Cobalt manganese oxides modified titania catalysts for oxidation of elemental mercury at low flue gas temperature

Cobalt manganese oxides modified titania (CoxMnyTi) catalysts synthesized by a deposition-precipitation method were employed to oxidize gas-phase elemental mercury (Hg-0) without the aid of HCl at low temperature on a laboratory-scale fixed-bed reactor. The roles of O-2, NO, SO2 and H2O in Hg-0 oxidation over the optimal catalyst were also evaluated. The catalysts were characterized by N-2 adsorption-desorption, SEM, TEM, XRD, XPS and TPR to determine the pore and surface chemistry structures. The results showed that with optimal loading of 6% Co species on Mn30Ti, the Hg-0 oxidation efficiency could reach around 98% at 150 degrees C. A great increase in Hg oxidation over Co6Mn30Ti catalyst with the assistance of O-2 occurred via the Mars-Maessen mechanism. In comparison with pure N-2 atmosphere, the presence of NO can slightly promote the oxidation of Hg-0. The effects of SO2 and H2O with lower concentrations were insignificant. However, when SO2 further increased above 1000 ppm, a seriously inhibitory influence on Hg-0 oxidation was observed. The characterization results indicated that physical characteristics were not the main contributor for Hg-0 oxidation. The presence of CoOx led to a better dispersion and more amorphous species of MnOx over TiO2. Compared with those of Mn30Ti and Co30Ti catalysts, the chemisorbed oxygen of Co6Mn30Ti catalyst increased greatly, which played an important role in the promotion of Hg oxidation. (C) 2013 Elsevier B.V. All rights reserved.