Suppressing Deep Oxidation by Detached Nano-sized Boron Oxide in Oxidative Dehydrogenation of Propane Revealed by the Density Functional Theory Study

Abstract

The remarkable reactivity and selectivity of boron-based catalysts in the oxidative dehydrogenation (ODH) of light alkanes offer a sustainable path for the efficient conversion of light alkanes to olefins, while the origin of their unique ability to suppress deep oxidation remains to be studied. Concerning the leaking of boron oxide under ODH conditions, here, the ability of detached nano-sized boron oxide to eliminate propoxyl radicals, which is crucial to the high selectivity of olefins, was evaluated by means of density functional theory calculations. The results show that the barrier to the reaction is about 24 kcal/mol, suggesting that the detached nano-sized boron oxide can capture the propoxyl radicals under ODHP conditions to suppress the deep oxidation. The chemical environment may impose moderate influence by modulating their oxophilicity, and the boron sites that bear fewer hydroxyl groups show stronger affinity for the propoxyl radicals. This suggests that the inner tri-coordinated boron sites are more reactive than the edge boron sites in the elimination of alkoxyl radicals in the ODH of light alkanes, which is opposite to their ability to activate atmospheric dioxygen. This study enriches our understanding on the specific nature of boron-containing catalysts in suppressing the deep oxidation of light alkanes in their ODH.