Chemical Conversion of Lignocellulosics as Treated by Two-Step Hot-Compressed Water

Abstract

Chemical conversion of lignocellulosics in two-step semi-flow hot-compressed water treatment was investigated for Japanese beech (Fagus crenata) as one of the hardwoods and Japanese cedar (Cryptomeria japonica) as one of the softwoods, with the first step at 230°C / 10 MPa for 15 min to decompose hemicellulose and lignin, and the second step for cellulose at 270°C / 10 MPa / 15 min and 280°C / 10 MPa / 30 min for Japanese beech and Japanese cedar, respectively. As a result, totally 97.2% of Japanese beech and 87.8% of Japanese cedar could be solubilized by the hot-compressed water with 2.8% and 12.2% water-insoluble residue composed mainly of lignin, respectively. In addition to the hydrolyzed products, the dehydrated, fragmented and isomerized products as well as organic acids were additionally recovered in the water-soluble portion. The differences observed in lignin between Japanese beech and Japanese cedar would be due mainly to the inherent differences in lignin structure between hardwoods and softwoods. © Springer 2010.