Enhancing Stability and Activity of Fe-based Catalysts for Propane Dehydrogenation via Anchoring Isolated Fe-Cl Sites.

Abstract

The eco-friendly features and desirable catalytic activities of Fe-based catalysts make them highly promising for propane dehydrogenation (PDH). However, simultaneously improving their stability and activity remains a challenge. Here, we present a strategy to address these issues synergistically by anchoring single-atom Fe-Cl sites in Al3+ vacancies of Al2O3. As-synthesized Fe-Cl/Al2O3 catalyst exhibited greater charge transfer between Cl and Fe than that between O and Fe in conventionally impregnated single-atom Fe/Al2O3 catalysts, resulting in higher effective magnetic moments for Fe-Cl/Al2O3 compared to Fe/Al2O3. When tested in PDH, the durability of Fe-Cl/Al2O3 exceptionally lasted for 250 h under continuous regeneration conditions comprising 60% C3H8 (40% N2), followed by pure C3H8 at 600 °C while maintaining a high propylene space-time yield of 1.2 molC3H6 gFe-1 h-1, surpassing the performance of previously developed Fe-based PDH catalysts. We demonstrate that anchoring Fe-Cl into Al3+ vacancies simultaneously enhances stability and suppresses coke formation, owing to unique atomically dispersed Fe-Cl active structures. Compared with Fe/Al2O3 catalysts, charge transfer between Cl and Fe active centers reduces the activation energy barrier for C-H activation during C3H8 dehydrogenation, thereby improving catalytic activity; this may be related to their spin state as observed in in-situ X-ray emission spectroscopy studies during PDH.