X射线光电子能谱
煅烧
热重分析
初湿浸渍
化学
氧烷
扩展X射线吸收精细结构
拉曼光谱
选择性
光谱学
分析化学(期刊)
无机化学
化学工程
吸收光谱法
有机化学
沸石
催化作用
光学
物理
工程类
量子力学
作者
Mustafizur Rahman,Antonia Infantes‐Molina,Adam S. Hoffman,Simon R. Bare,Kayla L. Emerson,Sheima J. Khatib
出处
期刊:Fuel
[Elsevier]
日期:2020-10-01
卷期号:278: 118290-118290
被引量:51
标识
DOI:10.1016/j.fuel.2020.118290
摘要
The effect of the Si/Al ratio of the ZSM-5 support on the structure and activity of Mo/HZSM-5 catalysts in methane dehydroaromatization (MDA) was studied. ZSM-5 (with Si/Al = 15, 25, and 40) supported Mo oxide catalysts (MoOx/ZSM-5) with 3 and 10 wt% Mo loading were prepared by incipient wetness impregnation followed by calcination in air at 500 °C. The as-prepared catalysts were activated by temperature programmed reduction in hydrogen in order to maximize Mo dispersion. To understand the structure-activity relationship, the fresh and spent samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption isotherms, Scanning Transmission Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (STEM-EDS), X-ray absorption spectroscopy (EXAFS and XANES), thermogravimetric analysis (TGA), and Raman spectroscopy. The results show that the Si/Al ratio does not influence the the local structure around the Mo centers. It does however affect the number of available Brønsted acid sites in the support and the amount of Mo species entering the zeolite channels. A lower Si/Al ratio and higher Mo loading resulted in a higher Mo occupation within the zeolite channels. The higher channel occupation directly correlated with higher benzene selectivity and yield, as well as a lower catalyst deactivation rate.
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