Assessment of Different Niobium-Based Catalytic Systems for 5‑Hydroxymethylfurfural Production from Glucose and...

This study investigates the production of 5-hydroxymethylfurfural (HMF) from glucose and microcrystalline cellulose using niobium-based catalytic systems in acetone/water media, under short reaction times. Three catalytic strategiesindividual, hybrid, and impregnatedwere evaluated by combining niobium pentoxide (Nb₂O₅) or niobium phosphate (NbOPO₄) with phosphotungstic acid (HPW), in both powder and pellet forms. Among these systems, NbOPO₄ powder exhibited the best performance for glucose conversion, achieving a yield of 38.5% and a volumetric rate of 26.9 g/L·h, while cellulose conversion required an HPW/NbOPO₄ impregnated system, yielding 18.9% with a volumetric productivity of 88.1 g/L·h. Further, recyclability tests for glucose conversion showed that NbOPO₄ powder remained active for seven consecutive cycles, whereas the pellet formed partially deactivated after four cycles. Together with the use of relatively green solvents, short reaction times, and noncorrosive conditions, these results support the development of efficient, reusable, and environmentally friendly catalytic systems for carbohydrate valorization. Overall, the combination of competitive productivity at short residence times in a low-hazard solvent system positions these niobium-based catalysts favorably relative to many reported heterogeneous HMF routes that rely on longer reaction times and less sustainable solvents. Moreover, the pelletized catalyst format is directly compatible with fixed-bed continuous-flow reactors, facilitating catalyst handling, separation, and regeneration.