Stepwise or Concerted Mechanisms of Benzene Ethylation Catalyzed by Zeolites? Theoretical Analysis of Reaction Pathways

Acharya, Dev Raj; Chen, Wei; Yuan, Jiamin; Liu, Zhiqiang; Yi, Xiaoyan; Xiao, Yao; Zheng, Anmin

doi:10.1007/s10562-021-03549-0

Cited by 8 publications

(12 citation statements)

References 37 publications

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“…The zeolite-catalyzed alkylation of alkenes and aromatics is a common reaction to increase the alkyl chain of alkenes and decorate aromatic rings with alkyl groups, widely occurring in different zeolite-catalyzed reactions, [270][271][272] such as dual-cycle MTO, 94,273,274 toluene disproportionation, 275,276 benzene ethylation, [277][278][279][280] and alkylation of phenol and substituted phenols. 281 Alcohols, ethers, and alkenes can act as the alkylated agents by dehydration and protonation, 282 and there are two alkylated pathways in zeolites, i.e., stepwise and concerted mechanisms.…”

Section: Carbocations In Alkene or Aromatic Alkylationmentioning

confidence: 99%

Carbocation chemistry confined in zeolites: spectroscopic and theoretical characterizations

Chen

Liu

et al. 2022

Chem. Soc. Rev.

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Section: Carbocations In Alkene or Aromatic Alkylationmentioning

confidence: 99%

Carbocation chemistry confined in zeolites: spectroscopic and theoretical characterizations

Chen

Liu

et al. 2022

Chem. Soc. Rev.

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“…Alkene/alkanol protonation and C–C bond formation occur concurrently; , for alkanol reactants, H 2 O ejection also occurs in this step. This step is followed by deprotonation of the alkylated species, closing the catalytic cycle by regenerating the H + site. − In contrast, during the stepwise mechanism, the π-bonded alkene or molecularly bound alkanol species reacts with H + to form an alkoxide intermediate; , in the case of alkanol reactants, H 2 O is ejected as a product as the alkanol forms a respective alkoxide. − This alkoxide then reacts with the aromatic compound to form an alkylated species in a subsequent C–C formation step, followed by deprotonation to reform the H + site. − …”

Section: Introductionmentioning

confidence: 99%

Kinetic, Spectroscopic, and Theoretical Study of Toluene Alkylation with Ethylene on Acidic Mordenite Zeolite

Ithisuphalap,

Nolen,

Monroe

et al. 2023

ACS Catal.

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“…Mechanistically, the prototypical alkylation of benzene with ethene or ethanol in the H-ZSM-5 zeolite has represented the main case study in the computational investigation of zeolite-catalyzed alkylation reactions. − There is consensus that two main reaction pathways are possible: (i) a stepwise mechanism (TS0, TS1, and TS3 in Figure ) and (ii) a concerted mechanism (TS2 and TS3 in Figure ). In the former, ethene or ethanol is first chemisorbed on the zeolite walls as a surface ethoxide species (SES, Figure b).…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Characterization of Zeolite-Catalyzed Aromatic Electrophilic Substitution at Realistic Operating Conditions

Bocus

Vanduyfhuys

Proft

et al. 2022

JACS Au

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Zeolite-catalyzed benzene ethylation is an important industrial reaction, as it is the first step in the production of styrene for polymer manufacturing. Furthermore, it is a prototypical example of aromatic electrophilic substitution, a key reaction in the synthesis of many bulk and fine chemicals. Despite extensive research, the reaction mechanism and the nature of elusive intermediates at realistic operating conditions is not properly understood. More in detail, the existence of the elusive arenium ion (better known as Wheland complex) formed upon electrophilic attack on the aromatic ring is still a matter of debate. Temperature effects and the presence of protic guest molecules such as water are expected to impact the reaction mechanism and lifetime of the reaction intermediates. Herein, we used enhanced sampling ab initio molecular dynamics simulations to investigate the complete mechanism of benzene ethylation with ethene and ethanol in the H-ZSM-5 zeolite. We show that both the stepwise and concerted mechanisms are active at reaction conditions and that the Wheland intermediate spontaneously appears as a shallow minimum in the free energy surface after the electrophilic attack on the benzene ring. Addition of water enhances the protonation kinetics by about 1 order of magnitude at coverages of one water molecule per Brønsted acidic site. In the fully solvated regime, an overstabilization of the BAS as hydronium ion occurs and the rate enhancement disappears. The obtained results give critical atomistic insights in the role of water to selectively tune the kinetics of protonation reactions in zeolites.

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Stepwise or Concerted Mechanisms of Benzene Ethylation Catalyzed by Zeolites? Theoretical Analysis of Reaction Pathways

Cited by 8 publications

References 37 publications

Carbocation chemistry confined in zeolites: spectroscopic and theoretical characterizations

Carbocation chemistry confined in zeolites: spectroscopic and theoretical characterizations

Kinetic, Spectroscopic, and Theoretical Study of Toluene Alkylation with Ethylene on Acidic Mordenite Zeolite

Mechanistic Characterization of Zeolite-Catalyzed Aromatic Electrophilic Substitution at Realistic Operating Conditions

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