Theoretical insight into the interaction mechanism between V_2O_5/TiO_2 (001) surface and arsenic oxides in flue gas

摘要

The arsenic oxides in flue gas can cause severe poisoning and deactivation of the vanadium-titanium-based denitrification catalyst. Investigation of the interaction mechanism between arsenic oxides and denitrification catalyst can provide theoretical guidance for the development of anti-arsenic poisoning catalyst. To this end, the periodic V2O5-TiO2 (001) models were constructed to represent the actual vanadium-titanium-based catalyst in this study. Density functional theory (DFT) calculations were applied to explore the interaction mechanism between the catalyst surface and typical arsenic oxide (As2O3) in flue gas. Stable adsorption configurations and adsorption energies for As2O3 and NH3 adsorption were calculated, the detailed interaction pathways and reaction barriers were also obtained. The results indicate that As2O3 is chemisorbed on the catalyst surface, strong interaction and electron transfer occur after As2O3 adsorption. The adsorption strength of NH3 on Lewis and Bronsted sites are decreased after As2O3 adsorption and the inhibition effect on the Lewis acid sites is much stronger. As2O3 is oxidized to As2O5 on catalyst surface, the Lewis acid sites (V = O) are destroyed and the valence of vanadium is decreased, which should be responsible for the catalyst deactivation. The analysis of the interaction pathway shows that As2O3 inclines to react with two adjacent V2O5 clusters to produce V2O4 because of the lowest energy barrier. Therefore, when the catalyst is poisoned by As2O3 in flue gas, the active component V2O5 inclines to generate V2O4, which is consistent with previous experimental researches.