In Situ NMR Investigations of Heterogeneous Catalysis with Samples Prepared under Standard Reaction Conditions

Haw, James F.; Goguen, Patrick W.; Xu, Teng; Skloss, Timothy W.; Song, Weiguo; Wang, Zhike

doi:10.1002/(sici)1521-3773(19980420)37:7<948::aid-anie948>3.3.co;2-c

Cited by 28 publications

(58 citation statements)

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“…Methanol (weight hourly space velocity (WHSV)=2 h −1 ) was reacted over H‐ZSM‐5 (Si/Al=30, 0.3 g ) in a fixed bed reactor in a temperature range of 300–400 °C. In each case, the catalysts were compressed to wafers that were crushed and sieved to obtain 60–80 mesh particles, and then the particles were activated in place prior to the reaction by heating at 400 °C in flowing helium for 1 h. For the co‐reaction of 13 C‐labeled benzene (99 % 13 C, denoted as [ 13 C 6 ]benzene) with unlabeled methanol ( 13 C natural abundance, denoted as methanol), a pulse‐quench reactor was used to quench the reaction by reducing the reaction temperature with liquid nitrogen within a very short period (<1 s) 32. Typically, when the reaction proceeded in a pulse‐quench reactor for a pre‐set period, the reaction was thermally quenched by pulsing liquid nitrogen onto the catalyst bed, which was achieved by using high‐speed valves controlled by a GC computer.…”

Section: Methodsmentioning

confidence: 99%

New Insight into the Hydrocarbon‐Pool Chemistry of the Methanol‐to‐Olefins Conversion over Zeolite H‐ZSM‐5 from GC‐MS, Solid‐State NMR Spectroscopy, and DFT Calculations

Wang

Zheng

et al. 2014

Chemistry A European J

136

148

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Over zeolite H-ZSM-5, the aromatics-based hydrocarbon-pool mechanism of methanol-to-olefins (MTO) reaction was studied by GC-MS, solid-state NMR spectroscopy, and theoretical calculations. Isotopic-labeling experimental results demonstrated that polymethylbenzenes (MBs) are intimately correlated with the formation of olefin products in the initial stage. More importantly, three types of cyclopentenyl cations (1,3-dimethylcyclopentenyl, 1,2,3-trimethylcyclopentenyl, and 1,3,4-trimethylcyclopentenyl cations) and a pentamethylbenzenium ion were for the first time identified by solid-state NMR spectroscopy and DFT calculations under both co-feeding ([(13) C6 ]benzene and methanol) conditions and typical MTO working (feeding [(13) C]methanol alone) conditions. The comparable reactivity of the MBs (from xylene to tetramethylbenzene) and the carbocations (trimethylcyclopentenyl and pentamethylbenzium ions) in the MTO reaction was revealed by (13) C-labeling experiments, evidencing that they work together through a paring mechanism to produce propene. The paring route in a full aromatics-based catalytic cycle was also supported by theoretical DFT calculations.

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Section: Methodsmentioning

confidence: 99%

New Insight into the Hydrocarbon‐Pool Chemistry of the Methanol‐to‐Olefins Conversion over Zeolite H‐ZSM‐5 from GC‐MS, Solid‐State NMR Spectroscopy, and DFT Calculations

Wang

Zheng

et al. 2014

Chemistry A European J

136

148

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“…For the MTH reaction, the contact time is typically from several tenths of a second to several tens of seconds. Haw and co‐workers developed a pulse‐quench technique (Figure ) to capture the intermediates in a short time reaction. This device allows for both continuous‐flow and pulse reactions.…”

Section: In Situ Solid‐state Nmr Approachesmentioning

confidence: 99%

Mechanism of Methanol‐to‐hydrocarbon Reaction over Zeolites: A solid‐state NMR Perspective

Wang¹,

Xu²

2020

ChemCatChem

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The versatile methanol‐to‐hydrocarbon (MTH) process on acidic zeolites allows for a production of olefins, aromatics and gasoline from a wide range of non‐fossil resources. Elucidation of the MTH reaction mechanism is helpful to improve product selectivity as well as develop high performance catalysts. The application of solid‐state NMR in the investigation of MTH reaction has significantly contributed to get insight into the MTH chemistry. In this review, we summarize mechanistic insight that has been gained into the MTH reaction by using solid‐state NMR spectroscopy. Special emphasis is given to the observation and determination of C1 species and active intermediates particularly cyclic carbocations to uncover the exact reaction route for the initial C−C bond formation and the hydrocarbon pool mechanism. The detection of host‐guest interactions involved in the MTH reaction with the advanced 13C‐27Al double‐resonance NMR is discussed for a better understanding of the active sites and the reactivity of hydrocarbon pool species.

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“…Figure 3 uses the schematic nomenclature for a supramolecular site to outline the ''hydrocarbon pool mechanism'' that operates in MTO catalysis. The reader is referred to the original literature, especially the work of Kolboe [9][10][11][12][13][14][15] and our own papers [16][17][18][19][20][21][22][23][24][25], as well as our review [7] for historical perspectives on the development of the hydrocarbon pool mechanism. In this and the following figures, we assume the existence of one acid site per cage.…”

Section: Organic Component Of the Catalystmentioning

confidence: 99%

Well-defined (supra)molecular structures in zeolite methanol-to-olefin catalysis

2005

Self Cite

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Methanol-to-olefin (MTO) conversion on microporous silico-aluminophosphates is particularly well-suited for the application of molecular-level concepts to the development of well-defined supported catalysts. The active site of a typical MTO catalyst is a nm-size inorganic cage with an essential organic component. Opportunities for altering the selectivity of such catalysts include tailoring the organic component and modification of the cage with additional inorganic material through ship-in-a-bottle synthesis. The latter possibility has already been realized experimentally by the development of a useful and practical phosphate-modified catalyst.

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In Situ NMR Investigations of Heterogeneous Catalysis with Samples Prepared under Standard Reaction Conditions

Cited by 28 publications

References 0 publications

New Insight into the Hydrocarbon‐Pool Chemistry of the Methanol‐to‐Olefins Conversion over Zeolite H‐ZSM‐5 from GC‐MS, Solid‐State NMR Spectroscopy, and DFT Calculations

New Insight into the Hydrocarbon‐Pool Chemistry of the Methanol‐to‐Olefins Conversion over Zeolite H‐ZSM‐5 from GC‐MS, Solid‐State NMR Spectroscopy, and DFT Calculations

Mechanism of Methanol‐to‐hydrocarbon Reaction over Zeolites: A solid‐state NMR Perspective

Well-defined (supra)molecular structures in zeolite methanol-to-olefin catalysis

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