(41a) Keynote Speaker Abstract: Design of Hydrophobic Zeolites Containing Lewis Acid Active Sites for the Isomerization of Glucose In Aqueous Media

Davis, M. E., California Institute of Technology
Nikolla, E., California Institute of Technology
Moliner, M., Instituto de Tecnologia Quimica (UPV-CSIC)
Hwang, S., California Institute of Technology

We have reported that tin or titanium-containing zeolite beta catalysts (Sn-Beta or Ti-Beta) catalyze the isomerization of glucose to fructose in aqueous media at low pH in the presence of HCl and an inorganic salt (Proc. Natl. Acad. Sci., 107 (2010) 6164, ACS Catal, 1 (4), (2011) 408). Our current efforts are focused on obtaining a fundamental understanding of the nature of the active site in the Sn or Ti-Beta zeolite and the mechanism of the isomerization reaction of glucose to fructose. For example, we have utilized solid-state NMR experiments to probe the environment of tin in the zeolite.  Sn-Beta zeolite is synthesized with labeled Sn-119 in order to provide a solid that can be effectively analyzed by solid-state NMR. We have also performed NMR experiments with deuterated and C-13 labeled glucose to study the interactions of the reactant with the tin active site in the zeolite. Detailed kinetic studies including isotope-labeling experiments have been conducted in order to obtain kinetic parameters such as activation energies and rate limiting steps for the isomerization of glucose to fructose. An overall picture of the state of the tin active center and the reaction pathway is emerging. In this presentation, we will discuss the important features of the catalytic materials that are necessary for obtaining reactivity. Control of the zeolite hydrophobicity and framework localization of either the tin or titanium are critical to achieving activity when the reaction medium is water.