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129Xe-n.m.r. study of rare earth-exchanged Y zeolites

✍ Scribed by Q.J. Chen; T. Ito; J. Fraissard

Publisher: Elsevier Science
Year: 1991
Tongue: English
Weight: 444 KB
Volume: 11
Category: Article
ISSN: 0144-2449
DOI: 10.1016/s0144-2449(05)80225-8

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✦ Synopsis

The dehydration of RENaY, where RE --La 3÷ and Ce 3+, has been studied by the 129Xe n.m.r, technique. The [RE (OH)=] {3-')+ cations migrate from the supercages toward the prisms and sodalite cages when x = 0 for La 3+ and x = 0 or 1 for Ce 3+. The chemical shift bs.RE of the xenon adsorbed by the totally dehydrated REY samples, obtained by extrapolating the asymptote of 6 = f[Xe] to [Xe] = 0 is less than that of NaY. A model for the redistribution of the lattice charges is proposed to explain the hydrothermal stability of these zeolites. Study of the rehydration process has demonstrated that these samples are more hydrophobic and that, in the presence of water vapor at 25°C, the migration of these cations toward the supercages is very slowly reversible.

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