Ultrasound-Assisted Sequential Extraction for Lignocellulose Pyrolysis Bio-Oil Fractionation. Part I: Method Development

The work herein presents a novel ultrasound-assisted sequential extraction (UASE) method for fractionating bio-oils derived from lignocellulosic biomass pyrolysis. The fractionation method uses hexane, toluene, and dichloromethane, to produce fractions with distinctive composition with minimal sample loss as no stationary phases are used. Characterization of the fractions and the original bio-oil by gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H NMR), gas chromatography–mass spectrometry (GCMS), and pyrolysis-GCMS, revealed marked compositional differences between the fractions. Lighter fractions contained a high concentration of light aromatic compounds, ideal for hydrogenation into fuel, whereas heavier fractions showed similarity to lignin standards with an increased presence of sugar-like compounds. This study introduces a novel fractionation technique for bio-oil analysis and establishes a framework to standardize bio-oil quality assessment, with plans to apply these methods to various bio-oils in future research.