Characterization of alumina supported nickel-ruthenium systems Original Research Article

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