TY - JOUR
T1 - Effect of Si/Al ratio of ZSM-5 support on structure and activity of Mo species in methane dehydroaromatization
AU - Rahman, Mustafizur
AU - Infantes-Molina, Antonia
AU - Hoffman, Adam S.
AU - Bare, Simon R.
AU - Emerson, Kayla L.
AU - Khatib, Sheima J.
N1 - Funding Information:
This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award DE-SC0019074. AIM thanks the Ramon y Cajal Program RyC-2015-17870 (Spanish Ministry of Economy and Competitiveness, Spain) and RTI2018-099668-B-C22 Project (Spanish Ministry of Science, Innovation and Universities) for XPS and TEM-EDS measurements. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Co-ACCESS, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences. The authors would like to thank Dr. Daniel Unruh from the Department of Chemistry and Biochemistry at Texas Tech University for his help in acquiring the XRD patterns. The authors would like to thank Dr. Benjamin J. Wylie and Collin G. Borcik from the Department of Chemistry and Biochemistry at Texas Tech University for performing MAS-NMR measurements. The authors would like to thank Dr. Julius Warzywoda at Texas Tech University for his assistance in acquiring the Raman spectra.
Funding Information:
This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award DE-SC0019074. AIM thanks the Ramon y Cajal Program RyC-2015-17870 (Spanish Ministry of Economy and Competitiveness, Spain) and RTI2018-099668-B-C22 Project (Spanish Ministry of Science, Innovation and Universities) for XPS and TEM-EDS measurements. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Co-ACCESS, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences. The authors would like to thank Dr. Daniel Unruh from the Department of Chemistry and Biochemistry at Texas Tech University for his help in acquiring the XRD patterns. The authors would like to thank Dr. Benjamin J. Wylie and Collin G. Borcik from the Department of Chemistry and Biochemistry at Texas Tech University for performing MAS-NMR measurements. The authors would like to thank Dr. Julius Warzywoda at Texas Tech University for his assistance in acquiring the Raman spectra.
Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2020/10/15
Y1 - 2020/10/15
N2 - 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.
AB - 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.
KW - Brønsted acid sites
KW - Methane dehydroaromatization
KW - MoC
KW - MoO
KW - Supported molybdenum carbide
UR - http://www.scopus.com/inward/record.url?scp=85086435070&partnerID=8YFLogxK
U2 - 10.1016/j.fuel.2020.118290
DO - 10.1016/j.fuel.2020.118290
M3 - Article
AN - SCOPUS:85086435070
VL - 278
JO - Fuel
JF - Fuel
SN - 0016-2361
M1 - 118290
ER -