Catalytic oxidation and capture of elemental mercury from simulated flue gas using Mn-doped titanium dioxide

摘要

Titanium dioxide (TiO2) and Mn-doped TiO2 (Mn(x)-TiO2) were synthesized in a sol-gel method and characterized by BET surface area analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Gasphase elemental mercury (Hg-0) oxidation and capture by the Mn-doped TiO2 catalyst was studied in the simulated flue gas in a fixed-bed reactor. The investigation of the influence of Mn loading, flue gas components (SO2, NO, O-2, and H2O) showed that the Hg-0 capture capability of Mn(x)-TiO2 was much higher than that of pure TiO2. The addition of Mn inhibits the grain growth of TiO2 and improves the porous structure parameters of Mn(x)-TiO2. Excellent Hg-0 oxidation performance was observed with the catalyst with 10% of Mn loading ratio and 97% of Hg-0 oxidation was achieved under the test condition (120 A degrees C, N-2/6%O-2). The presence of O-2 and NO had positive effect on the Hg-0 removal efficiency, while mercury capture capacity was reduced in the presence of SO2 and H2O. XPS spectra results reveal that the mercury is mainly present in its oxidized form (HgO) in the spent catalyst and Mn4+ doped on the surface of TiO2 is partially converted into Mn3+ which indicates Mn and the lattice oxygen are involved in Hg-0 oxidation reactions.