Abstract: The present invention provides a process for preparing 3,3,3-trifluoropropene (1243zf), the process comprising: (a)fluorinating CCl3CH2CH2CI (250fb) to produce a reaction product comprising CF3CH2CH2CI (253fb) in the liquid phase in a first reactor, using HF as the fluorinating agent; and (b)(i) dehydrohalogenating 253fb to produce 1243zf in the vapour phase in the presence of a catalyst in a second reactor; or (b)(ii) dehydrohalogenating 253fb to produce 1243zf in a second reactor, wherein the reaction product comprising 253fb produced in step (a) has subjected to one or more purification steps before step (b). The present invention also provides an azeotropic or near-azeotropic composition comprising HF and 253fb.