XE-129 NMR-STUDY OF Y3-EXCHANGED, LA3+-EXCHANGED, AND CE3+-EXCHANGED X-ZEOLITES()

The Xe-129 n.m.r. spectrum of adsorbed xenon has been used to locate t he Y3+, Ce3+, and La3+ ions that are exchanged into NaX zeolite. The c hemical shift of xenon adsorbed on yttrium-X zeolite follows a concave plot against the adsorbed xenon concentration, very similar to the pr evious Xe-129 n.m.r. study of Mg2+, Ca2+, and Ni2+ in Y zeolites. This result suggests strong adsorption of xenon on the Y3+ ion located ins ide the zeolite supercage. In contrast, the Xe-129 n.m.r. chemical shi ft for the CeX and LaX zeolites indicates that the cations are located in hexagonal prisms or sodalite cages inaccessible to the xenon atoms . The example of the Y3+ cation proves that not all trivalent cations migrate outside the supercages during thermal treatment of the solid.