Effect of H2S/HCl on the removal of elemental mercury in syngas over CeO2–TiO2

• CeTi sorbent was developed to remove Hg0 from syngas.
• H2S and HCl significantly promote Hg0 removal when they did not coexist.
• The combination of H2S and HCl showed a prohibitive effect on Hg0 removal.
• Hg0 removal mechanism in the presence of H2S over CeTi sorbents was proposed.
• TPD technique was applied to identify the mercury species.

CeTi sorbent (CeO2 supported on TiO2) was employed to remove elemental mercury (Hg0) from syngas when H2S and/or HCl are present. CeTi sorbents exhibited higher Hg0 removal efficiency compared with S-impregnated activated carbon. H2S and HCl were the most effective syngas components responsible for Hg0 removal when they were employed separately. When 400 ppm H2S and 10 ppm HCl were introduced separately with a balance of dry N2, over 97% of the Hg0 was removed under the experimental conditions. However, the combination of H2S and HCl exerted a prohibitive effect on Hg0 removal, which could be attributed to two causes: (1) the HCl consumed the surface oxygen active for Hg0 removal, hence limiting Hg0 removal by H2S; and (2) the H2S competed with Hg0 for active adsorption sites, limiting the Hg0 removal by HCl. On the basis of the temperature-programmed decomposition (TPD) analysis and X-ray photoelectron spectroscopy (XPS) characterization of the sorbents, a Hg0 removal mechanism in the presence of H2S over CeTi sorbents was proposed, suggesting that surface oxygen on the of CeTi sorbent supported the transformation of H2S to active surface sulfur, through which Hg0 could be captured resulting in the formation of HgS.