Xe-129 NMR investigations for the textural characterization of sol-gel derived amorphous microporous silica

The aim of this work was to evaluate the potentialities of Xe-129 NMR as an innovative technique for the textural characterization of microporous amor phous materials. We applied this technique to a series of sol-gel derived m eso- and microporous silica materials with relatively narrow pore size dist ributions. The study of the Xe chemical shifts (delta(Xe)) as a function of the Xe pressure (P-Xe) is classically used to extrapolate delta(Xe) to zer o xenon loading. This parameter can be related to the mean sample pore size using models which cannot however be considered as generally applicable fo r every type of material. In this study, several original results related t o the NMR line shapes and to the slopes, s(Xe), of the lines delta(Xe) = f( P-Xe) have been obtained. NMR data have been interpreted on the basis of th e sample textural characteristics determined by N-2 adsorption. Extension o f the results to other microporous materials such as zeolites has also been , considered. The results showed that s(Xe) is a useful parameter which can be related to the pore hydraulic radius of the different amorphous and zeo litic microporous materials investigated.