Supported vanadium- and tungsten-based catalysts for selective and sustainable oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid with H2O2 in water

Abstract

In this study, an efficient and eco-friendly route for the selective synthesis of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), via oxidation of 5-hydroxymethylfurfural (HMF) with aqueous H₂O₂ using polymer-supported peroxidovanadium (pV) and peroxidotungsten (pW) compounds as catalysts, is described. The heterogeneous non-noble metal catalysts were prepared by immobilizing the peroxido derivatives of vanadium(V) and tungsten(VI) on polystyrene (PS) resin functionalized with niacin (N/PS) or asparagine (A/PS). The synthesized catalysts VO-N/PS and WO-A/PS were well characterized by elemental analysis, FTIR, Raman, NMR, XRD, XPS, SEM, EDX, BET and TGA analysis. The catalysts displayed excellent activity in facilitating quantitative conversion of HMF to provide the target product, HMFCA with >99% selectivity and a TON value of 50. Significant ‘green’ attributes of the catalytic protocol include the use of water as a solvent, aqueous H₂O₂ as a clean and safe oxidant and workable reaction temperature and time (60 °C, 1.3 h). Importantly, the catalysts are cost-effective, stable, and can be easily separated from the reaction mixture and recycled at least for five cycles without any significant reduction in activity or selectivity.