An improved process is described for producing chlorotrifluoroethylene, a useful monomer for making high strength chlorofluoropolymers, comprising passing a mixture of 1,1,2-trichloro-1,2,2-trifluoroethane, ethylene, hydrogen chloride and elemental oxygen in the vapor phase, at a temperature from about 350.degree. to 525.degree. C., over a catalyst consisting essentially of a mixture of copper chloride and an alkali metal chloride, preferably a eutectic mixture, occluded in a molecular sieve, having an average pore size diameter in the range of about 5 to 11 angstroms.A new catalyst composition is also described, useful in oxyhydrochlorination processes conducted at temperatures above 350.degree. C., consisting essentially of a mixture of copper chloride and an alkali metal chloride, preferably a eutectic mixture, occluded in a molecular sieve, having an average pore size diameter in the range of about 5 to 11 angstroms.