2,6-Dimethylpyridine has been adsorbed on different samples of γ-Al2O3, fluorinated γ-Al2O3, and decationated Y zeolites. The ir spectra of the adsorbed base have been obtained after desorption at different temperatures. It has been shown that the 2,6-dimethylpyridine cannot differentiate among different types of Lewis sites (Na+, tricoordinated aluminum, AlO+, etc.). The 1618-cm−1 absorption band appearing in γ-Al2O3 is related to weak Brønsted sites, and its frequency increases when the acid strength is increased by fluorination. This band has not been observed on NaHY zeolites for which the Brønsted acid strength is higher.
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