Method for improving conversion rate and purity of phosphorus pentafluoride

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to a method for improving the conversion rate and purity of phosphorus pentafluoride, which comprises the following steps: (1) adding a hexafluorophosphoric acid aqueous solution with the mass fraction of 45% into a strong acid pyrolyzing agent, heating to the temperature of 1, and reacting to prepare mixed gas; (2) cooling the mixed gas to a temperature range of 2, and condensing to obtain refined mixed gas; (3) introducing the refined mixed gas into a purified washing solution at the temperature of 3 DEG C, and carrying out deep separation and purification to obtain high-purity phosphorus pentafluoride; the method provided by the invention solves the problems of high impurity index and poor purity in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and particularly relates to a method for improving the conversion rate and purity of phosphorus pentafluoride. Background Art

[0002] Phosphorus pentafluoride (PF5) is a colorless gas with a pungent foul odor at room temperature and pressure, with a melting point of -93.8°C and a boiling point of -84.6°C. Phosphorus pentafluoride has a wide range of uses in semiconductor manufacturing, polymer synthesis, and catalysts. In recent years, in the battery field, phosphorus pentafluoride has been used to prepare hexafluorophosphate as an electrolyte, and its purity is particularly important to the quality of the electrolyte, especially for the preparation of sodium hexafluorophosphate in sodium batteries, which requires high-purity phosphorus pentafluoride. However, the existing technology for preparing phosphorus pentafluoride has a low conversion rate and produces a large amount of toxic by-products during the production process, which not only damages the environment but also leads to a low purity of phosphorus pentafluoride. The phosphorus pentafluoride produced cannot meet the product index requirements of sodium batteries. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for improving the conversion rate and purity of phosphorus pentafluoride and to solve the problems existing in the prior art.

[0004] The present invention adopts a technical solution to achieve its purpose: a method for improving the conversion rate and purity of phosphorus pentafluoride, comprising the following steps:

[0005] (1) adding a 45% by mass aqueous hexafluorophosphoric acid solution to a strong acid pyrolysis agent, heating the temperature to temperature 1 for reaction, and producing a mixed gas;

[0006] (2) cooling the mixed gas to a temperature within the range of 2 and condensing the mixed gas to obtain a refined mixed gas;

[0007] (3) The purified mixed gas is introduced into a purification washing liquid at a temperature of 3 for deep separation and purification to obtain high-purity phosphorus pentafluoride.

[0008] Furthermore, in step (1), the strong acid pyrolysis agent is prepared by adding anhydrous hydrogen fluoride to fuming sulfuric acid.

[0009] Furthermore, the weight ratio of the anhydrous hydrogen fluoride to the fuming sulfuric acid is 1:(4-9).

[0010] Furthermore, the fuming sulfuric acid is fuming sulfuric acid with a free SO3 content of 65%.

[0011] Furthermore, in step (3), the purification washing liquid is anhydrous hydrogen fluoride.

[0012] Furthermore, the temperature 1 in step (1) is 80°C-140°C.

[0013] Furthermore, in step (2), the temperature 2 is -15°C to -20°C.

[0014] Furthermore, in step (3), the temperature 3 is 0°C-10°C.

[0015] The beneficial effects of the present invention are as follows: the method provided by the present invention solves the problem of high moisture and sulfate indicators and poor purity caused by the use of polyphosphoric acid in the prior art to synthesize phosphorus pentafluoride, and the purity of the prepared phosphorus pentafluoride gas reaches 99.99%, sulfate is less than 10ppm, and moisture is less than 10ppm, meeting the index requirements of sodium battery products; compared with the current existing technology, the method can achieve the preparation of high-purity phosphorus pentafluoride at a lower investment cost and production cost, and at the same time, the by-product sulfuric acid is non-volatile, which solves the environmental problem caused by the high volatility of the by-product hydrochloric acid in the prior art. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0017] Example 1

[0018] (1) Add 1 part by weight of anhydrous hydrogen fluoride to 6 parts by weight of fuming sulfuric acid with a free SO3 content of 65%, mix well, add 45% by mass of hexafluorophosphoric acid aqueous solution, raise the temperature to 80°C-140°C, and carry out thermal decomposition reaction of hexafluorophosphoric acid to produce a mixed gas. In this step, ICP is used to detect the phosphate radical in the remaining liquid. When the detection result is less than 0.1%, the reaction is terminated. The reaction mechanism of this step is: HPF6=HF↑+PF5↑, (Side reaction 1), (Side reaction 2), H2O+SO3=H2SO4;

[0019] (2) The obtained mixed gas is passed into a condenser, cooled to -15°C to -20°C for condensation, and the condensate is removed to obtain a refined mixed gas. This step can remove most of the sulfur trioxide, fluorine-containing phosphorus oxides and hydrogen fluoride. The reaction mechanism is as follows:

[0020] POF3+2HF(g)=PF5↑+H2O,

[0021] H2O+SO3(L)=H2SO4,

[0022] SO3(L)+HF=HSO3F;

[0023] (3) The refined mixed gas is passed into anhydrous hydrogen fluoride at 0°C-10°C for deep separation and purification to obtain high-purity phosphorus pentafluoride. The purity is 99.99% after testing, the water content is 8.2ppm by Karl Fischer method, and the sulfate content is <10ppm by turbidimetry. This step can effectively remove residual sulfur trioxide, fluorine-containing phosphorus oxide and hydrogen fluoride. The reaction mechanism is as follows:

[0024] POF3+2HF(L)=PF5↑+H2O,

[0025] SO3(g)+HF(L)=HSO3F.

[0026] Example 2

[0027] (1) adding 1 part by weight of anhydrous hydrogen fluoride to 4 parts by weight of fuming sulfuric acid having a free SO3 content of 65%, mixing them evenly, adding a 45% by weight aqueous hexafluorophosphoric acid solution, heating the mixture to a temperature between 80°C and 140°C, and performing a thermal decomposition reaction of the hexafluorophosphoric acid to produce a mixed gas. In this step, the phosphate radical in the remaining liquid is detected by ICP, and the reaction is terminated when the detection result is less than 0.1%;

[0028] (2) passing the obtained mixed gas into a condenser, cooling it to a temperature within the range of -15°C to -20°C, removing condensate, and obtaining a refined mixed gas;

[0029] (3) The refined mixed gas is passed into anhydrous hydrogen fluoride at 0°C-10°C for deep separation and purification to obtain high-purity phosphorus pentafluoride. The purity is 99.99% after testing, the water content is 8.7 ppm by Karl Fischer method, and the sulfate content is <10 ppm by turbidimetric method.

[0030] Example 3

[0031] (1) adding 1 part by weight of anhydrous hydrogen fluoride to 9 parts by weight of fuming sulfuric acid having a free SO3 content of 65%, mixing them evenly, adding a 45% by weight aqueous hexafluorophosphoric acid solution, heating the mixture to a temperature within the range of 80°C to 140°C, and performing a thermal decomposition reaction of the hexafluorophosphoric acid to produce a mixed gas. In this step, the phosphate radical in the remaining liquid is detected by ICP, and the reaction is terminated when the detection result is less than 0.1%;

[0032] (2) passing the obtained mixed gas into a condenser, cooling it to a temperature within the range of -15°C to -20°C, removing condensate, and obtaining a refined mixed gas;

[0033] (3) The refined mixed gas is passed into anhydrous hydrogen fluoride at 0°C-10°C for deep separation and purification to obtain high-purity phosphorus pentafluoride. The purity is 99.99% after testing, the water content is 8.5 ppm by Karl Fischer method, and the sulfate content is <10 ppm by turbidimetric method.

[0034] Example 4

[0035] (1) adding 1 part by weight of anhydrous hydrogen fluoride to 7 parts by weight of fuming sulfuric acid having a free SO3 content of 65%, mixing them evenly, adding a 45% by weight aqueous hexafluorophosphoric acid solution, heating the mixture to a temperature between 80°C and 140°C, and performing a thermal decomposition reaction of the hexafluorophosphoric acid to produce a mixed gas. In this step, the phosphate radical in the remaining liquid is detected by ICP, and the reaction is terminated when the detection result is less than 0.1%;

[0036] (2) passing the obtained mixed gas into a condenser, cooling it to a temperature within the range of -15°C to -20°C, removing condensate, and obtaining a refined mixed gas;

[0037] (3) The refined mixed gas is passed into anhydrous hydrogen fluoride at 0°C-10°C for deep separation and purification to obtain high-purity phosphorus pentafluoride. The purity is 99.99% after testing, the water content is 8.3 ppm by Karl Fischer method, and the sulfate content is <10 ppm by turbidimetric method.

[0038] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-mentioned embodiments, ordinary technicians in this field should understand that any technician familiar with this technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed by the present invention, or make equivalent replacements for some of the technical features therein. These modifications, changes or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention.

Claims

1. A method for improving the conversion rate and purity of phosphorus pentafluoride, characterized in that: The following steps are involved: (1) adding a 45% by mass aqueous hexafluorophosphoric acid solution to a strong acid pyrolysis agent, heating the temperature to temperature 1 for reaction, and producing a mixed gas; (2) cooling the mixed gas to a temperature within the range of 2 and condensing the mixed gas to obtain a refined mixed gas; (3) The purified mixed gas is introduced into a purification washing liquid at a temperature of 3 for deep separation and purification to obtain high-purity phosphorus pentafluoride.

2. The method for improving the conversion rate and purity of phosphorus pentafluoride according to claim 1, characterized in that: In step (1), the strong acid pyrolysis agent is prepared by adding anhydrous hydrogen fluoride to fuming sulfuric acid.

3. The method for improving the conversion rate and purity of phosphorus pentafluoride according to claim 2, characterized in that: The weight ratio of the anhydrous hydrogen fluoride to the fuming sulfuric acid is 1:(4-9).

4. The method for improving the conversion rate and purity of phosphorus pentafluoride according to claim 3, characterized in that: The fuming sulfuric acid is fuming sulfuric acid with a free SO3 content of 65%.

5. The method for improving the conversion rate and purity of phosphorus pentafluoride according to claim 1, characterized in that: In step (3), the purification washing liquid is anhydrous hydrogen fluoride.

6. The method for improving the conversion rate and purity of phosphorus pentafluoride according to claim 1, characterized in that: In step (1), the temperature 1 is 80°C-140°C.

7. The method for improving the conversion rate and purity of phosphorus pentafluoride according to claim 1, characterized in that: In step (2), the temperature 2 is -15°C to -20°C.

8. The method for improving the conversion rate and purity of phosphorus pentafluoride according to claim 1, characterized in that: In step (3), the temperature 3 is 0°C-10°C.