High yield and isolation of 2,5-furandicarboxylic acid from HMF and sugars in ionic liquids, a new prospective for the establishment of a scalable and efficient catalytic route

Abstract

The synthesis of 2,5-furandicarboxylic acid (FDCA) for the production of the sustainable bioplastic polyethylenefuroate (PEF) represents a topic of strong scientific and commercial interest. However, despite extensive research, the development of an efficient process for the synthesis of FDCA still faces difficult challenges. The principle cause is the strong dependence of the reactions involved on the solvent employed and difficulties in isolating the intermediate 5-HMF, leading to issues in performing the oxidation step which is favoured only in water, while 5-HMF formation is promoted in ionic liquids and other organic solvents. In this study we exploited ionic liquids as efficient solvents for the synthesis of HMF from sugars with MnO₂ as catalysts for the in situ oxidation of HMF into a dialkylimidazolium furan carboxylate ([dbmim]-FDC). The advantage in forming the imidazolium salt instead of the diacid form lies in the easier separation of this compound from the reaction mixture at low concentration (<2%) through antisolvent addition (ethanol) and its conversion into FDCA through acidification. This process represents a new efficient methodology to isolate FDCA directly from sugars such as glucose and fructose at isolated yield higher than 80% from these substrates, representing a step forward for the development of a techno-economically efficient process for the production of biobased plastics.