Microwave-assisted dehydration of fructose and inulin to HMF catalyzed by niobium and zirconium phosphate catalysts

•The dehydration of fructose and inulin to HMF with NbPO and ZrPO was investigated.•The reactions were optimized using sustainable conditions in water under MW heating.•The different acid properties of NbPO and ZrPO influence their catalytic behaviour.•The optimization of HMF synthesis with ZrPO was confirmed by a statistical modelling.•Both catalysts result very promising, obtaining HMF yields up to 40 mol% with ZrPO.

5-Hydroxymethyl-2-furaldehyde (HMF) is a key bio-based platform for the production of renewable monomers and bio-fuels. However, most of its syntheses are carried out under not sustainable conditions. In this work, the production of HMF from fructose and inulin was investigated following the Green Chemistry principles, adopting aqueous medium, appreciable substrate concentration (10 wt%), low loading of heterogeneous acid catalyst (niobium or zirconium phosphate) and microwave heating. Both the catalysts resulted very active and promising, in particular zirconium phosphate and the performances were related to their different acid characteristics. The optimization of HMF synthesis with zirconium phosphate was also supported by a statistical modelling, which shows that the highest yield to HMF (about 40 mol%) is ascertained at high temperature (190 °C) and short reaction time (8 min). The catalysts resulted recyclable maintaining their starting activity almost unchanged.

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