Crucial role of titanium dioxide support in soot oxidation catalysis of manganese doped ceria

Abstract

The influence of an anatase-TiO₂ support on the diesel soot oxidation catalytic activity of manganese doped ceria is investigated. The soot conversion light-off temperature is significantly lowered with the application of anatase-TiO₂ as the support in comparison to the unsupported and γ-Al₂O₃ supported CeO₂–MnO_x catalysts. Additionally, considerable enhancement in bulk and surface defects is observed for CeO₂–MnO_x/TiO₂, which is attributed to the promotional role of the CeO₂/TiO₂ interface in the formation and stabilization of defect sites. The temperature programmed desorption of oxygen (O₂-TPD) study of CeO₂–MnO_x/TiO₂ indicates a sharp increase in oxygen desorption after a temperature of 500 K. In good correlation, the diesel soot conversion substantially increases after 550 K, but below this temperature the TiO₂ supported catalyst exhibits comparable activity to that of the γ-Al₂O₃ supported catalyst. Increased oxygen mobility at elevated temperatures might play a key role in the performance of the TiO₂ supported catalyst. Moreover, its structural stability and appreciable catalytic activity were retained even after high temperature annealing treatment.