Production of 2,5-Furandicarboxylic Acid by Optimization of Oxidation of 5-Methyl Furfural over Homogeneous Co/Mn/Br Catalysts

In this contribution, readily available 5-methyl furfural (MF) derived from biomass was used as an excellent substitute of the chemically unstable 5-hydroxymethylfurfural (HMF) for preparing the commercial precursor 2,5-furandicarboxylic acid (FDCA). MF was catalytically oxidized by air into FDCA in acetic acid over homogeneous Co/Mn/Br catalysts at 130–170 °C. It was found that both the substitute reactivity and the ring chemical stability have a remarkable impact on the yield of aromatic dicarboxylic acids. The effects of reaction temperature, pressure, catalyst composition and concentration, water concentration in the solvent, and substrate/solvent mass ratio on both the main reaction and the side reaction were investigated systematically and thoroughly using HPLC and an online tail gas monitoring system. Under optimized conditions, the oxidation of MF gave 100% conversion of MF and 75.8% yield of FDCA with 99.6% purity. It was also proven that the addition of 200 ppm cerium could work well at low temperatures (130–140 °C) for enhancing FDCA selectivity via suppressing the side reactions.