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The many roles of alkali metal-oxygen phases as catalyst components and promoters motivated a survey of the NMR properties of these compounds. Solid state 7 Li, 23 Na, 39 K, 87 Rb, and 133 Cs magic angle spinning NMR spectra are reported for the following alkali metal oxides, peroxides and superoxides:

Proximal sites consisting of a divalent metal cation as a hydroxide and/or oxide and an anion site in the zeolite framework are very active for the conversion of methyl halides to ethylene. These studies further support the effects of zeolite framework and halide leaving-group stability reported previously (/. Am. Chem. Soc. 1993,115,4732-4741) and demonstrate multiple roles for divalent metal sites. Whereas the basic zeolite CsX converted methyl iodide to hydrocarbons at temperatures as low as 498 K, this reaction commenced at 248 K on the multifunctional catalyst ZnX. The orders of activity Zn2+ > Cd2+ and Mg2+ > Ba2+ suggest that Lewis acidity is one of these roles. Zeolite CuY is very selective for ethylene formation. These reactions were studied by in situ 13C solid-state NMR, by in situ FTIR spectroscopy with a flow cell, and with conventional flow reactors. The active sites of ZnZSM-5 were also probed with solid-state NMR. The first intermediate is a framework-bound methoxy group. The 13C NMR and FTIR properties of this species have been correlated, and it is shown that this species is very similar or identical to that observed during methanol to gasoline chemistry. A detailed mechanism is proposed for the reaction of methyl halides on Zn and Mg zeolites that includes several explicit roles for the metal.

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