A green process for separation and recovery of 5-hydroxymethylfurfural from carboxylic acid–choline chloride deep eutectic solvents

Abstract

Deep eutectic solvents (DESs) have the advantages of low cost, non-toxicity, and biodegradability for the catalytic conversion of fructose to 5-hydroxymethylfurfural (5-HMF). However, the efficient separation of 5-HMF from DESs is essential and challenging for its high-value utilization. In this study, the efficient separation of 5-HMF from eight carboxylic acid-based DESs was achieved by four cycles of extraction using tetrahydrofuran (THF) with an overall extraction efficiency of more than 80.0% (30 °C). Besides, the addition of 1 mol L⁻¹ NaCl solution can significantly improve the extraction efficiency from 30.0% to 42.0%. In addition, the process of recovery and reuse of the extractant was proved to be quite effective, in which the purity of 5-HMF in the recovered product and the amount of THF in the recycled extractant can reach up to 90.0% and 97.0%, respectively. Finally, a thorough procedure for the preparation, separation, and recovery of 5-HMF was carried out to assess the viability of the optimized separation and recovery process. The results reveal outstanding extraction efficiency (77.9%), excellent yield of 5-HMF (63.3%), and high purity of 5-HMF in the final product (86.0%). This work expands the range of possible uses for 5-HMF by demonstrating an efficient and environmentally friendly method for separating and recovering 5-HMF while ensuring the reuse of the extractant.