Integrated Separation Process of C5 Sugars and Phenolics from Poplar Wood Using CO2-Assisted Hydrolysis Followed by Hydrogenolysis

Abstract

This study presents an efficient methodology to remove hemicellulose and lignin from lignocellulosic biomass by a three-step process to obtain C5 sugars, phenolics and high purity cellulose. The first step, a CO2-assisted hydrolysis pretreatment was conducted for the selective extraction of the hemicellulose fraction. The process effectively extracted hemicellulose at 180 °C with CO2 at 20 bar initial pressure for 10 min, during which a variety of monosaccharides and other intermediates were obtained. The second step, the catalytic hydrogenolysis of the pretreated feedstock, was performed in a cosolvent isopropyl alcohol–water system with Raney Ni as the catalyst, which can catalyze the depolymerization of lignin components for phenolic products. A variety of phenolic components with lower molecular weights were detected via GC–MS and HSQC. Further treatment with alkaline hydrogen peroxide was used to extract the remaining small amount of lignin and hemicellulose fractions in biomass and to obtain high pu...