Selective oxidation of furfural in a bi-phasic system with homogeneous acid catalyst

The selective catalytic oxidation of furfural to 2(5H)-furanone, succinic acid (SA) and maleic acid (MA) was studied. Under optimized conditions, furfural was oxidized to 2(5H)-furanone.with a yield of 60-62% in an aqueous/organic bi-phasic system using 1,2-dichloroethane or ethyl acetate as the solvent and formic acid as the catalyst, while the total yield of SA and MA was 15-20%. Compared with other homogeneous and heterogeneous acid catalysts, formic acid gave a much higher selectivity to 2(5H)-furanone because it reacted with hydrogen peroxide to generate performic acid that had a strong oxidizing nature and good solubility in both the aqueous and organic phases. The solvent had a significant influence on the product distribution. A simplified reaction network was established to quantitatively analyze the solvent effect based on the reaction rate constants. In the homogeneous system, the yield of 2(5H)furanone decreased while the yield of SA increased with an increasing dielectric constant of the solvent. The formic acid/furfural molar ratio, reaction temperature and furfural concentration were optimized for the selective oxidation of furfural to 2(5H)-furanone in the bi-phasic reaction system. (C) 2016 Elsevier B.V. All rights reserved.