Efficient pretreatment of cornstalks for lignin valorization using p-toluene sulfonic acid coupling ethylene glycol

Efficient extraction of lignin from intricate lignocellulose is a challenge for the high-value utilization of lignocellulosic biomass in sustainable biorefinery. In this work, a p -toluene sulfonic acid-coupling ethylene glycol (PTSA/EG) pretreatment was developed to extract lignin from cornstalks. The results showed that the synergistic effect between p -toluene sulfonic acid and ethylene glycol resulted in an increase in the delignification ratio from 43.43 to 85.37% compared with PTSA aqueous pretreatment. When the concentration of PTSA was 5 wt.%, the delignification ratio reached 85.37% at 383.15 K under the PTSA/EG pretreatment. Moreover, the lignin fractions obtained by water precipitation have high purity (>90%) and a low molecular weight (1777~2271 Da). The fractionated lignin was depolymerized with Ru/C catalyst and methanol at 508.15 K for 3 h. When the pretreatment temperature is 368.15 K, the fractionated lignin has a good depolymerization performance, and the detected monomers yield reaches 17.46%. Overall, pretreatment using PTSA and EG could realize the disruption of the degradation barrier of lignocellulose and fractionate lignin with specific structures by adjusting the pretreatment conditions, which was conducive to commercial applications in biomass refining.