Potential rare-earth modified CeO2 catalysts for soot oxidation

The physico-chemical properties of ceria (CeO2) and rare earth modified ceria (with La, Pr, Sm, Y) catalysts are studied and correlated with the soot oxidation activity with using O2 and O2+NO. CeO2 modified with La and Pr shows superior soot oxidation activity with O2 compared with the unmodified catalyst. The improved soot oxidation activity of rare earth doped CeO2 catalysts can be correlated to the increased meso/micro pore volume and the stabilisation of the external surface area. On the other hand, unreducible ions decrease the intrinsic soot oxidation activity of rare earth modified ceria with both O2 and NO+O2 due to the decreased amount of redox surface sites. The catalyst bulk oxygen storage capacity is not a critical parameter in determining the soot oxidation activity. The modification with Pr shows the best soot oxidation with both O2 and O2+NO compared with all other catalysts. KEY WORDS: diesel soot; rare earth; ceria; oxidation; catalysis. 1