Catalytic Properties of Perovskite-Type Mixed Oxides (ABO3) Consisting of Rare Earth and 3d Transition Metals. The Roles of the A- and B-Site Ions

Abstract The catalytic activities of perovskite-type mixed oxides (LnBO3 and Ln0.8Sr0.2CoO3, Ln=rare-earth (lanthanoid) elements, B=3d transition metals) for the oxidation of propane and methanol have been studied comparatively. It has been found that the catalytic activities of LnBO3 were principally determined by the B-site elements and were similar to those of the corresponding oxides of the B-site elements. The roles of the rare-earth ions of the A-site were secondary as long as they were trivalent. Upon the partial replacement of Ln3+ by Sr2+, the catalytic activities of LnCoO3 increased several times, the magnitude of the increase being similar among all the rare-earth ions. These results demonstrate that the kind and the valence of a B-site metal are of primary importance for the control of the catalytic activity for oxidation, almost regardless of the kind of trivalent rare-earth elements at the A-site.