Understanding the Unique Antioxidation Property of Boron-Based Catalysts during Oxidative Dehydrogenation of Alkanes.

Abstract

Boron-based catalysts show excellent performance in oxidative dehydrogenation (ODH) of light alkanes to alkenes with high selectivity and extremely good antioxidation properties. However, the anti-deep-oxidation mechanism remains unclear. Herein, we chose h-BN and B2O3 as representative boron-based catalysts to investigate their reactions with two important intermediates in the light alkane ODH, Et· (evolving to ethene) and EtO· (evolving to ethene or COx), to elucidate the origin of the antioxidation of alkanes. The density functional theory calculations reveal that surface boron sites could eliminate alkoxy in their vicinity, resulting in exceptional inhibition of alkane deep-oxidation. The analysis of the electronic and geometric structures of key stationary points showed that the oxophilicity of B determined the low deep-oxidation of alkanes, and the homoleptic coordination of B with all three ligating atoms being O moderately enhanced its oxophilicity. This work represents a novel conceptual advance in the mechanistic understanding of alkane ODH.