Improvement of Pt catalyst for soot oxidation using mixed oxide as a support

Catalytic activity of Pt catalysts for soot oxidation was studied using temperature programmed reactions. The activity of Pt loaded over TiO2–SiO2 (Pt/TiO2–SiO2) showed higher activity than other Pt/MOx systems (MOx=TiO2, ZrO2, SiO2, Al2O3, TiO2–ZrO2, TiO2–Al2O3, ZrO2–SiO2, ZrO2–Al2O3, SiO2–Al2O3). The activity was highest when the molar ratio of TiO2/(TiO2+SiO2) ranged from 0.4 to 0.7. The effect of pretreatment with a gas containing low SO2 concentrations on the activity was compared for Pt/SiO2, Pt/TiO2 and Pt/TiO2–SiO2. In the case of Pt/TiO2–SiO2, the activity was markedly promoted by the pretreatment whereas no variation in the activity was observed for Pt/SiO2. The difference in the behavior towards the SO2 pretreatment was attributed to property difference in the supports for sulfate accumulation. The high activity of Pt/TiO2–SiO2 was also confirmed under practical conditions with a diesel engine exhaust using a catalyst-supported diesel particulate filter (DPF).