CeO2-TiO2 Sorbents for the Removal of Elemental Mercury from Syngas

A series of CeO2-TiO2 (CeTi) sorbents with different CeO2/TiO2 mass ratios were prepared by an impregnation method and employed to remove elemental mercury (He) in simulated syngas. The CeTi sorbents with a CeO2/TiO2 mass ratio of 0.2 exhibited superior Hg-0 removal efficiency from 80 to 150 degrees C, which could be ascribed to the greater amount of surface chemisorbed oxygen resulted from Ce3+ on the sample surface. H2S was the most effective syngas component responsible for Hg-0 removal. The use of 400 ppm H2S resulted in 98% Hg-0 removal efficiency under the experimental conditions. H-2 and CO had a negligible effect on the efficiency of Hg removal. In the presence of H2S, a prohibitive effect of HCl and NH3 on Hg-0 removal was observed because of the consumption of the surface oxygen. Water vapor also inhibited Hg-0 removal due to competitive adsorption with H2S. Hg-0 removal over CeTi sorbents was proposed to follow the Eley-Rideal mechanism, in which active surface sulfur reacts with gas-phase Hg-0. This large oxygen storage capacity of CeTi sorbents is quite favorable to H2S catalytic oxidation and Hg-0 emission control in an extremely reducing environment, such as when there is a deficiency of O-2.