CoZn@N-ALC, highly-efficient magnetic Co nanoparticles anchored by lignin-based Nitrogen-doping carbon for hydrodeoxygenation of vanillin

The conversion of lignin-based platform compounds into valuable biofuels and chemicals through catalytic processes is an attractive approach for the efficient valorization of renewable lignocellulosic biomass. One such process is the hydrodeoxygenation (HDO) of lignin-based vanillin (VL) to produce 2-methoxy-4-methylphenol (MMP), which is a promising liquid fuel and intermediate for fine chemicals. However, the development of a cost-effective catalytic system with high activity and selectivity remains a challenge. In this study, we report the preparation of a highly-efficient magnetic Co nanoparticles catalyst, CoZn@N-ALC, using alkali lignin as an assembly macromolecular ligand, Zn as a sacrificial metal, and dicyandiamide as a nitrogen source before the pyrolysis process. Various characterization techniques, including powder X-ray diffraction (XRD), pyridine adsorption infrared spectroscopy (Py-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), isothermal nitrogen adsorption/desorption, and X-ray photoelectron spectroscopy (XPS), were employed to investigate the role of zinc and nitrogen in the construction process of CoZn@N-ALC and the influence of catalyst preparation conditions. The optimized CoZn@N-ALC catalyst demonstrated nearly 100 % conversion of VL, complete selectivity towards MMP, and easy separation from the aqueous HDO system. Structure-performance investigation and density functional theory (DFT) calculations suggest that the exceptional catalytic performance of this catalyst can be attributed to the selective adsorption of C=O bonds by abundant Co (1   1   1) active species and its Lewis acid sites. This work provides valuable insights into the rational design of efficient, non-noble metal nanoparticle catalysts based on alkali lignin for the conversion of lignin-based platform compounds.