La1-x Ca x FeO3-δ (x=0-1) perovskites prepared by the Pechini method: Catalytic activity in deep methane and CO oxidation

The catalytic activity of a series of La1-x Ca (x) FeO3-delta (x = 0-1) materials prepared by the Pechini method from polymer-salt stocks has been investigated, and the phase composition and microstructure of these materials before and after testing them in methane oxidation have been determined. The activity and stability of the materials depends on their composition and on the reaction temperature. The introduction of calcium into lanthanum ferrite up to x = 0.5 causes a nonmonotonic increase in the activity of the catalyst in methane oxidation. As x is further increased, the catalytic activity falls off. It has been analyzed how the activity of the catalysts is affected by variations of their imperfection and microstructure as a result of the introduction of calcium and under the action of the reaction medium. According to high-resolution transmission electron microscopy data, under the action of the reaction medium the perovskite structure undergoes partial degradation (in subsurface layers) leading to the formation of planar defects and to the release of iron oxide nanoparticles.