Conversion of Cellulose Into 5-Hydroxymethylfurfural (HMF) In a H2O/Tetrahydrofuran/Cyclohexane Biphasic System With Al2(SO4)3 As Catalyst

Abstract

A simple and efficient biphasic system consisting of H2O, tetrahydrofuran (THF), cyclohexane (CHX) and Al2(SO4)3 was employed to convert cellulose into 5-hydroxymethylfurfural (HMF) with high yield of 71.2%. The real volumes of organic phase (Vorg) and aqueous phase (Vaque) of the biphasic system at reaction temperature were measured to found out that over 80% of the added H2O was dissolved into the organic phase at reaction temperature, leading to high Vorg/Vaque (over 44/1) and high concentration of Al2(SO4)3 (over 0.34 g/mL) in aqueous phase. The high concentration of Al2(SO4)3 in aqueous phase could efficiently catalyze the conversion of cellulose into HMF, while the high Vorg/Vaque could protect the formed HMF from rehydration, all of which are responsible for the high efficiency of the system on conversion of cellulose into HMF. The addition of CHX into reaction mixture could decrease the solubility of Al2(SO4)3 and H2O in the organic phase, which could improve the stability of HMF in the reaction system, resulting higher yield of HMF from cellulose. Because of the high Vorg/Vaque of the reaction system, one microemulsion-like system and liquid film catalytic model are proposed for the cellulose-to-HMF process.