Catalytic performance of Pt supported on various metal oxides in the oxidation of carbon black

The effect of support materials for Pt catalysts on the oxidation of carbon black, a model diesel-exhaust soot was examined. Among eight kinds of Pt-supported metal oxides (Ta2O5, Nb2O5, WO3, SnO2, SiO2, TiO2, Al2O3 and ZrO2), Pt/Ta2O5 showed the highest activity towards the oxidation of carbon black in a model diesel exhaust, containing O2, H2O, NO and SO2 in N2. Pt catalysts supported on other non-basic metal oxides such as Nb2O5, WO3, SnO2 and SiO2 showed similar high activities. The high activity for these catalysts was attributed to their non-basicity and negligible affinity toward SO3 (or H2SO4), which results in less poisoning of the supported Pt and also in a smooth supply of SO3 to the carbon surface, which is oxidized by NO2 with a catalysis of SO3.