Radiotracers in fluorine chemistry : XIII. Catalysis by Fluorinated Surfaces: The Interaction of [ 36Cl]-Chlorine Labelled Hydrogen Chloride and 1,1-Dichlorotetrafluoroethane with Fluorinated Chromia Catalysts

Abstract

The behaviour of the [ 36Cl]-chlorine labelled compounds, anhydrous hydrogen chloride and 1,1-dichlorotetrafluoroethane, towards fluorinated chromia catalysts has been investigated under flow conditions at 623 and 688 K respectively. In each case [ 36Cl]-chlorine activity was deposited on the catalyst. Uptakes of chlorine, determined from radiochemical measurements and from neutron activation analyses, were comparable for a given catalyst irrespective of the reagent used. Flow of anhydrous hydrogen fluoride at 623 K or reactions of dichlorotetrafluoroethane isomers and 1,1,2-trichlorotrifluoroethane over [ 36Cl]-chlorine labelled fluorinated chromia, led to the removal of 75–85% of the radioactivity. The remainder was retained even on basic hydrolysis of the catalyst. The results are discussed in terms of a halogen exchange model for the behaviour of chlorofluoroethanes and suggestions are made regarding the nature of the catalytically active halogenating species.