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.