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

• The CoxMnyTi catalysts were synthesized by a deposition–precipitation method.
• CoOx led to a better dispersion and more amorphous species of MnOx over TiO2.
• The Co6Mn30Ti catalyst was highly active for Hg0 catalytic oxidation.
• The adsorbed HgO on catalyst can be released at higher temperature.

Cobalt manganese oxides modified titania (CoxMnyTi) catalysts synthesized by a deposition–precipitation method were employed to oxidize gas-phase elemental mercury (Hg0) without the aid of HCl at low temperature on a laboratory-scale fixed-bed reactor. The roles of O2, NO, SO2 and H2O in Hg0 oxidation over the optimal catalyst were also evaluated. The catalysts were characterized by N2 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 Hg0 oxidation efficiency could reach around 98% at 150 °C. A great increase in Hg0 oxidation over Co6Mn30Ti catalyst with the assistance of O2 occurred via the Mars-Maessen mechanism. In comparison with pure N2 atmosphere, the presence of NO can slightly promote the oxidation of Hg0. The effects of SO2 and H2O with lower concentrations were insignificant. However, when SO2 further increased above 1000 ppm, a seriously inhibitory influence on Hg0 oxidation was observed. The characterization results indicated that physical characteristics were not the main contributor for Hg0 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 Hg0 oxidation.