Al-Doping Promoted Aerobic Amidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxamide over Cryptomelane

Liquid-phase ammoxidation of biomass-derived platform compound 5-hydroxymethylfurfural (HMF) provides a sustainable route for the synthesis nitrogen-containing chemicals from renewable resources. A series of metal-cation-doped (In3+, Cr3+, Co2+, Ni2+, Cu2+, Zn2+, Al3+) cryptomelanes ([M]-K-OMS-2) were prepared and used as catalyst for the aerobic ammoxidation-hydration tandem reaction of HMF to 2,5-furandicarboxamide. Al-doped K-OMS-2 prepared with the refluxing method showed enhanced catalytic performance in comparison with K-OMS-2. Kinetic experiments indicated that the efficient synthesis of 2,5-furandicarboxamide over 0.15[Al]-K-OMS-2 catalyst was attributed to its higher activity on slow steps of alcohol oxidation and nitrile hydration during the amidation reaction of HMF. The results of XPS, O2-TPD-MS, and NH3-TPD-MS indicated that the Al-doping increased the lattice oxygen reactivity and the strength of strong acid sites, which were responsible for the enhanced efficiency of 0.15[Al]-K-OMS-2.