Au/MCr2O4 (M = Co, Mn, Fe) catalysts in the oxidations of CO, C2, and C3 hydrocarbons

Au/MIICr2O4 (MII = Co, Mn, Fe) catalysts have been tested in the total oxidation of ethane, propane, propene at 300 °C and of CO at 35 °C, and characterized by TEM, XPS and hydrogen thermo-programmed reduction (H2TPR). The catalytic activity has been found to depend on the nature of the oxidized compound. For the CO and ethane oxidation, the activity decreases in the sequence Au/CoCr2O4 > Au/MnCr2O4 ≫ Au/FeCr2O4 and follows the sequence of the decreasing reducibility of the supports and the catalysts, estimated from H2TPR measurements. The activity decreases with the increasing Au particle size in the same order, the reactions then seem structure sensitive. No correlations between the activity and reducibility or the particle size are observed for oxidation of the C3 hydrocarbons: the sequence of the activity for propane is: Au/FeCr2O4 > Au/CoCr2O4 > Au/MnCr2O4, whereas activity in propene oxidation does not change markedly within the studied catalysts. The reaction mechanism in the oxidation of propane and propene seems then to be different from that of oxidation of CO and ethane.