SURFACE CHARACTERIZATION OF CUO-ZNO-AL2O3 METHANOL-SYNTHESIS CATALYSTS BY XPS

In recent years great efforts have been devoted to understand the ZnO-CuO-Al//2O//3 catalysts structure and its relation to the catalytic behavior in hydrogen involving reactions, mainly methanol synthesis and water-shift reaction. The present communication is concerned with an XPS study of CuO-ZnO-Al//2O//3 well defined system of varying copper-zinc ratios (mainly 2 or 1) and alumina content (O less than equivalent to Al//2O//3 less than 20%). The aim was: (a) to analyze in situ the reduction process related to the copper component, establishing the oxidation states of copper as function of extent of reduction and showing how it is possible to provide a chemical picture of surface states by the analysis of Cu 2p//3/////2 photoemission and Cu L//3VV Auger peaks; (b) to assess the mutual interaction between the different and so closely associated phases, as ZnO-CuO or ZnO-Cu; (c) to investigate the role of alumina on the sintering phenomena