Effects of metal sites and acid sites on the hydrogenolysis of cornstalks in supercritical ethanol during lignin-first fractionation

Abstract

A lignin-first strategy is promising in lignin utilization to produce value-added aromatic compounds and their derivatives for achieving high efficiency. In this work, we explored the hydrogenolysis of cornstalk lignin in supercritical ethanol and investigated the effects of metal sites and acid sites during lignin-first fractionation. By comparison, the acid pretreatment of Ru/C catalysts significantly promotes the hydrogenolysis process, wherein Ru/C-acid (10) exhibits the best result with 42.9 wt% yield of monomer products (including aromatic monomers and hydrogenated monomers) at 260 °C, 3 MPa H₂ for 4 h. Catalysts were measured by BET, TEM and NH₃-TPD characterizations, and the hydrogenolysis products were compared by GC-MS, GPC, element analysis and FT-IR characterizations. The analysis results indicate that the active metal site and the abundant acid site are mainly responsible for the efficient lignin hydrogenolysis performance, and these two factors present a significant effect to achieve a high monomer yield.