Impact of benzene-ethanol extractives on deep eutectic solvent-mediated lignin extraction from poplar and eucalyptus

Deep eutectic solvents (DES), an emerging class of green solvents, have demonstrated remarkable efficiency in the fractionation of lignocellulosic biomass. Benzene-ethanol extractives in woody biomass significantly affect the efficiency of DES-mediated fractionation. Therefore, investigating influence of benzene-ethanol extractives on DES-mediated pre-treatment is essential for optimizing of poplar and eucalyptus fractionation. Removing benzene-ethanol extractives significantly increased the polar component of the surface free energy (SFE) in both poplar and eucalyptus biomass. This prominently enhanced the wettability of DES on the raw materials, thereby ameliorating heat and mass transfer effectiveness. Furthermore, the removal of these extractives was instrumental in modifying the surface pore structure of the raw materials, thereby facilitating a further meliorative fractionation effect of DES. Following the removal of the benzene-ethanol extract, the delignification efficiency for poplar and eucalyptus significantly increased to 81.92 % and 80.16 %, respectively. Concurrently, the extracted lignin exhibited higher hydroxyl content, a more complex aromatic ring structure, and improved thermal stability. All these findings substantiate that the removal of benzene-ethanol extractives represents a promising strategy for enhanced DES fractionation efficiency.