Preparation and characterization of palladium containing nickel–iron–cobalt perovskite catalysts for the complete oxidation of C1–C6 alkanes

Palladium containing nickel–iron–cobalt perovskite catalysts La(Co0.8Ni0.1Fe0.1)1−xPdxO3 with x = 0.05 and 0.15 were synthesized at 600 °C from citrate precursors obtained by freeze-drying. Structural and morphological characterization was carried out by XRD, B.E.T. surface measurements, TEM and XPS. The reduction properties of catalysts were examined by TPR with H2 combined with ex situ XRD measurements. The results obtained indicate the formation of cobalt-based perovskite phases in which Pd ions are incorporated into the crystal structure. For the sample with the higher Pd content, traces of PdO and/or La2PdO4 also appear. The oxide compositions are studied as catalysts for the complete oxidation of C1–C6 n-alkanes hydrocarbons. The highest light-off temperature (for achieving 50% conversion, T50) is observed for methane combustion and adding one further carbon atom to the hydrocarbon chain C1–C6 leads to a decrease in T50 with a step of 30–75 °C. The apparent activation energies for the reaction of complete oxidation was found to decrease from methane to n-butane. This effect correlates with the strength of the (weakest) H–C bond of the corresponding n-alkane.