| Abstract
| - This study investigated the chemical nature of impurity iron species and photoactive sites in the commerciallyavailable HZSM-5 zeolites with different Si/Al ratios. The samples were characterized by X-ray fluorescencespectroscopy, atomic absorption spectroscopy, X-ray absorption near-edge structure spectroscopy, extendedX-ray absorption fine structure spectroscopy, electron paramagnetic resonance spectroscopy, UV Ramanspectroscopy, and photocatalytic degradation of ethylene. The results revealed that the photocatalytic activityof the HZSM-5 originated from the isolated tetrahedrally coordinated iron−oxo species present in the zeoliteframework. The formation of such active isolated iron−oxo species was strongly influenced by the chemicalcompositions (e.g., Si/Al ratio, and iron content) and the preparation methods of zeolite. This could explainthe difference in photoactivity of the different types of HZSM-5 and FeZSM-5 zeolites. Possible mechanismsof the photocatalysis on the zeolites were also discussed.
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