Alkylation and transalkylation reactions of aromatics

S.R. Blaszkowski, R.A. Santen, van

Onderzoeksoutput: Hoofdstuk in Boek/Rapport/CongresprocedureConferentiebijdrageAcademic

8 Citaten (Scopus)

Samenvatting

A symposium. D. functional theory calcns. were carried out to analyze the reaction energy of solid-state acid-catalyzed Me-transfer reactions. Different mechanistic routes for the alkylation of C6H6 and PhMe by MeOH were compared. An associative reaction path via an intermediate complex of MeoH and the substrate is the preferred route. The activation energy is 123 and .apprx.120 kJ/mol for C6H6 and PhMe, resp. A MeO-mediated path involves very high activation barriers compared to the associative route. However, coadsorbed H2O gives a large redn. of the activation energy for this reaction. Different mechanisms for PhMe transalkylation, involving Ph2CH2 as an intermediate, directly via Me transfer, and MeO-mediated, were compared. For the 1st mechanism, the preferred route is that where the reaction chain of elementary reactions is propagated via H- transfer. The rate-detg. step is the initial dehydrogenation, with an activation energy of +277 kJ/mol, which is present only in the very 1st step of the reaction chain. In the following steps, the initial dehydrogenation is replaced by proton-assisted cracking of Ph2CH2 as the step with the highest activation barrier. The direct mechanisms via Me transfer or via intermediate MeO do present activation barriers that are lower than the dehydrogenation step but higher than via Ph2CH2/H- transfer-mediated reaction. For small-pore zeolites, where large mols. like Ph2CH2 cannot be formed, they should be considered as optional routes for the transalkylation reaction
Originele taal-2Engels
TitelTransition state modeling for catalysis : developed from a symposium sponsored by the Division of Computers in Chemistry at the 215th National Meeting of the American Chemical Society, Dallas, Texas, March 29-April 2, 1998
RedacteurenD.G. Truhlar, K. Morukuma
Plaats van productieWashington, DC
UitgeverijAmerican Chemical Society
Pagina's307-320
ISBN van geprinte versie0-8412-3610-0
DOI's
StatusGepubliceerd - 1999
Evenementconference; National Meeting of the American Chemical Society ; 215 (Dallas, Tex.) : 1998.03.29-04.02; 1998-04-29; 1998-05-02 -
Duur: 29 apr 19982 mei 1998

Publicatie series

NaamACS Symposium Series
Volume721
ISSN van geprinte versie0097-6156

Congres

Congresconference; National Meeting of the American Chemical Society ; 215 (Dallas, Tex.) : 1998.03.29-04.02; 1998-04-29; 1998-05-02
Periode29/04/982/05/98
AnderNational Meeting of the American Chemical Society ; 215 (Dallas, Tex.) : 1998.03.29-04.02

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  • Citeer dit

    Blaszkowski, S. R., & Santen, van, R. A. (1999). Alkylation and transalkylation reactions of aromatics. In D. G. Truhlar, & K. Morukuma (editors), Transition state modeling for catalysis : developed from a symposium sponsored by the Division of Computers in Chemistry at the 215th National Meeting of the American Chemical Society, Dallas, Texas, March 29-April 2, 1998 (blz. 307-320). (ACS Symposium Series; Vol. 721). American Chemical Society. https://doi.org/10.1021/bk-1999-0721.ch024