New insight into the intrinsic effect of sulfur dioxide on Hg0 oxidation in the absence/presence of SCR atmosphere

Collaborative control of Hg0 in selective catalytic reduction (SCR) device is considered to be feasible and cost-effective, whereas the negative impact of SO2 remains a thorny issue for industrial applications. Herein, the intrinsic effect mechanism of SO2 on Hg0 oxidation in the absence/presence of SCR atmosphere over the hollow nanotube CoMnTiOx was systematically investigated. It was demonstrated that SO2 possessed a bidirectional effect on Hg0 oxidation, the facilitating effect was attributed to the production of HgSO4 and the inhibiting effect was due to the formation of metal sulfate, which was exactly equilibrated when the deposition of sulfate on the catalyst reached 3.88 %. Interestingly, the presence of SCR atmosphere enhanced the suppression of SO2 on Hg0 oxidation, which was caused by the fact that SO2 + O2 consumed partial Hg0 to form HgSO4, upsetting the reaction equilibrium of HgO reduction induced by SCR atmosphere and ultimately aggravating the reduction process of the already generated HgO. This work provides a new and comprehensive insight into the effect of SO2 on Hg0 oxidation during the synergistic removal of Hg0 in SCR device, which is instructive in exploring strategies to mitigate the SO2 poisoning.