Catalytic transformations of biomass are becoming increasingly important for the sustainable production of chemicals. Gluconic acid, the product of selective oxidation of glucose, is widely used e.g. as a food additive, in pharmaceuticals and as chelating agent in detergents. However, the current commercial methods produce gluconate salts instead of the free acid. Therefore, there is great interest in developing methods for the direct production of gluconic acid.Gold nanoparticle catalysts are highly efficient catalysts for the oxidation of glucose in mildly alkaline conditions. Under acidic conditions however, deactivation of the catalysts has been reported, leading to significantly decreased activity and low conversion. Here, we present an efficient method for producing gluconic acid with high selectivity by microwave-assisted base-free oxidation of glucose over gold catalysts. The oxidation of glucose was studied using gold nanoparticles supported on metal oxides. Microwave heating (80-120 �) was applied on the reaction, and hydrogen peroxide was used as the oxidant. In only 10 minute reaction, gluconic acid was produced with 75 % yield and over 90 % selectivity using 0.1 mol % of Au. 1H-NMR analysis confirmed the formation of free gluconic acid in the reaction. No deactivation of the catalyst was detected upon recycling. The TOF values measured herein represent the highest observed in base-free oxidation of glucose up to date.

Microwave-assisted base-free oxidation of glucose on gold catalysts

248th National Meeting (2014)

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