Thermodynamics of branched alcohols - II. Solid-liquid equilibria for systems containing tert-butanol and long-chain n-alkanes. Experimental results and comparison with DISQUAC predictions

Solid-liquid equilibrium temperatures for tert-butanol + n-alkanes (C-18, C-19, C-20, C-21, C-22, C-23, C-24, C-25, C-26, C-28) systems have been measured by a dynamic method from 298.15 K to the melting point of the alkane. All the systems present an eutectic point at very low concentration of the alcohol. A first-order transition was observed for many of the n-alkanes considered. The experimental values are compared with those given by the DISQUAC model using the interaction parameters previously determined on the basis of vapor-liquid equilibria, VLE, and molar excess enthalpies, H-E, of systems containing the lower n-alkanes (n-C-6, n-C-7). Calculations were developed taking into account the solid-solid transition of the alkanes. The mean relative standard deviation for the equilibrium temperatures is 0.0073. Differences between experimental data and calculated results for SLE and H-E are analysed in terms of the Patterson effect. The possibility of improving predictions by modifying only the third dispersive interchange coefficient is discussed. Two values for this parameter are proposed depending on n, hereafter the number of C atoms in the n-alkane (n less than or equal to 8 and n greater than or equal to 9). In this way, the variation with the temperature of HE is better represented by the model for those systems including the longer n-alkanes. Predictions on SLE remain unchanged, because they depend essentially on the first interchange coefficients when the range of temperature considered, as in this case, is rather narrow. (C) 1998 Elsevier Science B.V. All rights reserved.