Total oxidation of propene and propane over gold–copper oxide on alumina catalysts: Comparison with Pt/Al2O3

Oxidation of propene and propane to CO2 and H2O has been studied over Au/Al2O3 and two different Au/CuO/Al2O3 (4 wt.% Au and 7.4 wt.% Au) catalysts and compared with the catalytic behaviour of Au/Co3O4/Al2O3 (4.1 wt.% Au) and Pt/Al2O3 (4.8 wt.% Pt) catalysts. The various characterization techniques employed (XRD, HRTEM, TPR and DR-UV–vis) revealed the presence of metallic gold, along with a highly dispersed CuO (6 wt.% CuO), or more crystalline CuO phase (12 wt.% CuO). A higher CuO loading does not significantly influence the catalytic performance of the catalyst in propene oxidation, the gold loading appears to be more important. Moreover, it was found that 7.4Au/CuO/Al2O3 is almost as active as Pt/Al2O3, whereas Au/Co3O4/Al2O3 performs less than any of the CuO-containing gold-based catalysts. The light-off temperature for C3H8 oxidation is significantly higher than for C3H6. For this reaction the particle size effect appears to prevail over the effect of gold loading. The most active catalysts are 4Au/CuO/Al2O3 (gold particles less than 3 nm) and 4Au/Co3O4/Al2O3 (gold particles less than 5 nm).