Lignin-based resin production from lignocellulosic biomass combining acidic saccharification and acetone-water treatment

The structure of lignin is formed by the cross-linking of phenolic compounds. Taking advantage of this structural property, the conversion method of lignin into resin material was developed in this study. Depolymerization of lignin is one of the most important factors for utilizing the basic frameworks of phenylpropanoids. Lignin is extractable from lignocellulosic biomass using acetone-water binary solution. Therefore, the simultaneous extraction and depolymerization of lignin under high temperature and high pressure from Japanese cedar was examined. Prior to the extraction process, cedar was treated with 50 wt% formic acid at 175 °C for the saccharification of hemicellulose and part of cellulose which could be contaminants in resin material. Next, the lignin extraction was conducted using 30 wt% of acetone at the higher temperature of 295 °C and 0.82 g/(g-lignin in material) was obtained. The curing property of the obtained sample was evaluated by differential thermal analysis and the detected exothermic energy during resinification was 18.2 μV/mg. In addition, it was confirmed by visual observation that the obtained sample resinified uniformly by heating at 150 °C. Thus, the effective production method of usable lignin-based resin was developed. Lastly, this treatment method was applied to eucalyptus, another type of lignocellulosic biomass, and was validated as effective.