Redox mechanism by lattice sulphur in an Fe-based catalyst for propane dehydrogenation with H2S co-feeding†

Abstract

Iron-based catalysts supported on SiO₂ (Fe/SiO₂) exhibit unique resistance to sulphur poisoning and sustained activity for propane dehydrogenation (PDH) under hydrogen sulfide (H₂S) co-feeding. In this study, noble metals (Pd, Pt, Ru) were incorporated to enhance catalytic performance, among which Ru significantly improved both activity and durability. Transient pulse experiments coupled with mass spectrometry revealed that the PDH reaction proceeds via a regenerable redox mechanism involving lattice sulphur (S²⁻), where Ru promotes both the release and re-incorporation of S²⁻ species. Spectroscopic analysis using XPS and Ru K-edge EXAFS showed that Ru exists in both metallic and sulphidic forms, and that interfacial electron transfer from Fe to Ru increases the Fe oxidation state. DFT calculations based on a Ru–FeS interface confirmed this electron redistribution and identified balanced activation barriers for key steps such as C–H activation (81.3 kJ mol⁻¹) and S²⁻ regeneration (80.8 kJ mol⁻¹). The synergy between structural characterization and theoretical modelling supports a robust and reversible lattice-sulphur-mediated catalytic cycle. These findings establish Ru–Fe/SiO₂ as a promising redox catalyst for selective PDH under H₂S-rich conditions, and demonstrate a viable strategy for utilizing sulfur-containing streams in alkane upgrading.