Extraction and Recovery of High-Value Chemical Compounds from Aqueous Phase Pyrolysis Bio-Oil

Pyrolysis bio-oil is a complex mixture rich in oxygenated compounds with significant commercial potential. Among its fractions, the bio-oil aqueous phase (BOAP) contains valuable phenolics, furanics, alcohols, and carboxylic acids that can be recovered and valorized. This study investigates liquid–liquid extraction (LLE) as a strategy for recovering value-added chemicals from Eucalyptus globulus BOAP using both conventional and bio-based solvents. Solvent screening was performed with toluene, heptane, hexane, ethyl acetate (EA), cyclopentyl methyl ether (CPME), 2-methyltetrahydrofuran (2-MTHF), turpentine, and octanoic acid. A systematic thermodynamic modeling framework was applied to select the most suitable model for process simulation. A representative BOAP mixture was implemented in Aspen Plus and validated against experimental equilibrium data at 293.15 K and 101.3 kPa. Subsequently, techno-economic assessment (TEA) was conducted to evaluate process performance. The results showed that aromatic and moderately polar solvents, particularly toluene, CPME, and 2-MTHF, achieved extraction efficiencies exceeding 80% for phenolic and furanic compounds, whereas non-polar aliphatic solvents such as hexane and heptane exhibited lower extraction capacities. Carboxylic acid extraction increased with solvent carbon chain length, while methanol remained predominantly in the aqueous phase. Root mean square error (RMSE) analysis identified NRTL-HOC as the most reliable thermodynamic model, with deviations ranging from 0.07 to 0.19, outperforming COSMO-RS and COSMO-SAC approaches. TEA results revealed a strong influence of solvent selection on process economics. EA provided the lowest minimum selling price (MSP) of approximately 2,525 USD/ton, followed by 2-MTHF, while CPME and hexane were less economically attractive due to higher operating costs. Overall, bio-based ethers demonstrated competitive extraction performance, highlighting their potential as sustainable alternatives for BOAP valorization.