Heterogeneous catalysts based on vanadyl phosphate for fructose dehydration to 5-hydroxymethyl-2-furaldehyde Original Research Article

Vanadyl phosphate (VOP) was used as acid catalyst in the dehydration of fructose aqueous solutions to afford 5-hydroxymethyl-2-furaldehyde (HMF). Promising results, in terms of activity (turnover frequency (TOF) ≈ 200 mmol HMF/gcat h) and selectivity, have been achieved. New catalytic systems, obtained by substitution of some VO3+ groups with trivalent metals (Fe3+, Cr3+, Ga3+, Mn3+, Al3+), were also checked. In particular, when Fe-substituted VOP was employed the highest up to now reported activities were obtained working on concentrated fructose solutions in the presence of a low amount of catalyst (TOF up to 376). Notwithstanding the high concentration of the substrate in aqueous medium neither insoluble polymeric by-products nor HMF rehydration compounds were formed. Finally, preliminary experiments carried out with VOP catalysts supported on inorganic oxides allowed to conclude that this approach is promising, provided that a support with proper acid character is adopted.