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

Highlights: • Ce–MnO_x/Ti-PILC exhibited high Hg⁰ removal activity. • SO₂ restrained Hg⁰ oxidation and adsorption due to the formation of SO₄²⁻. • The formation of NH₃ to NH₄⁺ restrained the Hg⁰ adsorption and oxidation. - Abstract: The adsorption and oxidation of elemental mercury (Hg⁰) under various flue gas components were investigated over a series of Ce–MnO_x/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 500 ppm SO₂ in the flue gas significantly restrained the Hg⁰ adsorption and oxidation over 6%Ce–6%MnO_x/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%MnO_x/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%MnO_x/Ti-PILC exhibited a relatively high value (72%) at 250 °C, which indicated the practicability to use Ce–MnO_x/Ti-PILC for Hg⁰ removal under SCR conditions.