Improved Catalytic Performance of Ethane Dehydrogenation in the Presence of CO2 over Zr-Promoted Cr/SiO2

The Zr-, Ce-, Sr-, and Sn-promoted Cr/SiO2 catalysts were prepared by the incipient wetness impregnation method, then characterized by N-2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, H-2-TPR, CO2-TPD, UV-vis, high-angle annular dark-field imaging-scanning transmission electron microscopy-energy dispersive X-ray spectroscopy elemental mapping, Raman, and thermogravimetric techniques to study the structural evolution under the preparation/reaction conditions, and applied to catalyze ethane oxidative dehydrogenation with CO2. The results suggested that the Cr6+ species were indispensable for activating the dehydrogenation reaction thanks to the oxidation-reduction cycle between Cr6+ and Cr3+. The type of the promotor also affected significantly the ability of replenishing the lattice oxygen through the disassociation of CO2, leading to the different catalytic performances. The Zr-promoted sample had the best performance in converting the reactants as well as the catalytic stability.