The mechanism of aromatic dealkylation in methanol-to-hydrocarbons conversion on H-ZSM-5: What are the aromatic precursors to light olefins?

Ilias, Samia; Bhan, Aditya

doi:10.1016/j.jcat.2013.11.003

Cited by 95 publications

(50 citation statements)

References 32 publications

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“…In contrast, ZSM-5 is a strongly acidic zeolite that can catalyze several reactions, including olen oligomerization, aromatic alkylation, toluene disproportionation, methanol-to-hydrocarbon conversions (including MTG, MTO, MTP), and light hydrocarbon cracking and aromatization. [7][8][9][10][11] This clearly indicates that the acidity of S-1 zeolite needs to be increased to broaden its catalytic applications.…”

Section: Introductionmentioning

confidence: 99%

Silicalite-1 zeolite acidification by zinc modification and its catalytic properties for isobutane conversion

Liu

et al. 2018

RSC Adv.

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A series of Zn-modified Silicalite-1 (S-1) zeolites (Zn x /S-1) were prepared by the wetness-impregnation method and applied in the catalytic conversion of isobutane. The structure and location of Zn species in Zn x /S-1 were investigated using UV-Vis and N 2 physical adsorption. The acidity and origin of the acid sites in Zn x /S-1 were studied by NH 3 -temperature programmed desorption and Fourier-transform infrared analysis. The catalytic performance of Zn x /S-1 for isobutane conversion was investigated in a fixed-bed microreactor. In the experiments, the acidity of S-1 zeolite was dramatically increased by modification with Zn, with both Lewis and Brønsted sites identified in Zn x /S-1. The relationship between Brønsted acid sites and Zn-OH groups on ZnO clusters of Zn x /S-1 was also revealed for the first time.Furthermore, Zn x /S-1 catalysts exhibited excellent catalytic performances in both isobutane dehydrogenation and butene isomerization reactions. A high selectivity of total butene products ranging from 84.6 to 97.2 was achieved on the catalysts with different Zn loadings. Moreover, the linear correlation between isobutane conversion and the acid amount (determined by NH 3 -TPD) confirmed that the weak-to-medium acid sites in Zn x /S-1 should play a key role in isobutane conversion.

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Section: Introductionmentioning

confidence: 99%

Silicalite-1 zeolite acidification by zinc modification and its catalytic properties for isobutane conversion

Liu

et al. 2018

RSC Adv.

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“…[4e, 8d, 13a, 21] Most recently, the effect of co-feeding of aromatics on the distribution of ethene and propene was systematically investigated by Lercher and co-workers. [22] In addition, Bhan et al [21] demonstrated that tetramethylbenzene was the preferable precursor to ethene and propene in H-ZSM-5 zeolite. Parallel to the experimental works, McCann et al carried out the first theoretical study to rationalize the formation of isobutene on H-ZSM-5 by connecting MBs and previously observed cyclopentenyl and benzenium ions.…”

Section: Introductionmentioning

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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“…[9] On the other hand, isotopic scrambling experiments indicated that tetramethylbenzene wast he precursor to ethene and ap aring pathway was claimed. [10] Carbocations are generally believed as criticali ntermediates in variousacid-catalyzed reactions. In the MTO reaction,avariety of carbocation intermediates were observed on different zeolitea nd zeolite-type catalysts.…”

Section: Introductionmentioning

confidence: 99%

Experimental Evidence on the Formation of Ethene through Carbocations in Methanol Conversion over H‐ZSM‐5 Zeolite

Wang

et al. 2015

Chemistry A European J

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The methanol to olefins conversion over zeolite catalysts is a commercialized process to produce light olefins like ethene and propene but its mechanism is not well understood. We herein investigated the formation of ethene in the methanol to olefins reaction over the H-ZSM-5 zeolite. Three types of ethylcyclopentenyl carbocations, that is, the 1-methyl-3-ethylcyclopentenyl, the 1,4-dimethyl-3-ethylcyclopentenyl, and the 1,5-dimethyl-3-ethylcyclopentenyl cation were unambiguously identified under working conditions by both solid-state and liquid-state NMR spectroscopy as well as GC-MS analysis. These carbocations were found to be well correlated to ethene and lower methylbenzenes (xylene and trimethylbenzene). An aromatics-based paring route provides rationale for the transformation of lower methylbenzenes to ethene through ethylcyclopentenyl cations as the key hydrocarbon-pool intermediates.

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The mechanism of aromatic dealkylation in methanol-to-hydrocarbons conversion on H-ZSM-5: What are the aromatic precursors to light olefins?

Cited by 95 publications

References 32 publications

Silicalite-1 zeolite acidification by zinc modification and its catalytic properties for isobutane conversion

Silicalite-1 zeolite acidification by zinc modification and its catalytic properties for isobutane conversion

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

Experimental Evidence on the Formation of Ethene through Carbocations in Methanol Conversion over H‐ZSM‐5 Zeolite

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