EFFECTIVE RECOVERY OF CHEMICAL SPECIES FROM LIGNIN IN WATER-PHENOLIC SOLVENTS UNDER SUPERCRITICAL CONDITIONS

摘要

Biomass has been proposed an alternative source of chemicals to save as fossil resources such as coal and petroleum. However, lignin, one of the major constituents of wood, can be converted into chemicals in low yields because lignin is easily denatured by acid or heat. Consequently, most of lignin is utilized only as fuels. The conversion of lignin into liquid products and chemicals with supercritical water has been investigated. Johnson et al. conducted the liquefaction of organosolv lignin in supercritical water using Pt catalysts at 648 K under 27.6 MPa of hydrogen and bund that the yield (maximum 4.4%) of hydrolysis products such catechol increased with reaction time. Yokoyama et al. examiined decomposition of organosolv lignin in supercritical water at 623 - 693 K up to 40 MPa and reported that the yield (maximum 40%) of oil and that of products containing hydroxyl groups increased and that ( minimum 30%) of char decreased with increasing water density. These results indicate that hydrolysis is an important reaction for disassembly of lignin in supercritical water. However, the formation of char due to re-polymerization occurs at the same time and lignin is converted into chemicals in low yields.