Removal of Elemental Mercury from Coal Pyrolysis Gas Using Fe-Ce Oxides Supported on Lignite Semi-coke Modified by the Hydrothermal Impregnation Method

In this paper, Fe-Ce mixed oxides supported on lignite semi-coke were prepared by the hydrothermal impregnation method. The sorbents were employed to capture elemental mercury from coal pyrolysis gas. The influences of hydrothermal impregnation temperature, mole ratio of Fe/Ce, reaction temperature, and H2S concentration on Hg-0 removal efficiency were investigated in a fixed-bed reactor. The physicochemical properties of the sorbent samples were characterized by X-ray diffraction, Brunauer-Emmett-Teller, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The results showed that the Fe/Ce-modified semi-coke sorbents, synthesized by hydrothermal impregnated at 200 degrees C, had larger specific surface areas and pore volumes than the original semi-coke. The sorbent with a Fe/Ce molar ratio of 0.4:0.2 exhibited the highest Hg-0 removal efficiency of 83.5% at 150 degrees C. On the basis of the XPS characterization of the sorbent, a mechanism of Hg-0 removal over the Fe0.4Ce0.2/SC200 sorbent was proposed, suggesting that H2S could react with Fe/Ce mixed to form active sulfur, with which Hg-0 could react to form HgS. In addition, the stability and regeneration of the sorbent were also investigated.