14-O-02-17O NMR studies of the structure and basic properties of zeolites

Publisher Summary This chapter presents the double orientation rotation (DOR) and multiple quantum magic angle spinning (MQMAS) nuclear magnetic resonance (NMR) techniques, which are applied in the high field of 17.6 T to the study of several oxygen-17 enriched zeolites with the ratio silicon/aluminum (Si/Al) = 1. The tendency that the isotropic chemical shift of the 17 O NMR decreases with increasing bond angle (or s-character of the oxygen hybrid orbital) is confirmed by this study. A linear correlation exists for the oxygen sites in the zeolites A and LSX if the data are limited to the sodium form of the hydrated zeolites. Ion exchange of the hydrated zeolites generates strong chemical shift effects. The increase of the basicity of the oxygen framework of the zeolite LSX is reflected by a downfield shift of ca. 10 parts per million (ppm) going from the lithium to the cesium form. The substitution of sodium by thallium in the zeolite A causes a shift of 34 ppm for the O3 signal.