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Mo/HMCM-22 catalysts for methane dehydroaromatization: A multinuclear MAS NMR study
Ma, D; Shu, YY; Han, XW; Liu, XM; Xu, YD; Bao, XH
刊名JOURNAL OF PHYSICAL CHEMISTRY B
2001-03-08
DOI10.1021/jp002011k
105期:9页:1786-1793
收录类别SCI
文章类型Article
WOS标题词Science & Technology ; Physical Sciences
类目[WOS]Chemistry, Physical
研究领域[WOS]Chemistry
关键词[WOS]NUCLEAR-MAGNETIC-RESONANCE ; SUPPORTED MOLYBDENUM OXIDES ; BRONSTED ACID SITES ; MO-BASED CATALYSTS ; STATE AL-27 NMR ; ZEOLITE MCM-22 ; MO/HZSM-5 CATALYSTS ; HZSM-5 ZEOLITE ; H-1 MAS ; DEHYDRO-AROMATIZATION
英文摘要Detailed NMR investigations on fresh and coked Mo/HMCM-22 catalysts for methane dehydro-aromatization were presented. Al-27 MAS and Si-29 MAS as well as corresponding CP/MAS NMR experiments have proved that an interaction between molybdenum and the zeolite lattice occurs during the impregnation and calcination processes of the catalysts. With Bronsted acid sites serving as a powerful trap, molybdenum migrates into the internal channels of the zeolite and reacts preferentially with bridging hydroxyls groups. Thus, molybdenum is anchored to the framework aluminum through an oxygen bridge, which, in turn, modifies the acidic properties of the HMCM-22 and leads to a high dispersion of the molybdenum. If this kind of interaction becomes stronger, expelling of aluminum from the zeolite lattice would occur, with the forming of both octahedral nonframework aluminum and Al-2(MoO4)(3) crystallites, The latter can be hydrated to [Al(OH)(n)(H2O)(6-n)](n)(MoO4) (n = 1 or 2) in a water-saturated desiccator and can give a line at ca. 14 ppm in the Al-27 MAS NMR spectrum. UV-Raman results suggest that the carbonaceous deposits on the catalysts are mainly hydrogen-deficient aromatic type, which are also verified by H-1 --> Si-29 CP/MAS and H-1 --> Al-27 CP/MAS NMR, as well as the failure for conducting the C-13 CP/MAS NMR experiment. H-1 --> Al-27 CP/MAS NMR experiments indicate that most of the coke is deposited on framework aluminum (Bronsted site). Regeneration in an oxygen atmosphere leads to the formation of a considerable amount of Al-2(MoO4)(3) crystallites. However, the catalytic activity can be properly restored after the regeneration; thus, the idea of taking this species as the detrimental factor for this reaction can be ruled out. On the other hand, lattice destruction of the zeolite is suggested to be responsible for the poor performance exhibited by the 10Mo/HMCM-22 catalyst. The synergic effect between molybdenum and Bronsted acid sites is considered to be the main reason for the outstanding catalytic performance of the 6Mo/HMCM-22 catalyst.
语种英语
WOS记录号WOS:000167267900018
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被引频次:76[WOS]   [WOS记录]     [WOS相关记录]
文献类型期刊论文
条目标识符http://cas-ir.dicp.ac.cn/handle/321008/138849
专题中国科学院大连化学物理研究所
作者单位Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China
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GB/T 7714
Ma, D,Shu, YY,Han, XW,et al. Mo/HMCM-22 catalysts for methane dehydroaromatization: A multinuclear MAS NMR study[J]. JOURNAL OF PHYSICAL CHEMISTRY B,2001,105(9):1786-1793.
APA Ma, D,Shu, YY,Han, XW,Liu, XM,Xu, YD,&Bao, XH.(2001).Mo/HMCM-22 catalysts for methane dehydroaromatization: A multinuclear MAS NMR study.JOURNAL OF PHYSICAL CHEMISTRY B,105(9),1786-1793.
MLA Ma, D,et al."Mo/HMCM-22 catalysts for methane dehydroaromatization: A multinuclear MAS NMR study".JOURNAL OF PHYSICAL CHEMISTRY B 105.9(2001):1786-1793.
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