Selective oxidation of CO over CuO-CeO2 catalyst: effect of calcination temperature

CuO-CeO2 catalysts were prepared by a conventional co-precipitation method and tested for the selective oxidation of carbon monoxide in the presence of excess hydrogen and carbon dioxide. N2 adsorption results showed that the BET surface area and pore volume of the CuO-CeO2 catalyst decreased with increase of calcination temperature whereas average pore diameter increased. From the results of XRD and XPS, we determined the oxidation state of copper in the catalyst. With the increase of calcination temperature, cupric oxide was formed near the surface of the catalyst at first and then appeared on the surface of the catalyst, indicating that the CuO-CeO2 catalyst was in the form of a solid solution and cupric oxide was formed due to phase separation which then migrated to the surface of the catalyst with the increase of calcination temperature. CO chemisorption data exhibited the amounts of CO uptake of the CuO-CeO2 catalyst. The amount of reversible CO uptake showed a volcano curve with calcination temperature. The CuO-CeO2 catalyst batch which was calcined at 700 °C had the best activity because this catalyst formed the most stable state of Cu–Ce–O solid solution and could chemisorb CO reversibly.