Ketonization of Acetic Acid over Iron Oxide: Intertwined In Situ Changes of Active Sites and the Contradictory Role of Oxygen Vacancies

Abstract

Iron oxides are catalytically active for the ketonization of acetic acid in bio-oil upgrading. However, due to the complex reaction pathway and phase evolution of iron oxide, the underpinning catalytic mechanism is still far from fully understood. Through purposely designed experiments, advanced characterization, and density functional theory (DFT) modeling, this work confirmed a higher activity of magnetite than hematite for a lower activation energy and a higher reaction order with respect to acetic acid vapor pressure. For pristine hematite, the oxidation of acetic acid causes a gradual loss of lattice oxygen and an in situ phase change of hematite into magnetite. The α-H abstraction step..