Catalytic Hydrogenolysis of Lignin into Phenolics by Internal Hydrogen over Ru Catalyst

Abstract

Lignin is a by-product of biorefineries and pulp and paper manufacturers. Lignin is a renewable source of phenolic precursors for fuels and chemicals. Hydrogenolysis of lignin cleaves the abundant β-O-4 bonds and releases phenolics. However, selective hydrogenolysis of lignin’s β-O-4 bonds is challenging because it requires high-pressure H₂. Here we show efficient hydrogenolysis of lignin model compounds and technical lignin by Ru/C catalyst and internal hydrogen. The aliphatic hydroxyl groups (C_α OH) in lignin enabled Ru-catalyzed dehydrogenation of internal hydrogen and the formation of reactive keto intermediate, which facilitated the β-O-4 cleavage into phenolic monomers. Furthermore, solvents that had high donor number (Lewis basicity) enhanced the yield of phenolic monomers, equal to 27.9 wt.% from technical lignin. These findings offer a novel approach for biorefineries to design lignin isolation processes and/or solvent systems to maximize phenolic monomers and to control product selectivity/stability.

Citation

Hossain, Md. Anwar; Saelee, Tinnakorn; Tulaphol, Sarttrawut; Rahaman, Mohammad Shahinur; Phung, Thanh Khoa; Maihom, Thana; Praserthdam, Piyasan; Praserthdam, Supareak; Yelle, Daniel J.; Sathitsuksanoh, Noppadon. 2022. Catalytic Hydrogenolysis of Lignin into Phenolics by Internal Hydrogen over Ru Catalyst. ChemCatChem. 14(20): 10.1002. https://doi.org/10.1002/cctc.202200549.