Modified LaCoO3 nano-perovskite catalysts for the environmental application of automotive CO oxidation

Modified perovskite-type oxides were synthesized through co-precipitation and conventional citrate methods. The synthesized perovskite materials had the nominal compositions of LaCoO3, LaCo0.8Cu0.2O3, La0.8Sr0.2Co0.8Cu0.2O3, and La0.8M0.2FeO3 (where M = Ce and Sr). The catalytic activity of the perovskite samples (for low-temperature CO oxidation) was measured using a quartz reactor with an inlet gas mixture containing 97% N2, 1% O2, and 2% CO. The prepared perovskite samples were characterized by SEM, nitrogen adsorption (BET), XRF, and XRD analyses. The perovskite catalysts showed good structural and chemical stability up to 600 °C and high activity for the catalytic CO oxidation reaction. The catalyst samples prepared by the citrate method achieved the same CO conversion at lower temperatures than those prepared by the co-precipitation method. This was attributed to a better-formed perovskite crystals by the citrate method. A new perovskite composition, La0.8Sr0.2Co0.8Cu0.2O3, showed higher activity for CO conversions higher than 80%. This catalyst achieved 100% CO oxidation at 355 °C. Hence, for the environmental application of the automotive emission control, it can completely eliminate the poisonous CO gas. Among the other four synthesized perovskite formulations, the LaCoO3 sample performed best in the whole range of CO conversions. SEM pictures of the perovskite samples produced by the citrate method showed that the particles sizes were close to 100 nm.