Structure and catalytic activity of mixed oxides of perovskite structure

Abstract

Abstract The La 1-x Ce x BO 3 (B=Ti, Cr, Mn, Fe, Ni, Co) mixed oxides of perovskite structure present a catalytic activity for CO oxidation and No reduction which increases with increasing Ce content. LaCoO 3 and LaMnO 3 are the more active compounds for both CO oxidation and NO reduction. The oxidation of CO by O 2 follows a suprafacial type mechanism where the adsorbed oxygen is the active species. The reduction of NO by CO is best expalined by a redox mechanism. Ce is only incorporated in a limited amount in the perovskite structure and a concomitant formation of CeO 2 is also observed. For a low Ce content, CeO 2 is highly dispersed on the surface of the catalyst particles, while larger particles are obtained at higher Ce content. The presence of Ce leads to an increase in both CO oxidation and NO reduction activities. The CO oxidation is dependent on the dispersion of CeO 2 on the mixed oxides particles. On the other hand, the NO reduction does depend on the Ce content in the perovskite structure.