Roles of Lewis acid derived from NiMo alloy in Hydrodeoxygenation of lignin-derived phenols

It is highly desired to use non-noble metal catalysts for efficiently upgrading biomass into biofuels and value-added products. A series of Ni-Mo bimetallic catalysts were synthesized using hydrothermal method; and employed in the hydrodeoxygenation (HDO) of guaiacol to cyclohexane. The resulting highly dispersed catalyst with an optimal Ni/Mo ratio, Ni 0.75 Mo 0.25 ZrO 2 demonstrated outstanding HDO performance with a 100 % yield of cyclohexane under 250 ℃ and 5 MPa due to the synergistic effect of NiMo alloy and metallic Ni. Further characterization results reveal that enhanced catalytic activity is primarily attributed to the improved dispersion of metal on ZrO 2 support, facilitated by the formation of NiMo alloy. The introduction of Mo into the Ni framework alters the surface structure, breaking up the continuous Ni surface into smaller ensembles. Additionally, the presence of Mo reduces the d-band electron density of Ni, creating an electron deficient Ni-Mo interface that increase the Lewis acid sites. This modification increases the number of available Lewis acid sites, promoting efficient catalytic processes. Furthermore, the altered surface structure enhances the interaction between the oxygen atom and Mo, thereby facilitating the conversion of cyclohexanol to cyclohexane. This catalyst was found also exceptionally efficient in cleaving the α-O-4 and β-O-4 ether linkages in various lignin-derived model compounds. Together with excellent stability and remarkable adaptability, this bimetallic catalyst exhibits promising potential in production of diesel from lignin resources to pave the way for green and sustainable supply of fuels.