Highly efficient hydrodeoxygenation of lignin-derived diphenyl ether over bifunctional Co/CoO catalysts under mild conditions

Designing high-activity catalysts for hydrodeoxygenation (HDO) of lignin models remains challenging, especially for Co-based materials. In this study, we prepared a bifunctional Co/CoO nanoparticle catalyst anchored on a nitrogen-doped phenolic resin nanospheres (CNS) support. In the HDO of diphenyl ether (DPE), the 2Co/CNS-550 catalyst achieved 100 % conversion and an 85.3 % yield of cyclohexane at 200 °C. The reaction mechanism of DPE over 2Co/CNS-550 was elucidated through comprehensive catalyst characterizations, kinetic experiments, and density functional theory (DFT) calculations. Several lignin-derived compounds were investigated, and nearly 100 % conversion of various lignin derivatives was achieved. This demonstrates the catalyst's remarkable potential for biofuel production through the catalytic HDO of lignin derivatives. The high activity is attributed to the synergistic effect of metallic state Co and CoO nanoparticles. The metallic state Co nanoparticles maintain stable HDO activity for C–O bonds, while the CoO nanoparticles enhance H2 activation and DPE adsorption. This study highlights a promising approach for using nonprecious metal cobalt catalysts to convert lignin derivatives into biofuels.