Removal of gaseous elemental mercury from simulated syngas over Fe2O3/TiO2 sorbents

Abstract

Fe2O3/TiO2 sorbents synthesized by the sol-gel method were employed to capture elemental mercury in simulated syngas. It was found that Fe2O3/TiO2 sorbents exhibited an outstanding Hg0-removal efficiency of over 95% in the temperature range 50–150 °C; however, the Hg0-adsorption capacity was limited by high temperatures (above 150 °C). H2S significantly promoted Hg0 capture, whereas CO, H2, and H2O suppressed Hg0 removal. After a 10-hour adsorption test, and five adsorption–regeneration cycles at 150 °C, the Hg0-removal efficiency was maintained at approximately 95% and 90%, respectively, confirming that the sorbent showed stability and reusability. Hg0 adsorption with H2S over the Fe2O3/TiO2 sorbents occurred via the Eley–Rideal mechanism, in which active sulfur sites originating from the oxidation of H2S reacted with gaseous Hg0 to form HgS. A possible reaction pathway for Hg0 removal has also been proposed. The fresh and spent sorbents were explored by X-ray photoelectron spectroscopy and Hg0-temperature-programmed desorption, indicating that the surface Fe3+ species and stored oxygen both contributed to H2S oxidation and Hg0 capture. It can be concluded that Fe2O3/TiO2 sorbents appeared to be promising and efficient sorbent for mercury removal from syngas in industrial application.