Process for the purification of chlorofluorohydrocarbons

A process for removing olefinic impurities of the formula C.sub.m H.sub.n F.sub.p Cl.sub.q where m=2-3, n=1-4, p=1-6, q=0-4 and n+p+q=2m, from hydrogen-containing chlorofluorohydrocarbons of the formula C.sub.a H.sub.b F.sub.c Cl.sub.d where a=2-3, b=1-5, c=1-7, d=0-4 and b+c+d=2a+2, which comprises passing the contaminated chlorofluorohydrocarbons in the gas phase at temperatures of 200.degree. to 400.degree. C. and pressures of from 1 to 50 bar over a zeolite which, in the anhydrous and template-free form, has the formula Z.multidot.Al.sub.2 O.sub.3 .multidot.x (SiO.sub.2) in which Z=H, NH.sub.4, M(I).sub.2 O, M(II)O or M(III).sub.2 O.sub.3 where M(I) is an alkali metal, M(II) is an alkaline earth metal and M(III) is a rare earth metal having an atomic number from 57-71 in the Periodic Table of the Elements, and x is a number from 2 to 2000.