A DFT study on the sulfur resistance mechanism of elemental mercury catalytic oxidation over Mn-Mo/CNT

The strong sulfur resistance of Mn-Mo/CNT during the process of elemental mercury catalytic oxidation at low temperature has been demonstrated in experiment. However, there remains a dearth of in-depth research on the sulfur resistance mechanism. This work aims to explore the sulfur resistance mechanism through density functional theory (DFT) calculations. The results reveal that SO2 can be effectively oxidized to SO3 through lattice oxygen on the surface of Mn-Mo/CNT. The speed control step is the step of SO3 3 dissociation, with an energy barrier of 2.50 eV. Additionally, O-2 can adsorb onto active sites to supplement the consumed lattice oxygen. The adsorbed O-2 can also oxidize SO2, and the highest energy barrier of this reaction is only 0.26 eV. SO3 3 can further react with the adsorbed Hg-0 to form HgSO4, and the speed control step is the step of Hg-0 oxidation. Specifically, when Hg-0 is adsorbed onto Mo active sites, its energy barrier of speed control step reaches 4.06 eV. Whereas, when Hg-0 is adsorbed on Mn site, the energy barrier of speed control step reduces to 3.18 eV. Generally, the coupling reaction process of Hg-0 oxidation and SO2/SO3 conversion over Mn-Mo/CNT is the reason of the promotion in sulfur resistance of this catalyst.