La1−xCaxMnO3 perovskites as catalysts for total oxidation of volatile organic compounds

La1−xCaxMnO3 perovskites were prepared by the citrate method and characterized by means of X-ray diffraction, temperature programmed desorption of oxygen, temperature programmed reduction, and measurement of specific surface area. The characterization results indicated that pure perovskite phases were obtained and their specific surface areas are appropriate for the application in catalytic oxidation. The unsubstituted perovskite, LaMnO3, could present a certain amount of Mn4+ and cationic vacancies, which is generally called oxidative nonstoichiometry. The electronic unbalance yield by the partial substitution of lanthanum by calcium, a cation of lower oxidation state, caused an oxidation state increase of part of the manganese occupying the B sites of the structure. Concurrently, the amount of cationic vacancies decreased with the increase of calcium amount. The catalytic activity was evaluated in the combustion of ethanol and n-hexane. Both reactions would occur by means of a suprafacial reaction mechanism in which the adsorbed oxygen species are relevant.

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► LaMnO3 contains Mn4+ and the amount increases with the substitution of La by Ca.
► The excess oxygen in LaMnO3 decreases with the substitution of La by Ca.
► La1−xCaxMnO3 perovskites are more active than pure Mn2O3 in ethanol combustion.
► The intrinsic activity in ethanol and n-hexane combustion is related to the adsorbed oxygen species.