Catalytic combustion of methane over perovskites

Perovskite-type oxides of the series La(1-x)A(x)MnO(3) (A = Sr, Eu and Ce) were prepared by the amorphous citrate process, leading to high surface area catalysts (up to 45 m(2) g(-1)). They were tested in a flow reactor for the total combustion of methane. Complete conversion was obtained over all of the catalysts between 500 and 600 degrees C and catalyst performance did not change significantly after 100 h on-stream. Specific activity was found to decrease monotonically with increasing the temperature of the O-2 TPD desorption peak maximum. The rate of methane combustion was low below 500 degrees C, then grew very fast, showing that two kinds of oxygen are active in these catalysts: an adsorbed oxygen species, that reacts at low temperature, and a lattice oxygen species, that becomes available at high temperature, boosting the catalytic activity. (C) 1998 Elsevier Science B.V.