Glucose to fructose isomerization over solid oxide catalysts

High yield routes for biomass to commodity chemicals and fuels via HMF or levulenic acid have been developed for fructose, other sugars, and polyols, but overall yields remain low starting from glucose. Isomerization of glucose to fructose is one route to improving yields, but immobilized enzymes may be impractical for commodity chemicals and fuels, and dilute acids can lead to mass loss as humins. Recently, large pore Ti- and Sn-substituted zeolites have been reported to convert glucose to fructose or methyl lactate. In this study, we describe glucose to fructose isomerization over solid Bronsted and Lewis acid oxide catalysts. Results show a small population of active, but unselective isomerization sites, and titrating away such sites with metal halides moderate catalyst reactivity. Isomerizations are run in water or methanol, 100-160°C, in glass batch reactors, and analysis by GC or HPLC. Catalyst characterization includes TEM, TGA, DRUV-vis, and N₂ physisorption.