Efficient one-pot conversion of corncob to formic acid using bi-functional MnCeOx/Nb2O5 catalyst

A new process for the production of formic acid from corncob waste was constructed by using MnCeO_x/Nb₂O₅ catalyst. Among pristine hemicellulose, cellulose or lignin in corncob, hemicellulose gave the maximum formic acid yield (61.2 %). Dilute hydrochloric acid (0.37 wt%) assisted-ball milling pretreatment of pristine cellulose reduced its crystallinity and increased formic acid yield from 2.6 % to 40.2 %, while lignin was hardly converted into formic acid (<7 %). In the assessment of Mn and Ce in MnCeO_x/Nb₂O₅, a synergistic effect was observed in formic acid formation. Formic acid yield obtained over Mn₆Ce₄O_x/Nb₂O₅ was 1.5-fold higher that obtained over MnO_x/Nb₂O₅. Formic acid yield as high as 0.56 g/g could be obtained directly from pretreated corncob, demonstrating potential for converting agro-waste biomass into formic acid over Mn₆Ce₄O_x/Nb₂O₅ catalyst. Mechanistic studies revealed that arabinose, glyceric acid and glycolic acid were main intermediates in the conversion of corncob to formic acid.