New ternary deep eutectic solvents with cycle performance for efficient pretreated radiata pine forming to lignin containing cellulose nanofibrils

Ternary deep eutectic solvents (TDESs) as a new class of solvents play a key role in fabrication of lignin containing cellulose nanofibrils (LCNF), however, current work requires a considerable time and thus limits industrial application of TDES. Herein, a novel strategy was proposed to produce lignin containing cellulose nanofibrils (LCNF) by TDESs based on benzyltrimethylammonium chloride (BTMAC), formic acid (FA), and maleic acid (MA). The TDESs could remove 87.80% of lignin and 89.15% of hemicellulose from Radiata Pine while most of the cellulose reserved under optimum pretreatment conditions (TDES = 100 wt%, T = 130 °C, t = 1.5 h). Benefiting from the increase in cellulase accessibility, desired sugar yield of 98.9% was obtained. Moreover, the proposed TDESs could be regarded as a green medium for the production of containing cellulose nanofibrils (LCNF) in which lignin has been esterified. The LCNF displayed a well-individualized structure with a wide size distribution (32.3–146.9 nm), which was closely associated with lignin content. 13C−1H HSQC 2D NMR test was performed to illustrate the molecular − structural features of lignin and polysaccharide in LCNF. In addition, the self-standing LCNF films exhibited excellent UV-blocking, higher thermal stability, and mechanical strength. Most importantly, LCNF films showed strong barrier property to oil and air owing to lower surface free energy and smaller pore structure. Briefly, this work highlights the pretreatment performance of TDESs for cascade utilization of lignocellulosic biomass to high-value products.