ESCA, XRD, AND IR CHARACTERIZATION OF ALUMINUM-OXIDE, HYDROXYFLUORIDE, AND FLUORIDE SURFACES IN CORRELATION WITH THEIR CATALYTIC ACTIVITY IN HETEROGENEOUS HALOGEN EXCHANGE-REACTIONS

The catalytic activity of certain aluminum oxides, hydroxyfluorides, a nd fluorides applied to dismutation reactions of the CHCl3-nFn haloalk ane series has been studied. In most cases the catalyst surface has to be modified so that it is catalytically active. A haloalkane flow has been used for the activation procedure. The alteration of the solid p hases is followed by XRD and IR. ESCA is applied for the characterizat ion of the solid surfaces before and after treatment with the haloalka nes. As a result of our measurements, we can state that the catalytica lly active phase which is formed during the activation of the solid sa mples is stoichiometrically and structurally similar to the beta-AlF3 structure. Using separately synthesized predried beta-AlF3, it could b e observed that this sample immediately possess catalytic activity. Th e nature of the catalytically active species which can be formed using different solid starting substances is discussed. It is possible to d raw a correlation between the ESCA results and the catalytic behaviour of a number of solid samples. (C) 1994 Academic Press, Inc.