Synthesis of 5-hydroxymethylfurfural from glucose in a biphasic medium with AlCl3 and boric acid as the catalyst

In combination with non-corrosive and low-toxic boric acid, AlCl3 ·6H2O was found to be effective for the synthesis of 5-hydroxymethylfurfural (5-HMF) from glucose. In this work, a 5-HMF yield of ≈ 60 % was obtained at 170°C for 40 min in a H 2 O/THF biphasic solvent mixture. An addition of NaCl not only improved the partition coefficients but also inhibited by-product formation. THF was identified as an ideal extraction solvent in biphasic systems containing C4 solvents. However, low concentration of ZnCl 2 , CoCl 2 ·6H 2 O, MnCl 2 ·4H 2 O, NiCl 2 ·6H 2 O, FeCl 3 ·6H 2 O were not suitable for the catalyst system, while ZrOCl 2 ·8H 2 O, InCl 3 ·4H 2 O showed high activity for the reaction. Boric acid increased the amount of Lewis acid sites in the reactive phase and enhanced the isomerization of glucose to fructose. A mechanism of the AlCl 3 ·6H 2 O and boric acid catalyzed glucose dehydration reaction was proposed to proceed through the isomerization of glucose to fructose followed by the transformation of fructose to 5-HMF.