Oxidation of 5-[(Formyloxy)methyl]furfural to Maleic Anhydride with Atmospheric Oxygen Using α-MnO 2 /Cu(NO 3 ) 2 as Catalysts

A novel approach to produce renewable maleic anhydride (MA) from bio-based platform chemical 5-[(formyloxy)methyl]furfural (FMF) was developed with air or pure oxygen at atmospheric pressure using α-MnO 2 /Cu(NO 3 ) 2 as catalysts with the assistance of K 2 S 2 O 8 . The synergy of α-MnO 2 /Cu(NO 3 ) 2 ensured a high yield of MA through a Mn IV /Mn II redox couple facilitated by redox cycle of Cu II /Cu I and NO 3 – /NO 2 /NO with the assistance of O 2 . In this oxidation, FMF was first oxidized to 2,5-diformylfuran (DFF), as an intermediate, and then DFF underwent oxidation decarbonylation, hydration, and 1,4-rearrangement to form 5-hydroxyl-2(5 H )-furan-one, followed by the oxidation to MA. Compared with the MA yield of less than 45% from the oxidation of 5-hydroxymethylfurfural, FMF showed a higher oxidation efficiency than MA with a yield of up to 89% under mild conditions.