CeO2 doping boosted low-temperature NH3-SCR activity of FeTiOx catalyst: A microstructure analysis and reaction mechanistic study
2022
Tan, Wei | Xie, Shaohua | Shan, Wenpo | Lian, Zhihua | Xie, Lijuan | Liu, Annai | Gao, Fei | Dong, Lin | He, Hong | Liu, Fudong
FeTiOₓ has been recognized as an environmental-friendly and cost-effective catalyst for selective catalytic reduction (SCR) of NOₓ with NH₃. Aimed at further improving the low-temperature DeNOₓ efficiency of FeTiOₓ catalyst, a simple strategy of CeO₂ doping was proposed. The low-temperature (< 250 °C) NH₃-SCR activity of FeTiOₓ catalyst could be dramatically enhanced by CeO₂ doping, and the optimal composition of the catalyst was confirmed as FeCe₀.₂TiOₓ, which performed a NOₓ conversion of 90% at ca. 200°C. According to X-ray diffraction (XRD), Raman spectra and X-ray absorption fine structure spectroscopy (XAFS) analysis, FeCe₀.₂TiOₓ showed low crystallinity, with Fe and Ce species well mixed with each other. Based on the fitting results of extended X-ray absorption fine structure (EXAFS), a unique Ce-O-Fe structure was formed in FeCe₀.₂TiOₓ catalyst. The well improved specific surface area and the newly formed Ce-O-Fe structure dramatically contributed to the improvement of the redox property of FeCe₀.₂TiOₓ catalyst, which was well confirmed by H₂-temperature-programmed reduction (H₂-TPR) and in situ XAFS experiments. Such enhanced redox capability could benefit the activation of NO and NH₃ at low temperatures for NOₓ removal. The detailed reaction mechanism study further suggested that the facile oxidative dehydrogenation of NH₃ to highly reactive -NH₂ played a key role in enhancing the low-temperature NH₃-SCR performance of FeCe₀.₂TiOₓ catalyst.
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