Activity of catalysts supported on heat-resistant ceramic cloth for diesel soot oxidation

We investigated catalysts that promote the soot oxidation using a heat-resistant ceramic cloth (mullite; 70%Al2O3–30%SiO2) as a substrate for the catalyst. The catalytic activity was evaluated by a temperature (T10), at which 10% of carbon black (CB) combined with the catalyst-bearing cloth was oxidized during a temperature raise process under simulated air conditions (flow rate = 0.5 L min−1, CB = 5 mg, cloth = 0.1 g), and by a balance point temperature (BPT) assessed by the changing rate of pressure drop through the catalyst-bearing cloth with time under practical diesel exhaust conditions (flow rate = 45 L·min−1, PM concentration = 40 mg m−3, cloth = 38 g). Among the catalysts tested under the simulated conditions, Pt combined with metal oxides which have a low melting point such as V2O5 and MoO3 showed high activities (T10 = ca. 490 °C). Under the practical conditions, V2O5 + Pt-loaded cloth showed a performance of a filtration rate of 59% with a BPT of 553 °C. Mobility of the catalyst over the cloth surface and easiness of reduction and oxidation of the catalyst were suggested to be important for promotion of soot oxidation.