Lignin-First Depolymerization of Lignocellulose into Monophenols over Carbon Nanotube-Supported Ruthenium: Impact of Lignin Sources.

Lignin-first depolymerization of lignocellulosic biomass into aromatics is of great significance to sustainable biorefinery. However, it remains a challenge, owing to the variance between lignin sources and structures. In this study, ruthenium supported on carbon nanotubes (Ru/CNT) exhibits efficient catalytic activity toward lignin hydrogenolysis to exclusively afford monophenols in high yields. Catalytic tests indicate that the yields of aromatic monomers are related to lignin sources and decrease in the order: hardwoods > herbaceous plants > softwoods. Experimental results demonstrate that the scission of C-O bonds and the high selectivity to monomeric aromatic compounds over the Ru/CNT catalyst are enhanced by avoiding side condensation. Furthermore, the fabricated Ru/CNT shows good reusability and recyclability, applicability, and biomass feedstock compatibility, rendering it a promising candidate for lignin valorization. These findings pave the way for rational design of highly active and stable catalysts to potentially address challenges in lignin chemistry.