Journal
APPLIED CATALYSIS B-ENVIRONMENTAL
Volume 200, Issue -, Pages 297-308Publisher
ELSEVIER
DOI: 10.1016/j.apcatb.2016.07.020
Keywords
Low-temperature NH3-SCR; Nitrogen oxides (NOx); Surface Ce3+ species; In situ FTIR; Reaction mechanism
Funding
- National Nature Science Foundation of China [21507029, 21501138]
- Nature Science Foundation of Hebei Province [B2016502063]
- Open Foundation of Key Laboratory of Industrial Ecology and Environmental Engineering [KLIEEE-15-02]
- China Ministry of Education
- Fundamental Research Funds for the Central Universities [2016MS109, 2015ZD25]
- Australian Research Council [DP150103026]
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A series of transition metals (Co, Cu and Fe) were selected to decorate Ce-Ti mixed oxide to elevate the low-temperature activity of selective catalytic reduction of NOx by NH3 (NH3-SCR) reaction, by adjusting the ratio of surface Ce3+ species and oxygen vacancies. Among them, Co-Ce-Ti sample exhibited the excellent low-temperature activity and broadened temperature window, which could be attributed to the improvement of the physico-chemical properties and the acceleration of the reactions in the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Owing to the different ionic sizes of Co2+ and Ce4+, the lattice distortion of Ce-Ti mixed oxide was greatly aggravated and subsequently increased the ratio of Ce3+ and the surface adsorbed oxygen, which benefited the generation of adsorbed NOx species and improved the reaction in the L-H mechanism. Meanwhile, the coordinatively unsaturated cationic sites over the Co-Ce-Ti sample induced more Lewis acid sites and enhanced the formation of the adsorbed NH3 species bounded with Lewis acid sites, which were considered as the crucial intermediates in E-R mechanism, and therefore facilitating the reaction between the adsorbed NH3 species and NO molecules. The enhancements in both the reactions from L-H and E-R mechanisms appeared to directly correlated with the improved deNO(x) performance on the Co-Ce-Ti sample, and the L-H mechanism could be the dominate one at low temperatures due to its rapid reaction rate. (C) 2016 Published by Elsevier B.V.
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