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. The 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 mol_C3H6 g_Fe⁻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.