Mn ₂ O ₃ with High Intrinsic Activity for HMF Aerobic Oxidation to FDCA: The Effect of Surface Area and Kinetic Analysis

The aerobic oxidation of HMF to FDCA offers a promising pathway for biomass utilization, especially for producing the biobased polymer PEF. Herein, a series of Mn 2 O 3 with various specific surface areas were prepared via a facile two-step process. The catalytic results demonstrated that Mn 2 O 3 exhibited a higher intrinsic activity (3.3 mg FDCA ·m –2 ·h –1 ) than common manganese oxides, such as Mn 3 O 4 and different crystalline phases of MnO 2 (α, β, and δ). Under optimized conditions, the Mn 2 O 3 -140-A catalyst achieved an FDCA selectivity of 91.3% at ∼100% HMF conversion, with a carbon balance of 97.8%. Combined characterization and catalytic testing revealed a clear positive linear correlation between specific surface area and activity, attributed to the increased concentration of accessible active sites associated with oxygen vacancies. Kinetic analysis identified the slowest steps in the two reaction pathways (DFF path and HMFCA path) and their dependence on reaction temperature. These findings demonstrate that Mn 2 O 3 can act as a promising catalyst for HMF aerobic oxidation to FDCA, and provide valuable insights for the design of advanced Mn 2 O 3 catalysts.