Mechanistic Studies on Hydrodeoxygenation of Furfural to 2-Methyl Furan Via Ring C-H Bond Activations

Removal of excess oxygen-containing functional groups in furanic compounds, e.g. furfural and 5-hydroxymethylfurfural to 2-methyl furan and dimethylfuran, is a key step in the upgrade of cellulosic and hemicellulosic biomass-derived molecules. Mildly oxidized Ru/C catalyst shows remarkable activity and selectivity towards the hydrodeoxygenation reactions; however, molecular level understanding on the catalyst surface-mediated chemical transformation is still lacking. We show that both metal-mediated hydrogenation and Lewis acid-mediated MPV reaction are responsible for hydrogenating C=O to C-OH. In addition, isotopic labeling experiments with detailed mass fragmentation analysis demonstate that ring C-H bond activations are necessary for the C-OH bond scission.