(66j) Reductive Depolymerization of Lignin By Bifunctional Ru-Based Catalysts Supported on Tungstated-Zirconia

Catalytic hydrodeoxygenation, which can lead to oxygen-atom removal, ring hydrogenation, and ring-opening, is an effective strategy to depolymerize lignin and increase overall bio-oil conversion yield. In this study, a bifunctional catalyst, low-loading Ru (0.2-0.5 wt.%) supported on tungstated zirconia was evaluated for ring hydrogenation and ring opening of lignin model compounds and technical lignin derived from corn stover. The Ru/W-Zr-O catalyst showed comparable selectivity towards ring-hydrogenation as the Ru/Al₂O₃ catalyst. The selectivity shifted towards aromatics ring-opening when ethanol was used as the solvent. The highest long-chain alkanes bio-oil conversion yielded 90.6% with 79.4% selectivity. By comparing experimental data with the analysis of various calculated bond activation energies of lignin model compounds using density functional theory, we propose that the overall ring-opening reaction mechanism follows the route of “aromatics → cyclic hydrocarbon → linear hydrocarbon”. This work provided promise of designing efficient catalysts supported on tungstated zirconia for selective degradation of lignin by fine-tuning the properties of bifunctional catalysts and solvents.