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

For the selective oxidation of CO in excess hydrogen, gamma-Al2O3-supported CuO-CeO2-based catalysts were investigated. Effects of the composition of Cu and Cc metals and the addition of Co as a promoter to the catalyst on the catalytic activity and the selectivity for the CO oxidation against H-2 were determined as a function of temperature. The effects of the feeding ratio of O-2 to CO and the presence of H2O and/or CO2 in the feeding reactant were also examined. Among the catalysts tested, CuO-CeO2/gamma-Al2O3 incorporating Co by 0.2 wt.% was the most active to show the CO conversion >99% in the wide temperature window of 150-220degreesC 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/gamma-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. 205-230degreesC. 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 210-224degreesC, whereas no such temperature window existed for the CuO-CeO2/gamma-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. (C) 2004 Elsevier B.V. All rights reserved.