Lignin depolymerization via hydrogenolysis is a promising pathway to produce renewable phenolic monomers.¹ However, our understanding of this process is limited by lignin heterogeneous structure, following complex deconstruction mechanism and yielding broad product distribution after β-O-4 ether linkages.² We developed a rapid extrapolated time zero ¹H–¹³C heteronuclear single quantum coherence nuclear magnetic resonance (HSQC₀ NMR) sequence that enables to quantify native lignin structural features with whole plant cell wall (WPCW) NMR spectroscopy, overcoming fast spin relaxation in gel phase.^3,4 This analytical method is a promising tool to gain new insights towards native lignin structure.

Kinetic and mechanistic studies of β-O-4 model compounds depolymerization were then performed and confirmed higher reactivity of lignin end-units when adsorbed on a Ru/C catalyst. The obtained reaction network and NMR structural insights were applied to multiscale LigninGraphs libraries via a kinetic Monte Carlo framework to model lignin hydrogenolysis.^5,6 Reductive Catalytic Fractionation was successfully modelled and first-ever predicted by our algorithm using dimer kinetic data. This model can notably establish structure-reactivity relationships, that expands our knowledge of lignin structure and understanding of extraction processes. Reaching unexpected insights for lignin engineering, we could ultimately guide the design of highly reactive lignin moieties towards hydrogenolysis.

Qiang Li

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