A three-way deep eutectic solvent integrating solubilization-Brønsted/Lewis acids for efficient 5-hydroxymethylfurfural production from cellulose

Abstract

A three-way deep eutectic solvent (DES) integrating solubilization-Brønsted/Lewis acids was developed for the efficient synthesis of HMF in a one-pot method without additional catalysts. The conversion strategy for microcrystalline cellulose (MCC) involved formic acid (FA)/LiCl DES pretreatment to yield regenerated microcrystalline cellulose (RMC), followed by conversion with dimethyl sulfoxide (DMSO) as the solvent at 180 °C for 20 min to obtain an excellent yield of 61.4% HMF. The formation of RMC indicated that the combined disruption of both intra- and inter-molecular hydrogen bonds (HBs) of MCC by the FA/LiCl DES results in a decrease in the crystallinity index (CI) and degree of polymerization (DP) of MCC, with a significant impact on HMF synthesis. The influence of reaction temperature, time, and MCC dosage on the HMF yield was examined utilizing the response surface methodology (RSM) with the Box–Behnken design. According to the quadratic model, the highest HMF yield was 63.1% at 176 °C, over 24 min, and with 132 mg MCC dosage. Furthermore, the DES/DMSO system demonstrated the capacity to maintain a yield of 53.7% HMF after four cycles. The results of this study provided a green/simple method for the efficient conversion of MCC into HMF using DES pretreatment without additional catalysts.