Effect of WO3 doping on the mechanism of mercury oxidation by HCl over V2O5/TiO2 (001) surface: Periodic density functional theory study

Abstract

Commercial vanadium-titanium-based selective catalytic reduction (SCR) catalyst exhibits a certain ability for mercury removal during the denitrification process of coal-fired flue gas. WO3 is an important additive agent for SCR catalyst, yet few studies have been reported on the role of WO3 during mercury oxidation process. In this study, periodic V2O5/TiO2 and V2O5-WO3/TiO2 slab models were constructed. Density functional theory (DFT) calculations were applied to explore the effects of WO3 on the mercury removal mechanism over the SCR catalyst. The effects of WO3 doping on the electronic structure of the catalyst were investigated. The adsorption configurations and energies of mercury species before and after WO3 doping were calculated. The reaction pathways and energy barriers of mercury oxidation were further analyzed. The results indicate that WO3 promotes the charge transfer on the catalyst surface and enhances the reaction activity. The adsorption energies of Hg and HgCl on the catalyst surface decrease after WO3 doping, while the adsorption energies of HgCl2 increase. Additionally, WO3 doping reduces the energy barrier of mercury oxidation, thus enhancing the mercury removal capacity of the SCR catalyst. The oxidation process of mercury over the vanadium-titanium-based SCR catalyst follows the Langmuir-Hinshelwood mechanism, which is different from previous theoretical results.