Selective hydrodeoxygenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran on Ru-MoOx/C catalysts

Selective hydrogenation of 5-hydroxymethylfurfural (HMF) has potential application in high quality biofuels. Herein, the catalytic hydrodeoxygenation (HDO) of HMF to 2,5-dimethylfuran (DMF) was investigated using bi-functional Ru-MoOx/C catalyst prepared by initial wetness impregnation. The high dispersion and electronic transfer between Ru and MoOx were demonstrated by a series of characterization techniques. During this HDO process, the synergy effect between metallic Ru and acidic MoOx species in the RuMoOx/C catalyst plays an essential role in obtaining maximized target product DMF (79.4%) via effective aldehyde group hydrogenation by Ru followed by dehydration over MoOx. This work also elucidated that DMF production proceeded through two distinct pathways: the 2,5-hydroxymethyl furan intermediate was preferable by the aldehyde group hydrogenation of HMF over the Ru-MoOx/C catalyst. Over MoOx/C catalyst, comparatively, 5-methyl furfural was the key intermediate by direct hydrogenolysis of the hydroxyl group in HMF. This kind of catalyst is stable for the first two runs by maintaining the target product yield. After the third run, the catalyst showed deactivation gradually but could be almost completely recovered after regeneration by H-2 reduction.