Liquid–Liquid equilibria of ternary and quaternary systems including 2,2,4-trimethylpentane, benzene, ethanol, and water at 303.15 K

Abstract

Tie-line data for ternary systems including ethanol (C₂H₆O), water (H₂O), benzene (C₆H₆), and 2,2,4-trimethylpentane (C₈H₁₈) were investigated. Phase diagrams of {w ₁H₂O + w ₂C₂H₆O + (1 − w ₁ − w ₂)C₆H₆} and {w ₁H₂O + w ₂C₂H₆O + (1 − w ₁ − w ₂)C₈H₁₈} ternary systems were obtained at 303.15K, while {w ₁H₂O + w ₂C₈H₁₈ + (1 − w ₁ − w ₂)C₆H₆} ternary system was taken from literature. A quaternary system containing these four compounds {w ₁C₂H₆O + w ₂C₆H₆ + w ₃C₈H₁₈ + (1 − w ₁ − w ₂ − w ₃)H₂O} was also studied at the same temperature. From our experimental results, we can conclude that this quaternary system presents a very low water tolerance. Small quantities of water from ambient humidity or infiltration into storage tanks could produce phase separation with a considerable loss of C₂H₆O drawn into the aqueous phase. On the other hand, the results also show that the aqueous phase contains a higher concentration of C₆H₆ compared to C₈H₁₈. The ternary experimental results were correlated with the NRTL and UNIQUAC equations, and predicted with the UNIFAC group contribution method. The three models lead to accurate results according to the two overall errors. In order to predict the equilibrium data for the quaternary system the UNIFAC method was used. This method predicts the binodal surface, satisfactorily although its prediction of the ethanol distribution ratio is rather poor.

Keywords:

• Phase equilibria
• Quaternary system
• Ternary systems
• Gasohol
• Ethanol

Acknowledgments

Financial support from the Consejo de Investigaciones de la Universidad Nacional de Tucumán, Argentina (CIUNT, Grant 26/E139) is gratefully acknowledged.