Rare-Earth Manganites: Catalysts with Low Ammonia Yield in the Reduction of Nitrogen Oxides

Rare-earth manganites such as La$_{1-x}$Pb$_{x}$MnO$_{3}$, with 0.3 < x < 0.6, and their perovskite-like homologs are active catalysts for the reduction of nitric oxide to molecular nitrogen. At low temperatures, innocuous nitrous oxide rather than ammonia is the main side product. The activity of single crystalline catalysts and of ceramic catalysts of this type is substantially improved by etching with dilute acids.