Structural and chemical promoter effects of alkali (earth) and cerium oxides in CO oxidation on supported gold

Nanostructured Au/Al2O3 catalysts prepared by deposition–precipitation with urea were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) and tested for low temperature CO oxidation. The paper is focused on the effect of two different kinds of additives on the structure and reactivity of Au/Al2O3 for CO oxidation: (1) alkali (earth) metal oxides and (2) ceria. The structural properties of nanosized Au particles are drastically affected by the presence of additives. The main role of the alkali (earth) metal oxides is to stabilize the small Au particles against sintering, such that when BaO is added to Au/Al2O3, full CO conversion is already achieved at room temperature. For this reaction ceria addition does not result in a higher activity. However, when both BaO and CeOx are added to Au/Al2O3, the catalytic performance of the multicomponent catalyst resembles that of Au/BaO/Al2O3.