A method for preparing high-purity phosphorus pentafluoride gas

Abstract

This invention belongs to the field of inorganic fluoride preparation technology, and relates to a method for preparing high-purity phosphorus pentafluoride gas. A phosphorus pentafluoride mixed gas is passed into dimethyl carbonate, and the mixture is sequentially heated and pressurized for reaction, cooled to precipitate, and filtered to obtain a phosphorus pentafluoride complex solid. The phosphorus pentafluoride complex solid is then sequentially washed, re-dissolved, and distilled to obtain high-purity phosphorus pentafluoride gas. Compared to traditional methods using multi-stage distillation and washing, this method can efficiently and easily remove impurities such as hydrofluoric acid and hydrogen chloride from the phosphorus pentafluoride gas, and does not generate a large amount of waste acid. The purity of the prepared gas is above 99.9%, and the gas yield is above 90%. When high-purity phosphorus pentafluoride gas is used in lithium-ion batteries, it can meet the performance requirements of lithium-ion battery electrolytes.

Description

Technical Field

[0001] This invention belongs to the field of inorganic fluoride preparation technology, and relates to a method for preparing high-purity phosphorus pentafluoride gas. Background Technology

[0002] Phosphorus pentafluoride is an important inorganic fluoride widely used in industry, including electronics, semiconductor manufacturing, polymer materials, and catalysis. As a raw material for the synthesis of lithium hexafluorophosphate, the preparation methods of phosphorus pentafluoride have attracted considerable attention.

[0003] Currently, the preparation methods of phosphorus pentafluoride mainly include two categories: direct and indirect methods. The direct method typically involves a gas-solid reaction between elemental phosphorus and fluorine gas. However, this method suffers from problems such as difficulty in controlling the reaction process, high technological complexity, and high cost. The indirect method currently has two mainstream processes. One uses polyphosphoric acid as a raw material, reacting it with fuming acid and hydrofluoric acid to prepare phosphorus pentafluoride. Its problems include numerous byproducts, and the azeotropic reaction between phosphorus pentafluoride gas and hydrofluoric acid, limiting the purity of the phosphorus pentafluoride gas. The reaction also generates a large amount of fluorine-containing waste acid. The other method uses phosphorus pentachloride as a raw material, reacting it with hydrofluoric acid to prepare phosphorus pentafluoride. Its advantages are fewer reaction byproducts and relatively lower cost. The disadvantage is that the hydrogen chloride produced in the reaction has a boiling point close to that of phosphorus pentafluoride gas, making it difficult to separate them by distillation, thus limiting its application. For example, patent document CN119490166A discloses a continuous or semi-continuous method for preparing high-purity phosphorus pentafluoride. The method includes the following steps: (1) reacting a mixed gas containing phosphorus pentafluoride with solid aluminum fluoride to prepare solid aluminum hexafluorophosphate, wherein the mixed gas contains phosphorus pentafluoride, hydrogen fluoride, and hydrogen chloride; (2) heating the obtained solid aluminum hexafluorophosphate to 250–450°C for thermal decomposition, and collecting the high-purity phosphorus pentafluoride gas. This method has advantages such as no need for high pressure or low-temperature physical separation, safe and controllable reaction, high product purity, and suitability for industrial production. However, this method still faces challenges in continuous preparation due to issues with reaction condition optimization and high cost.

[0004] Therefore, developing an efficient and simple method for separating phosphorus pentafluoride gas from hydrofluoric acid and hydrogen chloride is of great significance. In particular, the preparation of high-purity phosphorus pentafluoride gas that meets the performance requirements of lithium-ion battery electrolytes is a current research focus and challenge. The new preparation method needs to overcome various problems existing in current technologies, improve the purity of phosphorus pentafluoride, and reduce costs. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a method for preparing high-purity phosphorus pentafluoride gas, which can remove impurities such as hydrofluoric acid and hydrogen chloride from the phosphorus pentafluoride gas, resulting in a gas purity of over 99.9% and a gas yield of over 90%.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing high-purity phosphorus pentafluoride gas. A phosphorus pentafluoride mixed gas is passed into dimethyl carbonate (DMC), and the mixture is subjected to heating and pressurization reaction, cooling and precipitation, and filtration to obtain a phosphorus pentafluoride complex solid. The phosphorus pentafluoride complex solid is then washed, dissolved, and distilled to obtain high-purity phosphorus pentafluoride gas.

[0007] Furthermore, the phosphorus pentafluoride mixture contains phosphorus pentafluoride gas, hydrogen chloride, and hydrogen fluoride, with a mass percentage of 41-42%: 54-56%: 2-5%. This invention uses a phosphorus pentafluoride mixture as a raw material, wherein the mixture is the gas produced by the reaction of phosphorus pentachloride with hydrofluoric acid.

[0008] Furthermore, the amount of dimethyl carbonate added is 1 to 1.2 times the mass of the phosphorus pentafluoride mixture. After the mixed gas is introduced, phosphorus pentafluoride will complex with DMC, hydrogen chloride has poor solubility in DMC and is discharged, and hydrogen fluoride will dissolve in DMC and will not complex with the solvent.

[0009] Furthermore, the heating and pressurizing reaction is carried out at a temperature of 45-60°C, a pressure of 0.2-0.3 MPa, and a time of 10-20 min. The reaction is preferably conducted in a reaction vessel.

[0010] Furthermore, the cooling precipitation temperature is 15~25℃, and the holding time is 3~4h. During this process, the system is statically and slowly cooled to 15~25℃ and held at the corresponding temperature for 3~4h to ensure that the complex solid of phosphorus pentafluoride and DMC precipitates slowly, reducing solvent coating in the precipitated solid.

[0011] Furthermore, the time for the heating and pressurizing reaction temperature to drop to the precipitation temperature is 0.5~1.5h.

[0012] Furthermore, the filtration is performed using nitrogen positive pressure filtration; after filtration, a white phosphorus pentafluoride complex solid is obtained.

[0013] Furthermore, the detergent used for washing the phosphorus pentafluoride complex solid includes dimethyl carbonate, and the washing is performed ≥2 times. The amount of detergent used each time is 0.4 to 0.6 times the mass of the phosphorus pentafluoride complex solid.

[0014] Furthermore, the amount of solvent used during the redissolution is 2 to 3 times the mass of the washed phosphorus pentafluoride complex solid, and the solvent includes dichloromethane (DCM).

[0015] Furthermore, the distillation is carried out in a distillation vessel.

[0016] Furthermore, the bottom temperature of the distillation vessel is 90~100℃, the pressure of the distillation column is 0.8~0.9Mpa, and the condensation temperature at the top of the distillation column is -30~35℃.

[0017] The gas obtained by the above-mentioned method for preparing high-purity phosphorus pentafluoride gas has a purity of over 99.9% and a yield of over 90%.

[0018] The beneficial effects of this invention are: The preparation method provided in this invention, compared to the traditional method using multi-stage distillation and washing, involves passing a phosphorus pentafluoride mixed gas into DMC. The phosphorus pentafluoride then complexes with the DMC to form a solid complex. Hydrogen chloride, which has poor solubility in DMC, is discharged. Hydrofluoric acid dissolves in the solvent and does not complex with it. This method efficiently and easily removes impurities such as hydrofluoric acid and hydrogen chloride from the phosphorus pentafluoride gas without generating large amounts of waste acid. The solid complex is then washed, dissolved again, and distilled to obtain high-purity phosphorus pentafluoride gas. The obtained gas has a purity of over 99.9% and a yield of over 90%. When this high-purity phosphorus pentafluoride gas is used in lithium-ion batteries, it can meet the performance requirements of lithium-ion battery electrolytes. Attached Figure Description

[0019] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a picture of the white phosphorus pentafluoride complex solid product obtained after positive pressure filtration in Example 1 of the present invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All mentioned embodiments are implemented based on the technical solutions of the present invention, and detailed implementation processes are given. However, it should be stated that the scope of protection of the present invention is not limited to the following embodiments.

[0022] The following embodiments provide detailed implementation procedures for the technical solutions of the present invention. Unless otherwise specified, the experimental methods used in the following experimental examples are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0023] Example 1

[0024] A method for preparing high-purity phosphorus pentafluoride gas, comprising the following steps: 1. Pass 100 g of mixed gas (phosphorus pentafluoride content 42%, hydrogen chloride content 56%, hydrogen fluoride content 2%) into a reactor containing 100 g of DMC. The reactor temperature is 45℃ and the pressure is 0.3 MPa.

[0025] 2. The gas introduction time is 30 min, and stirring continues for 20 min after the gas introduction is completed.

[0026] 3. After stirring, slowly cool down to 15℃ for 1 hour, and then keep warm at 25℃ for 2 hours.

[0027] 4. After the heat preservation was completed, the mixture was filtered under positive pressure under nitrogen protection to obtain 71 g of white solid. Figure 1 Each sample was washed twice with 35.5 g of DMC.

[0028] 5. The remaining 69 g of solid after washing was added to a solution containing 138 g of DCM, dissolved, and then transferred to a distillation vessel.

[0029] 6. The bottom temperature is 100℃, the distillation column pressure is 0.9Mpa, the top condensation temperature is -30℃, the purity of the gas collected at the back end is 99.95%, the gas mass is 38 g, and the yield is 90.5%.

[0030] Example 2

[0031] A method for preparing high-purity phosphorus pentafluoride gas, comprising the following steps: 1. Pass 100 g of mixed gas (phosphorus pentafluoride content 41%, hydrogen chloride content 54%, hydrogen fluoride content 5%) into a DMC reactor containing 100 g of gas. The reactor temperature is 60℃ and the pressure is 0.2 MPa.

[0032] 2. The gas introduction time is 20 min, and stirring continues for 10 min after the gas introduction is completed.

[0033] 3. After stirring, slowly cool down to 25°C for 1 hour, and then keep warm at 25°C for 3 hours.

[0034] 4. After the heat preservation is completed, the mixture is filtered under positive pressure under nitrogen protection to obtain 70 g of white solid, which is washed twice with 35 g of DMC.

[0035] 5. The remaining 68 g of solid after washing was added to a solution containing 204 g of DCM, dissolved, and then transferred to a distillation vessel.

[0036] 6. The bottom temperature is 90℃, the distillation column pressure is 0.8Mpa, the top condensation temperature is -35℃, the purity of the gas collected at the back end is 99.92%, the gas mass is 37.5 g, and the yield is 91.5%.

[0037] In summary, the preparation method provided in this invention, compared to the traditional method using multi-stage distillation and washing, allows for efficient and convenient removal of impurities such as hydrofluoric acid and hydrogen chloride from the phosphorus pentafluoride gas after the mixed phosphorus pentafluoride gas is introduced into DMC, forming a complex solid. Hydrogen chloride, with its poor solubility in DMC, is discharged; hydrofluoric acid dissolves in the solvent and does not complex with it. This method avoids generating large amounts of waste acid. The complex solid is then washed, dissolved again, and distilled to obtain high-purity phosphorus pentafluoride gas. The obtained gas purity is above 99.9%, and the gas yield is above 90%. When this high-purity phosphorus pentafluoride gas is used in lithium-ion batteries, it can meet the performance requirements of lithium-ion battery electrolytes.

[0038] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-purity phosphorus pentafluoride gas, characterized in that, A mixture of phosphorus pentafluoride gas is passed into dimethyl carbonate and subjected to heating and pressurization reaction, cooling precipitation, and filtration to obtain a solid phosphorus pentafluoride complex. The solid phosphorus pentafluoride complex is then washed, dissolved, and distilled to obtain high-purity phosphorus pentafluoride gas.

2. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The phosphorus pentafluoride mixture contains phosphorus pentafluoride gas, hydrogen chloride, and hydrogen fluoride, and the mass percentages of the phosphorus pentafluoride gas, hydrogen chloride, and hydrogen fluoride are 41~42%: 54~56%: 2~5%.

3. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The amount of dimethyl carbonate added is 1 to 1.2 times the mass of the phosphorus pentafluoride mixture.

4. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The heating and pressurizing reaction is carried out at a temperature of 45~60℃, a pressure of 0.2~0.3Mpa, and a time of 10~20min.

5. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The temperature at which the precipitation occurs is 15~25℃, and the holding time is 3~4h.

6. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The filtration process uses nitrogen positive pressure filtration.

7. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The washing of the phosphorus pentafluoride complex solid uses a detergent including dimethyl carbonate, and the washing is performed ≥ 2 times. The amount of detergent used each time is 0.4 to 0.6 times the mass of the phosphorus pentafluoride complex solid.

8. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The amount of solvent used during the redissolution is 2 to 3 times the mass of the washed phosphorus pentafluoride complex solid, and the solvent includes dichloromethane.

9. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The distillation is carried out in a distillation vessel.

10. The method for preparing high-purity phosphorus pentafluoride gas according to claim 1, characterized in that, The bottom temperature of the distillation vessel is 90~100℃, the pressure is 0.8~0.9Mpa, and the top condensation temperature is -30~35℃.

Images