Microwave-assisted synthesis of Zn-Fe adsorbent supported on alumina: Effect of Zn to Fe ratio on syngas desulfurization performance

Before syngas from gasification of biomass could be used as synthesis fuel or chemical feedstock, it requires the removal of hydrogen sulfide (H₂S) to meet the purity standard level of those applications. In this study, Zn-Fe/Al₂O₃ were successfully synthesized by a microwave-assisted wet incipient impregnation technique for use as adsorbent for H₂S removal. The characterization of synthesized adsorbents showed that the oxide form of Zn and Fe present on the surface of adsorbents were zinc oxide (ZnO), magnetite (Fe₃O₄), and zinc ferrite (ZnFe₂O₄). While the reduction of adsorbent was mostly due to that of iron oxide. The reduced adsorbents might consist of ZnO/Fe₃O₄/FeO/Fe on alumina as support. At relatively high space velocity (26,000 h⁻¹) the adsorbents were able to reduce the H₂S concentration from 250 ppm at the inlet to around 45 ppm, 35 ppm, and 25 ppm at the outlet by adsorbent 1ZnFe, 2ZnFe, and 3ZnFe; respectively. The removal efficiency for adsorbent 1ZnFe, 2ZnFe, and 3ZnFe were 82%, 86%, and 90%; respectively. Results also shown an increase in adsorbent lifetime with the increase of the Zn to Fe ratio.