Effect of Rare Earth Additives on the Catalytic Performance of Rh/ZrO2 Three-Way Catalyst

The catalytic activity of Rh/ZrO2 for NO-CO-C3H6- O-2 reaction under stoichiometric conditions was significantly improved by addition of rare earth. Among the catalysts tested here, Y-doped Rh/ZrO2 (Rh/Y/ZrO2) showed the highest three-way catalytic performance. The catalytic activity of rare earth-doped Rh/ZrO2 was strongly related to the Rh dispersion, which was improved by using rare earth-doped ZrO2 with large amount of surface basic sites. The role of rare earth additive was considered to control the surface basicity of ZrO2 and stabilize the Rh species in high dispersion state. Y-stabilized ZrO2 was found to be effective support for Rh catalyst in NO-CO-C3H6- O-2 reaction. The site geometry and the surface electric state of Rh can be altered by interacting with Y2O3, leading us to consideration that the presence of suitable Rh-Y2O3 interaction is responsible for high NO reduction activity of Rh/Y-ZrO2.