Selective Conversion of Furfural to Maleic Anhydride and Furan with VOx/Al2O3 Catalysts

Furfural can be converted into maleic anhydride (73?% yield) through selective gas phase oxidation at 593 K with O2 by using VOx/Al2O3 (10 atV?nm-2) as solid catalysts. The use of lower temperatures and/or O2 pressures result in the additional formation of furan (maximum 9?% yield). Mechanistically, furfural (C5H4O2) is oxidized stepwise to furan (C4H4O), 2-furanone (C4H4O2), and finally, maleic anhydride (C4H2O3). The specific structure of the supported vanadium oxides and reaction conditions (temperature and reactants pressures) all influence furfural oxidation catalysis. We have found that Al2O3-supported polyvanadates are intrinsically more active (2.70 mmol?h-1?g-at?V-1) than monovanadates (VO4) and V2O5 crystals (0.89 and 0.70 mmol?h-1?g-at?V-1, respectively) in maleic anhydride and furan formation rates (553 K, 1.6 kPa furfural, 2.5 kPa O2). Our alternative approach enables the use of biomass instead of petroleum to synthesize maleic anhydride and furan from furfural. The potential variety of industrial applications is of enormous interest for the development of future biorefineries.