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Influence of the A-Site Cation in ACoO3 (A: La, Pr, Nd, and Gd) Perovskite-Type Oxides on Catalytic Activity for Methane Combustion. -The effects of rare earth ions in ACoO3 perovskites on the thermal behavior and the catalytic activity for the methane oxidation are investigated by XRD, TG, TEM, gas adsorption and O2 evolution measurements. For all samples one oxygen evolution step occurs at 1100 K. At the beginning of the desorption step superstructures of the perovskite framework adopting brownmillerite-type structures are formed. The total amount of oxygen which evolves above 1100 K increases with decreasing size of the rare earth cation. The catalytic activities at 830 K, expressed as reaction rates referred to the BET surface area, increase in the order PrCoO3LaCoO3 ¡ NdCoO3 ¡ GdCoO3. With the exception of Pr no significant effect of the A-site cations on the catalytic activity is observed. -(BAIKER, A.; MARTI, P. E.; KEUSCH, P.; FRITSCH, E.; RELLER, A.; J. Catal. 146 (1994) 1, 268-276; Dep. Chem. Eng.

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