Selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over MnOx–CeO2 composite catalysts†
The selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) has attracted much attention recently, as FDCA could be used as a polymer precursor to produce recyclable bio-based polymers. But most studies focused on the design of noble metal catalysts for the efficient oxidation of HMF to FDCA, here, non-noble metal catalysts, MnOx–CeO2 mixed oxides, were prepared by a co-precipitation method and used in the direct aerobic oxidation of HMF to FDCA. As high as 91% yield of FDCA was achieved over the MC-6 (Mn/Ce = 6) catalyst and the catalyst can be reused five times without much loss of catalytic activity, this is the best result for non-noble metal catalyzed HMF oxidation to FDCA in the aqueous phase. Structural analysis revealed that surface Mn4+ ions are the active sites and play key roles for the oxidation of HMF in the absence of noble metals. In addition, the reaction mechanism over the MnOx–CeO2 catalyst was also proposed based on the synergistic interaction between Mn and Ce oxides.