Preparation and characterization of palladium containing nickel-iron-cobalt perovskite catalysts for complete oxidation of propane

Palladium containing nickel-iron-cobalt perovskite catalysts La(Co0.8Ni0.1Fe0.1)(1-x)PdxO3 with x=0.05 and 0.15 were synthesized at 600 degrees C from citrate precursors obtained by freeze-drying. Structural and morphological characterization was carried out by XRD, BET surface measurements, TEM and XPS. The reduction properties of catalysts were examined by TPR with H-2 combined with ex-situ XRD measurements. The results obtained indicate 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 La2Pd2O5 also appear. The oxide compositions are studied as catalysts for complete oxidation of propane as model substance of saturated hydrocarbons. The reaction parameters as light-off temperatures (for achievement of 50 % conversion, T-50), pre-exponential factors and the apparent activation energies were determined, internal diffusion effect being taken into account within the applied reactor model. The observed increase in the reaction rate constant when palladium is incorporated in into the perovskite structure is accordance with the concentration and forms of the palladium, exposed on the catalytic surface.