Methane catalytic combustion on La-based perovskite type catalysts in high temperature isothermal conditions

The rate constants in isothermal conditions at 900 degreesC have been measured for a series of La1-xSrxFeO3 unsupported oxide (0 less than or equal tox less than or equal to0.5) with the perovskite structure. The best catalytic performances were obtained, in terms of catalytic activity per weight of catalyst for x=0.2, and in terms of catalytic activity per unit surface area for 0.3 less than or equal tox less than or equal to0.5. A deactivation, mainly due to the sintering of the catalysts, was observed with the time on stream at 900 degreesC. This deactivation can be lowered by supporting the perovskite phase on BaAl12O19. but unfortunately, an important CO formation occurred, increasing with the time on stream. From pulses experiments, two oxidation sites behaving differently have been revealed: a very reactive one leading to a fast and selective CO2 formation and a less reactive one, selective for the CO+H-2 formation which could arise from the partial reduction of the very reactive site. (C) 2001 Elsevier Science B.V. All rights reserved.