CHARACTERIZATION OF ALUMINA-SUPPORTED NICKEL-RUTHENIUM SYSTEMS

A series of alumina supported ruthenium-nickel catalysts with varying amounts of both components have been examined by temperature-programme d reduction (TPR), oxidation (TPO) and X-ray diffraction (XRD). At a l ow doping content of ruthenium the promoting influence on the reductio n of the oxidic nickel phase is clear but insignificant. The reduction of bimetallic catalysts occurs at much lower temperatures, as compare d to a monometallic nickel catalyst, convincingly showing that rutheni um and nickel must be in close interaction with each other. However, d ue to the bidispersive character of the ruthenium oxide phase in calci ned samples, only partial alloying of both metals takes place during t he catalyst reduction. An exposure of the reduced samples to oxygen up until relatively high temperature (773 K) does not destroy the bimeta llic particles.-The increase of the reoxidation temperatures above 800 K leads gradually to the full segregation of nickel and ruthenium oxi de species.