Influence of gold and manganese as promoters on surface and catalytic performance of Fe 2O 3/Al 2O 3 system

Abstract

The physicochemical, surface and catalytic properties of pure and doped Fe 2O 3/Al 2O 3 solid catalysts with Au and Mn 2O 3 calcined at 300, 500 and 700 °C were investigated. The dopant concentration of Au was varied between 0.4 and 1.6 mol%, while Mn 2O 3 concentration was varied between 1.0 and 8.0 mol%. The techniques employed were DTA, XRD, TPR, EDX, nitrogen adsorption at −196 °C, CO oxidation by O 2 at 225–275 °C and H 2O 2 decomposition in aqueous solution at 30–50 °C. The results obtained revealed that the doping of Fe 2O 3/Al 2O 3 solids with different amounts of Au and Mn 2O 3 changed the degree of crystallinity of Al 2O 3 and Fe 2O 3 phases. The doping process led to a progressive increase in the specific surface area of the treated solid catalysts to an extent proportional to the amount of Au and Mn 2O 3 added. This process led also to a progressive increase in the catalytic activities of the investigated solid catalysts towards CO oxidation by O 2 and H 2O 2 decomposition. The doping of solid catalysts with Au calcined at 300, 500 and 700 °C exhibited catalytic activity in CO oxidation by O 2 higher than those measured for solid catalysts doped with Mn 2O 3 calcined at the same temperatures. Opposite results have been observed in case of H 2O 2 decomposition. These findings indicate that the active sites taking part in CO oxidation by O 2 are different from those involved in H 2O 2 decomposition.