Oxidation of Oxygenated Volatile Organic Compound Over Monometallic and Bimetallic Ru–Au Catalysts

Abstract

Temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) of methanol and oxygen were used to probe the surface properties, relating to the oxidation reaction of methanol (a representative of oxygenated volatile organic compounds) over a series of monometallic and bimetallic Ru–Au catalysts. The relative amounts of ruthenium and gold in these bimetallic catalysts were found to strongly affect their surface characteristics (TPR and TPD profiles, BET surface areas, surface morphologies observed in SEM micrographs, and XRD patterns) and methanol oxidation activity. Although ruthenium and gold were immiscible in their bulk state, the TPR profiles, SEM micrographs, and XRD patterns provided evidence for the interactions between ruthenium and gold in the bimetallic catalysts, especially the 3.32 wt% Ru–0.61 wt% Au/SiO2 exhibiting the highest methanol oxidation activity. After the oxidation reaction, even though Ru was oxidized to RuO2, the interaction between ruthenium and gold on silica still remained the same. The support material was also found to affect both the catalyst characteristics and the methanol oxidation activity. No bimetallic clusters were observed on the Ru–Au catalysts supported on alumina. Various products, including CO2, were found when using the catalysts supported on alumina, causing a higher methanol conversion than the catalysts supported on silica. The objective of the present work was to develop comprehensive information for the interactions of the oxygenated VOC with mono- and bimetallic Ru–Au catalyst surfaces as a function of temperature and gold content. The outcomes of this work directly provide a better understanding of the catalytic oxidation of oxygenated VOCs on the bimetallic Ru–Au catalysts.