CeO₂ promoted Ag/TiO₂ catalyst for soot oxidation with improved active oxygen generation and delivery abilities

To evaluate the usability of TiO₂ support for silver in soot oxidation, Ag/TiO₂ and Ag/CeO₂ catalysts were prepared and soot oxidation experiment was performed. The catalytic activity of silver was more enhanced on P25 and rutile than on anatase and CeO₂ in tight contact, as evidenced from comparing the activities of supports and silver impregnated catalysts. The reasons for the difference in active metal enhancement were elucidated by various characterization methods (TEM, H₂ TPR, and XPS), and it is verified that it resulted not from dispersion of silver but from oxidation ability. On the other hand, Ag/P25 showed poor activity in loose contact because of low contact between silver and soot. To improve the loose contact activity of the Ag/P25 catalyst, CeO₂ was introduced for active oxygen delivery. The synthesized CeO₂-Ag/P25 catalyst showed enhanced loose contact activity when compared with Ag/P25 and Ag/CeO₂ due to synergistic effects from the active oxygen supply ability of silver on P25 and the oxygen transfer ability of loaded CeO₂. Thermal stability of the catalyst was identified by recycling test to 800℃, and the maintained T₂₀ and T₅₀ demonstrated its durability for practical use in automobile exhaust removal.