Relatively Electron-Rich Ni Nanoparticles Supported on α-Al2O3 for High-Efficiency Hydrogenolysis of Lignin and Its Derivatives under Mild Conditions

Catalytic C–O bond hydrogenolysis is an essential route to produce sustainable chemicals and fuels from lignin and its derivatives. Herein, various Ni-based catalysts were successfully prepared and evaluated in the C–O bond hydrogenolysis of lignin-derived diphenyl ether (DPE) and benzyl phenyl ether (BPE). It is found that 10%Ni/α-Al2O3 shows the highest activity for cleaving C–O bonds of DPE and BPE at low reaction temperatures and low H2 pressures. Compared to 10%Ni/γ-Al2O3 and 10%Ni/γ-Al2O3-2, 10%Ni/α-Al2O3 exhibits a higher initial reaction rate for the conversion of DPE and BPE. Different characterizations reveal that the high activity of 10%Ni/α-Al2O3 is ascribed to relatively electron-rich Ni metals, providing a large number of Ni–Ni bonds, which is mainly responsible for a rapid H2 adsorption–activation–dissociation and for driving substrate hydrogenolysis. Furthermore, 10%Ni/α-Al2O3 not only catalyzes C–O bond hydrogenolysis of other lignin derivatives but also achieves the depolymerization of real lignin to produce guaiacol with a high yield.