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

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

Design of a Sorbent to Enhance Reactive Adsorption of Hydrogen Sulfide

A series of novel zinc oxide–silica composites with three-dimensionally ordered macropores (3DOM) structure were synthesized via colloidal crystal template method and used as sorbents for hydrogen sulfide (H₂S) removal at room temperature for the first time. The performances of the prepared sorbents were evaluated by dynamic breakthrough testing. The materials were characterized before and after adsorption using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that the composite with 3DOM structure exhibited remarkable desulfurization performance at room temperature and the enhancement of reactive adsorption of hydrogen sulfide was attributed to the unique structure features of 3DOM composites; high surface areas, nanocrystalline ZnO and the well-ordered interconnected macroporous with abundant mesopores. The introduction of silica could be conducive to support the 3DOM structure and the high dispersion of zinc oxide. Moisture in the H₂S stream plays a crucial role in the removal process. The effects of Zn/Si ratio and the calcination temperature of 3DOM composites on H₂S removal were studied. It demonstrated that the highest content of ZnO could reach up to 73 wt % and the optimum calcination temperature was 500 °C. The multiple adsorption/regeneration cycles showed that the 3DOM ZnO–SiO₂ sorbent is stable and the sulfur capacity can still reach 67.4% of that of the fresh sorbent at the fifth cycle. These results indicate that 3DOM ZnO–SiO₂ composites will be a promising sorbent for H₂S removal at room temperature

XRD patterns of laterite ores roasted under Ar at different temperatures.

<p>(a) raw ore, (b) 87°C, (c) 268°C, (d) 587°C, (e) 1126°C.</p

The effect of the reduction temperature on nickel–iron beneficiation (reduced for 120 min in the presence of 20 wt% sodium sulphate).

<p>The effect of the reduction temperature on nickel–iron beneficiation (reduced for 120 min in the presence of 20 wt% sodium sulphate).</p

MS fragmentation intensities of H₂O during the thermal decomposition of the Na₂SO₄/laterite blends.

<p>MS fragmentation intensities of H₂O during the thermal decomposition of the Na₂SO₄/laterite blends.</p

The effect of the reduction temperature on nickel–iron beneficiation (reduced for 120 min).

<p>The effect of the reduction temperature on nickel–iron beneficiation (reduced for 120 min).</p

Kinetic parameters for laterite decomposition.

<p>Kinetic parameters for laterite decomposition.</p

MS fragmentation intensities of SO₂ during thermal decomposition of the Na₂SO₄/laterite blends.

<p>MS fragmentation intensities of SO₂ during thermal decomposition of the Na₂SO₄/laterite blends.</p

Plots of <i>ln(−ln(1−α)/T</i>^<i>2</i><i>)</i> vs. <i>1/T</i> for laterite decomposition recalculated by the multi-step integral method.

<p>(a), 238–278°C; (b), 554–602°C; (c), 1100–1145°C.</p

The main chemicals and nickel distribution of the studied laterite (wt%).

<p>The main chemicals and nickel distribution of the studied laterite (wt%).</p