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

Abstract

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 Zn^II and Ni^II.