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Production of 5-Hydroxymethylfurfural from Glucose in Water by Using Transition Metal-Oxide Nanosheet Aggregates

Metal-oxide nanosheet aggregates were prepared by exfoliation and subsequent aggregation of layered metal oxides and used for the conversion of glucose to 5-hydroxymethylfurfural (HMF) in water. Three aggregated nanosheets, HNbWO6, HNb3O8, and HTiNbO5, yielded HMF in water at 393–413 K, whereas ion-exchange resins and H-form zeolites did not. The catalytic activity of the nanosheets decreased in the order HNbWO6 > HNb3O8 > HTiNbO5, which correlates with their acidity. The HNbWO6 nanosheets exhibited higher selectivity for HMF than niobic acid, and the selectivity was improved in the water–toluene biphasic system. The selectivity for HMF over HNbWO6 nanosheets was higher from glucose than from fructose. Kinetic analysis suggested that in addition to fructose, an intermediate species was involved in the reaction pathway of HMF production from glucose.