Efficient production of low molecular weight lignin from eucalyptus wood through methanol-alkali system

With the high phenolic hydroxyl content and excellent bioactivity, low molecular weight lignin (LMW-Lignin) holds tremendous potential for various applications in energy storage and antibacterial materials. However, conventional sources of lignin currently available are characterized by large molecular weights, and many of their active functional groups remain unreleased, limiting their exploitation for potential applications. In this study, we investigated the inhibition effect of methanol on the recondensation of lignin fragments under a hydrothermal system of methanol/sodium hydroxide, using eucalyptus wood flour as the raw material. Our findings revealed that, in the hydrothermal alkaline system,& sdot;OCH3 free radicals formed from methanol can effectively target and react with the active sites (C alpha and C beta) on the dissolved lignin side chains, resulting in the formation of stable methoxyl structures and preventing the formation of C-C bonds and polycondensation of dissolved lignin. Optimized conditions, including 20% CH3OH (methanol content), 14% NaOH (sodium hydroxide content), and a reaction temperature of 160 celcius, led to a weight-average molecular weight of 1478 for the lignin product, with a yield of 62.90%.