Deep eutectic solvent (DES) as both solvent and catalyst for oxidation of furfural to maleic acid and fumaric acid

Efficient conversion of furfural to valuable chemicals is attracting attention because it is one of the bulk feedstocks in biomass refinery. Maleic acid (MA) and fumaric acid (FA) are two types of bulk monomers that can be prepared from furfural. Here, a simple method was developed to oxidize furfural to both MA and FA in a green deep eutectic solvent (DES). DES contained oxalic acid and choline chloride (ChCl); oxalic acid worked as both the main content of the solvent and acidic catalyst for the conversion. It was found that the conversion of furfural could reach 100%, while the yield of MA and FA reached 95.7% under a mild reaction temperature of 50 °C, which provided a green and efficient route for the synthesis of valuable monomers from furfural.