Chemical Engineering Science | 2021
The kinetic mechanism of acetylene hydrogenation to prepare ethane over FexOy clusters: A DFT study
Abstract
Abstract The acetylene hydrogenation reaction over FeO, Fe2O3 and Fe3O4 clusters are theoretically investigated, via C2H2 adsorption, approach of molecular H2 to cluster, H2 dissociation on Fe O bond, and the sequential addition reaction of H atom. Over FeO cluster, the extremely high barrier for the addition reaction of H atom adsorbed on O atom (of cluster) predicts the impossible acetylene hydrogenation. Over Fe2O3 cluster, the overall barriers for H2 dissociation, addition reaction of two hydrogen atom are respectively 26.6, 32 and 31.8\xa0kcal·mol−1 during the acetylene hydrogenation to form ethylene and 26.5, 35.5 and 9.1\xa0kcal·mol−1 for its further hydrogenation to produce ethane. During the further hydrogenation pathway, the migration of semi-hydrogenated product C2H3 requires extra energy of 30.7\xa0kcal\xa0mol−1. These barriers are lower than those of the pathways over Fe3O4 cluster. Hence, among three FexOy clusters, hydrogenation of acetylene to produce ethane on Fe2O3 cluster is kinetically most favorable.