Embedded CoFeZr Nanostructures in Silicalite-1 for Catalytic Conversion of Propane with CO₂

During propane dehydrogenation in the CO2 atmosphere (PDH-CO2), Fe-based catalysts deactivate due to undue reduction of active FeOx to Fe or FeCx and thus engender carbon deposits. Herein, CoFeZr@Silicalite-1 (S-1) with the embedment of Co, Fe, and Zr nanostructures in S-1 was constructed and exhibited stable catalysis for the PDH-CO2 reaction at 550 °C with high selectivity to propylene. 0.5CoFeZr@S-1 persisted a propylene selectivity of 97% and a propane conversion of 23% over a time-on-stream of 120 h. X-ray diffraction, in situ X-ray photoelectron spectroscopy, and temperature-programmed reduction of hydrogen characterization confirmed the interactions between Co, Fe, and Zr, due to their incorporation into the S-1 framework. On the one hand, the interconversion of the formed Co2+-O tetrahedron and Co2+-O octahedron during the reaction promoted electron transfer between Fe3+ and Fe2+ of the FeOx species, stabilizing the active phase and the catalytic cycle. On the other hand, the resulting medium-strong base sites improved C3H8 conversion and diminished carbon deposition by exerting the reverse water–gas shift (RWGS) and the reverse Boudouard reactions, respectively. Moreover, the HCOO*- and CH3O*-mediated pathway for this RWGS-propelled PDH was proposed based on in situ DRIFTS characterization.