Oxidation of Furfural to Maleic Acid and Fumaric Acid in Deep Eutectic Solvent (DES) under Vanadium Pentoxide Catalysis

Furfural is an alternative feedstock and has been used for the production of maleic acid (MA) and fumaric acid (FA) by an oxidation process. Deep eutectic solvents (DESs) were used as the green solvents while sodium chlorate was used as an oxidant and vanadium pentoxide was used as the catalyst at 70–90 ℃ under atmospheric pressure. It was found that several acidic DESs are valid, such as acetic acid/choline chloride (AA/ChCl) and propionic acid/choline chloride (PA/ChCl), and AA/ChCl DES was selected as the solvent for the conversion. The optimal DES is AA/ChCl, and the effect of the amount of oxidant, time, and temperature on the yield of the MA and FA has been systematically studied, and the conversion of furfural can reach 100% while the yield of the MA and FA reached 66.5% under reaction temperature of 80 ℃ for 12 h, which provides a new green route to synthesis valuable monomers from furfural.