QUANTIFICATION OF BRONSTED ACIDITY IN MORDENITES

FTIR and NMR spectroscopy have been applied to quantification of Brons ted acid sites in various mordenite samples. A standardised deconvolut ion procedure has been developed for reliable decomposition of the com plex hydroxyl region in the infrared spectra of mordenites into high f requency and low frequency peaks, and the peak extinction coefficients have been determined. As a result, the overall number of Bronsted aci d sites, their distribution between main channels and side pockets, an d the amount of extraframework aluminium can be determined, Results ob tained by both FTIR and NMR are in good agreement and support each oth er. For instance, it is shown that for fully exchanged H-MOR, the dist ribution of Bronsted hydroxyls between main channels and side pockets is approximately 2:1. On partial ion exchange Na-MOR --> HNa-MOR, prot ons are first introduced into main channel sites, with Na remaining in the side pockets. (C) 1997 Academic Press.