Comparison of solvents for the recovery of low-molecular carboxylic acids and furfural from aqueous solutions

•Various types of solvents were tested for extraction of formic acid, acetic acid and furfural from aqueous solutions.•Alamine 336 and 2-MTHF solvents showed the most promising results among the tested solvents.•The use of diluent is required with Alamine 336 to prevent the formation of a third phase.•A low mixing rate was necessary with Alamine 336 to avoid emulsion formation and increase the rate of phase separation. Liquid–liquid extraction of formic acid, acetic acid and furfural from an aqueous synthetic acid hydrolysis process stream is studied. Different types of extractants are first evaluated and two solvents that can efficiently recover the compounds, 2-methyltetrahydrofuran (2-MTHF) and tri-n-octylamine in toluene (Alamine 336-toluene) are then studied further. Important considerations in solvent selection were the efficiency of solvent regeneration and the recovery of the extractives from the loaded solvents. Solvent regeneration experiments were carried out under a vacuum in a spinning band distillation unit. Both solvents showed good regeneration characteristics. The rate of phase separation for Alamine 336 increased, without the formation of an emulsion, when performing extractions at low mixing rates. The use of toluene as a diluent for Alamine 336 prevented the formation of a third intermediate phase. In general, the equilibrium favors the extraction of formic acid for Alamine 336 and the extraction of furfural for 2-MTHF. For acetic acid there was only a small difference in the distribution coefficients for both solvents.