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.