Co–CeO₂ Interaction Induces the Mars–van Krevelen Mechanism in Dehydrogenation of Ethane

Introducing a catalyst for dehydrogenation of ethane (EDH) for steam cracking represents a promising solution with high feasibility to realize efficient ethylene production. We investigated EDH over transition-metal-doped CeO₂ catalysts at 873 K in the presence of steam. Ce_0.8Co_0.2O₂ exhibited high EDH activity and selectivity to ethylene (ca. 95%). In the absence of H₂O, the catalytic activity dropped rapidly, indicating the promotive effect of H₂O on ethylene formation. Catalytic experiments with water isotopes (D₂O and H₂¹⁸O) demonstrated that EDH over Ce_0.8Co_0.2O₂ proceeds through the Mars–van Krevelen (MvK) mechanism in which the reactive lattice oxygen in Ce_0.8Co_0.2O₂ contributes to EDH. The consumed lattice oxygen was subsequently regenerated with H₂O. X-ray diffraction and in situ X-ray absorption fine structure spectroscopy revealed that cobalt species were mainly present as CoO under EDH conditions and that redox between Co²⁺ and Co⁰ proceeded concomitantly with EDH. In contrast with Ce_0.8Co_0.2O₂, no contribution of the lattice oxygen of CoO to EDH was verified in the case of CoO supported on α-Al₂O₃, which exhibited lower activity than Ce_0.8Co_0.2O₂. Therefore, Co–CeO₂ interactions are expected to play a crucially important role in controlling the characteristics of the reactive lattice oxygen suitable for EDH via the MvK mechanism.