Selective dissociation and conversion of hemicellulose in Phyllostachys heterocycla cv. var. pubescens to value-added monomers via solvent-thermal methods promoted by AlCl3

Abstract

Selective dissolution of hemicellulose from Phyllostachys heterocycla cv. var. pubescens (shortened to pubescens afterwards), and conversion of dissolved hemicellulose into value-added monomers (such as furfural and levulinic acid) promoted by AlCl₃ under solvent-thermal conditions were investigated. Solid biomass samples were characterized by chemical titration and XRD techniques. Liquid products were analyzed by GC-FID, HPLC, and GPC. In the AlCl₃ promoted dissociation of hemicellulose from pubescens, the conversion of hemicellulose reached 72.6 wt% without significant degradation of cellulose and lignin (only 10.4 wt% and 13.3 wt%, respectively) after hydrothermal treatment at a rather low temperature of 120 °C for 4 h. The extracted hemicellulose could be divided mainly into two parts, that is, monomers (such as xylose, furfural and acetic acid, about 36.1%) and oligomers (about 63.9%). THF and SiO₂ were added, forming a SiO₂–AlCl₃–H₂O/THF system, for the further conversion of the oligomers and monomers derived from hemicellulose. The selectivity towards total monomers could reach 97.6% based on the converted pubescens. High selectivity towards value-added monomers (39.1% furfural and 48.3% levulinic acid) was obtained at 160 °C.