Reaction mechanism for the influence of SO2 on Hg0 adsorption and oxidation with Ce0.1-Zr-MnO2

Abstract The removal of Hg 0 from flue gas has been one of the primary challenges in the control of mercury emission. The presence of even small amounts of SO 2 has a significant influence on the Hg 0 removal process, and the mechanism of this process has not been thoroughly explained to date. To understand the mechanism for SO 2 influence, the influence of SO 2 on the Hg 0 adsorption and Hg 0 oxidation components of the Hg 0 removal process were investigated separately based on Ce 0.1 -Zr-MnO 2 . SO 2 was shown to have serious negative effects on the Hg 0 adsorption process due to the reaction between SO 2 and Mn-based active sites, as determined by TGA and XPS results. In contrast, for the Hg 0 oxidation process Mn-SO 4 2− formed through the reaction between SO 2 and Mn-based active sites, and Mn-SO 4 2− had a certain contribution to Hg 0 oxidation. Moreover, XPS results indicated that SO 2 reacts with O 2 to form SO 3 which adsorbed on the catalyst surface and act as new active sites, promoting Hg 0 oxidation via: Hg + SO 3  + 1/2O 2  → HgSO 4 . This phenomenon caused the catalyst to retain Hg 0 oxidation activity in the presence of SO 2 for a relatively long time.