期刊
FUEL
卷 278, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.fuel.2020.118290
关键词
MoO3; Mo2C; Supported molybdenum carbide; Methane dehydroaromatization; Bronsted acid sites
资金
- Office of Science, Office of Basic Energy Sciences [DESC0019074]
- Ramon y Cajal Program (Spanish Ministry of Economy and Competitiveness, Spain) [RyC-2015-17870]
- U.S. Department of Energy, Office of Basic Energy Sciences [DE-AC0276SF00515]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences
- Ramon y Cajal Program (Spanish Ministry of Science, Innovation and Universities) [RTI2018-099668-B-C22]
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 degrees 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), N-2 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 Bronsted 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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