XPS and FTIR study of Ru/Al2O3 and Ru/TiO2 catalysts: Reduction characteristics and interaction with a methane-oxygen mixture

The oxidation state of alumina- and titania-supported Ru catalysts has been investigated as a function of reduction temperature, as well as by followi ng the interaction with a methane-oxygen mixture at 773 and 973 K, employin g XPS and FTIR techniques. It is found that the chemical behavior of Ru dep ends strongly on the material on which it is supported. Over Al2O3, rutheni um is incompletely reduced by treatment with hydrogen at 573 and 823 K, whi le oxidized Ru species are also detected following exposure of the catalyst to a methane-oxygen mixture at 773 and 973 K. In contrast, over TiO2, ruth enium is more easily reduced and is stabilized in its reduced state followi ng hydrogen treatment at 823 K. During treatment with the methane-oxygen mi xture, no reoxidation of Ru occurs. The interaction between Ru and TiO2, wh ich inhibits the oxidation of ruthenium under conditions of partial oxidati on of methane, is related to the unique ability of the Ru/TiO2 catalyst to promote the direct route of synthesis gas formation.