Selective conversion of aqueous glucose to value-added sugar aldose on TiO2-based photocatalysts

We describe here a photocatalytic process for direct conversion of glucose to value-added chemicals (arabinose and erythrose) and H-2 in water under mild reaction conditions without additional acid or base. The total selectivity for the production of arabinose and erythrose on rutile TiO2-based photocatalyst reaches 91% at 65% conversion. More importantly, it has been demonstrated for the first time that the photodegradation of glucose initially involves C1-C2 bond cleavage (alpha-scission) to produce arabinose in the presence of water as solvent. To unravel the high selectivity on rutile TiO2, EPR and glucose reaction were carried out on rutile TiO2 in the presence of H2O2. It was found that the selectivity of the products is mainly dependent on the reactive oxygen species: the hydroxyl radicals ((OH)-O-center dot) may lead to low selectivity, while the peroxy species lead to a high selectivity. The advantages of the photocatalytic approach for conversion of biomass to value-added chemicals include (1) operation at low reaction temperature, (2) benign environmental effects due to using only water as both solvent and oxidant precursor, and (3) being wasteless due to high selectivity with H-2 as the by-product. (c) 2014 Elsevier Inc. All rights reserved