Phase Equilibria for Ternary Liquid Systems of (Water + Carboxylic Acid + 1‐Heptanol) at 293.15 K: Modelling Considerations

Abstract

Des données d'équilibre liquide-liquide pour des courbes de solubilité et des compositions extrêmes de lignes d'équilibre sont présentées pour des mélanges d'[eau (1) + acide formique, ou acide acétique, ou acide propanoïque (2) + 1-heptanol (3)] à T = 293,15 K et P = (101,3 ± 0,7) kPa. Les propriétés et les équilibres liquide-liquide (LLE) des systèmes ternaires associés ont été corrélés à l'aide d'une méthode solvatochrome SERLAS. Les lignes d'équilibre ont également été prédites avec le modèle UNIFAC original. Le modèle proposé permet de mieux caler les données pour les systèmes ternaires, l'erreur moyenne étant de 3,8 % pour tous les systèmes considérés.

Estimation of liquid‐liquid equilibrium of type 2 systems (water + valeric acid + monobasic ester or dibasic ester or alcohol) using SERLAS, SERLAS‐modified, and SERLAS‐integrated

“…The separation factors S , D M , S M , and O F , all defined as the property Pr (log mean), can be expressed through a log‐basis Equation , which combines the Pr 0 property (log mean) at x 2 = 0 region with an integration term containing six physical descriptors ( Γ L , δ H , , β , α , δ ). Here, Γ L is the thermodynamic factor derived from UNIFAC‐Dortmund, is the modified Hildebrand solubility parameter, and , δ *, α *, and β * are the modified solvatochromic parameters, as defined by Senol and Senol et alMore specifically, thermodynamic factors of activity coefficients, Γ L , are essential for considering the nonideality of the liquid phase; δ H is characteristic of cohesive energy density (square of δ H ) when dealing with enthalpies or free energies of solution; a polarity/polarizability term ( π + dδ ) measures the endoergic effects of solute‐solvent dipole‐dipole and dipole‐induced dipole interactions, i.e. the solvatochromic parameter π is an index of polarity/polarizability, which measures the ability of a component to stabilize a charge or a dipole by virtue of its dielectric effect and δ is a polarizability correction parameter reflecting differences in the component polarizability; the β scale is the HBA (hydrogen‐bond acceptor) ability of the solute to accept a proton in a solute‐to‐solvent hydrogen bond and α is the HBD (hydrogen‐bond donor) ability of the solute to donate a proton in a solvent‐to‐solute hydrogen bond.…”

“…F 1 and F 2 are correction factors that account for the limiting condition x 2 = 0 for which Pr = Pr 0 (Equation ). The calculation of the physical indices Γ L , , , δ *, and α * has been discussed further previously …”

“…Procedurally, for implementing SERLAS, it is necessarily required to characterize and determine all the individual variables and model parameters initially. Typically, a special subprogram is added to the main algorithm to first calculate the thermodynamic factors Γ L relative to the organic phase using the derivative approaches of the activity coefficients applied to the UNIFAC–Dortmund model, as described in detail elsewhere . As might be expected, the calculations could be very sensitive to numerical stability.…”

“…This paper compares the calculations with UNIFAC‐original, SERLAS (solvation energy relation for liquid associated systems), and modified versions of the latter to give a realistic picture of whether the selected model structure is appropriate for a design application or not. Although SERLAS becomes a powerful tool allowing the calculation of types 1 and 2 LLE systems, it also poses some drawbacks such as a need for specifying the boundary conditions for two immiscibility gaps and determining the contribution of activity coefficients to LLE behaviour.…”

“…Special attention was paid to parameterize SERLAS‐integrated using hydrogen‐bond and solubility indices coupled with the activity coefficient characteristics. This was accomplished by combining SERLAS with UNIFAC‐Dortmund, so that the strengths of both methods are being leveraged on a fundamental basis, enabling a real description of the type 2 phase behaviour. Basically, SERLAS‐integrated method is becoming conceptually in compliance with solubility, hydrogen‐bonding, and group‐contribution theories as far as solvent effects are concerned.…”