Influence of particle morphology on catalytic performance of CeO2/ZrO2 for soot oxidation

The effect of size and morphology of CeO2/ZrO2 catalysts, prepared by impregnation [CZ(IMP)], coprecipitation [CZ(CP)] and deposition-precipitation [CZ(DP)] methods, on the soot oxidation performance was investigated. TEM observation revealed that CeO2 particles are well dispersed with the size of 10nm on ZrO2 support for CZ(IMP). In case of CZ(CP), the agglomeration of CeO2-ZrO2 solid solution particles was recognized. On the other hand, large CeO2 particles (50 nm) were independently present in CZ(DP). Soot oxidation activity of CeO2/ZrO2 was strongly dependent on the morphology of CeO2 particles and decreased in the order of CZ(IMP) > CZ(CP) > CZ(DP). From isotopic transient kinetics analysis using O-18(2), the lattice oxygen in the surface region of CeO2 particles in CZ(IMP) was highly reactive compared with those in the surface and bulk of CeZrOx solid solution in CZ(CP), resulting in high soot oxidation activity. (C) 2015 The Ceramic Society of Japan. All rights reserved.