Green, efficient delignification of hybrid Pennisetum (Pennisetum americanum×P. purpureum) using steam explosion assisted p-toluenesulfonic acid treatment

Abstract

Effective separation of lignin is a prerequisite for the high-value application of lignocellulosic biomass. In this work, the delignification of hybrid Pennisetum (Pennisetum americanum×P. purpureum, HP) using environmentally-friendly steam explosion assisted p-toluenesulfonic acid (p-TsOH) treatment was investigated. The enhancement mechanism of steam explosion was studied by structural analysis of lignin separated using a double enzymatic hydrolysis method. The results showed that the p-TsOH delignification process could be successfully simulated by a second-order kinetic model. After steam explosion at logR0= 3.89, the activation energy for lignin p-TsOH extraction decreased by 30%, the extraction capacity increased by 60%, and the fractionation yield of lignin reached 89.21%, enabling rapid and near-complete dissolution of lignin. Characterization of physicochemical properties using BET, GPC, and XRD techniques indicated that the specific surface area of HP dramatically increased after steam explosion (from 0.9 to 5.02 m2 g−1), while the lignin molecular weight significantly decreased. The 2D-HSQC spectra further revealed that various linkages (e.g., β-O-4, β-5, and BE) in lignin underwent varying degrees of cleavage after steam explosion, and the depolymerization reaction was dominant. These modifications by steam explosion collectively led to changes in the lignin fractionation process. This work provides a green and efficient method for delignification of HP, which helps to maximize the utilization of HP for biorefinery industries.