Lignin is an aromatic polymer that constitutes up to 30 wt% of woody biomass and is considered the largest source of renewable aromatics. Valorization of the lignin stream is pivotal for making biorefining sustainable. Monomeric units in lignin are bound via C–O and C–C bonds. The majority of existing methods for the production of valuable compounds from lignin are based on the depolymerization of lignin via cleavage of relatively labile C–O bonds within lignin structure, which leads to yields of only 36–40 wt%. The remaining fraction (60 wt%) is a complex mixture of high-molecular-weight lignin, generally left unvalorized. Here we present a method to produce additional valuable monomers from the high-molecular-weight lignin fraction through oxidative C–C bond cleavage. This oxidation reaction proceeds with a high selectivity to give 2,6-dimethoxybenzoquinone (DMBQ) from high-molecular-weight lignin in 18 wt% yield, thus increasing the yield of monomers by 32%. This is an important step to make biorefining competitive with petroleum-based refineries.
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The data that support the plots within this paper and other findings of this study, such as 1H NMR, 13C NMR and HPLC spectra, as well as experimental procedures and quantum chemical calculations are available in the Supplementary Information.
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E.S. and J.S.M.S. thank the Swedish Energy Agency (Energimyndigheten, grant nos. 47448-1, 45903-1 and 41262-1). T.R. and J.S.M.S. thank the Bio-based Industries Joint Undertaking under the European Union’s Horizon 2020 research and innovation program (grant no. 744349). M.D.M.-M. thanks COST (grant no. FP-1306-STSM). M.J. and X.Y. thank Olle Engkvists Stiftelse (grant no. 189-0209) and Åke Åkessons Stiftelse (grant no. 1943229).
J.S.M. Samec is the founder of RenFuel, a company working on lignin valorization. The other authors do not declare any competing interests.
Peer review information Nature Chemistry thanks Jeremy Luterbacher and the other, anonymous, reviewer(s) for their contribution to the peer review of this file.
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Subbotina, E., Rukkijakan, T., Marquez-Medina, M.D. et al. Oxidative cleavage of C–C bonds in lignin. Nat. Chem. 13, 1118–1125 (2021). https://doi.org/10.1038/s41557-021-00783-2
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