Catalytic hydrogenolysis lignin to obtain phenols: A review of selective cleavage of ether bonds

Abstract

Lignin depolymerized phenolic compounds and biofuel precursors are ideal value-added products for lignin residues generated in biorefineries and modern paper pulp facilities. Hydrogenolysis of lignin is an efficient depolymerization method for the production of carbon-neutral sustainable fuels and platform chemicals. Lignin is underutilized due to its complex structure, mainly because of its complex interunit linkage crosslinks such as α-O-4, β-O-4, 4-O-5, and β-5. This paper centers on the hydrolysis reaction of three major ether bonds (α-O-4, β-O-4, 4-O-5) in lignin and lignin model compounds based on different catalysts for hydrogenative degradation and catalytic systems. The methods and strategies to inhibit the condensation reactions are summarized. In particular, density functional theory calculation of the reaction pathways are combined with isotopically labeled reaction pathways to deeply analyze the hydrogenation degradation mechanism of biomass and further improve the yield of monophenols during the hydrogenation degradation of lignin. Finally, a brief summary of the challenges and prospects of lignin hydrogenation degradation is proposed.

Research progress on lignin-based carbon electrode materials in rechargeable batteries

“…The extended network of lignin is constructed from monomers of coniferyl alcohol, sinapyl alcohol, and p-coumarin alcohol in random order through intermolecular C-O and C-C bonds (Yue et al 2016;Shao et al 2017;Feghali et al 2018;Du et al 2023). In nature, lignin is produced by free radical polymerization of three aromatic alcohols, with different lignocellulosic species, then varying the proportions of p-coumaryl, pinacol and mustelol (Rinaldi et al 2016;Ralph et al 2019).…”