Disassembly of lignin and chemical recovery—rapid depolymerization of lignin without char formation in water–phenol mixtures

Depolymerization of lignin was examined in a water–phenol mixture at 673 K. No char formation was found and the 99 wt.% of the products was soluble in tetrahydrofuran after a reaction time of 1 h. We confirmed depolymerization of lignin by gel permeation chromatography that showed smaller molecular weight distribution for products than that of original lignin. Within a reaction time of 0.1 h, lignin, whose average molecular weight was 2100, was converted into compounds that have average molecular weight of 660. With reaction time, amount of the higher molecular weight compounds first decreased and that of lower molecular weight compounds increased. The chemical species in the products were identified by gas-chromatography-frame ionization detector and mass spectroscopy. These results indicate the synergistic effect of phenol and water in the depolymerization of lignin without char formation.