Studies on the acidity of mordenite and ZSM 5. 2. Loss of Broensted acidity by dehydroxylation and dealumination

Autor:	C. Den Heijer, M. Crocker, M. H. W. Sonnemans
Rok vydání:	1993
Předmět:	Chemistry Inorganic chemistry General Engineering Infrared spectroscopy Molecular sieve Chemical reaction Mordenite law.invention law Titration Calcination Physical and Theoretical Chemistry ZSM-5 Zeolite
Zdroj:	The Journal of Physical Chemistry. 97:440-445
ISSN:	1541-5740 0022-3654
DOI:	10.1021/j100104a028
Popis:	Quantitative determination of Broensted acid site concentrations in calcined H-mordenite and H-ZSM-5 by means of conductometric titration and infrared spectroscopy reveals that the concentration of Broensted acid sites present is lower than would be expected on the basis of the aluminum content. This discrepancy is attributed to dealumination and dehydroxylation processes occurring during calcination. A model is proposed according to which the degree of these processes strongly depends on the concentration of vicinal aluminum T sites in the zeolite: Broensted acid sites associated with these T sites are lost, and the remaining Broensted acidity is related to the concentration of the (remaining) isolated aluminum T sites. This model quantitatively correlates the experimentally determined concentration of Broensted acid sites with the concentration of isolated aluminum T sites. 33 refs., 4 figs., 2 tabs.
Databáze:	OpenAIRE
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