Low-temperature redox activity and alcohol ammoxidation performance on Cu- and Ru-incorporated ceria catalysts

Abstract

Transition-metal-incorporated cerium oxides with Cu and a small amount of Ru (Cu_0.18Ru_0.05CeO_z) were prepared, and their low-temperature redox performance (<423 K) and catalytic alcohol ammoxidation performance were investigated. Temperature-programmed reduction/oxidation under H₂/O₂ and in situ X-ray absorption fine structure revealed the reversible redox behavior of the three metals, Cu, Ru, and Ce, in the low-temperature redox processes. The initially reduced Ru species decreased the reduction temperature of Cu oxides and promoted the activation of Ce species. Cu_0.18Ru_0.05CeO_z selectively catalyzed the production of benzonitrile in the ammoxidation of benzyl alcohol. H₂-treated Cu_0.18Ru_0.05CeO_z showed a slightly larger initial conversion of benzyl alcohol than O₂-treated Cu_0.18Ru_0.05CeO_z, suggesting that the reduced structure of Cu_0.18Ru_0.05CeO_z was active for the ammoxidation. The integration of both Cu and Ru resulted in the efficient promotion of ammoxidation, in which the Ru species were involved in the conversion of benzyl alcohol and Cu species were required for selective production of benzonitrile.