Tandem CO2 Valorization and Ethane Dehydrogenation: Elucidating the Nature of Highly Selective Iron Oxide Active Sites

Abstract

Iron oxide-based catalysts can selectively covert CO2 to added-value CO in parallel with on-purpose ethylene production via ethane dehydrogenation (CO2-EDH). The 5Fe/10NiMgZr catalyst, calcined at 700 °C for 5 h, reached 90% selectivity, at a single-pass C2H6 conversion of ∼23.3%, during CO2-EDH at 650 °C. X-ray characterization techniques (XRD, XPS, XAS, and XRS), along with structural modeling were used to elucidate the nature of highly selective active sites toward C-H bond scission. Under reaction conditions, Fe atoms are incorporated into the support lattice, as it was exemplified by XRS at Mg L2,3- and O K-edges. The dynamic structural modifications, occurring during CO2-EDH, highlighted the pivotal role of the support, reaching an ethylene yield of 21%. Mg coordination altered from octahedral to tetrahedral. The latter was accompanied by an electronic modification, which had a strong impact on the catalyst acidity, based on Fourier transform infrared spectroscopy combined with in situ adsorption of pyridine, resulting in an unpresented ethylene selectivity for Fe oxide-based catalysts.