Abstract
Native lignin in woody biomass was selectively converted to lignophenol with p-cresol and concentrated sulfuric acid through the phase separation system. The lignophenol was treated in 0.5 N NaOH solution at 170 °C for 30 min to give phenylcoumaran type aromatic dimers by the selective cleavage of Cβ-O-4 linkages assisted with intramolecular nucleophilic attack to Cβ position. Thorough washing of the acidinsoluble fraction with NaOH under ultrasonic irradiation enabled to isolate the aromatic dimers in acidsoluble fraction quantitatively. The yield of the dimers reached around 40 and 60% for Hinoki and Eucalyptus lignophenol, suggesting that the dimers could be obtained in high yields of 13 and 17% based on Hinoki and Eucalyptus, respectively. The resulting dimers demonstrated a potential for a plasticizing agent of lignin-based polymers.
