Effect of Si/Al ratio of ZSM-5 support on structure and activity of Mo species in methane dehydroaromatization

FUEL

卷:278

Article

Rahman, Mustafizur¹  Infantes-Molina, Antonia²  Hoffman, Adam S.³  Bare, Simon R.³  Emerson, Kayla L.¹  Khatib, Sheima J.¹ 

[1] Texas Tech Univ, Dept Chem Engn, Lubbock, TX 79409 USA

[2] Univ Malaga, Fac Sci, Dept Inorgan Chem Crystallog & Mineral, Campus Teatinos, Malaga 29071, Spain

[3] SLAC Natl Accelerator Lab, Stanford Synchrotron Radiat Lightsource, Menlo Pk, CA 94025 USA

关键词: MoO3;    Mo2C;    Supported molybdenum carbide;    Methane dehydroaromatization;    Bronsted acid sites;   

DOI  :  10.1016/j.fuel.2020.118290

来源: Elsevier

【 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 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.

【 授权许可】

Free