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题名: Studies of the Active Sites for Methane Dehydroaromatization Using Ultrahigh-Field Solid-State Mo-95 NMR Spectroscopy
作者: Hu, Jian Zhi1;  Kwak, Ja Hun1;  Wang, Yong1;  Peden, Charles H. F.1;  Zheng, Heng2, 3;  Ma, Ding;  Bao, Xinhe2
刊名: JOURNAL OF PHYSICAL CHEMISTRY C
发表日期: 2009-02-19
DOI: 10.1021/jp8107914
卷: 113, 期:7, 页:2936-2942
收录类别: SCI
文章类型: Article
WOS标题词: Science & Technology ;  Physical Sciences ;  Technology
类目[WOS]: Chemistry, Physical ;  Nanoscience & Nanotechnology ;  Materials Science, Multidisciplinary
研究领域[WOS]: Chemistry ;  Science & Technology - Other Topics ;  Materials Science
英文摘要: In this contribution, we show that the spin-lattice relaxation time, T-1, corresponding to zeolite exchanged molybdenum species in Mo/HZSM-5 catalysts is about 2 orders of magnitude shorter than the corresponding T, for small MoO3 crystallites. Such a difference is utilized to differentiate the exchanged Mo species from MoO3 agglomerates in Mo/H7-SM-5 catalysts and to readily estimate their relative fractions present in catalysts with varying Mo loading. A good linear correlation between the amount of zeolite exchanged species and the aromatics formation rate during catalytic methane dehydroaromatization is obtained. This result significantly strengthens our prior conclusion that the exchanged Mo species are the active centers for this reaction on Mo/HZSM-5 catalysts (J. Am. Chem. Soc. 2008, 130, 3722-3723). Of more general interest for Mo-exchanged zeolites, the results may provide useful data for analyzing the binding of exchanged Mo species in zeolite cages. In particular, the NMR data suggest a possible saturation loading for the exchanged Mo species at a Mo/Al ratio of approximately 0.5 for the ZSM-5 zeolite used in this study (Si/Al = 25). Furthermore, for polycrystalline MoO3 powder samples, the parameters related to the electric field gradient (EFG) tensor, the chemical shift anisotropy (CSA), and the three Euler angles required to align the CSA principal axis system with the quadrupolar principal axis system are determined by analyzing both the magic angle spinning (MAS) and. static Mo-95 spectra. The new results obtained from this study on MoO3 powders should help to clarify some of the contradictions in prior literature reports of studies of Mo-containing solids by Mo-95 NMR.
关键词[WOS]: BRONSTED ACID SITES ;  ANGLE-SPINNING NMR ;  MAS NMR ;  HYDRODESULFURIZATION CATALYSTS ;  DEHYDRO-AROMATIZATION ;  ZEOLITE CATALYSTS ;  MO ;  NAPHTHALENE ;  QUADRUPOLE ;  CONVERSION
语种: 英语
WOS记录号: WOS:000263299600040
Citation statistics: 
内容类型: 期刊论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/141247
Appears in Collections:中国科学院大连化学物理研究所_期刊论文

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作者单位: 1.Pacific NW Natl Lab, Inst Interfacial Catalysis, Richland, WA 99352 USA
2.Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China
3.SW Res & Design Inst Chem Ind Chengdu, Chengdu, Peoples R China

Recommended Citation:
Hu, Jian Zhi,Kwak, Ja Hun,Wang, Yong,et al. Studies of the Active Sites for Methane Dehydroaromatization Using Ultrahigh-Field Solid-State Mo-95 NMR Spectroscopy[J]. JOURNAL OF PHYSICAL CHEMISTRY C,2009,113(7):2936-2942.
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