Novel Promotion of Sulfuration for Hg⁰ Conversion over V₂O₅–MoO₃/TiO₂ with HCl at Low Temperatures: Hg⁰ Adsorption, Hg⁰ Oxidation, and Hg²⁺ Adsorption

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In this work, the commercial selective catalytic reduction (SCR) catalyst V 2 O 5 –MoO 3 /TiO 2 was sulfureted with H 2 S to improve both its capability for elemental mercury (Hg 0 ) removal at low temperatures and its resistance to SO 2 and H 2 O. Hg 0 removal over both V 2 O 5 –MoO 3 /TiO 2 and sulfureted V 2 O 5 –MoO 3 /TiO 2 involved the catalytic oxidation of Hg 0 to HgCl 2 and the chemical adsorption of gaseous Hg 0; therefore, the effect of sulfuration on Hg 0 chemical adsorption and the catalytic oxidation of Hg 0 to HgCl 2 over V 2 O 5 –MoO 3 /TiO 2 and its resistance to SO 2 and H 2 O were investigated using Hg balance analysis. Kinetic analysis showed that the rates of the chemical adsorption and oxidation of Hg 0 were both in direct proportion to the concentration of physically adsorbed Hg 0 . The physical adsorption of gaseous Hg 0 on V 2 O 5 –MoO 3 /TiO 2 was remarkably promoted after sulfuration, and the physical adsorption of gaseous Hg 0 over sulfureted V 2 O 5 –MoO 3 /TiO 2 was scarcely inhibited by SO 2 and H 2 O. Therefore, the performance of V 2 O 5 –MoO 3 /TiO 2 for Hg 0 removal and its resistance to SO 2 and H 2 O were both improved after sulfuration. Even more remarkably, sulfureted V 2 O 5 –MoO 3 /TiO 2 can adsorb gaseous HgCl 2, which resulted from Hg 0 oxidation. Therefore, sulfureted V 2 O 5 –MoO 3 /TiO 2 showed an excellent performance to recover Hg 0 from coal-fired power plants, which can then be converted to liquid Hg.