INVESTIGATION OF CONFORMATIONAL CHANGES OF ORGANIC MOLECULES SORBED IN ZEOLITES BY HR MAS NMR SPECTROSCOPY

摘要

The application of ~1H NMR spectroscopy to the investigation of organic molecules sorbed in catalytic systems like zeolites is often limited due to the poor spectral resolution. During the last years a notable enhancement in resolution of the spectra is achieved when random local magnetic fields due to susceptibility effects are partially averaged out by the application of magic angle spinning techniques (MAS). High resolution (HR) MAS NMR spectroscopy is used to investigate the dynamics of olefinic hydrocarbons in NaX zeolites and their conformational changes in the adsorbed state. The high precision arrived in the measurements allows the determination of chemical shifts and coupling constants of ~1H NMR spectra in dependence on loading and temperature, which are used in order to get deeper insights into the dynamics of the adsorption process. In this paper for the first time conformational changes of adsorbed molecules could be investigated by means of HR MAS NMR spectroscopy.