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张涛等:Nature of active Fe species and reaction mechanism over high-efficiency Fe/CHA catalysts in catalytic decomposition of N2O

发布时间:2020-11-30

ABSTRACT:

Fe/CHA catalysts for N2O decomposition with various Fe loadings (Fe/SAPO-34 and Fe/SSZ-13) were synthesized by a solid-state ion exchange method. Under the same reaction conditions, obviously superior activities of Fe/CHA catalysts were observed in comparison with the current state-of-the-art Fe/zeolite, i.e., Fe/FER. Meanwhile, Fe/CHA catalysts exhibited a robust high-temperature hydrothermal stability. The characterization results and density functional theory (DFT) calculations indicated that the dispersion of Fe species over Fe/CHA catalysts was strongly influenced by the nature of the support, although SAPO-34 and SSZ-13 have similar morphology. Combined with the catalytic performance, dinuclear [HO-Fe-O-Fe-OH]2+ species were identified as the most active Fe species for Fe/CHA catalysts in the N2O decomposition reaction. Furthermore, the dimeric Fe species in SSZ-13 were more active than those in SAPO-34, due to lower Fe-O binding energies. Finally, DFT calculations provided a comprehensive understanding of the N2O decomposition mechanism over Fe/CHA catalysts.

KEYWORDS:  N2O decomposition, Fe/CHA, Dispersion, Active Fe species, Mechanism investigation

摘要: 采用固态离子交换法合成了不同铁负载量的Fe/CHA催化剂(Fe/SAPO-34和Fe/SSZ-13)。在相同的反应条件下,与目前最先进的铁基分子筛催化剂,即Fe/FER相比,Fe/CHA催化剂的活性明显更高。同时,Fe/CHA催化剂表现出良好的高温水热稳定性。表征结果和密度泛函理论(DFT)计算表明,尽管SAPO-34和SSZ-13具有相似的形貌,但铁物种在Fe/CHA催化剂上的分散受到载体性质的强烈影响。结合催化性能,双核[HO-Fe-O-Fe-OH]2+物种被确定为N2O分解反应中Fe/CHA催化剂最活跃的铁物种。此外,由于Fe-O结合能较低,SSZ-13中的二聚铁比SAPO-34中的更活跃。最后,密度泛函理论计算提供了对Fe/CHA催化剂上N2O分解机理的全面理解。

关键词: N2O分解,Fe/CHA,分散度,活性Fe物种,机理研究

原载于Journal of Catalysis (SCI, Q1, 2020 Impact Factor= 7.888)

原文链接:https://doi.org/10.1016/j.jcat.2020.10.015