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

A simple and efficient biphasic system consisting of H 2 O, tetrahydrofuran (THF), cyclohexane (CHX) and Al 2 (SO 4 ) 3 was employed to convert cellulose into 5-hydroxymethylfurfural (HMF) with high yield of 71.2%. The real volumes of organic phase (V org ) and aqueous phase (V aque ) of the biphasic system at reaction temperature were measured to found out that over 80% of the added H 2 O was dissolved into the organic phase at reaction temperature, leading to high V org /V aque (over 44/1) and high concentration of Al 2 (SO 4 ) 3 (over 0.34 g/mL) in aqueous phase. The high concentration of Al 2 (SO 4 ) 3 in aqueous phase could efficiently catalyze the conversion of cellulose into HMF, while the high V org /V aque 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 Al 2 (SO 4 ) 3 and H 2 O 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 V org /V aque of the reaction system, one microemulsion-like system and liquid film catalytic model are proposed for the cellulose-to-HMF process.