On the mechanism of selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over supported Pt and Au catalysts

The mechanism of selective oxidation of aqueous 5-hydroxymethylfurfural (HMF) at high pH was studied over supported Pt and Au catalysts. Results from labeling experiments conducted with 18 O 2 and H 2 18 O indicated that water was the source of oxygen atoms during the oxidation of HMF to 2-hydroxymethylfurancarboxylic acid (HFCA) and 2,5-furandicarboxylic acid (FDCA), presumably through direct participation of hydroxide in the catalytic cycle. Molecular oxygen was essential for the production of FDCA and played an indirect role during oxidation by removing electrons deposited into the supported metal particles. A reaction path for HMF oxidation to FDCA was proposed. Isotopically-labeled reagents were used to show that hydroxide from liquid water was the source of oxygen added to HMF during oxidation over Pt and Au catalysts.