Highly efficient conversion of camphor tree sawdust into bio-oil and biochar products by liquefaction in ethanol-water cosolvent

Abstract

The liquefaction of camphor tree sawdust (CTS) in ethanol-water cosolvent is preliminarily explored in this study. Remarkably, efficient conversion of CTS is achieved as a result of the synergetic effects between ethanol and water during liquefaction process. The liquefaction of CTS in isometric ethanol-water cosolvent at 280 ℃ for 30 min results in higher conversion rate (98.4 wt.%), bio-oil yield (61.5 wt.%) and energy recovery rate (94.5%) compared to pure water/ethanol treatments. In addition, the application of ethanol-water cosolvent promotes the contents of esters and ketones in bio-oil, while suppresses the formation of nitrogenous compounds. Meanwhile, the percentage of low-boiling-point compounds in bio-oil reaches 30.8%, falling between that in pure water treatment (21.6%) and that in pure ethanol treatment (51.5%). The corresponding biochar products obtained in ethanol-water cosolvent treatment also possess better thermal stability, surface characteristics (specific surface area, 9.1 m2/g and pore volume, 0.0319 m3/g) and nutrient compositions (total nutrients, 21.4 g/kg). In consideration of the yield and quality of bio-oil and biochar products, ethanol-water cosolvents may be the first choice for the liquefaction of CTS, rather than pure water/ethanol.