Catalytic reactions of chlorofluoroethanes at fluorinated alumina and chromia aerogels and xerogels: A comparison of reaction pathways in alumina- and chromia-based catalysts

The differences in the dynamic behaviour of 1,1,2-trichlorotrifluoroethane over fluorinated alumina or chromia catalysts at moderate temperatures are significant. Alumina-based catalysts favour the isomerization of CCl₂FCClF₂ followed by the dismutation of CCl₃CF₃ so formed. Fluorinated chromias are less selective since halogen exchange and isomerization reactions both occur. An explanation in terms of the differences in Al---X, X=Cl or F, bond energies compared with their Cr---X counterparts is suggested. The identity of the catalyst precursor has little effect in the chromium case and no effect in the case of aluminium.