Catalytic performance of supported precious metal catalysts for the combustion of diesel particulate matter

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.