Acidity of dealuminated mordenites studied by infrared spectroscopy
- 1 January 1983
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 79 (4) , 805-813
- https://doi.org/10.1039/f19837900805
Abstract
The hydroxy groups of dealuminated mordenites having SiO2/Al2O3 molar ratios 14–44 have been studied by means of infrared spectroscopy. The intensity of the low-frequency (3609 cm–1) band decreases with increasing the SiO2/Al2O3 ratio and the intensity of the high-frequency (3738 cm–1) band increases. Using pyridine as adsorbate the acidity of this mordenite series has been determined and it was found that on dealumination the number of strong acid sites increases with a simultaneous decrease of the total number of acid sites. The SiOH groups which are formed during dealumination increase the strength of the remaining acid sites. A band at 1462 cm–1 is observed after pyridine desorption at ca. 673 K and is assigned as a characteristic band of pyridine adsorbed on stronger Lewis sites. Increased dealumination renders the Brönsted sites more accessible to pyridine at lower temperatures.Keywords
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