Properties of boron-substituted ZSM-5 and ZSM-11 zeolites

Using NMR and IR spectroscopy boron-substituted pentasil zeolites are found to contain four-coordinated B in the hydrated state and three-coordinated B in the dehydrated state. In addition a new tetrahedral B site assigned to (HO) 2B(H 2O)(OSi) was characterized by its NMR quadrupole coupling consta...

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Bibliographic Details
Published in:Journal of catalysis 1987-11, Vol.108 (1), p.1-14
Main Authors: Coudurier, G., Auroux, A., Vedrine, J.C., Farlee, R.D., Abrams, L., Shannon, R.D.
Format: Article
Language:English
Subjects:
Catalysis
Catalysts: preparations and properties
Catalytic reactions
Chemistry
Exact sciences and technology
General and physical chemistry
General. Nomenclature, chemical documentation, computer chemistry
Theory of reactions, general kinetics
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
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Summary:Using NMR and IR spectroscopy boron-substituted pentasil zeolites are found to contain four-coordinated B in the hydrated state and three-coordinated B in the dehydrated state. In addition a new tetrahedral B site assigned to (HO) 2B(H 2O)(OSi) was characterized by its NMR quadrupole coupling constant and asymmetry parameter. Ammonia adsorption microcalorimetry gave heats of adsorption of ~65 kJ/mol for HBZSM-11 and showed that B-substituted pentasils have only very weak acidity. Calcination at 800 °C increased the heat of NH 3 adsorption to ~170 kJ/mol by creation of strong Lewis acid sites. The lack of strong Brønsted acid sites in HBZSM-11 was confirmed by poor catalytic activity in methanol conversion and in toluene alkylation With methanol.
ISSN:0021-9517
1090-2694
DOI:10.1016/0021-9517(87)90150-3