An effective chemical pretreatment method for lignocellulosic biomass with substituted imidazoles

Lignocellulosic biomass is the most abundant naturally renewable organic resource for biofuel production. Because of its recalcitrance to enzymatic degradation, pretreatment is a crucial step before hydrolysis of the feedstock. A variety of pretreatment methods have been developed and intensively studied to achieve optimal yield without imposing significant adverse impact on the environment. Herein, we present a novel chemical pretreatment method using substituted heterocycles with low temperature and short residence time requirements. 1-Methylimidazole (MI) is a precursor to some imidazolium-based ionic liquids. In this study, its potential utilization as a biomass pretreatment agent is being investigated for the first time. At mild conditions, such as 25°C for 5 min at ambient pressure, a substantial increase in the hydrolysis rate throughout the entire course of conversion for cellulose substrate was obtained. Furthermore, the pretreatment effectiveness of MI on both untreated and steam-exploded lignocellulosic biomass including loblolly pine, switchgrass, and sugarcane bagasse has been studied and MI was found to be an efficient delignifier. Remarkable rate enhancement was also observed for the non-woody lignocellulosic substrates after a short period of MI pretreatment at ambient conditions. The mechanism of MI pretreatment is explored through analysis of cellulose physical properties including crystallinity index, degree of polymerization, accessibility, and lignin dissolution quantification.