Solid State NMR Characterization of Sn-Beta Zeolites that Catalyze Glucose Isomerization and Epimerization

High resolution, multi-nuclear solid state nuclear magnetic resonance (NMR) characterizations are carried out in order to obtain insights into the structural features of Sn-beta zeolites that catalyze glucose isomerization or epimerization reactions in water and methanol solvents. In particular, we focus on investigating the local structural changes to catalytically-active framework Sn sites of different Sn-119-labeled beta zeolites, including the calcined, dehydrated, rehydrated, and post-sugar isomerization catalysis forms. Magic angle spinning (MAS) and cross polarization MAS (either from H-1 or F-19) Sn-119 NMR spectra provide evidence for changes to the local framework Sn coordination in the presence of water and sugar molecules, and provide insights into structural features of adsorbed intermediates that may be relevant in sugar isomerization reaction pathways.