Lignin containing numerous phenylpropane units is considered to be a renewable and abundant resource for the production of value-added aromatic chemicals. A series of nonprecious metal/bimetallic catalysts were prepared for the catalytic hydrogenolysis of organosolv poplar lignin (OPL) in ethanol/isopropanol solvent in this work. Effects of Ni/C, Cu/C, NiCu/C, and NiW/C catalysts on OPL depolymerization were investigated, where the NiCu/C catalyst was found to be optimal for the conversion of OPL to phenolic monomers at a yield of 63.4 wt % at 270 °C for 4 h without external H2. The synergistic effect of mixed solvent was remarkable during the catalytic hydrogenolysis process, leading to the increased yield of monomer products. The catalytic process of OPL conversion and possible reaction route of ethanol/isopropanol solvent were proposed with regard to the analysis of products and fresh/spent catalysts. The effects of reaction temperature, reaction time, catalyst recyclability, solvent recyclability, and feedstock adaptability were investigated in view of bio-oil and monomer yields. This work provides an economical and sustainable method for the efficient conversion of lignin to high-value chemicals.

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Lignin is the only naturally renewable aromatized polymer consisting of several phenyl propane structures linked by C−O and C−C bonds, so lignin can be depolymerized into value-added chemicals or liquid fuels. In this study, M 5 Zn 5 AlO x (M = Co, Ni and Cu) catalysts were obtained by the co-precipitation method and then were used in organosolv lignin depolymerization. Among these catalysts, the Ni 5 Zn 5 AlO x catalyst possessed the largest surface area and abundant surface oxygen vacancies as well as strong acidic sites on the surface, giving the highest yield of monophenols (about 14.49 wt %). The effect of Ni/Zn ratios on the lignin depolymerization was also investigated, and it was found that the surface area and the proportion of surface oxygen vacancies and strong acidic sites of the NiZnAlO x catalysts increased and then decreased with the Ni/Zn ratios increasing. Similarly, the yield of monomeric compounds increased and then decreased with the Ni/Zn ratios increasing. The highest yield of monophenols was 17.18 wt % obtained over the Ni 3 Zn 7 AlO x catalyst, a remarkable monomer yield from organosolv lignin. The two-dimensional 1 H-13 C heteronuclear single-quantum coherence nuclear magnetic resonance spectroscopy of bio-oil revealed that the linkage bonds in lignin could be effectively broken over the Ni 3 Zn 7 AlO x catalyst. This study provided an effective route to obtain high-value chemicals from organosolv lignin under nickel-based catalysts.