Pd-integrated lanthanum-transition metal perovskites for methanol partial oxidation

Abstract

Palladium integrated lanthanum-transition metal perovskites (LaMnO 3, LaFeO 3, and LaCoO 3) were employed in methanol partial oxidation to formaldehyde. The crystallinity of these perovskites remained unchanged by incorporating up to 5 mol% Pd cations into their respective frameworks. Such a cation replacement could yield a positive effect on particle size and catalyst reducibility. The Pd cation exists in perovskites mostly as Pd 2+. Under partial oxidation conditions, the reactivity and formaldehyde selectivity of Pd-free perovskites were relatively low compared to their Pd-impregnated counterparts. Most importantly, the reaction mechanism could be promoted diversely. For Pd-free perovskites, methanol combustion, methanol oxidation to syngas and water, and methanol dehydrogenation were found to be prominent. In contrast, methanol partial oxidation to formaldehyde and methanol dehydrogenation were the major pathways of Pd-integrated catalysts. Both reactions can be seen as major factors in the elevation of formaldehyde selectivity.