Process for the manufacture of phosphorous pentafluoride


1287202 Phosphorous pentafluoride; phosphoryl fluoride-sulphur trioxide complex USS ENGS & CONSULTANTS Inc 10 March 1970 11527/70 Heading C1A Phosphorous pentafluoride is produced by reacting POF 3 with SO 3 to form an adduct (POF 3 .SO 3 ) which reacts with hydrogen fluoride to form PF 5 and sulphuric acid. The invention includes a liquid reaction product of SO 3 and POF 3 which comprises a POF 3 .SO 3 adduct and the new compound phosphoryl fluoride-sulphur trioxide (POF 3 .SO 3 ) per se. It is advantageous to mix POF 3 with liquid SO 3 at reduced temperatures and to allow the mixture to warm to room temperature before further reaction with HF at a reduced pressure. In an example an evacuated reactor was cooled to - 196‹ C. and charged with SO 3 (10À0 g.) and POF 3 (13À3 g.). On warming to room temperature a pressure of 200 p.s.i. developed temporarily. The resulting slurry was stirred to dissolve all the SO 3 resulting in a clear colourless liquid. This liquid was transferred to an evacuated aluminium cylinder (250 c.c.) containing HF (6À8 g.) at - 40‹ C. A pressure of 50 p.s.i. developed and the cylinder was slowly warmed to 60‹ C. After 1 hour the cylinder was cooled to 25‹ C. and PF 5 (81% yield) vented into cold trap maintained at - 196‹ C. with liquid nitrogen.




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