Halogen exchange reactions for CFC alternatives.. The behaviour of fluorine-18 labelled hydrogen fluoride towards prefluorinated chromia containing nickel(II) or zinc(II)

Highly active catalysts are required for the conversion of CF3CH2Cl to the CFC-alternative refrigerant, CF3CH2F, by HF vapour under heterogeneous conditions. Chromia impregnated with a very low level of zinc(II) is a superior catalyst precursor to chromia alone. The behaviour of prefluorinated chromia and prefluorinated chromia containing zinc(II) or nickel(II) towards fluorine-18 labelled HF indicates that two types of labile surface fluoride are present, only one of which is catalytically active. Proposals are made to account for the role of ZnII and NiII.