Base-free Air Oxidation of Chitin-derived Glucosamine to Glucosaminic Acid by Zinc Oxide-supported Gold Nanoparticles

Graphical Highly-valued glucosaminic acid was produced by the oxidation of chitin derived glucosamine under ambient air and base-free conditions. In this study, glucosaminic acid (GlcNA) was produced with the highest yield of ∼85% from chitin biomass-derived glucosamine (GlcN) at 35 °C under atmospheric air in water, by using zinc oxide-supported gold nanoparticles (Au/ZnO). The Au/ZnO catalyst prepared by the deposition-precipitation (DP) method displayed remarkably superior catalytic performance to that prepared by the deposition-reduction (DR) method, which led to >2-fold enhancement in product yield. A lower apparent activation energy (E a ) was observed over the Au/ZnO (DP) for GlcNA formation compared with the Au/ZnO (DR) catalyst. Based on control tests and structural characterizations, the average particle size of Au nanoparticles (NPs) and the surface oxygen vacancy (O V ) sites were the crucial factors on the catalytic activity. The work puts forward a green, mild and efficient approach to synthesize valuable amino acid from ocean-based chitin biomass resources with air as the oxidant, adding on new possibilities of chitin biorefinery.