The project will investigate the oxidative dehydrogenation (ODH) of ethane to produce ethylene - a high volume chemical intermediate. A novel approach is employed that utilizes a core-shell catalyst design in combination with a chemical looping redox cycle to achieve ODH without direct feed of oxygen. The combined approach potentially eliminates a costly and energy-intensive process for separating oxygen from air, while also reducing carbon emissions. The work will provide multi-disciplinary educational opportunities for graduate and undergraduate students, as well as outreach activities to high school students and teachers for stimulating interest in STEM careers.
The core-shell redox catalyst is both an active catalyst and an effective lattice oxygen ion donor for ethane ODH in a chemical-looping scheme. The work plan tests three key hypotheses: 1) Chemically and structurally compatible primary (cobalt/iron) oxides and perovskites can be assembled into a stable core-shell arrangement for ethane ODH under a cyclic redox mode; 2) The surface properties of the core-shell redox catalyst can be tailored by tuning the metal cation oxidation state and defect structure of the mixed ionic-electronic conductor (MIEC) shell, rendering a highly effective catalyst for ethane ODH in the absence of gaseous oxidants; 3) Ethane ODH reaction occurs primarily on the perovskite surface via homolytic C-H bond cleavage through a modified Mars-van Krevelen mechanism. To test these hypotheses, phase-compatible core and shell materials will be identified and then assembled into core-shell particles. The effects of perovskite A-site and B-site substitutions on ODH activity and selectivity will be investigated and correlated to the defect structure and cation oxidation state of the shell material. Kinetic and mechanistic aspects will be investigated over pellets and thin films replicating the core-shell and shell structures using in-situ Raman and FT-IR/DRIFTS, a molecular beam reactor coupled with an X-ray photoelectron spectrometer, and pulse isotope studies. The studies will potentially result in fundamentally new materials and schemes that can significantly improve the efficiency for ethylene production from natural gas while reducing emissions.
