Effects of flue gas components on removal of elemental mercury over Ce–MnOx/Ti-PILCs

Abstract

The adsorption and oxidation of elemental mercury (Hg0) under various flue gas components were investigated over a series of Ce–MnOx/Ti-PILC catalysts, which were synthesized by an impregnation method. To discuss the mechanism, the catalysts were characterized by various techniques such as N2 adsorption–desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) analysis and X-ray photoelectron spectroscopy (XPS). The results indicated that the presence of 500ppm SO2 in the flue gas significantly restrained the Hg0 adsorption and oxidation over 6%Ce–6%MnOx/Ti-PILC due to the formation of SO42− species. Hg0 could be oxidized to HgCl2 in the presence of HCl, because the Deacon process occurred. NO would react with active oxygen to form NO2-containing species, which facilitated Hg0 oxidation. While the presence of NO limited the Hg0 adsorption on 6%Ce–6%MnOx/Ti-PILC due to the competitive adsorption of NO with Hg0. The addition of NH3 in the flue gas significantly restrained Hg0 adsorption and oxidation, because the formed NH4+ species covered the active adsorption sites on the surfaces, and further limited Hg0 oxidation. However, when NO and NH3 were simultaneously added into the flue gas, the Hg0 oxidation efficiency of 6%Ce–6%MnOx/Ti-PILC exhibited a relatively high value (72%) at 250°C, which indicated the practicability to use Ce–MnOx/Ti-PILC for Hg0 removal under SCR conditions.