CHARACTERIZATION OF SUPPORTED CATALYST SYSTEMS WITH SURFACE SPECTROSCOPIES

Supported catalysts of transition metals and their oxides are widely u sed for a variety of reactions. They typically consist of a high surfa ce area oxide as support material (e.g. Al2O3, TiO2, SiO2) and finely dispersed metal or metal oxide particles (e.g. Rh, MoO3, V2O5) as acti ve components (or their precursor) and promoters. The catalytic proper ties are determined by these components, their structural arrangement, and their interactions. Studies of real and model catalyst systems ar e reported for which low-energy ion scattering (LEIS) is used in combi nation with other spectroscopies, such as RES, AES, TDS, XPS, and Rama n spectroscopy. The applicability of these techniques to real systems and the relevance of model catalysts is discussed. The results shown d emonstrate the usefulness of these spectroscopies for the characteriza tion of supported catalysts, in particular for the analysis of the com position and the arrangement of the topmost atomic layers. Among the e xamples given are special aspects of catalyst impregnation, the invest igation of solid-solid wetting which may be relevant to catalyst prepa ration and strong metal-support interactions (SMSI effect) in supporte d Rh metal catalysts.