A green route for esterification of kraft lignin with long-chain fatty acid in water

다국어 초록 (Multilingual Abstract)

Water, as a reaction solvent, has received considerable attention in synthetic organic chemistry due to being low-cost and green. In this study, green esterification of Kraft lignin and oleic acid at room temperature was investigated, and only water was used as a reaction solvent. A surfactant-combined system (p-toluenesulfonic acid/4-dodecylbenzenesulfonic acid) was designed to simultaneously solubilize lignin and disperse oleic acid, producing microreactors for esterification. After the reaction, adding water into the reaction mixture could easily precipitate the lignin ester. Its yield was 30.3 ± 0.9%. The lignin ester was characterized by 1H NMR, FT-IR, GPC, TGA, DSC, PSA, and contact angle analyzer. The results showed the successful esterification of lignin and oleic acid, indicating the effectiveness and feasibility of esterification of macromolecules in water. Due to long oleyl chains substituting hydroxyl groups of lignin, the lignin ester showed a significant decrease in glass transition temperature, an obvious increase in contact angle, and exhibited excellent thermoplasticity and hydrophobicity. Additionally, the result of PSA showed some lignin-ester particles fell in the nano-size range.