Synthesis and Characterization of Fe-Substituted ZSM‑5 Zeolite and Its Catalytic Performance for Alkylation of Benzene with Dilute Ethylene

• Published in: Industrial & engineering chemistry research 2020-12, Vol.59 (52), p.22413-22421
• Main Authors: Bian, Kai, Zhang, Anfeng, Yang, Hong, Fan, Benhan, Xu, Shutao, Guo, Xinwen, Song, Chunshan
• Format: Article
• Language: English
• Subjects: Kinetics, Catalysis, and Reaction Engineering
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.0c01909

A series of Fe-substituted ZSM-5 zeolite samples with an almost constant Si/(Fe + Al) molar ratio of 50 but varied levels of Fe substitution were synthesized via an in situ seed-induced hydrothermal method in a fluoride medium. Additionally, a hierarchical Fe-substituted sample with high diffusion capability was also produced by a subsequent alkaline treatment. The textural and acidic properties of these samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Raman, Fourier transform infrared (FT-IR), UV–vis, H2-temperature programmed reduction (TPR), Ar adsorption–desorption, NH3-temperature-programmed desorption (TPD), X-ray fluorescence (XRF), 27Al, and 29Si magic-angle spinning (MAS) NMR analysis. These analyses revealed that Fe3+ species were effectively integrated into the MFI framework of the Fe-substituted samples. The as-synthesized samples displayed orthogonally intergrown crystal plates of increased aspect ratios with increased Fe-substitutions. More significantly, the resulted Fe-substituted samples displayed a noticeably reduced acid strength compared to the pure ZSM-5. Evaluated by the benzene alkylation reaction with dilute ethylene, the 50% partially Fe-substituted ZSM-5 sample showed a combined high ethyl selectivity and long catalytic lifetime among all catalysts studied, which is attributed to its suitably balanced acid strength.