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

Journal Article · Thu Jan 14 04:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100104a028· OSTI ID:6486660

Sonnemans, M H.W.; Heijer, C den; Crocker, M ^[1]

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1. Koninklijke/Shell-Laboratorium, Amsterdam (Netherlands)

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.

• OSTI ID: 6486660
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:2; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ALUMINIUM
BROENSTED ACIDS
CALCINATION
CHEMICAL REACTIONS
DECOMPOSITION
ELEMENTS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MATHEMATICAL MODELS
METALS
MINERALS
MORDENITE
POTENTIOMETRY
PYROLYSIS
SILICATE MINERALS
SPECTROSCOPY
THERMOCHEMICAL PROCESSES
TITRATION
ZEOLITES