Dehydration of glucose to 5-hydroxymethylfurfural and 5-ethoxymethylfurfural by combining Lewis and Brønsted acid
In this work, glucose was transformed into 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) in the presence of AlCl3·6H2O and a Brønsted solid acid catalyst (PTSA–POM). GVL (γ-valerolactone)–water and ethanol–water solvent systems were evaluated in the dehydration reaction of glucose into HMF and EMF, respectively. Water content and dosage of AlCl3·6H2O were examined in the conversion of glucose into HMF, and some valuable chlorides (FeCl3·6H2O, NiCl2·6H2O, CrCl3·6H2O etc.) were also used in contrast with AlCl3·6H2O. Some different organic solvents were added to the ethanol–water system to explore whether it would be beneficial to the generation of EMF. A high yield of HMF (60.7%) was obtained at 140 °C within 60 min in GVL–water (10 : 1) solvent system, and total yield 42.1% of EMF and HMF (30.6% EMF, 11.5% HMF) was achieved at 150 °C after 30 min in an ethanol–water (9 : 1) solvent system.