SURFACE CHARACTERIZATION OF CuO-ZnO-Al2O3 METHANOL-SYNTHESIS CATALYSTS BY XPS

ln recent years great efforts have been devoted to understand the ZnO-CuO-Al2O3 catalysts structure and its relation to the catalvtic behaviour in hydrogen involving rections. mainlv methanol svnthesis and water-shift reaction. However. although copper based catalvsts are activated by reduction before use, several aspects related to the nature and oxidation state of surface Cu-species as well as their catalytic behaviour are not completely understood. In fact, whereas some authors bv bulk techniques claimed Cu+1 dissolved in ZnO lattice others proposed the formation of Cu2O upon reduction of CuO-ZnO catalysts: apart from that only a few surface studies have been published on these systems. The present communication is concerned with an XPS study of CuO -ZnO-Al2O3 well defined system of varying copper-zinc ratios (mainly 2 or I ) and alumina content (0