Ba0.9A0.1MnO3 (A = Ce, La, Mg) Perovskite-Type Mixed Oxides: Effect of Partial Substitution of Ba on the Catalytic Performance for the Oxidation of CO in Simulated Automobile Exhaust Conditions

BaMnO3 (BM) and Ba0.9A0.1MnO3 (BM-A) (A = Ce, La or Mg) perovskite-type mixed oxides were synthesized by the aqueous sol–gel method; thoroughly characterized by ICP-OES, XRD, H2-TPR, BET, and O2-TPD; and tested as catalysts for CO oxidation under simulated automobile exhaust conditions. The characterization results indicate that the main effects of the partial substitution of Ba with A-metal in BM perovskite are the maintenance of the hexagonal structure of the perovskite and the increase in reducibility and oxygen mobility. All samples catalyze the CO to CO2 oxidation reaction in the different reactant mixtures employed, showing the best performance for the mixture with the lowest CO/O2 ratio and in the presence of a dopant in the BM perovskite formulation. BM-La is the most active catalyst for improving CO oxidation, as it is the most reducible, and because is able to evolve oxygen at intermediate temperatures.