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

In this work, we report the experimental values of the excess quantities H_m^E and V_m^E 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 (∂H_m^E/∂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 (x_az, T_az/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.