Lignin is the only large-volume renewable source of aromatic chemicals. Efficient depolymerization and deoxygenation of lignin while retaining the aromatic functionality are attractive but extremely challenging. Here we report the selective production of arenes via direct hydrodeoxygenation of organosolv lignin over a porous Ru/Nb2O5 catalyst that enabled the complete removal of the oxygen content from lignin. The conversion of birch lignin to monomer C7–C9 hydrocarbons is nearly quantitative based on its monomer content, with a total mass yield of 35.5 wt% and an exceptional arene selectivity of 71 wt%. Inelastic neutron scattering and DFT calculations confirm that the Nb2O5 support is catalytically unique compared with other traditional oxide supports, and the disassociation energy of Caromatic–OH bonds in phenolics is significantly reduced upon adsorption on Nb2O5, resulting in its distinct selectivity to arenes. This one-pot process provides a promising approach for improved lignin valorization with general applicability.

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Conversion of lignin into monocyclic hydrocarbons as commodity chemicals and drop-in fuels is a highly desirable target for biorefineries. However, this is severely hindered by the presence of stable interunit carbon-carbon linkages in native lignin and those formed during lignin extraction. Herein, we report a new multifunctional catalyst Ru/NbOPO4 that achieves the first example of catalytic cleavage of both interunit C-C and C-O bonds in one-pot lignin conversions, yielding 124-153% of monocyclic hydrocarbons; that is 1.2-1.5 times those yields obtained from the established nitrobenzene oxidation method. This catalyst also exhibits high stability and selectivity (up to 68%) to monocyclic arenes over repeated cycles. The mechanism of the activation and cleavage of 5-5 C-C bonds in biphenyl, as a lignin model adopting the most robust C-C linkages, has been revealed via in situ inelastic neutron scattering, coupled with modelling. This study breaks the conventional theoretical limit on lignin monomer production.

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