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

CeTi sorbent (CeO2 supported on TiO2) was employed to remove elemental mercury (Hg-0) from syngas when H2S and/or HCl are present. CeTi sorbents exhibited higher Hg-0 removal efficiency compared with S-impregnated activated carbon. H2S and HCl were the most effective syngas components responsible for Hg-0 removal when they were employed separately. When 400 ppm H2S and 10 ppm HCl were introduced separately with a balance of dry N-2, over 97% of the Hg-0 was removed under the experimental conditions. However, the combination of H2S and HCl exerted a prohibitive effect on Hg-0 removal, which could be attributed to two causes: (1) the HCl consumed the surface oxygen active for Hg-0 removal, hence limiting Hg-0 removal by H2S; and (2) the H2S competed with Hg-0 for active adsorption sites, limiting the Hg-0 removal by HCl. On the basis of the temperature-programmed decomposition (TPD) analysis and X-ray photoelectron spectroscopy (XPS) characterization of the sorbents, a Hg-0 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 Hg-0 could be captured resulting in the formation of HgS. (C) 2013 Elsevier B.V. All rights reserved.