Conversion of fructose to 5-hydroxymethylfurfural using 1,4-bis(4-sulfobutyl)-DABCO-1,4-diium tetrachloroaluminate ionic liquid in [CholineCl][Citric acid] deep eutectic solvent

Abstract

In recent years, there has been a significant interest from both domestic and international researchers in ionic liquids as they are recognized as environmentally friendly solvents and catalysts. From 5-hydroxymethylfurfural (HMF), a substrate derived from carbohydrate, various important compounds particularly the 2,5-dimethylfuran can be synthesized because it could be used as a biofuel and valuable substance. Furan derivatives such as 5-alkoxymethylfurfural, 2,5-furandicarboxylic acid, 5-hydroxymethylfuroic acid, bis-hydroxymethylfuran and 2,5-dimethylfuran have significant applications in the fields of fuel and polymers. This paper presented the preparation of 8 ionic liquids containing Brønsted acid and Lewis acid site, intending to utilize them as catalysts for converting carbohydrates into 5-hydroxymethylfurfural (HMF). Several factors affecting the performance of HMF were investigated, including the type and catalyst loading, temperature, solvent, and reused. The results showed that 1,4-bis(4-sulfobutyl)-DABCO-1,4-diium tetrachloroaluminate (IL1) exhibited potential as a catalyst for the synthesis of HMF from fructose. This reaction was conducted at a temperature of 100℃ for 5 min with the yield of approximately 60% when using [CholineCl][Citric acid] deep eutectic solvent. This catalyst, IL1/[CholineCl][Citric acid], was successfully recovered and reused for four times. This demonstrated the efficacy of various ionic liquids as catalysts for the synthesis of HMF from fructose. Further study on this catalyst is needed for the application in the producing fuel precursors derived from carbohydrates on an larger scale.