Effect of EPPS Buffer on the Liquid-Liquid Equilibria of Carboxylic Acids (Acetic Acid or Propionic Acid)-Water-Methyl Isobutyl Ketone at Elevated Temperatures

The capacity of methyl isobutyl ketone (MIBK) containing 5 wt % 4-(2-hydroxyethyl)-1-piperazine propanesulfonic acid (EPPS) buffer has been demonstrated to boost the distribution coefficient and separation factor in the extraction process of carboxylic acids (acetic acid or propionic acid). Liquid-liquid extraction is a useful technique for recovering acetic acid and propionic acid from an aqueous fermentation broth. In this study, the effect of EPPS buffer on the liquid-liquid equilibria (LLE) of water-acetic acid-MIBK and water-propionic acid-MIBK systems were measured at a temperature range of 298.15-318.15 K and atmospheric pressure (P = 0.1 MPa). The distribution coefficient (D) and separation factor (S) were calculated at each tie-line, and the reliability of the tie-lines was evaluated using the Othmer-Tobias and Hand plot correlations. With the addition of 5 wt % EPPS in the water-carboxylic acids-MIBK system, the separation factor increased by 7.2 times of the EPPS-free system. The NRTL model predicts the new LLE tie-lines within reasonable accuracy for this quaternary system. By adjusting constituent binary parameters, the NRTL model satisfactorily correlated the liquid-liquid equilibria of the water + acetic acid + MIBK + EPPS and the water + propionic acid + MIBK + EPPS system.