Synthesis and Characterization of γ‑Fe₂O₃ for H₂S Removal at Low Temperature

Abstract

The performance of γ-Fe₂O₃ as sorbent for H₂S removal at low temperatures (20–80 °C) was investigated. First, γ-Fe₂O₃/SiO₂ sorbents with a three-dimensionally ordered macropores (3DOM) structure were successfully prepared by a colloidal crystal templating method. Then, the performance of the γ-Fe₂O₃-based material, e.g., reference γ-Fe₂O₃ and 3DOM γ-Fe₂O₃/SiO₂ sorbents, for H₂S capture was compared with that of α-Fe₂O₃ and the commercial sorbent HXT-1 (amorphous hydrated iron oxide). The results show that γ-Fe₂O₃ has an enhanced activity compared to that of HXT-1 for H₂S capture at temperatures over 60 °C, whereas α-Fe₂O₃ has little activity. Because of the large surface area, high porosity, and nanosized active particles, 3DOM γ-Fe₂O₃/SiO₂ sorbent shows the best performance in terms of sulfur capacity and utilization. Moreover, it was found that moist conditions favor H₂S removal. Furthermore, it was found that the conventional regeneration method with air at high temperature was not ideal for the composite regeneration because of the transmission of some amount of γ-Fe₂O₃ to α-Fe₂O₃. However, simultaneous regeneration by adding oxygen in the feed stream allowed the breakthrough sulfur capacity of FS-8 to increase up to 79.1%, which was two times the value when there was no O₂ in the feed stream