Efficient Ni-Cu/AC Bimetal Catalyst for Hydrogenolysis of Lignin to Produce High-Value-Added Chemicals

Efficient depolymerization of natural lignin is the key step to convert lignin to sustainable and added-value chemicals. In this paper, a carbon-supported Ni-Cu bimetallic catalyst was developed for the hydrogenation of poplar lignin and beta-O-4 model compounds. Five Ni-Cu bimetallic catalysts were prepared by immobilizing Ni and Cu at fixed Ni loading (5%) and varied Cu loading (0%, 5%, 10%, 20%, 30%) on activated carbon (AC). All the Cu-Ni/AC bimetal catalysts exhibited higher catalytic activity than either Ni/AC or Cu/AC catalysts. 5Ni-5Cu/AC gave the highest bio-oil yield of 40.2 wt% for the hydrogenation of. poplar lignin. The XPS, XRD, and HRTEM characterization of the catalysts showed that elemental copper and Cu-Ni alloy were formed on the surface of 5Ni-5Cu/AC catalyst, which could promote the efficient depolymerization of lignin into phenolic monomers. The possible mechanism for the lignin depolymerization was also studied and proposed based on the beta-O-4 bond model compounds. This study provides a viable strategy for the conversion of lignin into added-value chemicals with low cost catalyst.