XE-129 NMR INVESTIGATION OF ETS-10 TITANOSILICATE MOLECULAR-SIEVES

A newly discovered large-pore titanosilicate molecular sieve, ETS-10, has found increasingly important commercial use such as a desiccant in chlorofluorocarbon-free air conditioners. Its useful properties are d ue to unique three-dimensional channel structure and charge distributi on in the material. Although the framework structure of Na-ETS-10 was established recently; the effect of cations on the local pore structur e remains to be described. This issue is systematically investigated a s a function of proton exchange in the present work using Xe-129 NMR s pectroscopy. Different from the behaviors of conventional zeolites suc h as Y and ZSM-5, the ''porosity'' of ETS-10 is significantly affected by proton exchange: the effective ''pore'' diameter and Xe uptake are both reduced due to the formation of defects in 12-member ring channe ls. Xe adsorption isotherms reveal that energetically different adsorp tion sites coexist in the 12-member ring channels of Na-ETS-10. Proton exchange reduces the difference by proton delocalization.