(735c) Probing Reactions at the Solid-Liquid Interface By Operando Solid-State NMR Spectroscopy

Scott, S. L., University of California, Santa Barbara
Qi, L., University of California
Hoyt, D. W., Pacific Northwest National Laboratory
Walter, E. D., Pacific Northwest National Laboratory
Washton, N. M., Pacific Northwest National Laboratory
Foston, M., Georgia Institute of Technology
Chamas, A., University of California
Reactions of biomass-derived carbohydrates and phenolics in porous catalysts take place at solid-liquid interfaces where the local composition of the fluid phase can be very different from that of the bulk solution. Many such reactions take place in semi-aqueous solvent mixtures whose micro-heterogeneity is enhanced inside the catalyst pores. Solid-state NMR spectroscopy can probe molecular dynamics at solid-liquid interfaces, however, the demanding reaction conditions used in hydrothermal biomass transformations are particularly challenging for NMR methods. Customized chemically-resistant high pressure rotors were adapted to withstand elevated temperatures and pressures. Magic-angle-spinning spectra were recorded to monitor the populations of adsorbed molecules and measure the kinetics of their transformations. Examples involving glucose-fructose isomerization in basic zeolites and hydrogenolysis of aryl ethers will be presented, in which selective isotope labeling (13C, 2H) was used to enhance sensitivity and provide mechanistic information.