Heterogeneous Catalysis for Aerobic Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid under Base‐Free Conditions

Abstract 2,5‐Furandicarboxylic acid (FDCA) is a biomass‐derived monomer for the production of poly(ethylene 2,5‐furandicarboxylate) (PEF), which is a novel polyester that can serve as a sustainable alternative to traditional petroleum‐based poly(ethylene terephthalate) (PET). Currently, the industrial production of FDCA depends on the thermo catalytic aerobic oxidation of 5‐hydroxymethylfurfural (HMF) using heterogeneous catalysts in aqueous solution, in which process equivalent homogeneous bases are usually needed to promote the oxidation of hydroxymethyl and aldehyde groups and simultaneously improve the solubility of oxidative products via forming carboxylate. The involvement of massive base causes risks of equipment corrosion and necessitates subsequent product separation and purification with a large amount acid. In this context, the base‐free aerobic oxidation of HMF to FDCA has attracted much concern. Nowadays, by developing supported catalysts with multiple catalytic sites, using diluted substrate and finding good solvent for FDCA, much progress has been achieved in this field. This review provides the state of the art of the heterogeneous catalysis for aerobic oxidation of HMF to FDCA under base‐free conditions, highlighting the catalytic mechanism to shed light on the catalyst design principles.