2,6-dimethylpyridine as a probe of the strength of Brønsted acid sites: study on zeolites. Application to alumina

The positions of nu8a and nu*(NH) bands in the spectrum of protonated 2,6-dimethylpyridine vary with the strength of Brønsted acidity: the higher the nu*(NH) wavenumber and the lower the nu8a wavenumber, the stronger the acidity. The results obtained with 2,6-dimethylpyridine adsorption correlate wi...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2005-04, Vol.7 (8), p.1861-1869
Main Authors: OLIVIERO, Laetitia, VIMONT, Alexandre, LAVALLEY, Jean-Claude, SARRIA, Francisca Romero, GAILLARD, Marina, MAUGE, Francoise
Format: Article
Language:English
Subjects:
Acids - chemistry
Adsorption
Aluminum Oxide - chemistry
Chemistry
Exact sciences and technology
General and physical chemistry
Ion-exchange
Pyridines - chemistry
Spectroscopy, Fourier Transform Infrared
Surface physical chemistry
Zeolites - chemistry
Zeolites: preparations and properties
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Summary:The positions of nu8a and nu*(NH) bands in the spectrum of protonated 2,6-dimethylpyridine vary with the strength of Brønsted acidity: the higher the nu*(NH) wavenumber and the lower the nu8a wavenumber, the stronger the acidity. The results obtained with 2,6-dimethylpyridine adsorption correlate with those obtained by CO adsorption experiments on a series of faujasite zeolites (LiHNaY, KHNaY, HY, HY(SA), HNaX). These relations were extended to gamma-Al2O3 having weak Brønsted acidity, not detected by pyridine and hardly detected by CO. The number (0.1 per nm2) and the strength (corresponding to delta nu (OH) by CO = 155 cm(-1)) of the most acidic OH groups of Al2O3, as well as the position of the corresponding nu (OH) band (
ISSN:1463-9076
1463-9084
DOI:10.1039/b500689a