(Liquid plus liquid) equilibria of ternary and quaternary systems including 2,2,4-trimethylpentane, benzene, methanol, and water at T=303.15 K

Tie-line results for ternary systems including methanol (CH4O), water (H2O), benzene (C6H6), and 2,2,4-trimethylpentane (C8H18) were investigated. Phase diagrams of {w(1)H(2)O + w(2)CH(4)O + (1 - w(1) - w(2))C6H6}, {w(1)H(2)O + w(2)CH(4)O + (1 - w(1) - w(2)) C8H18}, {w(1)H(2)O + w(2)C(8)H(18) + (1 - w(1)w(2))C6H6}, and {w(1)CH(4)O + w(2)C(6)H(6)+ (1 - w(1) - w(2))C8H18} ternary systems were obtained at T = 303.15 K. A quaternary system containing these four compounds {w(1)CH(4)O + w(2)C(6)H(6) + w(3)C(8)H(18)+ (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 shows very small water tolerance, Minor quantities of water from ambient humidity or infiltration into storage tanks could produce phase separation with a considerable loss of CH4O drawn into the aqueous phase. On the other hand, the results also show that the aqueous phase contains a higher concentration of C6H6 compared with C8H18. The ternary experimental results were correlated with the NRTL and UNIQUAC equations, and predicted with the UNIFAC group contribution method. This last method was also used to predict the equilibrium values for the quaternary system. An analysis of the overall errors shows that the NRTL and UNIQUAC equations appear to be more accurate than the UNIFAC method for the ternary systems, particularly for {w(1)CH(4)O + w(2)C(6)H(6) + (1 - w(1) - w(2))C8H18}, where this method predicts an immiscibility region much larger than the experimentally observed one. However, it is still satisfactory for the quaternary system. (C) 2001 Academic Press.