Oxidation of Glucose Using Mono- and Bimetallic Catalysts under Base-Free Conditions

Oxidation of glucose to gluconic and glucaric acid using molecular O-2 in aqueous solution is an environmentally friendlier alternative to the conventional method, which uses nitric acid as the oxidant. However, obtaining a satisfactory yield of the desirable product, glucaric acid, especially under base-free conditions, is still a challenge. In this paper, optimization of Pt-based mono- and bimetallic catalysts is reported by tuning four factors: support type, synthesis method, reductant used in the synthesis, and choice of the second metal. All four of these factors influence the glucaric acid selectivity. Among the tested combinations, the Pt-Cu/TiO2 bimetallic catalyst showed similar to 60% glucaric acid selectivity in one-step glucose oxidation under base-free conditions at 90 degrees C and 15 bar O-2. The catalyst consists of Pt metal particles (similar to 2.8 nm diameter on average) with a dominant presence of the alloyed Pt-Cu phase, as confirmed by X-ray diffraction and transmission electron microscopy analyses. These results provide valuable insights for the rational design of glucose oxidation catalysts.