Green Process for Extraction of Lignin by the Microwave-Assisted Ionic Liquid Approach: Toward Biomass Biorefinery and Lignin Characterization

A facile and efficient strategy for the extraction of lignin and lignocellulosic biomass processing is crucial for sustainability of current biorefineries. In this work, lignin was extracted from eucalyptus by a ionic liquid-based microwave-assisted approach. The lignin samples were analyzed and compared to evaluate the extraction efficiency of the approach in terms of yields, associated sugars, and S/G ratios. It was found that 97.6% (w/w) of eucalyptus biomass was extracted by ILs-MAE process at 140 degrees C and 24.6% of lignin (based on Klason lignin) was released. Nearly half the amount of lignin (45.8%) was extracted by [C2C1 im][OAc] under low-intensity microwave irradiations. Changes in microwave power showed great changes in biomass deconstruction and lignin extraction by ILs. The 2D HSQC NMR results indicated that more number of C-C and C-O-C bonds could be degraded by this green extraction process. The depolymerization mechanism of the lignin extracted by IL-MAE process was proposed. This study provides panoramic perspectives of the green avenues for lignin extraction and depolymerization of biomass and helps us to develop more cost-effective strategies for biomass biorefineries.