Solid state NMR characterization of Sn-Beta catalysts

Abstract

High-resoln. multi-nuclear solid state NMR characterization has been performed to obtain insight into the mechanism of glucose reactions with Sn-beta zeolites. Glucose isomerization or epimerization reactions in water and non-aq. environments were examd. thoroughly, and correlations between catalyst structural changes and reaction selectivity were the primary focus in this study. In particular, we investigated local structural changes around the catalytically active Sn sites of ^(119)Sn-labeled beta zeolite in different states, including in their as synthesized form, after calcination in flowing air, after adsorption of sugar mols., and after performing catalytic reaction cycles. Magic angle spinning (MAS) and cross polarization (CP) (either from ^1H or ^(19)F) MAS ^(119)Sn NMR spectra provided insight into changes in local Sn coordination in the framework of zeolite beta under various conditions. Other NMR results, including ^(13)C NMR of adsorbed glucose or methanol, and ^(19)For ^(29)Si NMR of zeolite framework, will be used in interpretations of the catalytic reaction mechanisms.

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