Adsorption and Oxidation of Elemental Mercury over Ce-MnOx/Ti-PILCs

A series of innovative Ce-Mn/Ti-pillared-clay (Ce-Mn/Ti-PILC) catalysts combining the advantages of PILCs and Ce-Mn were investigated for elemental mercury (Hg-0) capture at 100-350 degrees C in the absence of HCl in the flue gas. The fresh and used catalysts were characterized by scanning electron microscopy (SEM), nitrogen adsorption-desorption, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalyst characterization indicated that the 6%Ce-6%MnOx/Ti-PILC catalyst possessed a large specific surface area and high dispersion of Ce and Mn on the surface. The experimental results indicated that the 6%Ce-6% MnOx/Ti-PILC catalyst exhibited high H-0 capture (>90%) at 100-350 degrees C. During the first stage of the reaction, the main Hg-0 capture mechanism for the catalyst was adsorption. As the reaction proceeded, the Hg-0 oxidation ability was substantially enhanced. Both the hydroxyl oxygen and the lattice oxygen on the surface of the catalysts participated in Hg-0 oxidation. At a low temperature (150 degrees C), the hydroxyl oxygen and lattice oxygen from Ce4+ -> Ce3+ and Mn3+ -> Mn2+ on the surface contributed to Hg-0 oxidation. However, at a high temperature (250 degrees C), the hydroxyl oxygen and lattice oxygen from Mn4+ -> Mn3+ contributed to Hg-0 oxidation. Hg-0 oxidation was preferred at a high temperature. The 6%Ce-6%MnOx/Ti-PILC catalyst was demonstrated to a good Hg-0 adsorbent and catalytic oxidant in the absence of HCl in the flue gas.