External authors:

• Junior Lorenzo-Llanes ( Pontificia Universidad Catolica de Chile )
• Jose Palomar ( Autonomous University of Madrid )

Abstract:

Bio-oil's aqueous phase (BAP) has received particular interest for recovering value-added chemicals. To this end, liquid-liquid extraction (LLE) has proven its suitability for bio-oil fractionation and product recovery. The present work aimed to assess greener solvents (e.g., bio-based and terpene-based) for recovering acetic acid and acetol as model compounds of the BAP via physical and reactive LLE. A solvent screening (>2000 compounds) based on the distribution coefficient (K-d) of each solute in the solvent/water biphasic system estimated by COSMO-RS was used. Then, the solvents' environmental, safety, and human health impacts were assessed. The selected candidates were used to validate the COSMO-RS predictions through LLE measurements. In the reactive LLE, the selected extracting solvents were mixed with trioctylamine (TOA) or tributyl phosphate (TBP) used as the reactive extractants. Finally, the temperature and extractant fraction effects were assessed in terms of the K-d for the best diluent + extractant pairs. For acetic acid, 2-methyltetrahydrofuran (K-d = 1.8) outperformed the rest of the solvents during the physical extraction, whereas for acetol, 2-methyl-2-butanol (K-d = 0.44) was the solvent with the best performance. Moreover, attractive K-d values were obtained for acetic acid (K-d = 0.91) and acetol (K-d = 0.37) using 2-phenylethanol. In the reactive LLE, TOA-based extractants improved the acetic acid K-d up to 10 times compared to the physical extraction, with no improvement on acetol. For TBP-based extractants, no clear improvements were observed. Acetic acid selectivity was maximized at 293 K, and a TOA mass fraction between 40 and 50 % for all the diluents.