Selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Au/CeO2 catalysts: the morphology effect of CeO2

Abstract

5-Hydroxymethylfurfural (HMF) which is derived from cellulosic biomass is an important platform for value added downstream chemicals and fuels via diversified processes. Nanoceria rods, cubes and octahedra were synthesized by a hydrothermal method and used as supports for preparing Au/CeO₂ catalysts via deposition–precipitation. The morphology effect of CeO₂ in the Au/CeO₂ catalysts was investigated in selective oxidation of HMF to 2,5-furandicarboxylic acid (FDCA). The Au/CeO₂-rod was more efficient for the oxidation of HMF and the TOF value of Au/CeO₂-rod was 6.3 (min⁻¹), which was 7 times as high as that of Au/CeO₂-cube (0.9 min⁻¹) and 32 times as high as that of Au/CeO₂-oct (0.2 min⁻¹). The experimental results and catalyst characterization implied that the oxygen vacancies on the Au–CeO₂ interface determined the catalytic activity by affecting the size, and valence of Au and the interfacial acidic properties. The Au/CeO₂-rod with the highest oxygen vacancies presented the higher proportion of cationic gold and more interfacial Lewis acidic sites between ceria and Au nanoparticles. Moreover, a synergistic effect between the interfacial Lewis acid, homogeneous base and neighboring Au particles promoted the oxidation reaction via efficiently activating the hydroxyl, aldehyde and molecular O₂.