Chemisorption and catalysis on LaMO3 oxides

Abstract

The adsorption of oxygen and isobutene and the catalytic activity for propene and isobutene oxidation have been studied on a series of LaMO₃(M = Cr, Mn, Fe, Co and Ni) perovskite oxides. Coadsorption results point to the non-competitive adsorption of oxygen and isobutene; i.e. these molecules adsorb on different centres. Oxygen adsorption underwent a remarkable increase after isobutene had been preadsorbed on these oxides (enhanced adsorption). Activation energies for complete oxidation ranged between 16 kcal mol^–1(LaMnO₃, LaCoO₃ and LaNiO₃) and 31 kcal mol^–1(LaFeO₃). LaCrO₃ showed some activity for methacrolein formation. Adsorption and catalytic-activity profiles showed maxima for LaMnO₃ and LaCoO₃. These results are discussed within the framework of the ideas of Dowden and Wells on the local symmetry of surface cations and its influence on chemisorption and catalysis and show the importance of localized interactions in the processes studied.