Abstract: A series of Ce1-xZrxO2 (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) composite oxides were prepared by the co-precipitation method. Gold catalysts with 1% loading supported on CeO2, ZrO2, and Ce1-xZrxO2 were prepared by the modified impregnation method. The effect of Zr/Ce molar ratios on the activity for low-temperature CO oxidation and water-gas shift reaction was studied. All samples were characterized by nitrogen adsorption, X-ray diffraction, transmission electron microscopy, and H2 temperature-programmed reduction. The results showed that compared with pure CeO2 and ZrO2, the surface area of Ce1-xZrxO2 increases and its pore diameter decreases slightly. The presence of zirconium oxide in cerium oxide makes the reduction of cerium ions on the surface more difficult whereas it makes the reduction of the cerium ions in the phase easier. Loading gold particles onto Ce1-xZrxO2 support improves the reduction of the support, and good dispersion of gold particles is found on ZrO2 and Ce1-xZrxO2 supports due to the strong interaction between the gold particles and the oxide supports. These catalysts show good activity for low-temperature CO oxidation and water-gas shift reaction in the order Au/ZrO2>Au/ Ce1-xZrxO2>Au/CeO2. However, Au/Ce0.5Zr0.5O2 gives higher activity with 80% CO conversion at 623 K for water-gas shift reaction. Large pore diameter of ZrO2 and Ce1-xZrxO2 with respect to CeO2 is responsible for the high activity.

Key words: ceria, zirconia, composite oxide, gold catalyst, carbon monoxide oxidation, water-gas shift