X-ray Absorption Fine Structure Analysis of the Local Environment of Fe in Fe/Al-MFI

摘要

An MFI zeolite framework containing iron and aluminum has been prepared and characterized by X-ray absorption spectroscopy.Extended X-ray absorption fine structure analysis indicates that in the as-prepared zeolite Fe is present in the framework but migrates to extraframework sites upon thermal activation at elevated temperature.In the absence of framework Al, Fe forms small particles of Fe_3O_4 When Al is included in the zeolite, extraframework Fe associates with framework Al in a manner identical to that observed in Fe-exchanged H-ZSM-5.Therefore, the presence of framework Al in the MFI structure plays a critical role in stabilizing atomically dispersed Fe.