30.0, 1:32.0, 1:34.0, 1:36.0, 1:38.0, 1:40.0, 1:42.0, 1:44.0, 1:46.0 or 1:48.0.
[0039] In one specific embodiment, the molar ratio of anhydrous phosphoric acid to anhydrous hydrogen fluoride is 1:(6.6–12.0). Within this range, excess anhydrous hydrogen fluoride ensures that the anhydrous phosphoric acid is fully reacted, further improving the conversion rate of anhydrous phosphoric acid.
[0040] For example, the molar ratio of anhydrous phosphoric acid to anhydrous hydrogen fluoride is 1:6.6, 1:7.0, 1:8.0, 1:9.0, 1:10.0, 1:11.0 or 1:12.0.
[0041] In one specific embodiment, the molar ratio of phosphorus pentoxide to anhydrous hydrogen fluoride is 1:(13.2–24.0). Within this range, an excess of anhydrous hydrogen fluoride ensures that phosphorus pentoxide is fully reacted, further improving the conversion rate of phosphorus pentoxide.
[0042] For example, the molar ratio of phosphorus pentoxide to anhydrous hydrogen fluoride is 1:13.2, 1:14.0, 1:15.0, 1:16.0, 1:17.0, 1:18.0, 1:19.0, 1:20.0, 1:21.0, 1:22.0, 1:23.0 or 1:24.0.
[0043] In one specific embodiment, the oxyphosphoric acid compound is polyphosphoric acid; the molar ratio of polyphosphoric acid to anhydrous hydrogen fluoride is 1:(26.4–36.0). Exemplarily, the molar ratio of polyphosphoric acid to anhydrous hydrogen fluoride is 1:26.4, 1:28.0, 1:30.0, 1:32.0, 1:34.0, or 1:36.0. When polyphosphoric acid is chosen as the oxyphosphoric acid compound, and the molar ratio of polyphosphoric acid to anhydrous hydrogen fluoride is within the aforementioned range, polyphosphoric acid and anhydrous hydrogen fluoride exhibit better mass transfer during the reaction, which is beneficial for achieving a higher yield. Simultaneously, it can reduce the amount of anhydrous hydrogen fluoride used to a certain extent, which not only saves costs but also improves the purity of hexafluorophosphoric acid.
[0044] In one specific embodiment, after the reaction is complete, the reaction system is cooled to -10 to 20°C and purged with nitrogen to obtain hexafluorophosphoric acid. Although increasing the reaction temperature can effectively improve the conversion rate of oxygen-containing phosphorus compounds and significantly suppress the generation of side reactions by controlling the pressure, as the reaction temperature rises to a certain level, hexafluorophosphoric acid still has a certain possibility of further reaction, producing phosphorus pentafluoride and phosphorus trifluoride oxyfluoride. Therefore, the reaction system after the reaction may contain unreacted hydrogen fluoride, as well as phosphorus pentafluoride and phosphorus trifluoride oxyfluoride produced by the side reactions. In order to further eliminate the influence of side reactions, after the reaction is complete, the temperature of the reaction system is lowered to -10 to 20°C, and then purged with nitrogen to remove the residual hydrogen fluoride and the byproducts phosphorus pentafluoride and phosphorus trifluoride oxyfluoride from the reaction system, thereby obtaining hexafluorophosphoric acid with higher purity.
[0045] Furthermore, the nitrogen purging time should be no less than 3 hours.
[0046] This invention does not specify the cooling rate; it is sufficient to reduce the temperature of the reaction system to the target temperature of -10 to 20°C.
[0047] In one specific embodiment, the mixture obtained by displacement is condensed, and the product at -20 to 5°C is collected to obtain recovered hydrogen fluoride. Since anhydrous hydrogen fluoride is often used in excess during the reaction to ensure the oxygen-containing phosphorus compounds react fully and to improve their conversion rate, the hydrogen fluoride can be separated by condensing the mixture obtained by displacement (including hydrogen fluoride, phosphorus pentafluoride, and phosphorus trifluoride oxyfluoride), thus obtaining recovered hydrogen fluoride. This recovered hydrogen fluoride can be used as a reaction raw material and reused in the reaction to prepare hexafluorophosphoric acid, reducing production costs.
[0048] The preparation method of hexafluorophosphate according to the present invention will be described in detail below through specific embodiments. It should be noted that the amount of oxygen-containing phosphorus compound fed in the following embodiments is 1 mol.
[0049] Example 1
[0050] Polyphosphoric acid (H6P4O) with a molar ratio of 1:26.4 13 Anhydrous hydrogen fluoride was added to a reaction vessel and mixed. The stirring was turned on, and the reaction vessel temperature was maintained at 75°C and the pressure was maintained at 1.0 MPa. After 1 hour of reaction, an aqueous solution of hexafluorophosphate was obtained. After the reaction was completed, the system temperature was lowered to -5°C and nitrogen was used for purging for 3 hours to obtain hexafluorophosphate. The mixture obtained by purging was subjected to two-stage condensation treatment at -15°C to obtain recovered hydrogen fluoride. The recovered anhydrous hydrogen fluoride can be used as a raw material in the above reaction.
[0051] Example 2
[0052] Phosphorus pentoxide and anhydrous hydrogen fluoride in a molar ratio of 1:30 were added to a reaction vessel and mixed. The mixture was stirred and the temperature of the reaction vessel was maintained at 65°C and the pressure at 1.5 MPa. After 2 hours of reaction, an aqueous solution of hexafluorophosphoric acid was obtained. After the reaction was completed, the temperature of the system was lowered to 10°C and nitrogen was used for purging for 5 hours to obtain hexafluorophosphoric acid. The mixture obtained by purging was subjected to two-stage condensation at -20°C to obtain recovered hydrogen fluoride. The recovered anhydrous hydrogen fluoride can be used as a raw material in the above reaction.
[0053] Example 3
[0054] Anhydrous phosphoric acid and anhydrous hydrogen fluoride in a molar ratio of 1:6.6 were added to a reaction vessel and mixed. The stirring was turned on, and the reaction vessel temperature was maintained at 85°C and the pressure at 0.4 MPa. After 0.5 h of reaction, an aqueous solution of hexafluorophosphoric acid was obtained. After the reaction was completed, the temperature of the system was lowered to 0°C and nitrogen was used for purging for 3 h to obtain hexafluorophosphoric acid. The mixture obtained by purging was subjected to two-stage condensation treatment at -20°C to obtain recovered hydrogen fluoride. The recovered anhydrous hydrogen fluoride can be used as a raw material in the above reaction.
[0055] Example 4
[0056] Polyphosphoric acid (H6P4O) with a molar ratio of 1:40 13 Anhydrous hydrogen fluoride was added to a reaction vessel and mixed. The stirring was turned on, and the reaction vessel temperature was maintained at 75°C and the pressure was maintained at 1.0 MPa. After 1 hour of reaction, an aqueous solution of hexafluorophosphate was obtained. After the reaction was completed, the system temperature was lowered to -5°C and nitrogen was used for purging for 3 hours to obtain hexafluorophosphate. The mixture obtained by purging was subjected to two-stage condensation treatment at -15°C to obtain recovered hydrogen fluoride. The recovered anhydrous hydrogen fluoride can be used as a raw material in the above reaction.
[0057] Example 5
[0058] Polyphosphoric acid (H6P4O) with a molar ratio of 1:48 13 Anhydrous hydrogen fluoride was added to a reaction vessel and mixed. The stirring was turned on, and the reaction vessel temperature was maintained at 75°C and the pressure was maintained at 1.0 MPa. After 1 hour of reaction, an aqueous solution of hexafluorophosphate was obtained. After the reaction was completed, the system temperature was lowered to -5°C and nitrogen was used for purging for 3 hours to obtain hexafluorophosphate. The mixture obtained by purging was subjected to two-stage condensation treatment at -15°C to obtain recovered hydrogen fluoride. The recovered anhydrous hydrogen fluoride can be used as a raw material in the above reaction.
[0059] Example 6
[0060] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1. The difference is that the temperature of the reactor is adjusted to 69°C and the reaction pressure is adjusted to 0.6 MPa; the system temperature after the reaction is completed is lowered to -10°C; and the temperature of the condensation treatment is adjusted to -10°C.
[0061] Example 7
[0062] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1. The difference is that the temperature of the reactor is adjusted to 73°C and the reaction pressure is adjusted to 0.8 MPa; the system temperature after the reaction is completed is reduced to 5°C; and the temperature of the condensation treatment is adjusted to -5°C.
[0063] Example 8
[0064] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1. The difference is that the temperature of the reactor is adjusted to 79°C and the reaction pressure is adjusted to 1.2 MPa; the system temperature after the reaction is completed is reduced to 15°C; and the temperature of the condensation treatment is adjusted to 0°C.
[0065] Example 9
[0066] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1. The difference is that the temperature of the reactor is adjusted to 83°C and the reaction pressure is adjusted to 1.4 MPa; the system temperature after the reaction is completed is reduced to 20°C; and the temperature of the condensation treatment is adjusted to 5°C.
[0067] Example 10
[0068] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1, except that the temperature of the reaction vessel is adjusted to 90°C.
[0069] Example 11
[0070] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1, except that the temperature of the reaction vessel is adjusted to 100°C.
[0071] Example 12
[0072] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1, except that the reaction pressure is adjusted to 1.6 MPa.
[0073] Example 13
[0074] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1, except that the reaction time is adjusted to 4 hours.
[0075] Example 14
[0076] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 1, except that polyphosphoric acid (H6P4O) is used instead of polyphosphoric acid. 13 The molar ratio of anhydrous hydrogen fluoride to hydrogen fluoride was adjusted to 1:24.
[0077] Example 15
[0078] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 2, except that the molar ratio of phosphorus pentoxide to anhydrous hydrogen fluoride is adjusted to 1:12.
[0079] Example 16
[0080] The preparation method of hexafluorophosphate in this embodiment is basically the same as that in Example 3, except that the molar ratio of anhydrous phosphoric acid to anhydrous hydrogen fluoride is adjusted to 1:6.
[0081] Comparative Example 1
[0082] The preparation method of hexafluorophosphate in this comparative example is basically the same as that in Example 1, except that the reaction temperature is adjusted to 60°C and the reaction pressure is adjusted to 0.3 MPa.
[0083] Comparative Example 2
[0084] The preparation method of hexafluorophosphate in this comparative example is basically the same as that in Example 1, except that the reaction temperature is adjusted to 105℃.
[0085] Comparative Example 3
[0086] The preparation method of hexafluorophosphate in this comparative example is basically the same as that in Example 1, except that the reaction pressure is adjusted to 0.3 MPa.
[0087] Comparative Example 4
[0088] The preparation method of hexafluorophosphate in this comparative example is basically the same as that in Example 1, except that the reaction temperature is adjusted to 60°C.
[0089] Comparative Example 5
[0090] The reactor equipped with a reflux condenser was cooled to 5°C. Next, anhydrous hydrogen fluoride was added to the reactor, and stirring was started to maintain the system temperature at 8°C. Then, polyphosphoric acid (H6P4O) was added dropwise to the reactor. 13 The molar ratio of hexafluorophosphate to anhydrous hydrogen fluoride was 1:24. The reaction temperature was controlled at 20-25℃ and the reaction pressure was 0.098MPa. After the addition was completed, the reaction was kept at the temperature for 2 hours. Finally, the temperature was lowered to 20℃ to obtain the hexafluorophosphate reaction solution.
[0091] Test case
[0092] The hexafluorophosphate aqueous solution prepared in the above examples and comparative examples was tested by ion chromatography to obtain the content of hexafluorophosphate in the reaction solution.
[0093] Hexafluorophosphate yield (%) = hexafluorophosphate content in the reaction solution * mass of the solution after reaction / theoretical mass of hexafluorophosphate generated from oxyphosphorus compounds × 100%.
[0094] The test results and calculation results are shown in Table 1.
[0095] Table 1
[0096]
[0097] As shown in Table 1:
[0098] Compared to Comparative Examples 1-5, the preparation methods of hexafluorophosphate in Examples 1-16 can achieve higher yields of hexafluorophosphate. The yield of hexafluorophosphate in Example 1 reaches 96.11%, significantly higher than that in Comparative Examples 1-5. Therefore, the preparation method of hexafluorophosphate in this invention can significantly improve the yield of hexafluorophosphate.
[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing hexafluorophosphate, characterized in that, Includes the following steps: Oxygen-containing phosphorus compounds are mixed with anhydrous hydrogen fluoride and reacted at a temperature of 65–100°C and a pressure of not less than 0.4 MPa to obtain hexafluorophosphoric acid.
2. The method for preparing hexafluorophosphate according to claim 1, characterized in that, The reaction temperature is 65–85°C, and / or the reaction time is 0.5–2 h.
3. The method for preparing hexafluorophosphate according to claim 1 or 2, characterized in that, The pressure in the reaction is 0.4–1.5 MPa.
4. The method for preparing hexafluorophosphate according to any one of claims 1-3, characterized in that, The oxygen-containing phosphorus compound includes at least one of polyphosphoric acid, anhydrous phosphoric acid, and phosphorus pentoxide.
5. The method for preparing hexafluorophosphate according to claim 4, characterized in that, The molar ratio of the polyphosphoric acid to the anhydrous hydrogen fluoride is 1:(26.4 to 48.0).
6. The method for preparing hexafluorophosphate according to claim 4, characterized in that, The molar ratio of the anhydrous phosphoric acid to the anhydrous hydrogen fluoride is 1:(6.6 to 12.0).
7. The method for preparing hexafluorophosphate according to claim 4, characterized in that, The molar ratio of phosphorus pentoxide to anhydrous hydrogen fluoride is 1:(13.2-24.0).
8. The method for preparing hexafluorophosphate according to claim 4, characterized in that, The oxygen-containing phosphorus compound is polyphosphoric acid; The molar ratio of the polyphosphoric acid to the anhydrous hydrogen fluoride is 1:(26.4 to 36.0).
9. The method for preparing hexafluorophosphate according to any one of claims 1-8, characterized in that, After the reaction was completed, the reaction system was cooled to -10 to 20°C and replaced with nitrogen to obtain hexafluorophosphoric acid.
10. The method for preparing hexafluorophosphate according to claim 9, characterized in that, The mixture obtained by displacement is condensed, and the product is collected at -20 to 5°C to obtain recovered hydrogen fluoride.