Efficient Epimerization of Glucose to Mannose over Molybdenum-Based Catalyst in Aqueous Media

Herein, the high activity and selectivity of activated carbon-supported molybdenum oxide catalysts (Mo/AC) in the epimerization of glucose to mannose is described. The catalysts afforded near-equilibrium glucose conversion (29.2%) and selectivity (94.5%) toward mannose in the epimerization of glucose. The catalysts were characterized by X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. It was found that the Mo/AC catalysts were mainly composed of highly dispersed MoO2 and MoO3 species. Compared to the soluble MoO3 catalyst, Mo/AC showed higher stability and better catalytic performances in the epimerization of glucose to mannose. Further, the deactivation of Mo/AC catalysts was attributed to the leaching of molybdenum oxides. Isotope labeling experiments revealed that the deuterium atom at the C-1 position of mannose is formed by glucose-D2 epimerization.