Mechanistic Pathways for the Dehydrogenation of Alkanes on Pt(111) and Ru(0001) Surfaces

Abstract

AbstractThe dehydrogenation of alkanes is a critical process to enable olefin upcycling in a circular economy. A suitable selective catalyst is required in order to avoid demanding reaction conditions and ensure the activation of the C−H bond rather than breaking the C−C bond, which is the weaker of the two. Herein, using periodic density functional theory, we have investigated the dehydrogenation of n‐pentane (as a model compound) on Pt and Ru surface catalysts. The results show that the first dehydrogenation occurs through the dissociative adsorption of the C−H bond, resulting in pentyl and H intermediates on the metal surfaces. A successive dehydrogenation creates pentene via a hydride di‐σ state, leaving the abstracted hydrogen atoms on the metal surfaces. In agreement with recent experiments, Pt and Ru catalysts show a similar reactivity trend: pentane dehydrogenation yields pent‐1‐ene and pent‐2‐ene. The simulations reveal that the 1st C−H dissociation is the rate‐determining step, whereas the double‐bonded alkenes (pent‐1‐ene and pent‐2‐ene) are formed due to fast successive dehydrogenation processes. Pt favors the formation of pent‐1‐ene, whereas Ru favors the formation of pent‐2‐ene.