Catalysis Today, Vol.75, No.1-4, 157-167, 2002
A comparative study of Pt/gamma-Al2O3, Au/alpha-Fe2O3 and CuO-CeO2 catalysts for the selective oxidation of carbon monoxide in excess hydrogen
Three different catalysts, namely Pt/gamma-Al2O3, Au/alpha-Fe2O3 and CuO-CeO2 were prepared (by wet impregnation, coprecipitation and a sol-gel method, respectively) and their catalytic performance for the selective oxidation of carbon monoxide in the presence of excess hydrogen was evaluated and compared. The effects of the presence of CO2 and H2O in the reactant feed on the activity and selectivity of these catalysts, as well as their stability under realistic reaction conditions were also investigated. Regardless of whether CO2 or both CO2 and H2O are present in the reactant feed, the Au/alpha-Fe2O3 catalyst is superior to the other two for the selective CO oxidation at relatively low reaction temperatures (<80-120 degreesC, depending on contact time and feed composition employed), while at higher reaction temperatures, best results are obtained with the CuO-CeO2 catalyst, which proved to be more active and remarkably more selective than the Pt/gamma-Al2O3 catalyst. The Au/alpha-Fe2O3 catalyst was the most sensitive, while the Pt/gamma-Al2O3 the most resistant towards deactivation caused by the presence of CO2 and H2O in the feed. Finally, while the Au/alpha-Fe2O3 catalyst lost a considerable portion of its activity during the first 80 h under reaction conditions, the CuO-CeO2 and Pt/gamma-Al2O3 catalysts exhibited a stable catalytic performance, at least during the time period tested in this work (7-8 days).
Keywords:carbon monoxide selective oxidation;excess hydrogen;influence of carbon dioxide;influence of water;stability;alumina-supported platinum;gold;iron oxide;copper;ceria