Low-Temperature Hydrodeoxygenation of Lignin Model Compounds over Defect-Engineered Nickel Catalysts

Catalytic hydrodeoxygenation (HDO) of aromatic aldehydes represents a core research direction in the efficient utilization of lignin. In this study, a cost-effective catalyst was constructed by incorporating rich lattice defects into Ni nanoparticles. The catalyst was synthesized via a uniform precipitation method, employing urea as the precipitant. By introducing aluminum nitrate during the precipitation process, nickel was effectively segregated to inhibit its growth and the generation of well-crystallized, defect-free Ni nanoparticles, thereby generating a substantial quantity of defective Ni nanoparticles with abundant lattice defects. The catalyst was characterized using XRD, TEM, HRTEM, EDS line and mapping scanning, XPS and H2-TPD, confirming the formation of Ni nanoparticles with a narrow size distribution of ~5 nm with numerous lattice defects. The hydrodeoxygenation of vanillin was employed to evaluate the catalyst’s activity, with investigations into the effects of Al content, solvents, temperature, H2 pressure, and reaction time. The reaction was successfully conducted at 363 K in water. The catalyst demonstrated excellent hydrodeoxygenation activity across a series of other aromatic aldehyde compounds. Cycle experiments confirmed the catalyst’s stability, maintaining its activity over at least five consecutive uses.