Characteristics of commercial selective catalytic reduction catalyst for the oxidation of gaseous elemental mercury with respect to reaction conditions

摘要

The performance of V₂O₅/TiO₂-based commercial SCR catalyst for the oxidation of gaseous elemental mercury (Hg0) with respect to reaction conditions was examined to understand the mechanism of Hg0 oxidation on SCR catalyst. It was observed that a much larger amount of Hg0 adsorbed on the catalyst surface under oxidation condition than under SCR condition. The activity of commercial SCR catalyst for Hg0 oxidation was negligible in the absence of HCl, regardless of reaction conditions. The presence of HCl in the reactant gases greatly increased the activity of SCR catalyst for the oxidation of Hg0 to oxidized mercury (Hg2+) such as HgCl₂ under oxidation condition. However, the effect of HCl on the oxidation of Hg0 was much less under SCR condition than oxidation condition. The activity for Hg0 oxidation increased with the decrease of NH₃/NO ratio under SCR condition. This might be attributed to the strong adsorption of NH₃ prohibiting the adsorption of HCl which was vital species promoting the oxidation of Hg0 on the catalyst surface under SCR condition.