From Lignin to Polyols: Combined Catalytic and Electrochemical Approach for Advanced Biomass Conversion

Lignin is the largest renewable aromatic resource, yet its structural complexity limits its integration into chemical value chains. This work presents a combined catalytic and electrochemical strategy for converting technical lignins into functionalized oligomers and polyol precursors for polyurethane applications. Technical Kraft lignin was subjected to catalytic hydrogenolysis followed by controlled oxidation, reducing high-molecular-weight fractions and generating lower-molecular-weight oligomers with modified side-chain functionalities. Subsequent electrochemical upgrading in a two-compartment cell enabled targeted functionality tuning under mild conditions (20–60 °C). RuO2 electrodes promoted a-functionalization-assisted ß–O–4 cleavage, while Cu-based catalysts reduced aldehydes to al-cohols with faradaic efficiencies above 60%. Multidimensional NMR and quantitative ³¹P{¹H} NMR analyses revealed hydroxyl-rich oligomeric structures with aromatic and aliphatic functionalities relevant for polyurethane chemistry. The integrated catalytic–electrochemical route provides a modular pathway toward renewable aromatic polyols, lignin-derived resin precursors, and circular carbon value chains.