Conversion of Methane to Benzene over Transition Metal Ion ZSM-5 Zeolites

Weckhuysen, Bert M.; Wang, Dingjun; Rosynek, Michael P.; Lunsford, Jack H.

doi:10.1006/jcat.1998.2011

Cited by 147 publications

(83 citation statements)

References 25 publications

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“…It is formed from P1 as oxygen is continually extracted from the bulk to supply surface production of formaldehyde and represents a more complete breakdown of the catalyst. Such a conclusion would appear reasonable as similar materials have been observed in both unsupported iron molybdate and Mo supported zeolites [55][56][57][58][59].…”

Section: Phase Formationsupporting

confidence: 74%

A Combined Multi-Technique In Situ Approach Used to Probe the Stability of Iron Molybdate Catalysts During Redox Cycling

et al. 2009

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A setup combining a number of techniques (WAXS, XANES and UV-Vis) has been used to probe the stability of an iron molybdate catalyst during redox cycling. The catalyst was first reduced under anaerobic methanol/ helium conditions, producing formaldehyde and then regenerated using air. Although in this test-case the catalyst and conditions differ from that of a commercial catalyst bed we demonstrate how such a setup can reveal new information on catalyst materials.

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Section: Phase Formationsupporting

confidence: 74%

A Combined Multi-Technique In Situ Approach Used to Probe the Stability of Iron Molybdate Catalysts During Redox Cycling

et al. 2009

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“…[1] Compared to the conventional liquid fuels production based on Fischer-Tropsch technology from syngas (CO + 2 H 2 ), MDA provides a simple, straightforward, and economic pathway from methane to aromatic hydrocarbons without intermediate steps. Intensive efforts have been devoted to the development of suitable catalysts, such as Zn/HZSM-5, [2] Fe/HZSM-5, [3] and Ga/HZSM-5, [4] and encouraging progress has been made, especially on Mo/ MCM-22, [5] Mo/HMCM-49, [6] and Mo/HZSM-5. [2,7] Challenging problems still exist, such as the rapid catalyst deactivation by coke and the limited methane conversion, which hinder the industrialization of MDA.…”

mentioning

confidence: 99%

Natural Gas to Fuels and Chemicals: Improved Methane Aromatization in an Oxygen‐Permeable Membrane Reactor

et al. 2013

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“…The other is the different sample preparation method with respect to that of Ding et In this case, it is likely the WO x rather than WC x that acts as the active phase for methane activation. Lunsford et al 18 did not detect the formation of WC x species during the methane dehydroaromatization by XPS technique either.…”

confidence: 94%

Solid state 13C NMR studies of methane dehydroaromatization reaction on Mo/HZSM-5 and W/HZSM-5 catalysts

Yang

Deng

et al. 2002

Chem. Commun.

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Methane dehydroaromatization on Mo/HZSM-5 and W/ HZSM-5 catalysts was studied by solid state 13 C NMR spectroscopy, both variation of the state of transition metal component and products such as ethane, benzene, ethene adsorbed on or in zeolite were observed after high temperature (900-1000 K) reaction.Catalytic conversion of methane to higher hydrocarbons remains an important challenge to chemists. Since 1993, considerable attention has been paid to the non-oxidative activation of methane to aromatics over Mo/HZSM-5 catalysts. [1][2][3][4][5] At present, it is generally accepted that the Brönsted acidity and channel structure of the zeolite as well as oxidation state of the transition metal component are crucial factors for the performance of this catalyst. 2 However, there are controversial views on both the reaction mechanism and the active phase of metals regarding this reaction. [3][4][5][6][7] Information directly from the surface of the catalysts in the process of the reaction is needed to understand the reaction, but the data on which to characterize the reaction is mostly from the off line gas phase detection. Solid state NMR has proved to be a powerful technique for characterizing structures of heterogeneous catalysts and elucidating reaction mechanisms. It can detect not only intermediates and products adsorbed in or on catalysts, but also the change of active sites in the process of catalytic reaction. [8][9][10] Recently, Ma et al. 11 observed the change of Brönsted acid sites and the formation of products, cokes in the process of methane dehydroaromatization over Mo/HZSM-5 by in situ 1 H MAS NMR. In this note, we studied methane dehydroaromatization reaction on Mo and W modified HZSM-5 catalysts by solid sate 13 C NMR spectroscopy for the first time.Mo/HZSM-5 and W/HZSM-5 catalysts were prepared using procedures described in the literature. 11,12 HZSM-5 (Si/Al = 25) powder was impregnated with an aqueous solution containing a given amount of ammonia heptammolybdate ((NH 4 ) 6 /He (20 ml min 21 ) for 24 h. About 0.5 g Mo/HZSM-5 or W/HZSM-5 power was placed into a 5 ml quartz tube, and activated in vacuum (10 25 Torr) at 673 K for 5 h. 0.25 mmol methane ( 13 C, 99%, Cambridge Isotope Inc.) was introduced at room temperature under vacuum and frozen on the catalyst with liquid N 2 and then the quartz tube was sealed. The sealed ampoules were heated at different temperatures for a specific period and then reaction was quenched by liquid N 2 . Prior to NMR measurement, the sealed ampoules were opened and the samples were transferred into a 7.5 mm ZrO 2 rotor (sealed by Kel-F cap) under a dry nitrogen atmosphere in a glove box. All the NMR experiments were carried out at 9.4 T on a Varian Infinityplus-400 spectrometer, equipped with a Chemagnetic triple-resonance 7.5 mm probe, with resonance frequencies of 400.12 and 100.4 MHz for 1 H and 13 C, respectively. Single pulse 13 C MAS (with 1 H decoupling, 1pda) and 1 H/ 13 C CP/MAS experiments were performed with 4 and 2 s relaxation delays, respectively. Th...

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Conversion of Methane to Benzene over Transition Metal Ion ZSM-5 Zeolites

Cited by 147 publications

References 25 publications

A Combined Multi-Technique In Situ Approach Used to Probe the Stability of Iron Molybdate Catalysts During Redox Cycling

A Combined Multi-Technique In Situ Approach Used to Probe the Stability of Iron Molybdate Catalysts During Redox Cycling

Natural Gas to Fuels and Chemicals: Improved Methane Aromatization in an Oxygen‐Permeable Membrane Reactor

Solid state 13C NMR studies of methane dehydroaromatization reaction on Mo/HZSM-5 and W/HZSM-5 catalysts

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