APPLICATION OF XE-129 2D-EXSY NMR TO INTRAPARTICLE AND INTERPARTICLE EXCHANGE IN ZEOLITES

2D-EXSY NMR methods were used to explore diffusion between different d omains in zeolites on two very different length scales. Measurements w ere made on xenon-containing samples consisting of a mixture of NaX an d NaY zeolite particles which give distinct resonance lines. The cross peaks observed were interpreted in terms of interparticle exchange, a nd exchange rates were measured as a function of particle size. This k ind of experiment with a length scale of microns to mm should be usefu l in model studies of diffusion in packed catalyst beds. Measurements also were made to study exchange on a much smaller length scale betwee n the main-channel and side-pocket sites in samples of microcrystallin e Na-mordenite. Exchange rates and site occupancies were measured as a function of temperature, yielding activation energies for xenon desor ption and intersite diffusion. Also, information was obtained on the d istribution of inequivalent side-pocket sites which leads to the large xenon NMR linewidths for this type of site.