ULTRA-HIGH-RESOLUTION SI-29 SOLID-STATE MAS NMR INVESTIGATION OF SORBATE AND TEMPERATURE-INDUCED CHANGES IN THE LATTICE STRUCTURE OF ZEOLITE ZSM-5

By preparing extremely highly crystalline, highly siliceous samples and careful optimization of all experimental parameters, it is possible to obtain **2**9Si MAS NMR spectra of zeolite ZSM-5 with line widths of 0. 06 ppm (6 Hz) at a proton frequency of 400 MHz, yielding a spectrum for the unloaded form in which up to 21 of the 24 resonances can be observed giving an unambiguous analysis. This ultra-high resolution makes it possible to clearly observe changes induced in the lattice structure by both temperature and the presence of organic sorbates. The change between the monoclinic (24 T -atoms) and orthorhombic (12 T-atoms) forms occurs between 355 and 357 degree C and in the case of p-xylene at approximately two molecules per 96 T atom unit cell.