Prediction of liquid phase equilibria for water + propionic acid +trans-decalin or cis-decalin and effect of naphthalene as additive

(Liquid–liquid) equilibrium (LLE) data were investigated for mixtures of (water + propionic acid + trans-decalin or cis-decalin) and (water + propionic acid + trans-decalin + naphthalene) at T= 298.15 K and P= 1019.0 hPa. The tie-line data were predicted by the UNIFAC method. The distribution coefficients and the separation factors for the immiscibility region are calculated to evaluate the effect of solvent type. Naphthalene was used as an solid additive to investigate the effect of non-polar additive on separation of the acid from aqeuous solution. It is concluded that trans-decalin is slightly better than cis-decalin but it is a cheaper and more stable solvent and may serve as an adequate solvent to extract propionic acid from its dilute aqueous solutions. Concentration effect of naphthalene also investigated and result showed that it could be very effective in separation of propionic acid from aqueous solution.