Recent advances in oxidative dehydrogenation of propane to propylene on boron-based catalysts

Oxygen-assisted oxidative dehydrogenation of propane (O2-ODHP) to propylene is a promising route that complements the existing oil-based processes to bridge the gap between continuously increasing market demand and productivity of propylene. This reaction i) is free from thermodynamic constraint and ii) features minimized coke deposition of the catalyst. A major challenge of ODHP lies in the over-oxidation to undesired carbon oxides (COx). Transition metal oxides have been extensively explored in the past decades; however, they suffer from a low olefin selectivity. Most recently, hexagonal boron nitride (h-BN) emergesas a promising candidate for ODHP, which shows a unique high selectivity toward light olefins (C2-C3) and negligible COx formation. To interpret the origin of such unique catalytic performance, significant efforts have been put forth in identifying active sites and developing an in-depth understanding of reaction mechanisms through combined experimental and computational approaches. In general, boron-oxide species are identified as the active sites, and a surface-induced gas-phase reaction mechanism has been proposed, though detailed scenarios vary. These findings explain the Eley-Rideal kinetic behavior and unique high olefin selectivity of h-BN. The breakthrough in h-BN catalysts revitalizes the exploration of boron-oxide catalysts because of their identical kinetic behavior and similar active sites to h-BN catalysts. With the accumulated knowledge, continuous endeavor is devoted to developing advanced boron-containing materials for enhanced activity and durability. This review aims to summarize the recent advances in ODHP on boron-based catalysts, with particular emphases on catalytic performance, kinetic behavior, stability and leaching issues, identification of active sites, and site-dependent reaction mechanisms, as well as the development of advanced boron-based materials. With this review, we expect to not only provide an overview to keep abreast of the state-of-the-art boron-containing catalytic materials for ODHP, but also to identify key descriptors for designing efficient boron-based catalysts with low-temperature activity.