Disclosed is a reactor and agitator useful in a high pressure process for making 1-chloro-3,3,3-trifluoropropene (1233zd) from the reaction of 1,1,1,3,3-pentachloropropane (240fa) and HF, wherein the agitator includes one or more of the following design improvements: (a) double mechanical seals with an inert barrier fluid or a single seal; (b) ceramics on the rotating faces of the seal; (c) ceramics on the static faces of seal; (d) wetted o-rings constructed of spring-energized Teflon and PTFE wedge or dynamic o-ring designs; and (e) wetted metal surfaces of the agitator constructed of a corrosion resistant alloy.