One-Pot Conversion of Starch into 5-Chloromethylfurfural and 5-Hydroxymethylfurfural in a Low-Transition Temperature Mixture

Abstract

The synthesis of platform molecules from food wastes is a topic of interest for the development of sustainable biorefineries. Starchy food wastes can serve as feedstocks to produce fine chemicals, fuels, and polymers by the hydrolysis of starch and further conversion into platform molecules such as 5-hydroxymethylfurfural (5-HMF) and 5-chloromethylfurfural (5-CMF). Conventionally, the synthesis of 5-CMF has relied on the use of concentrated hydrochloric acid (HCl) as a catalyst. However, recent studies have explored alternative methods, including eutectic solvents containing metal chlorides, which have facilitated 5-CMF production. This study presents a novel approach to synthesizing 5-CMF from starch using eutectic solvents without the need for either HCl or metal chloride additives. The synthesis was conducted using a low transition temperature mixture of choline chloride, citric acid, and boric acid in a biphasic system with dichloromethane as the extracting solvent. The synthesis was optimized using the response surface methodology through a Box–Behnken design. At 100 °C and 90 min of reaction time, up to 17 mol % 5-HMF and 13 mol % 5-CMF were produced, and in the optimized conditions of 120 °C and 135 min, up to 33 mol % 5-CMF with less than 1 mol % 5-HMF was obtained from starch. Moreover, it was shown that the low transition temperature mixture used in this study could be reused at least five times.