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Titolo:
Characterization of the acid sites in MCM-41-type materials by spectroscopic and catalytic techniques
Autore:
Hunger, M; Schenk, U; Breuninger, M; Glaser, R; Weitkamp, J;
Indirizzi:
Univ Stuttgart, Inst Chem Technol 1, D-70550 Stuttgart, Germany Univ Stuttgart Stuttgart Germany D-70550 l 1, D-70550 Stuttgart, Germany
Titolo Testata:
MICROPOROUS AND MESOPOROUS MATERIALS
fascicolo: 2-3, volume: 27, anno: 1999,
pagine: 261 - 271
SICI:
1387-1811(199902)27:2-3<261:COTASI>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
MESOPOROUS MOLECULAR-SIEVES; LIQUID-CRYSTAL TEMPLATE; MAS NMR; ALUMINOSILICATE MCM-41; PROBE-MOLECULES; ZEOLITES; STATE; DISPROPORTIONATION; ETHYLBENZENE; METHANOL;
Keywords:
Bronsted acid sites; catalytic test reactions; FTIR spectroscopy; MCM-41; solid-state NMR spectroscopy;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Weitkamp, J Univ Stuttgart, Inst Chem Technol 1, D-70550 Stuttgart, Germany Univ Stuttgart Stuttgart Germany D-70550 Stuttgart, Germany
Citazione:
M. Hunger et al., "Characterization of the acid sites in MCM-41-type materials by spectroscopic and catalytic techniques", MICROP M M, 27(2-3), 1999, pp. 261-271

Abstract

Temperature-programmed desorption of pyridine, FTIR and multinuclear NMR spectroscopy and catalytic test reaction have been applied to investigate acid sites in mesoporous materials with silicon/aluminum ratios of 266 and 20and in an amorphous aluminosilicate with n(Si)/n(Al) = 5.4. The results obtained by these methods indicate the presence of weak Bronsted acid sites in the aluminosilicate samples. Based on the spectroscopic data, a model of Bronsted acid sites in the aluminum-containing MCM-41 is proposed which consists of silanol groups with 3-4 framework aluminum atoms in their local structure. In the dehydrated ammonium form of the mesoporous aluminosilicate,these framework aluminum atoms have a tetrahedral oxygen coordination. Deammoniation leads to a strong broadening of the Al-27 echo NMR signal due toframework aluminum atoms which indicates a variation of their local geometry and/or oxygen coordination. Al-27 echo NMR studies of calcined and subsequently reammoniated samples indicate that this variation in the bonding state of framework aluminum atoms is a reversible process. (C) 1999 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/12/20 alle ore 10:16:56