Methane dehydro-aromatization over Mo/HZSM-5 in the absence of oxygen: A multinuclear solid-state NMR study of the interaction between supported Mo species and HZSM-5 zeolite with different crystal sizes
The interaction between Mo species and a conventionally microsized and particularly nanosized HZSM-5 support was studied by high-resolution multinuclear solid-state NMR techniques. As proved by {sup 27}Al and {sup 29}Si MAS as well as CP/MAS NMR investigations, this interaction was so strong that the framework aluminum of both microsized and nanosized HZSM-5 zeolites could be extracted. With increasing Mo loading, more nonframework aluminum, resonance at ca. 30 ppm, appeared in the {sup 27}Al MAS NMR spectrum of the Mo-loaded nanosized HZSM-5 catalyst. Meanwhile, this strong interaction led to the formation of more new Al{sub 2}(MoO{sub 4}){sub 3} crystallines on the nanosized HZSM-5 support than on the microsized HZSM-5 support. The appearance of Al{sub 2}(MoO{sub 4}){sub 3} crystallines resulted in fewer active catalysts for the methane dehydro-aromatization. The results of {sup 1}H MAS NMR using perfluorotributyl amine as a probe molecule demonstrated that Mo species preferentially reacted with the silanols and nonframework AlOH on the external surface of microsized and nanosized HZSM-5 zeolites. In addition, impregnated Mo species remained predominantly on the external surface of the nanosized HZSM-5 zeolite, although there was a possibility that they might migrate into the lattice channels of the microsized HZSM-5 zeolite. The migration of some Mo species into the zeolite channels might be beneficial for the conversion of methane to aromatics in the absence of oxygen.
- Research Organization:
- Chinese Academy of Sciences, Dalian Inst. of Chemical Physics, Dalian (CN)
- OSTI ID:
- 20005907
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 188; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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