On-Demand Regulation of Lignocellulosic Nanofibrils Based on Rapid Fractionation Using Acid Hydrotrope: Kinetic Study and Characterization

Lignocellulosic nanofibrils (LCNF) has caused great interest from researchers due to the benefits of high output, low operation cost, and weak environmental impact. The existence of lignin in LCNF can be applied to regulate the hydrophilicity and polarity, thereby endowing LCNF with unique properties. Consequently, it is crucial to tailor the production of LCNF with desirable characteristics for various applications. This work demonstrated the feasibility of on-demand regulation of lignocellulosic nanofibrils based on rapid fractionation using p-toluenesulfonic acid (p-TsOH) hydrolysis. Acid concentration of 20–80 wt %, hydrolysis temperature of 50–80 °C, and reaction duration of 20–120 min were employed to control the characteristic of reaction products. Different degrees of delignification and xylan dissolution over the entire reaction space were obtained and related to combined delignification factor (CDF) and combined hydrolysis factor (CHF), respectively. It was also found that the mean fibril height of LCNF were significantly affected by CDF and CHF, independent of each reaction process variables. Detailed characterization revealed that the resultant LCNF presented wide range of fibril height (10.6–86.4 nm) and excellent thermal stability (maximal weight loss temperature of approximately 360 °C). Overall, this work provides useful and fundamental knowledge for achieving LCNF with tailored characteristics, all of which are essential to many promising applications.