Determination of gallium in H(Ga)ZSM5 zeolites by 71Ga MAS NMR spectroscopy

C.R. Bayense, A.P.M. Kentgens, J.W. Haan, de, L.J.M. Ven, van de, J.H.C. Hooff, van

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Abstract

The 71Ga and 129Si magic angle spinning(MAS) NMR and some 1H NMR (CRAMPS) investigations were carried out on H(Ga)ZSM5 zeolites. Quantification of the 71Ga NMR responses, obtained for the acid form of the zeolite, showed that .apprx.70 +- 2% of the theor. signal intensity was measured, based on the total Ga content of the samples. Only signals from tetrahedral Ga were obsd. in a reproducible manner. The lack of Ga NMR response, which is ascribed to the presence of large elec. field gradients on part of the Ga nuclei, was found to depend on the nature of the counter ion in the zeolite. Max. NMR signal intensities were obtained for Rb+- and Cs+-exchanged zeolites. A model to explain these phenomena is presented. The gallosilicates were thermally stable up as ?600 Deg but in the presence of steam a loss of framework Ga was obsd. at >550 Deg. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)775-782
JournalJournal of Physical Chemistry
Volume96
Issue number2
DOIs
Publication statusPublished - 1992

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