Reactive Extraction of Levulinic Acid from Aqueous Solutions Using Trioctylamine with Diluents 2-Ethyl-1-hexanol, 4-Methylpentan-2-one, and Isoamyl Alcohol

Separating carboxylic acids from aqueous solutions is a challenge, and reactive extraction has been examined as an attractive alternative. This study investigates the reactive extraction of levulinic acid (LA) using trioctylamine (TOA) in various diluents, such as 2-ethyl-1-hexanol, 4-methylpentan-2-one (MIBK), and isoamyl alcohol. For this purpose, liquid-liquid equilibrium (LLE) data was experimentally obtained for the mix of LA + TOA + H₂O + diluents at T = 293.15 K and atmospheric pressure. From the obtained data, the ability of various TOA/diluent mixtures was evaluated in terms of distribution coefficient (K_D). Isoamyl alcohol was found to be an effective diluent at the diluted region (w_LA^aq < 0.1) with a K_D value of 9.4. However, increasing the concentration of LA resulted in approximately the same extraction ability as the other tested diluents with TOA. Furthermore, the nonrandom two-liquid (NRTL) excess Gibbs energy model was applied to correlate the tie lines. The root-mean-square deviations (RMSD) in liquid mass fraction obtained with the NRTL model for the experimental data of the above-mentioned different LLE systems of 2-ethyl-1-hexanol, MIBK, and isoamyl alcohol were 0.013, 0.018, and 0.016, respectively. Additionally, the K_D values of the systems were also computed.