Dehydration of glucose to 5-hydroxymethylfurfural and 5-ethoxymethylfurfural by combining Lewis and Brønsted acid

Abstract

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.