Impact of dual calcium and manganese substitution of La-deficient perovskites on structural and related catalytic properties: Future opportunities in next three-way-catalyst generation?

Abstract

The impact of La-deficiency and substitution by calcium and manganese in LaFeO3 has been investigated in Three-Way-Catalysis. Despite significant structural distortions, predominantly induced by calcium substitution, no significant phase segregation occurs. On the other hand, bulk and surface characterization revealed the stabilization of Mn4+ and Fe4+ in different extent. Kinetic analysis of CO and propene oxidation reactions and the NO reduction reaction showed that La0.7Fe0.8Mn0.2O3 exhibits the best performance. By contrast, a detrimental effect of calcium more pronounced for propene oxidation is observed. It was found that catalytic properties are neither related to bulk properties nor to the extent of specific surface area but are mostly governed by the redox couple Mn4+/Mn3+. The formation of Fe4+ improving with partial substitution of La by Ca in A-site was not found as a determining criterion.