Advancements in biomass conversion: Copper-catalyzed anaerobic dehydrogenation of 5-hydroxymethylfurfural to 2,5-diformylfuran

Developing cost-effective and inherently safe methods for accelerating the sustainable production of value-added chemicals from biomass presents a promising solution to the current energy crisis. This study introduces heterogeneous copper species anchored on a γ-Al2O3 catalyst (Cu/γ-Al2O3) with high dispersibility and small Cu particle size, synthesized via a straightforward incipient-wetness impregnation method. This method facilitates the selective anaerobic dehydrogenation of 5-hydroxymethylfurfural (HMF) into 2,5-diformylfuran (DFF) in the absence of any oxidant or hydrogen acceptor. An HMF conversion of 69.8 % and a DFF yield of 44.9 % were attained at 130 °C over a 12-h period. Extensive characterizations were conducted to elucidate the correlation between the catalyst's structure and its dehydrogenation activity. The findings indicated that strong L-acid sites, elevated Cu dispersions, small Cu particle size and an increased number of Cu+ active sites were conducive to enhanced dehydrogenation reactivity. The Cu/γ-Al2O3 catalyst demonstrated superior catalytic efficiency and stability. A possible reaction mechanism is suggested, integrating DFT calculations with experimental observations. This research offers valuable insights into the selective conversion of HMF to DFF and encourages further exploration into the dehydrogenation of biomass alcohols into high-value chemicals under oxidant-free conditions.