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Niobic acid (Nb2O5·nH2O) was immobilized on regenerated cellulose (Re-Cellulose) to afford a heterogeneous catalyst, termed Nb2O5·nH2O@Re-Cellulose, that was characterized by powder X-ray diffraction, microscopy (SEM and TEM) and spectroscopic (Raman and FTIR) techniques. The surface acidity of the catalyst was determined using FTIR spectroscopy employing pyridine as a molecular probe. The Nb2O5·nH2O@Re-Cellulose catalyst was investigated in the conversion of glucose into 5-hydroxymethylfurfural (HMF) in aqueous media. The catalyst can be reused several times without undergoing a significant loss in activity. [ABSTRACT FROM AUTHOR]

Conversion of carbohydrates into 5-hydroxymethylfurfural (HMF) is a valuable reaction for biomass efficient utilization. The silica-supported phosphotungstic acid (PTA) heterogeneous catalyst (SiO 2 -ATS-PTA) was prepared and characterized by XRD, FT-IR, pyridine-FTIR and SEM. The SiO 2 -ATS-PTA was used to catalyze the conversion of glucose, and it afforded 78.31% yield of HMF at 160 °C for 140 min. The SiO 2 -ATS-PTA could be reused for five runs without significant loss of catalytic activity. Furfural was the main byproduct. A kinetic analysis was carried out and the values of the activation energy and the pre-exponential factor for the reaction were 30.25 kJ mol −1 and 1.08 × 10 7  min −1 , respectively. [ABSTRACT FROM AUTHOR]