Bifunctional Catalysis of Mo/HZSM-5 in the Dehydroaromatization of Methane to Benzene and Naphthalene XAFS/TG/DTA/MASS/FTIR Characterization and Supporting Effects

Liu, Shetian; Wang, Linsheng; Ohnishi, Ryuichiro; Ichikawa, Masaru

doi:10.1006/jcat.1998.2310

Cited by 289 publications

(164 citation statements)

References 26 publications

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“…Based on IR experiments, Lunsford et al suggested that the Mo species are mainly introduced to the outer surface of the HZSM-5. 5 Liu et al 15 also concluded that the introduction of Mo has no effect on the intensity on the HZSM-5 support from pyridine IR results, indicating the location of Mo in the external surfaces of MFI. On the other hand, Xu et al 2 reported that the Brønsted acid sites decrease about 80% on the 6Mo/HZSM-5 catalyst.…”

Section: Ft-irmentioning

confidence: 98%

“…34 Iglesia et al studied Mo/ HZSM-5 catalysts prepared by using mechanical mixtures of MoO 3 and HZSM-5 via solid exchange reaction. [13][14][15][16] The authors also presented evidence that most of the Mo species migrate into the channels and are properly reduced by CH 4 into MoO x C y . Recently, in our proton MAS NMR study on HZSM-5 zeolite modified with perfluorotributyl amine we clearly distinguish the external and internal Brønsted sites.…”

Section: Ft-irmentioning

confidence: 99%

“…Nevertheless, more anchored Mo species results in less free Brønsted sites remaining inside the channels, and less consecutive channels. Therefore, for the best bi-functional catalyst, the amount of active Mo species, either in the form of Mo 2 C or MoO x C y , [13][14][15][16] and the amount of free Brønsted acid sites should be well balanced. One may put forward a question on what is the suitable balance between the free Brønsted acid sites and the anchored Mo species and thus to give the best catalytic performance.…”

Section: Catalytic Behavior and Bi-functional Feature Of Mo/mcm-22 Camentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] It is well accepted that the Mo/HZSM-5 is a bi-functional catalyst. Mo species, in the form of either Mo 2 C 5,6,9 or MoO x C y 4, [10][11][12][13] are responsible for methane activation, while the functions of the acid sites of zeolite are for the formation of benzene.…”

Section: Introductionmentioning

confidence: 99%

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The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization

Zhu

et al. 2005

Phys. Chem. Chem. Phys.

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The acid properties of Mo/HMCM-22 catalyst, which is the precursor form of the working catalyst for methane aromatization reaction, and the synergic effect between Mo species and acid sites were studied and characterized by various characterization techniques. It is concluded that Brønsted and Lewis acidities of HMCM-22 are modified due to the introduction of molybdenum. We suggest a monomer of Mo species is formed by the exchange of Mo species with the Brønsted acid sites. On the other hand, coordinate unsaturated sites (CUS) are suggested to be responsible for the formation of newly detected Lewis acid sites. Computer modelling is established and coupling with experimental results, it is then speculated that the effective activation of methane is properly accomplished on Mo species accommodated in the 12 MR supercages of MCM-22 zeolite whereas the Brønsted acid sites in the same channel system play a key role for the formation of benzene. A much more pronounced volcano-typed reactivity curve of the Mo/HMCM-22 catalysts, as compared with that of the Mo/HZSM-5, with respect to Mo loading is found and this can be well understood due to the unique channel structure of MCM-22 zeolite and synergic effect between Mo species and acid sites.

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Section: Ft-irmentioning

confidence: 98%

Section: Ft-irmentioning

confidence: 99%

Section: Catalytic Behavior and Bi-functional Feature Of Mo/mcm-22 Camentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization

Zhu

et al. 2005

Phys. Chem. Chem. Phys.

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“…Changes in the carbon-to-metal ratio can occur spontaneously under reaction conditions as in the induction period for methane aromatization on Mo/ZSM-5 catalysts. 18,19 The formation of interstitial molybdenum carbide leads to charge transfer to carbon, the expansion of the molybdenum lattice, and metal-carbon covalent bonding. 20 Excess carbon on the surface is expected to lead to site blocking.…”

Section: Introductionmentioning

confidence: 99%

Carbon−Nitrogen Place Exchange on NO Exposed β-Mo₂C

et al. 2005

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Atomic nitrogen and oxygen were deposited on -Mo 2 C through dissociative adsorption of NO. Reflectance absorbance infrared spectroscopy (RAIRS), thermal desorption, and synchrotron X-ray photoelectron spectroscopy (XPS) measurements were used to investigate the interplay between atomic nitrogen, carbon, and oxygen in the 400-1250 K region. The combination of the high resolution and high surface sensitivity offered by the synchrotron XPS technique was used to show that atomic nitrogen displaces interstitial carbon onto the carbide surface. Thermal desorption measurements show that the burnoff of the displaced carbon occurs at approximately 890 K. The incorporation of nitrogen into interstitial sites inhibits oxygen dissolution into the bulk. RAIRS spectroscopy was used to identify surface oxo, terminal oxygen, species formed from O 2 and NO on -Mo 2 C.

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Metal Carbides

Lee

2010

Encyclopedia of Catalysis

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Transition metal carbides of early transition metals attracted considerable attention as catalysts because of their availability with high specific areas and surface cleanness. Their refractory properties render them resistance against attrition and sintering under reaction conditions. They are catalytically active in many reactions, particularly those involving hydrogen transfer such as hydrotreating (hydrodesulfurization, hydrodenitrogenation, and hydrodeoxygenation), hydrogenation, dehydrogenation, isomerization, hydrogenolysis, reforming, and aromatization. Recently, they are also receiving attention as electrocatalysis. In many of these reactions, metal carbides behave like group 8–10 metals (Pt, Pd, Rh, Ru, etc) of high cost and limited supply and have potential to replace them. Structure, bonding, synthesis, and surface reactivity of transition metal carbides are discussed.

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Bifunctional Catalysis of Mo/HZSM-5 in the Dehydroaromatization of Methane to Benzene and Naphthalene XAFS/TG/DTA/MASS/FTIR Characterization and Supporting Effects

Cited by 289 publications

References 26 publications

The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization

The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization

Carbon−Nitrogen Place Exchange on NO Exposed β-Mo₂C

Metal Carbides

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Bifunctional Catalysis of Mo/HZSM-5 in the Dehydroaromatization of Methane to Benzene and Naphthalene XAFS/TG/DTA/MASS/FTIR Characterization and Supporting Effects

Cited by 289 publications

References 26 publications

The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization

The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization

Carbon−Nitrogen Place Exchange on NO Exposed β-Mo2C

Metal Carbides

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Carbon−Nitrogen Place Exchange on NO Exposed β-Mo₂C