LaMnO3 perovskite supported noble metal catalysts for the total oxidation of methane

Two series of LaMnO3 supported noble metal (Pt, Pd, Rh) catalysts prepared by the citrate method and calcined in air at 600 and 800 degrees C, respectively, were investigated. The catalysts resulting from method A were prepared by simultaneous incorporation of the noble metals during perovskite preparation and those following method B were generated by impregnation of the calcined perovskites with the noble metal compounds. The noble metals form solid solutions with the perovskite lattice. Reduction of the catalysts with hydrogen prior to the catalytic reaction led to a significant enhancement of the catalytic activity. During the catalytic reaction, the noble metal clusters are partially transformed to highly dispersed noble metal oxides or nonstoichiometric noble metal oxide phases, which are the catalytically active phases for the total oxidation of methane. The best results were obtained with the Pd containing catalysts prepared by method B.