Activity and characterization of the Co-promoted CuO–CeO2/γ-Al2O3 catalyst for the selective oxidation of CO in excess hydrogen Original Research Article

For the selective oxidation of CO in excess hydrogen, γ-Al2O3-supported CuO–CeO2-based catalysts were investigated. Effects of the composition of Cu and Ce metals and the addition of Co as a promoter to the catalyst on the catalytic activity and the selectivity for the CO oxidation against H2 were determined as a function of temperature. The effects of the feeding ratio of O2 to CO and the presence of H2O and/or CO2 in the feeding reactant were also examined. Among the catalysts tested, CuO–CeO2/γ-Al2O3 incorporating Co by 0.2 wt.% was the most active to show the CO conversion >99% in the wide temperature window of 150–220 °C with the CO oxidation selectivity of 94–50%. It was found from the catalyst characterization using temperature-programmed reduction/oxidation that the Co-promoted CuO–CeO2/γ-Al2O3, as compared with the catalyst without Co addition, had an increased number of CO oxidation-active sites capable of being easily reduced or oxidized at relatively low temperatures. However, the presence of CO2 and H2O in the feed decreased the low-temperature activity of the catalyst, and shifted the temperature window of CO conversion >99% to higher temperature region, i.e. 205–230 °C. Irrespective of the presence of both CO2 and H2O in the feed, the Co-incorporated catalyst was found to have the temperature window of CO conversion >99.9% within 210–224 °C, whereas no such temperature window existed for the CuO–CeO2/γ-Al2O3 catalyst. Temperature-programmed desorption of CO, CO2, or H2O was also conducted for understanding the catalytic reaction behavior in the presence of CO2 and/or H2O in the reactants.