Optimizing the Catalytic Performance of Ba_1-xCe_xMnO₃ and Ba_1-xLa_xCu_0.3Mn_0.7O₃ Perovskites for Soot Oxidation in...

Ba_1-xCe_xMnO₃ (BM-Ce_x) and Ba_1-xLa_xMn_0.7Cu_0.3O₃ (BMC-La_x) perovskite-type mixed oxides were synthesized using the sol-gel method adapted for aqueous media with different values of x (0, 0.1, 0.3, 0.6) to estimate the effect of the degree of the partial substitution of Ba by Ce or La on the structure and properties that are relevant for their use as catalysts for gasoline direct injection (GDI) soot oxidation. The samples were deeply characterized by ICP-OES, XRD, XPS, N₂ adsorption, H₂-TPR, and O₂-TPD, and their potential as catalysts for soot oxidation has been analyzed in various scenarios that replicate the exhaust conditions of a GDI engine. By comparing the catalytic performance for soot oxidation of the two tested series (BM-Cex and BMC-Lax) and in the two conditions used (100% He and 1% O₂ in He), it could be concluded that (i) in the absence of oxygen in the reaction atmosphere (100% He), BMC-La_0.1 is the best catalyst, as copper is also able to catalyze the soot oxidation; and (ii) if oxygen is present in the reaction atmosphere (1% O₂/He), BM-Ce_0.1 is the most-active catalyst as it presents a higher proportion of Mn(IV) than BMC-La_0.1. Thus, it seems that the addition of an amount of Ce or La higher than that corresponding to x = 0.1 in Ba_1-xCe_xMnO₃ and Ba_1-xLa_xCu_0.3Mn_0.7O₃ does not allow us to improve the catalytic performance of BM-Ce_0.1 and BMC-La_0.1 for soot oxidation in the tested conditions.