disclosed is a reactor and agitator useful in a high pressure process for making 1 - chloro - 3 , 3 , 3 - trifluoropropene from the reaction of 1 , 1 , 1 , 3 , 3 - pentachloropropane and hf , wherein the agitator includes one or more of the following design improvements : double mechanical seals with an inert barrier fluid or a single seal ; ceramics on the rotating faces of the seal ; ceramics on the static faces of seal ; wetted o - rings constructed of spring - energized teflon and ptfe wedge or dynamic o - ring designs ; and wetted metal surfaces of the agitator constructed of a corrosion resistant alloy .