Thermodynamics of mixtures containing ethers. Part I. DISQUAC characterization of systems of MTBE, TAME or ETBE with n-alkanes, cyclohexane, benzene, alkan-1-ols or alkan-2-ols. Comparison with Dortmund UNIFAC results

Abstract

Binary mixtures of methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME) or ethyl tert-butyl ether (ETBE) and n-alkanes, cyclohexane, benzene, alkan-1-ols or alkan-2-ols are characterized in terms of DISQUAC. The corresponding interaction parameters are reported. Systems with isomeric monooxaalkanes (linear or branched) and n-alkanes are characterized by the same QUASICHEMICAL (QUAC) interaction parameters. The DISPERSIVE (DIS) parameters are larger for those mixtures with tertiary-alkyl ethers. It is remarkable that in systems with alkan-1-ols, the first and third QUAC parameters are kept constant. The same trend is observed in many other alcoholic solutions previously studied. Mixtures with alkan-1-ols or alkan-2-ols differ only in the DIS parameters, which are larger for those systems with alkan-2-ols. Vapour–liquid equilibria (VLE), molar excess enthalpies (H^E), logarithms of activity coefficients at infinite dilution (ln γ_i^∞) or solid–liquid equilibria (SLE) are correctly described by DISQUAC. H^E values of ternary systems, including compounds considered in this work, are also represented by DISQUAC using binary parameters only. A complete comparison between DISQUAC calculations and those obtained from the Dortmund version of UNIFAC using the parameters available in the literature is included. DISQUAC improves results, except for VLE of mixtures including n-alkanes, which are slightly better represented by UNIFAC. This may be attributed to the fact that the empirical combinatorial term used in UNIFAC is more suitable, particularly for those systems with components very different in size. DISQUAC also improves results obtained from the ERAS model for H^E of alcoholic solutions (where association is expected). Thermodynamic properties are analysed in terms of the effective dipole moments (). The importance of structural effects is remarked.