CeO2 and TiO2 supported precious metal (Ag, Pt and Pd) catalysts were prepared by an impregnation method, and their catalytic performance for oxidation of simulated diesel particulate matter (PM) was investigated by thermogravimetry (TG), differential thermal analysis (DTA) and mass spectrometry (MS) under both tight-contact (TC) and loose-contact (LC) conditions. The simulated PM was prepared by liquid-phase adsorption of SOF (eicosane, C20H42) on soot (carbon black). Catalytic performance for the oxidation of simulated PM depended on both metal species and supports. CeO2 was inherently active for both SOF and soot oxidation, and TiO2 was nearly inactive. Pt was the most active species for SOF oxidation, followed by Pd and Ag. The SOF oxidation was independent of contact condition between the simulated PM and catalysts. Soot oxidation performance, on the other hand, drastically affected by the contact conditions, and Ag was far more active than Pt and Pd under both TC and LC conditions. Ag/CeO2 was the most active soot oxidation catalyst. The oxidation of soot was influenced by the coexisting SOF depending on catalytic materials and contact modes.
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