Lignin is the largest source of renewable aromatic compounds, making the recovery of aromatic compounds from this material a significant scientific goal. Recently, many studies have reported on lignin depolymerization and upgrading strategies. Electrochemical approaches are considered to be low cost, reagent free, and environmentally friendly, and can be carried out under mild reaction conditions. In this Review, different electrochemical lignin conversion strategies, including electrooxidation, electroreduction, hybrid electro‐oxidation and reduction, and combinations of electrochemical and other processes (e. g., biological, solar) for lignin depolymerization and upgrading are discussed in detail. In addition to lignin conversion, electrochemical lignin fractionation from biomass and black liquor is also briefly discussed. Finally, the outlook and challenges for electrochemical lignin conversion are presented.
It
has been known that the yield of lignin monomers during lignin
depolymerization is limited by the irreversible condensations of lignin
in the fractionation and/or depolymerization process. In this study,
we report a new oxidative catalytic fractionation (OCF) process with
a simple and effective one-pot but two-step approach to depolymerize
lignin to lignin-derived chemicals (LDCs) using polyoxometalate (POM)
as the only catalyst. First, the POM effectively catalyzed the methoxylation
of the active α-OH groups of lignin in a methanol and water
mixture at low temperature (100 °C), and 96% of the stabilized
lignin in the lignocellulose sawdust was extracted to the solution
simultaneously. Then the lignin solution was heated to an elevated
temperature (140 °C) in the same solvent. As a result, 74.0 wt
% of the lignin (based on the weight of the Klason lignin in the wood)
was converted to LDCs, including 45.9 wt % aromatic monomers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.