Catalytic Aerobic Oxidation of Biomass-based Furfural into Maleic Acid in Aqueous Phase with Metalloporphyrin Catalysts

Catalytic oxidation of renewable furfural into valuable maleic acid in aqueous solutions using metalloporphyrin catalysts was investigated for the first time. The synthesized catalysts were characterized by FT-IR, UV–vis, 1H NMR, elemental analysis, and TGA. The catalysts varied in metal active sites and functional groups, which had different effects on their catalytic activity. Furthermore, the effects of temperatures, reaction time, catalyst loading, and oxygen pressure were studied in detail. Maleic acid could be achieved in 44% yield by using FeT(p-Cl)PPCl as catalyst under optimal conditions. Finally, FeT(p-Cl)PPCl could be reused in five consecutive runs without a significant loss of activity.