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, and fluorides applied to dismutation reactions of the CHCl3-nFn haloalkane 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 phases is followed by XRD and IR. ESCA is applied for the characterization of the solid surfaces before and after treatment with the haloalkanes. As a result of our measurements, we can state that the catalytically active phase which is formed during the activation of the solid samples is stoichiometrically and structurally similar to the beta-AlF3 structure. Using separately synthesized predried beta-AlF3, it could be observed that this sample immediately possess catalytic activity. The nature of the catalytically active species which can be formed using different solid starting substances is discussed. It is possible to draw a correlation between the ESCA results and the catalytic behaviour of a number of solid samples. (C) 1994 Academic Press, Inc.