Reactive molecular dynamics simulation of Cr2O3 nanowires-catalyzed dehydrogenation and oxidation of butane at high temperature

Abstract

Transition metal oxides have garnered significant interest in hydrocarbon dehydrogenation, oxidation, and combustion reactions owing to their exceptional catalytic characteristics. Cr₂O₃ nanowires, serving as highly efficient catalysts, play significant roles in advancing energy conversion, pollutant degradation, and catalytic processes. In this study, ReaxFF reactive force field molecular dynamics simulations were performed to elucidate the reaction mechanism of Cr₂O₃ nanowire-catalyzed butane dehydrogenation and oxidation. Results showed that the reactions of butane with oxygen catalyzed by Cr₂O₃ nanowires mainly undergo four stages: (i) butane molecules adsorb onto the Cr₂O₃ surface at high temperatures; (ii) butane free radicals are formed by hydrogen extraction; (iii) active oxygen species (e.g., Cr-O, Cr-O-Cr, and Cr-O-O) on the chromium oxide surface interact with butane molecules to facilitate the dehydrogenation; and (iv) at 3000 K, butane molecules are rapidly consumed to form mainly C₂H₄, H₂O, and CH₂O along with traces of CO₂, H₂O₂, CO, and C₃H₆ as oxidation products. Moreover, elevated temperatures destabilize Cr₂O₃ nanowires, leading nanowires with smaller radii to agglomerate into spherical nanoparticles, thereby substantially impacting their catalytic efficacy. This investigation offers a comprehensive insight into the dehydrogenation and oxidation mechanisms of metal chromium oxide nanowires.