No abstract

The catalytic activity of Rh supported on Y-stabilized ZrO2 for NO–CO–C3H6–O2 reactions under stoichiometric conditions was improved by the addition of 5 mol % CeO2, whereas an excess amount of CeO2 of more than 10 mol % caused a decrease in the NO reduction activity. The improvement was ascribed to the formation of easily reducible Rh species through interaction with a Ce–Zr solid solution.

The catalytic activity of Rh/ZrO 2 for NO-CO-C 3 H 6 -O 2 reaction under stoichiometric conditions was significantly improved by addition of rare earth. Among the catalysts tested here, Y-doped Rh/ZrO 2 (Rh/Y/ZrO 2 ) showed the highest three-way catalytic performance. The catalytic activity of rare earth-doped Rh/ZrO 2 was strongly related to the Rh dispersion, which was improved by using rare earth-doped ZrO 2 with large amount of surface basic sites. The role of rare earth additive was considered to control the surface basicity of ZrO 2 and stabilize the Rh species in high dispersion state. Y-stabilized ZrO 2 was found to be effective support for Rh catalyst in NO-CO-C 3 H 6 -O 2 reaction. The site geometry and the surface electric state of Rh can be altered by interacting with Y 2 O 3 , leading us to consideration that the presence of suitable Rh-Y 2 O 3 interaction is responsible for high NO reduction activity of Rh/Y-ZrO 2 .