Catalytic oxidation of CO over V2O5/TiO2 and V2O5-WO3/TiO2 catalysts: A DFT study

• Published in: Fuel processing technology Vol. 213; p. 106678
• Main Authors: Mi, Teng-ge, Wu, Yang-wen, Zhou, Xin-yue, Li, Wen-tao, Zhao, Li, Liu, Ji, Lu, Qiang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-2021; Elsevier Science Ltd
• Subjects: Carbon monoxide; Catalysts; Catalytic oxidation; Chemical reduction; CO oxidation; Contaminants; Density functional theory; Flue gas; Nitrogen oxides; Oxidation; Reaction kinetics; Reaction mechanism; SCR catalyst; Selective catalytic reduction; Titanium dioxide; Tungsten oxides; V2O5/TiO2; Vanadium pentoxide; Vanadium pentoxide-Titanium dioxide; WO3 doping; Reaction mechanism; SCR catalyst; CO oxidation; V2O5/TiO2; WO3 doping
• ISSN: 0378-3820; 1873-7188
• DOI: 10.1016/j.fuproc.2020.106678

Vanadium‑titanium based selective catalytic reduction (SCR) catalysts are commercially applied for the denitrification of nitrogen oxides (NOx) in flue gas. Meanwhile, they are also catalytically effective to the abatements of many contaminants including carbon monoxide (CO) catalytic oxidation. Understanding the catalytic performance on CO oxidation is of great significance to develop modified SCR catalysts for the synergetic control of nitrogen oxides and CO. Two SCR catalyst models were constructed, i.e., V2O5/TiO2(001) and V2O5-WO3/TiO2(001). The mechanisms of CO oxidation over the above two catalyst surfaces were analyzed by density functional theory (DFT) calculations. The results show that the whole oxidation cycle of CO includes two reaction stages. In the first stage, CO reacts with terminal oxygen of VO site, following MvK mechanism, which is also the rate-determining step of the whole reaction process. In the second stage, the redundant oxygen Oe of the absorbed O2 molecule reacts with another CO molecule, which follows E-R mechanism. The activation energy barriers of the CO oxidation on V2O5/TiO2 surface are lower than those on V2O5-WO3/TiO2, indicating that WO3 doping inhibits CO oxidation. Moreover, the established reaction kinetics of elementary reactions would be helpful to model CO catalytic oxidation over the real SCR catalysts.
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•The CO oxidation mechanism on SCR catalysts is investigated.•The V=O site is responsible for CO oxidation.•The whole oxidation cycle of CO follows MvK and E-R reaction route.•WO3 doping reduces the reaction activity of V=O site for CO oxidation.•Rate constants of elementary reactions are provided.