Efficient base-free oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over copper-doped manganese oxide nanorods with tert-butanol as solvent

2,5-Furandicarboxylic acid (FDCA) is an important and renewable building block and can serve as an alternative to terephthalic acid in the production of bio-based degradable plastic. In this study, Cu-doped MnO2 nanorods were prepared by a facile hydrothermal redox method and employed as catalysts for the selective oxidation of 5-hydroxymethylfurfural (HMF) to FDCA using tert-butyl hydroperoxide (TBHP) as an oxidant. The catalysts were characterized using X-ray diffraction analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The effects of oxidants, solvents, and reaction conditions on the oxidation of HMF were investigated, and a reaction mechanism was proposed. Experimental results demonstrated that 99.4% conversion of HMF and 96.3% selectivity of FDCA were obtained under suitable conditions, and tert-butanol was the most suitable solvent when TBHP was used as an oxidant. More importantly, the Cu-doped MnO2 catalyst can maintain durable catalytic activity after being recycled for more than ten times.