Revealing structural features of lignin macromolecules from microwave-assisted carboxylic acid-based deep eutectic solvent pretreatment

Lignin is the most abundant aromatic source in nature, whose efficient utilization has been recognized as a key challenge in biorefinery. Deep eutectic solvents (DES) exhibit excellent solubility for lignin, and are promising solvent for facilitating the lignin-first biorefinery and valorization of lignin. Herein, microwave-assisted car-boxylic acid-based DES pretreatment was applied on corncob; the effects of the pretreatment on physical and chemical structures of lignin was investigated. The results showed that microwave-assisted DES pretreatment enhanced the deconstruction efficiency of corncob in terms of the high removal ratio and recovery yield of DES -lignin; Moreover, the resultant DES-lignin exhibited lower molecular weights and particle size than that from conventional DES pretreatment, and presented abundant phenolic OH groups. This study provide a highly efficient pretreatment approach for the agricultural residues and the sufficient understanding on structural and chemical characteristics of resultant DES-lignin will promote its subsequent conversion and application.