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

The performance of gamma-Fe2O3 as sorbent for H2S removal at low temperatures (20-80 degrees C) was investigated. First, gamma-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 gamma-Fe2O3-based material, e.g., reference gamma-Fe2O3 and 3DOM gamma-Fe2O3/SiO2 sorbents, for H2S capture was compared with that of alpha-Fe2O3 and the commercial sorbent HXT-1 (amorphous hydrated iron oxide). The results show that gamma-Fe2O3 has an enhanced activity compared to that of HXT-1 for H2S capture at temperatures over 60 degrees C, whereas alpha-Fe2O3 has little activity. Because of the large surface area, high porosity, and nanosized active particles, 3DOM gamma-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 gamma-Fe2O3 to alpha-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 O-2 in the feed stream.