Application of the UNIFAC and Nitta-Chao models to describing the behavior of methyl ester/alkane mixtures, and experimental data for (methyl n-alkanoates + n-heptadecane) binary mixtures

Abstract

J. Ortega and J.L. Legido, 1994. Application of the UNIFAC and Nitta-Chao models to describing the behavior of methyl ester/alkane mixtures, and experimental data for (methyl n-alkanoates+n-heptadecane) binary mixtures. Fluid Phase Equilibria, 95: 175-214. Excess molar properties, hE and vE, were determined based on the composition of binary mixtures of fourteen methyl esters (from ethanoate to n-pentadecanoate) and n-heptadecane at 298.15 K. The results showed all the mixtures to be endothermic and to undergo positive changes in excess volume. Both these effects decreased in a quasi-regular manner with the chain length of the methyl alkanoate. The excess enthalpies of the mixtures were compared with the values estimated by two group-contribution models, two different versions of the UNIFAC model, and the model of Nitta et al. [Nitta, T., Turek, E.A., Greenkorn, R.A. and Chao, K.C., 1977. A group contribution molecular model of liquids and solutions. AIChE J., 23: 144-160]. Using the UNIFAC model, the best prediction was achieved when all the methyl esters were considered to be alkyl ethanoates, which yielded a mean overall error of less than 5%. Application of the model of Nitta et al. to the mixtures considered yielded hE and vE values that differed substantially from the experimental values, with mean overall errors of 14% for the hE values and 34% for the vE values. Therefore, a comprehensive database of thermodynamic quantities for 368 binary mixtures was used to recalculate the alkane-ester interaction parameters and group parameters, which were then reapplied in the above-mentioned molecular model. This substantially improved the estimates of the properties for the pure components as well as those for the mixing quantities, achieving mean errors of less than 4% for hE and 17% for vE. © 1994.