Pattern of the Activity of (0.5-15)%CoO/CeO2 Catalysts in Carbon Monoxide Oxidation with Oxygen in Excess Hydrogen

Samples of (0.5-15)%CoO/CeO2, Co3O4, and CeO2 have been studied in the oxidation of CO to CO2 in a CO+O-2+H-2 mixture in a range of 40-340 degrees C. The highest activity in CO oxidation is exhibited by 10%CoO/CeO2 with a characteristic conversion of CO to CO2 of gamma(50) = 50% at T-50 approximate to 140 degrees C and gamma approximate to 100% at T = 180-220 degrees C. The CO2 yield decreases at 220-240 degrees C due to competition for oxygen in the CO and H-2 oxidation reactions; at T > 240 degrees C, it decreases due to the consumption of CO in the methanation reaction. According to XRD and H-2-TPR, cobalt oxide in the 10%CoO/CeO2 sample is present in two forms of a highly dispersed Co3O4 oxide (CoxOy clusters) interacting with the support and in the form of a Co3O4 phase. Carbon monoxide oxidation in a range of 60-180 degrees C occurs on CoxOy clusters. Under these conditions, the activity of particles of the Co3O4 phase in pure oxide and the 10%CoO/CeO2 catalyst is lower than that of the clusters. The effect of the properties of adsorption complexes formed involving the oxygen contained in the clusters and in the gas phase on the temperature dependence of CO conversion has been studied.