Base-free oxidative esterification of 5-hydroxymethylfurfural to furan-2,5-dimethylcarboxylate over n-doped carbon-supported Co/Fe bimetallic catalyst under batch-operation or continuous-flow conditions

Developing an efficient and easily available catalyst for the selective conversion of biomass-derived 5-hydroxymethylfurfural (HMF) into furan-2,5-dimethylcarboxylate (FDMC), a valuable biomass-based monomer, remains a high demand but formidable challenge. Herein, a facile strategy for the synthesis of N-doped carbon-supported Co/Fe bimetallic catalyst (CoFe-NC) was developed, which provided an outstanding FDMC yield of 93% in a batch reactor (base-free, 80 °C, 2 bar O2, 4 h). Interestingly, CoFe-NC also gave a high FDMC yield of 91% under continuous-flow conditions for 80 h (5 bar O2, 80 °C, GHSV 1320 h−1, LHSV 0.6 h−1, base-free). Notably, it is the first time that a non-noble catalyst gave such a high FDMC yield under continuous-flow conditions. The introduction of Fe could greatly improve both the electron intensity of Co-Nx species and basicity of the catalyst, which endowed CoFe-NC with improved O2 activation capacity and enhanced dehydrogenation activity for the oxidation-esterification of HMF. This work delineates the efficient strategy on the construction of N-doped carbon-supported non-noble catalyst, which might open a new avenue for developing highly efficient catalyst for FDMC production.