Synthesis and characterization of microporous EU-1/ZSM-5 composite zeolite containing iron

Microporous EU-1/ZSM-5 composite zeolites containing iron were synthesized using preset crystal seed method. The as-synthesized Fe-EU-1/ZSM-5 samples were characterized by a serious of techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric-derivative thermogravimetric (TG-DTG), N₂ adsorption/desorption, UV-visible diffuse reflectance spectroscopy (UV-Vis DRS) and X-ray absorption fine structure (XAFS). The results show that the composite zeolite is found consisting characteristic diffraction peaks for two kinds of zeolite structure: EU-1 and ZSM-5. The composite zeolite is a kind of molecular dispersion material with two crystal phases interaction and its micropore size is larger than Fe-EU-1 zeolite. With increasing the mass fraction of Fe in the original sol-gel, the characteristic diffraction peaks of composite zeolites in the 23.09° and 23.94° gradually migrate to lower angle direction. UV-vis spectrum shows that there is a broad absorption band at about 220~245 nm. The XAFS results show that the week pre-edge absorption peak for 1s→3d gradually strengthen, at the same time the absorption peak for 1s→4p in the top of absorption edge has tapper. The optimized synthesis conditions for the microporous EU-1/ZSM-5 composite zeolites containing iron are as follows: 0.075%~0.15% of the mass fraction of Fe in the original sol-gel, 15.0%~21.0% of the mass fraction of ZSM-5 zeolite in the original sol-gel and 50~60 of SiO₂/Al₂O₃ mol ratio of ZSM-5 zeolite.