Bifunctional behavior of Mo/HZSM-5 catalysts in methane aromatization
Catalytic functions of Mo/HZSM-5 toward methane aromatization are examined under various activation and reaction conditions. Molybdenum ions are necessary in the activation of methane. High benzene yields of around 7% are obtained with a selectivity of more than 96% at 973 K over a 2 wt% Mo/HZSM-5 catalyst in a tubular reactor. Pretreatment with hydrogen is found to be beneficial to the initialization of aromatization. The aromatization activity increases upon decreasing the Si/Al ratio in HZSM-5, indicating an acidity dependence. This is supported by the fact that a Mo catalyst supported on cesium-exchanged ZSM-5 looses its catalytic aromatization activity at all. The effective coordination between molybdenum ion sites and Broensted acid sites in the framework of ZSM-5 is important in the activation of the stable C-H bonds in methane and the eventual aromatization to form benzene. The constant O1s binding energy in the XPS spectra of both fresh and used catalysts suggests that coke formation does not occur on the SiO{sub 4} tetrahedra but rather on the molybdenum sites supported on the external surface of ZSM-5.
- Research Organization:
- Laval Univ., Ste-Foy, Quebec (CA)
- OSTI ID:
- 20000992
- Journal Information:
- Industrial and Engineering Chemistry Research, Journal Name: Industrial and Engineering Chemistry Research Journal Issue: 10 Vol. 38; ISSN IECRED; ISSN 0888-5885
- Country of Publication:
- United States
- Language:
- English
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