Effect of the preparation method on the catalytic activity of La1−xCaxFeO3 perovskite-type oxides

La1−xCaxFeO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4) perovskites prepared by two different methods, via precursor of citrate and via co-precipitation in basic medium, both calcined at 973 K have been investigated as catalysts for acetyl acetate and methane combustion. In the case of the citrate method, atomic absorption spectroscopy (AAS), BET specific area measurements, XRD analysis, Raman, SEM, FTIR, TPR and TPD of O2 suggest that a continuous substitution of calcium by lanthanum in the perovskite structure is reached. In the basic series, the insertion of calcium in the LaFeO3 lattice produces a substitution only up to x = 0.1. Higher calcium addition leads to segregated calcium phases. In the methane reaction, the substituted perovskites exhibit lower activity than the simple LaFeO3 perovskite, without the preparation method effect and extent of substitution. Meanwhile, for the acetyl acetate reaction, the most active perovskite (i.e., the lower ignition temperature) was obtained in the higher substituted La1−xCaxFeO3. For the basic series, the activity in the acetyl acetate combustion decreases as the substitution degree increases up to x = 0.2. At higher calcium content, the activity does not change. Therefore, perovskite catalyst activity mainly depends on the composition, preparation method and nature of the compound to be combusted.