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Titolo:
Influence of alkali and alkaline earth cations on the Bronsted acidity of zeolites
Autore:
Vayssilov, GN; Rosch, N;
Indirizzi:
Tech Univ Munich, Inst Phys & Theoret Chem, D-85747 Garching, Germany TechUniv Munich Garching Germany D-85747 hem, D-85747 Garching, Germany Univ Sofia, Fac Chem, BU-1126 Sofia, Bulgaria Univ Sofia Sofia Bulgaria BU-1126 fia, Fac Chem, BU-1126 Sofia, Bulgaria
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 19, volume: 105, anno: 2001,
pagine: 4277 - 4284
SICI:
1520-6106(20010517)105:19<4277:IOAAAE>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
DENSITY-FUNCTIONAL CALCULATIONS; PROTON AFFINITY; EXCHANGED ZEOLITES; ALUMINUM CONTENT; METAL-CATIONS; HETEROGENEITY; CHEMISTRY; FAUJASITE; CLUSTER; SITES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
32
Recensione:
Indirizzi per estratti:
Indirizzo: Vayssilov, GN Tech Univ Munich, Inst Phys & Theoret Chem, D-85747 Garching, Germany Tech Univ Munich Garching Germany D-85747 arching, Germany
Citazione:
G.N. Vayssilov e N. Rosch, "Influence of alkali and alkaline earth cations on the Bronsted acidity of zeolites", J PHYS CH B, 105(19), 2001, pp. 4277-4284

Abstract

We report a computational study on how alkali and alkaline earth metal cations affect the Bronsted acidity of a bridging OH group in their close vicinity. The zeolite fragment is modeled as a six-ring of faujasite structure which contains two or three aluminum centers. The calculations show that charge compensation by alkali or alkaline earth metal cations decreases the deprotonation energy (DE) of the bridging OH group relative to the completely protonic forms of the clusters; i.e., mixed forms of zeolites which contain both protons and metal cations for charge compensation exhibit sites that are more acidic than the corresponding pure protonic forms. The strongestdecrease in DE is found for calcium and sodium exchanged model clusters. An analysis of the properties of the bridging OH groups and the trends in calculated DE values reveals that the contribution of the metal cation to thestabilization of the deprotonated form of the cluster is important for thereduction of DE of the considered bridging OH group. We also discuss the influence of the metal cations on the core level shifts of the zeolite oxygen centers.

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Documento generato il 08/04/20 alle ore 12:13:37