Preparation process of high-purity phosphorus pentafluoride

Abstract

The invention discloses a preparation process of high-purity phosphorus pentafluoride, which comprises the following steps of: firstly adding phosphorous pentachloride into a feed hopper of a spiral feeder under the protection of dry gas in a glove box to assemble a gas circulation loop, and simultaneously adding inert gas into the gas circulation loop in advance; starting a spiral stirring reaction furnace, simultaneously injecting mixed gas of hydrogen fluoride and fluorine gas into the spiral stirring reaction furnace, and controlling the reaction process by controlling the rotation frequency of the phosphorous pentachloride in the spiral feeder, the temperature of gas flow at the outlet of the spiral stirring reaction furnace and the pressure of the gas circulation loop; freezing the phosphorus pentafluoride gas and the hydrogen fluoride gas generated in the reaction process and unreacted hydrogen fluoride gas by a condenser-evaporator, and collecting high-purity phosphorus pentafluoride gas after reaction. The method is simple and effective and can be operated easily.

Description

Technical field: [0001] The invention relates to a preparation process of phosphorus pentafluoride. Background technique: [0002] Phosphorus pentafluoride, molecular formula PF 5 , molecular weight 125.97, is a colorless gas. Does not corrode glass when dry, fumes strongly in moist air. The melting point is -91.6°C, the boiling point is -84.8°C, and the density is 5.80g / L. The critical temperature is greater than 25°C. The heat of fusion is 12.1kJ / mol, the heat of evaporation is 16.7kJ / mol, and the heat of formation is -1210kJ / mol. PF 5 Easy to hydrolyze and strong moisture absorption. A very small amount of moisture also makes it generate POF 3 and HF. When there is more water, it will be further hydrolyzed to generate phosphoric acid. In industry, phosphorus pentafluoride is used as a fluorinating reagent in the electronics industry and polymer manufacturing, and as a catalytic fluorinating agent in the field of organic synthesis. [0003] In the past 10 years, ...

AI Technical Summary

Problems solved by technology

A kind of production method of phosphorus pentafluoride is disclosed as CN1850592A, and this method comprises that phosphorus pentafluoride is sublimated and purified, and anhydrous hydrogen fluoride is rectified and purified, and then the refined phosphorus pentachloride is reacted with anhydrous hydrogen fluoride solution to obtain pentafluoride The mixed gas of phosphorus fluoride and hydrogen chloride, and then the mixed gas of phosphorus pentafluoride and hydrogen chloride is introduced into the anhydrous hydrogen fluoride solution of lithium fluoride to prepare lithium hexafluorophosphate. The disadvantage of this method is that the process steps are complicated and the production continuity is not good enough

CN101353161A then discloses another kind of production method of phosphorus pentafluoride, this method comprises phosphorus pentachloride and anhydrous hydrogen fluoride reaction, it is characterized in that, described reaction is carried out under the existence of solvent, and described solvent is selected from ether, acetonitrile , carbonate or ethyl acetate, etc., the main disadvantage of this method is PF 5 Can form complexes with ether, nitrile, carbonate or ethyl acetate, etc., resulting in PF 5 Difficulty separating

[0011] Currently using PCl 5 +HF→PF 5 Synthesis of PF by +HCl principle 5 There are mainly two problems in the gas: (1) phosphorus pentachloride and anhydrous hydrogen fluoride usually contain certain impurities such as moisture, alkali metals, heavy metal ions, etc., especially pentachloride Phosphate is very easy to absorb moisture and produce deliquescence, the product contains PCl 3 , POCl 3 and other impurities, and PF 5 It is a colorless gas, easy to hydrolyze, and has strong hygroscopicity. A small amount of moisture can also make it generate POF 3 And HF, when there is more moisture, it will further generate orthophosphoric acid. If the above-mentioned impurities, especially moisture, are brought into the lithium hexafluorophosphate product, it will lead to the reduction of its product performance; (2) PCl 5 The reaction with HF is a sharp and rapid exothermic process. If the heat cannot be transferred quickly in this process, the reaction process is prone to explosion and there are serious safety hazards. In order to overcome these problems, it has been proposed to divide the reaction into two steps: PCl 5 React with anhydrous hydrogen fluoride below -20°C to generate PF 5 , resulting in PF 5 Followed by HF to form white HPF 6 the crystal

HPF 6 Crystals are separated from the solution, and then heated to -10 ~ 20 ° C, HPF 6 Decomposition occurs and PF is newly formed 5 , this method not only has complex process steps and continuous production, but also cannot completely solve the problem caused by PCl 5 The reaction with HF is a sharp and rapid exothermic process resulting in a safety hazard

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