Catalytic oxidation of saturated hydrocarbons on multicomponent Au/Al2O3 catalysts: Effect of various promoters

The performance of unpromoted and MOx-(M: alkali (earth), transition metal and cerium) promoted Au/Al2O3 catalysts have been studied for combustion of the saturated hydrocarbons methane and propane. As expected, higher temperatures are required to oxidize CH4 (above 400 °C), compared with C3H8 (above 250 °C). The addition of various MOx to Au/Al2O3 improves the catalytic activity in both methane and propane oxidation. For methane oxidation, the most efficient promoters to enhance the catalytic performance of Au/Al2O3 are FeOx and MnOx. For C3H8 oxidation a direct relationship is found between the catalytic performance and the average size of the gold particles in the presence of alkali (earth) metal oxides. The effect of the gold particle size becomes less important for additives of the type of transition metal oxides and ceria. The results suggest that the role of the alkali (earth) metal oxides is related to the stabilization of the gold nanoparticles, whereas transition metal oxide and ceria additives may be involved in oxygen activation.