Characteristic analysis of fractionized light and heavy oil derived from Korean native kenaf via hydrothermal liquefaction

Bio-oil is a complex organic mixture originating from biomass that requires further classification prior to utilization. In this study, bio-oil produced by hydrothermal liquefaction (HTL) was fractionated into light and heavy oil to analyze individual characteristics. HTL was performed at different temperatures (200–350 °C), time (0–120 min), and ethanol concentration (25–75 vol %). The bio-oil yield was the highest at 275 °C, 30 min, and 75 vol %, containing 47.49% of light oil and 10.25% of heavy oil. In addition, the light oil yield decreased with increasing temperature, whereas heavy oil showed no pronounced difference. Conversely, elemental analysis showed that the decreases in atomic H/C and O/C ratios were more significant in heavy oil than in light oil. The TGA results showed that light oil mainly decomposed at a lower temperature than that of heavy oil, indicating their difference in thermal stability. FT-IR and GC-MS were performed to further analyze the differences between the two oils. The FT-IR spectra showed different characteristic bond peaks between light and heavy oil. The GC-MS results indicated that fatty acid esters were significant in heavy oil, whereas syringyl group compounds were the main compound group in both light and heavy oils. •Bio-oil was acquired under different temperature, time, and ethanol concentration. •Bio-oil was separated into light oil and heavy oil via liquid-liquid extraction. •Effect of temperature was most prominent in hydrothermal liquefaction. •Acquired bio-oil was relatively enriched with syringyl group compounds. •Fatty acid ethyl esters derived from extractives in kenaf were abundant in heavy oil.