Oxygen non-stoichiometry in perovskitic catalysts: Impact on activity for the flameless combustion of methane

摘要

Perovskite-like LaBO3 catalysts (B = Co, Mn, Fe), prepared by flame pyrolysis, and doped with Ce, Sr or with small amounts of Pd or Pt were used for the flameless combustion of methane. The effect of the dopants on the reducibility of the B metal ion has been analysed comparatively, trying to correlate this parameter with catalytic activity. The higher the B~(3+) ion reducibility, the lower was the light off temperature of the reaction. However, the correlation with the temperature of half conversion revealed that a too high reducibility of the catalyst depressed the second step of the Mars-van Krevelen reaction mechanism, i.e. the reoxidation of active site. The quantitative elaboration of the TPR pattern allowed to determine oxygen non-stoichiometry, at least for the LaCoO3 based samples. Furthermore, the available oxygen amount was correlated to catalytic activity.