Isobaric vapor - Liquid equilibrium data and excess properties of binary systems comprised of alkyl methanoates + hexane

Abstract

In this work, we report the experimental values of the excess quantities and and the isobaric equilibrium data (VLE) at 101.32 kPa for the four mixtures of alkyl methanoates (methyl to butyl) and hexane. The results indicate that for these four mixtures (∂ /∂T)p > 0 and(∂ /∂T)p > 0. VLE data were found to be thermodynamically consistent with the Fredenslund method. All the binary mixtures presented here, except for the system (butyl methanoate + hexane), present a minimum-boiling temperature azeotrope with coordinates (xaz, Taz/K), (0.832, 302.62) for (methyl methanoate + hexane), (0.703, 323.32) for (ethyl methanoate + hexane), and (0.283, 339.10) for (propyl methanoate + hexane). Simultaneous correlations performed with the VLE data and excess enthalpies using a simple polynomial model, with temperature-dependent coefficients, produced acceptable estimations. Application of the UNIFAC model in the versions of Hansen et al. (Ind. Eng. Chem. Res. 1991, 30, 2355−2358) and Gmehling et al. (Ind. Eng. Chem. Res. 1993, 32,178−193) produced similar predictions for all four systems, of which only the ones for the methyl methanoate + hexane mixture are acceptable. Differences increase steadily with increasing methanoate chain length. Estimation of enthalpies with the second of the versions indicated, however, produced mean errors of 10 %, which could be considered as acceptable