Liquid–liquid equilibria of ternary and quaternary systems with two hydrocarbons, an alcohol, and water at 303.15 K: Systems containing 2,2,4-trimethylpentane, toluene, methanol, and water, or 2,2,4-trimethylpentane, toluene, ethanol, and water

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Abstract
Tie-line data for ternary systems containing methanol (CH4O), ethanol (C2H6O), water (H2O), toluene (C7H8), and 2,2,4-trimethylpentane (C8H18) were investigated. Phase diagrams of {w1H2O+w2CH4O+(1−w1−w2) C7H8}, {w1CH4O+w2C7H8+(1−w1−w2)C8H18}, {w1 H2O+w2 C8H18+(1−w1−w2)C7H8}, and {w1H2O+w2C2H6O+(1−w1−w2)C7H8} ternary systems were obtained at 303.15 K, while data of the other partially miscible ternary systems: {w1H2O+w2C2H6O+(1−w1−w2)C8H18}, {w1H2O+w2C7H8+(1−w1−w2)C8H18}, and {w1H2O+w2CH4O+(1−w1−w2)C8H18} were taken from the literature. The quaternary systems {w1CH4O+w2C7H8+w3C8H18+(1−w1−w2−w3)H2O} and {w1C2H6O+w2C7H8+w3 C8H18+(1−w1−w2−w3)H2O} were also studied at the same temperature. From our experimental results we conclude that these quaternary systems present a very small water tolerance and that phase separation could produce a considerable loss of CH4O or C2H6O drawn into their respective aqueous phases. On the other hand, the aqueous phase generally contains a higher concentration of C7H8 than of C8H18 for both quaternaries. All the pairs of UNIQUAC interaction parameters obtained from the four ternary subsystems included in each quaternary system were averaged and then used to predict both quaternaries liquid–liquid equilibria (LLE) with this model. The UNIFAC group contribution method was used with the same purpose. The UNIQUAC equation appears to be more accurate than the UNIFAC method, particularly for {w1CH4O+w2C7H8+(1−w1−w2)C8H18} ternary system where UNIFAC predicts an immiscibility region much larger than experimentally observed, while for the {w1H2O+w2CH4O+(1−w1−w2)C7H8} ternary one it predicts a smaller region. Therefore, the UNIFAC method only provides qualitative results for these ternary systems. However, both the UNIFAC and UNIQUAC methods predict the quaternary systems with small and similar deviations.