Fractionation of woody biomass with impregnation of monophenol by prehydrolysis and the subsequent soda cooking

Abstract

In order to fractionate woody biomass, particularly focusing on the recovery of useful lignin, softwood and hardwood wood meal were impregnated with p-cresol or 2,6-xylenol in advance. Dilute acid hydrolysis of monophenol-impregnated wood meal with 1.1% sulfuric acid at 130 °C for 180 min separated hemicellulose-derived sugars for both softwood and hardwood. Thereafter, soda cooking with 0.5 N sodium hydroxide at 150 °C for 90 min delignified hardwood effectively to produce cellulose with a low lignin content; however, resulted in cellulosic pulp with a 50% lignin content for softwood. Lignin was recovered in higher yields and most became soluble in tetrahydrofuran and flowable with heat because lignin self-condensation was successfully prevented under acid hydrolysis by impregnated monophenols. 2,6-Xylenol was more effective than p-cresol. The prehydrolysis-soda cooking process with monophenols could potentially provide functional materials from cellulose, hemicellulose, and lignin without using sulfur.