Facilitated biomass fractionation by a p-toluenesulfonic acid-catalyzed γ-valerolactone pretreatment for co-production of glucose and levulinic acid from masson pine

Abstract

Development of green pretreatment strategies with excellent lignin removal ability is particularly important for masson pine biorefinery. γ-Valerolactone (GVL), as a green and recyclable solvent, has unique solvent characteristics to extract lignin. In this study, three acid catalysts, including sulfuric acid (H₂SO₄), hydrochloric acid (HCl) and p-toluenesulfonic acid (TsOH), were used to catalyze γ-valerolactone (GVL) pretreatment of masson pine. Among them, the TsOH-catalyzed GVL pretreatment achieved the highest lignin removal ratio and the best cellulose enzymatic hydrolysis yield. Under the optimized pretreatment conditions (150 ℃, 150 mM TsOH, GVL/H₂O (4:1, w/w), 1 h), the lignin removal ratio reached 89.0 %, achieving a 72 h glucose yield of 87.1 % from the pretreated residues. The solvent lignins from pretreatment liquid was separated and characterized by NMR analysis. Meanwhile, the hexoses in pretreatment liquid were further converted into levulinic acid (LA) using the TsOH-catalyzed bi-phase reaction systems. This study gives insights into developing a biorefining process for the effective utilization of masson pine.