Design of new gold catalysts supported on mechanochemically activated ceria-alumina, promoted by molybdena for complete benzene oxidation

Gold catalysts, supported on mechanochemically activated ceria-alumina, nonpromoted and promoted by molybdena, were studied in the reaction of complete benzene oxidation. Higher activity of Au-Mo catalysts was established in the low temperature region, while high temperatures samples, containing only gold exhibit higher benzene conversion and the cross-point of the curves depends on alumina content. The addition of alumina by mechanochemical treatment leads to a surface modification of ceria, e.g. oxygen vacancies are formed prevailing on the ceria surface. The molybdena loading leads to the oxygen vacancies occupation. The calculated hydrogen consumption and the enhanced reduction of ceria surface layers in general correlate with the activities of the catalysts. The XPS data supported the role of Ce3+ and partially charged gold particles in the formation of the complex AuV0Ce3+ as the active site for the redox processes. The modification of ceria in the presence of gold and the formation of oxygen vacancies in close contact with Ce3+ ensure the enhanced electron transfer. (C) 2007 Elsevier B.V. All fights reserved.