Hydrothermal Depolymerization of Kraft Lignins with Green C₁–C₃ Alcohol–Water Mixtures

Lignin is a potential renewable raw material for synthesis of aromatic molecules and materials. Particularly, Kraft-type lignins are abundantly available as byproduct wood paper industries. Currently, there practically no valuable products made using this highly complex polymer. Within work, we have investigated the straightforward, high-yield depolymerization two different technical (Indulin AT alkaline lignin) only mixture green short-chain (C1–C3) alcohols water solvents. As shown here, at temperature 220 °C, autogenous pressure, isopropanol/water co-solvent medium, it possible to cleave Kraft lignin without char-forming side reactions. The obtained so-called “light” oil contains guaiacol-based monomeric units 23 wt % yield together with liquid oligomers 13 combining liquid–liquid solid–liquid extraction. Two-dimensional nuclear magnetic resonance analysis residues showed that treatment caused marked breakdown intermolecular β–O–4 β–β bonds; thus, produced monomers lower molecular weight. results suggested synergistic effect between isopropanol water. No sign repolymerization reactions could be observed process.