聚集态的Fe氧化物在Fe/ZSM-5催化N2O直接分解中的作用

摘要

研究了以离子交换法制备的Fe/ZSM-5上聚合态的Fe氧化物(FeOx)在催化N2O直接分解中的作用。 Fe/ZSM-5催化剂利用600–900 oC的高纯Ar处理,使催化剂中的FeOx发生聚合。利用一系列的表征手段(XRD, BET, DRIFTS, UV/vis-DRS, XAFS, N2O脉冲和O2-TPD)对催化剂进行了表征。结果发现,分子筛骨架外的FeOx在Fe/ZSM-5催化N2O分解中起重要作用；通过研究高温处理的Fe/ZSM-5催化剂中不同FeOx的比例与催化剂活性的关系,得到多核的FeOx是催化N2O分解的主要活性物种；并且,无定形态的FeOx中键长较长的Fe–O键((Fe–O)2)是参与反应的重要物种。%The effects of aggregated Fe oxo (FeOx) species on N2O decomposition activity of aqueous ion‐exchanged Fe/ZSM‐5 were investigated. Aggregation of FeOx species was achieved by thermal treatment of the Fe/ZSM‐5 catalysts at different temperatures (600–900 °C) in pure Ar. The charac‐terizations were carried out using X‐ray diffraction, N2 physisorption, UV‐Vis diffuse reflectance spectroscopy, X‐ray absorption fine structure spectroscopy, pulse‐response analysis, and O2‐temperature‐programmed desorption. The FeOx species on the external framework of the ZMS‐5 zeolite played a dominant role in N2O decomposition over Fe/ZSM‐5. By studying the relationship between the contents of the various existing iron species and activity of the different catalysts, pol‐ynuclear FeOx appeared to be the main active phase for N2O decomposition. Additionally, Fe–O with a long bond length ((Fe–O)2) in amorphous polynuclear FeOx was positively correlated to the activi‐ty of the catalysts, indicating that (Fe–O)2 was the active species for N2O decomposition.