Study of Ce/Pr ratio in ceria-praseodymia catalysts for soot combustion under different atmospheres

The effect of Ce/Pr ratio on ceria-praseodymia on structural and surface properties is studied. The catalytic activity towards soot combustion under NOx/O-2 and O-2/N-2 atmospheres is also evaluated, together with the NO oxidation activity to NO2. CexPr1-xO2-delta compositions (x = 0.8, 0.5 and 0.2) have been prepared along with ceria and praseodymia. Catalysts were prepared by co-precipitation. The Ce0.5Pr0.5O2-delta composition, was also prepared by nitrate calcination. Ceria-praseodymia mixed oxides yield reduction profiles shifted to lower temperatures, higher NO oxidation activities to NO2 and improved catalytic activities for soot combustion with respect to pure ceria. Ce0.5Pr0.5O2-delta was the most active one. Under NOx/O-2, it has greater soot combustion activity if it is prepared by nitrate calcination. However, under O-2/N-2, the co-precipitation method is more favorable because of the better dopant insertion achieved in the ceria lattice, which seems to lead better oxygen mobility on the surface and in the bulk oxide.