Aqueous-Natural Deep Eutectic Solvent-Enhanced 5-Hydroxymethylfurfural Production from Glucose, Starch, and Food Wastes

Graphical HMF synthesis in NADES : High yield of 5-hydroxymethylfurfural (HMF) is obtained in a cheap and green natural deep eutectic solvent (NADES) system with a low amount of SnCl 4 catalyst from different biomass materials, including glucose, starch, and food wastes. The addition of water obviously improves the reactivity and economy of the NADES mixture. This is a green and efficient method to utilize carbohydrate resources for HMF production in a robust solvent system. 5-Hydroxymethylfurfural (HMF) has been regarded as an essential building block for synthesizing chemicals and biofuels, but the direct conversion of biomass to HMF is still a critical challenge. In this study, a cheap and green aqueous-natural deep eutectic solvent (A-NADES) was used to efficiently produce HMF from various carbohydrates, with a low amount of SnCl 4 as the catalyst. High HMF yields of 64.3, 64.0, 61.3, and 54.5 % were obtained from glucose, starch, rice waste, and bread waste at 130 °C in the A-NADES/MIBK (methyl isobutyl ketone) biphasic system, respectively. Mechanistic study results revealed that the water in A-NADES was the key factor in facilitating the conversion of Sn atom existent forms and promoted the HMF production. The choline chloride in NADES stabilized the HMF product with the cooperation of extraction solvent MIBK and inhibited the side reactions of HMF. This study investigated the multiple interaction functions of A-NADES to feedstocks and proposed a practical application of novel solvents to facilitate biomass and food waste conversion with a green method.