A Periodic Density Functional Theory Study of Cumene Formation Catalyzed by H-Mordenite

Rozanska, Xavier; Barbosa, Lamm Luis Antonio; Santen, van Ra Rutger

doi:10.1021/jp049227x

Cited by 40 publications

(42 citation statements)

References 63 publications

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“…2 Structure VIII again shows the bifunctional role of the zeolite acid sites, and the participation of oxygen atoms that are not bonded to the alkoxide intermediate. Other C-C bond forming reactions (such as ethylene dimerization to form n-butenes) proceed in a similar fashion (Namuangruk et al, 2005).…”

Section: Classical Brønsted Acid Catalysismentioning

confidence: 98%

“…Both alkoxide (IV), and carbenium ion (V) intermediates are highly reactive, and can form new carbon-carbon bonds with organic molecules physisorbed inside the zeolite pores. An important industrial reaction conducted over zeolites is the synthesis of cumene from propene and benzene (Rozanska et al, 2005). 2 It has been reported that the kinetically relevant pathway for the formation of cumene is a sequential reaction in which propene reacts with a Brønsted acid site to form an isopropoxide intermediate.…”

Section: Classical Brønsted Acid Catalysismentioning

confidence: 99%

“…An important industrial reaction conducted over zeolites is the synthesis of cumene from propene and benzene (Rozanska et al, 2005). 2 It has been reported that the kinetically relevant pathway for the formation of cumene is a sequential reaction in which propene reacts with a Brønsted acid site to form an isopropoxide intermediate. This isopropoxide intermediate (VI), then reacts with a benzene molecule to form cumene and regenerate the Brønsted acid site (see VIII in Figure 2).…”

Section: Classical Brønsted Acid Catalysismentioning

confidence: 99%

“…This bimolecular reaction has been investigated extensively, and recent studies have shown that the stability of the transition state (VIII), greatly depends not only on the stabilization effect of the acid site, but also on the stability provided by the surrounding zeolite pore structure to the bulky intermediate (Rozanska et al, 2005). 2 Structure VIII again shows the bifunctional role of the zeolite acid sites, and the participation of oxygen atoms that are not bonded to the alkoxide intermediate.…”

Section: Classical Brønsted Acid Catalysismentioning

confidence: 99%

“…This reflects advances in spectroscopic techniques-IR, NMR ), 1 X-ray spectroscopy, etc., extensive use of in situ characterization methods, sophisticated use of computational chemistry (Rozanska et al, 2005), 2 and tremendous success in the synthesis and characterization of new materials. In this perspective, I describe selected examples of progress in zeolite catalysis that illustrate how our ability to elucidate in molecular detail the structure of the catalytic site and its surroundings can be used to understand activity and selectivity.…”

Section: Introductionmentioning

confidence: 99%

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Chemical diversity of zeolite catalytic sites

Lobo¹

2008

AIChE Journal

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Section: Classical Brønsted Acid Catalysismentioning

confidence: 98%

Section: Classical Brønsted Acid Catalysismentioning

confidence: 99%

Section: Classical Brønsted Acid Catalysismentioning

confidence: 99%

Section: Classical Brønsted Acid Catalysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chemical diversity of zeolite catalytic sites

Lobo¹

2008

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Computer Simulations of Shape Selectivity Effects

Smit¹,

Maesen

2008

Handbook of Heterogeneous Catalysis

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Introduction Today, almost every gasoline molecule has seen the interior of a zeolite and experienced the effect of shape selectivity. Given the economical importance [1][2][3][4][5] implied by this statement, one would expect that we have a very good understanding of the mechanisms underlying shape selectivity. Clearly, we do have a very good understanding of the chemical reactions that take place inside the pores of a zeolite. In addition, many mechanisms have been proposed to explain the various product distributions that have been observed experimentally. However, we are still very far away that by looking at a zeolite structure we can provide a prediction of the products.Let us consider as a simple example the conversion of n-decane in an acid zeolite. The chemistry tells us that isomerization reactions take place giving mono-, di-, and tribranched isomers. These isomerization reactions compete with cracking, and this results in a large number * Corresponding author.

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Application of QM simulations and multivariate analysis in the study of alkene reactivity in the zeolite H‐ZSM5

Gleeson

2008

Journal of Chemometrics

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Application of QM simulations and multivariate analysis in the study of alkene reactivity in the zeolite H-ZSM5 Duangkamol Gleeson a *Reported herein are the results of an investigation into the effect of the extended framework of the zeolite ZSM-5 on the reaction energetics and structures of (a) the physisorbed complex formed between the zeolite and six alkenes, (b) the corresponding chemisorbed alkoxide intermediate and (c) the transition states (TS) connecting the two. For this, quantum mechanical (QM) simulations of ZSM-5 in the presence and absence of the zeolite framework have been employed. A 46T density functional theory (DFT) cluster model and a 3T:46T DFT:UFF ONIOM model are used to represent the former scenario and a simple 3T DFT cluster model for the latter. The structural implications of neglecting the zeolite framework have been rigorously compared using the multivariate statistical method principal components analysis (PCA). This method allows one to assess the correlated nature of the changes in structure along the reaction coordinate, for multiple different alkenes, in a facile, reliable way. . ZSM-5 is a well-studied medium pore-size zeolite from the MFI family. It is characterized by a three-dimensional pore system consisting of sinusoidal 10T ring with intersecting 10T ring channels. While the Brønsted acid site locations can be similar in different 10T ring zeolites, they can display considerable selectivity differences, including the production of isobutene from linear butanes [1]. This is because the framework topologies can alter the catalytic reactions through (a) moderation of the pKa of the Brønsted acid site, (b) hinder/allow the formation of key intermediates due to the local pore volume, (c) stabilize stationary points on the potential energy surface through long range interactions as a result of high Si/Al ratios or the presence of heavy metal additives or (d) impose diffusional limitations as a result of coking/time on stream.Quantum mechanical (QM) calculations [3][4][5][6][7] are often used to model the reactivity and selectivity of zeolites since through a consideration of the relative energies and structures of the zeolite-substrate complexes, transition states (TS) and products, one can often get insights into chemical processes not possible by experimental techniques. A common feature of zeolite simulations is their consideration of acidity, focusing either on the non-bonded 'physisorption' of various small molecules to the Brønsted acid site [8], or more complex reactions that occur at it. Alkoxide intermediate formation involves the transfer of the Brønsted proton on the zeolite O1 atom to the C1 of the alkene with the subsequent formation of a bond between the C2 and O2 atoms of the substrate and zeolite, respectively (Figure 1). Theoretical studies on alkoxide intermediates have often been restricted to relatively small cluster models [9][10][11] Studies comparing gas phase cluster models to those that encode information about the active site are generally restricted to ...

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A Periodic Density Functional Theory Study of Cumene Formation Catalyzed by H-Mordenite

Cited by 40 publications

References 63 publications

Chemical diversity of zeolite catalytic sites

Chemical diversity of zeolite catalytic sites

Computer Simulations of Shape Selectivity Effects

Application of QM simulations and multivariate analysis in the study of alkene reactivity in the zeolite H‐ZSM5

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