Adsorption Reaction Mechanism Of The Flue Gas Mercury On SCR Catalyst

Mercury emissions are of global concern due to their toxicity, ability to be transported in the environment, adverse effects on the ecosystem and its neurological health impacts. The mechanism of release, emission and control of mercury is still unclear. SCR(Selective Catalytic Reduction) have been shown to be effective in oxidizing mercury that can be subsequently captured in downstream wet flue gas desulfurization (WFGD) system. In this work, we focused on describing the mechanism of the heterogeneous reaction of mercury adsorption and oxidation on SCR catalyst.The adsorption of Hg, HgCl, HgCl₂, and HCl on the SCR catalyst were studied with the application of DFT(Density Functional Theory) . The results show that the adsorption of Hg on the surface is stronger than that of HCl, and Hg adsorption on the V₂O₅ surface reaction is the first step in the oxidation reaction of Hg on the surface. The adsorption HgCl and HgCl₂ on the surface are chemisorption, the adsorption of HgCl is stronger than that of HgCl₂. This indicates that the adsorption geometry of HgCl is an important intermediate state during the reaction process.The effects of halogen elements, NH₃, SO₂ and NO on Hg adsorption on V₂O₅ surface were investigated. The results showed that HCl promotes the adsorption of Hg. Compared with HCl, HBr and HI promote the adsorption of Hg more strongly. NH₃ adsorption inhibits the adsorption and oxidation of Hg, due to a certain competitive adsorption between Hg and NH₃ on the V₂O₅ surface. SO₂ and NO have no significant effects on the adsorption of Hg.We obtained the transition state structure of Hg oxidation reaction, and proposed a possible Hg oxidation mechanism on the V₂O₅ surface. Deacon reaction mechanism was also studied on the V₂O₅ surface. The activation energies were calculated. This study provide a basic theory for predicting mercury oxidation on the V₂O₅ surface.