System and method for preparing high-purity phosphorus pentafluoride

Abstract

The invention relates to a system and a method for preparing high-purity phosphorus pentafluoride. The high-purity phosphorus pentafluoride is prepared from raw materials comprising PCl3, Cl2 and anhydrous HF by performing on-line purification treatment on the raw materials, performing on-line direction transformation on the intermediate product PCl5 into the PF5, performing on-line purification on the crude PF5, and the like. Preparation of the high-purity phosphorus pentafluoride is realized by the economic, high-efficiency and conveniently-operated method. The system and the method are characterized in that the high-purity phosphorus pentafluoride is prepared by performing on-line purification on the crude PF5 by two-stage condensers; and the temperatures of the two-stage condensers are respectively -50 to 19 DEG C and -85 to -76 DEG C.

Description

technical field [0001] The invention relates to a method for preparing high-purity phosphorus pentafluoride, which is used to prepare lithium-ion battery electrolyte LiPF 6 necessary raw materials. Background technique [0002] In commercial Li-ion batteries, LiPF 6 Is the most important electrolyte lithium salt. LiPF 6 Its appearance is white powder or fine particles, its chemical properties are stable, and it does not react with most inorganic or organic substances, but it will decompose into hydrofluoric acid when it meets water. It must be used in a dry atmosphere with a humidity of less than 10ppm to prevent decomposition. . When LiPF 6 When used as lithium ion battery electrolyte lithium salt, there are strict requirements on its quality parameters, especially the content of moisture and free acid (calculated as HF) in the product. In general, LiPF is required 6 The moisture content in the medium is less than 20ppm, and the free acid content is less than 80ppm. ...

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Problems solved by technology

For example, the patent CN1850592A proposes a PF 5 The production method, mainly PCl 5 Sublimation purification, anhydrous HF rectification purification, the purified PCl 5 Contact with anhydrous HF to prepare PF 5 and HF mixed gas, and then pass the mixed gas into the anhydrous HF solution dissolved in LiF to make LiPF 6 , the disadvantage of this method is that it is difficult to convert PCl by sublimation 5 Impurities such as moisture in the

Patent CN101353161A makes PCl in the presence of organic solvents such as ether, acetonitrile and carbonate 5 Contact with anhydrous HF to prepare PF 5 The disadvantage of this method is that the PF 5 It can form complexes with organic solvents such as ether, acetonitrile, and carbonate, resulting in partial PF 5 cannot be completely separated

Patent CN101844754A uses anhydrous HF mixed with fluorine gas and PCl 5 A mixed reaction is carried out, the purpose of which is to use fluorine gas to convert PCl 5 The moisture in the reaction is removed, and the method exists that fluorine gas preferentially interacts with PCl 5 Possibility of reaction, so the water in the reaction system cannot be completely removed

[0005] Currently using PCl 5 +HF→PF 5 Synthesis of PF by +HCl principle 5 The main problem is that the PCl used 5 Raw materials are generally obtained through purchase, PCl 5 Because it is easy to absorb moisture, it may deliquescence in contact with air during packaging, transportation and use. Products often contain moisture, PCl 3 , POCl 3 It is difficult to remove impurities such as conventional sublimation and chemical drying, so the PF prepared by the above method 5 Often contains water, PF 3 、POF 3 and other impurities, the above impurities will be in the LiPF 6 Into the product during the preparation process, resulting in reduced performance of the target product

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