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Titolo:
Protonation of an H2O dimer by a zeolitic Bronsted acid site
Autore:
Zygmunt, SA; Curtiss, LA; Iton, LE;
Indirizzi:
Valparaiso Univ, Dept Phys & Astron, Valparaiso, IN 46383 USA Valparaiso Univ Valparaiso IN USA 46383 Astron, Valparaiso, IN 46383 USA Argonne Natl Lab, Div Chem, Argonne, IL 60439 USA Argonne Natl Lab Argonne IL USA 60439 ab, Div Chem, Argonne, IL 60439 USA Argonne Natl Lab, Div Sci Mat, Argonne, IL 60439 USA Argonne Natl Lab Argonne IL USA 60439 Div Sci Mat, Argonne, IL 60439 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 15, volume: 105, anno: 2001,
pagine: 3034 - 3038
SICI:
1520-6106(20010419)105:15<3034:POAHDB>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
HYDROGEN-BONDED COMPLEXES; DENSITY-FUNCTIONAL THEORY; AB-INITIO CALCULATIONS; MOLECULAR ADSORPTION; WATER-ADSORPTION; CLUSTER-MODELS; H-ZSM-5; GAUSSIAN-2; IR; CATALYSTS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
29
Recensione:
Indirizzi per estratti:
Indirizzo: Zygmunt, SA Valparaiso Univ, Dept Phys & Astron, Valparaiso, IN 46383 USA Valparaiso Univ Valparaiso IN USA 46383 paraiso, IN 46383 USA
Citazione:
S.A. Zygmunt et al., "Protonation of an H2O dimer by a zeolitic Bronsted acid site", J PHYS CH B, 105(15), 2001, pp. 3034-3038

Abstract

The potential energy surface for the interaction of a water dimer with theBronsted acid site in a zeolite represented by a Si4AlO4H13 cluster is examined using the B3LYP density functional method. Local energy minima corresponding to both neutral and ion-pair adsorption structures were located, aswell as the transition state for proton transfer to the dimer. The neutralcomplex is more stable than the ion-pair structure by 2.9 kcal/mol.at the highest level of calculation. In all structures both ends of the adsorbed species form hydrogen bonds (H . . .O) to the zeolitic cluster. The zero point energy corrections cause the energy of the ion-pair structure to rise above that of the transition state, indicating that the ion-pair structure isnot a true local energy minimum on the potential energy surface. These results reveal that, like the protonated water monomer complex, the protonatedwater dimer complex is a transition state for proton exchange between adjacent framework oxygen atoms in our cluster model of the zeolite. However, since the energy differences between the three structures investigated here are so small, the protonated water dimer might possibly be a true equilibrium structure for a particular zeolite framework. The calculated vibrationalfrequencies for the adsorbed complexes are compared with experimental infrared spectra. This comparison suggests that experimental spectra for zeolite-water systems with loadings of two or more water molecules per acid site are a superposition of features from both neutral and ion-pair-water complexes. This interpretation is consistent with the calculated energies of the two complexes.

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Documento generato il 05/12/20 alle ore 13:46:23