Behaviour of binary mixtures of an alkyl methanoate+an n-alkane. New experimental values and an interpretation using the UNIFAC model

Abstract

This paper presents an interpretation on the behaviour of mixtures containing alkyl methanoates with n-alkanes from a structural point of view. New experimental data of molar excess properties, h^E and v^E, are measured at 298.15 K and 101.32 kPa for this work to complete the existing information. Mixtures corresponding to methyl methanoate+n-alkanes showed excess quantities higher than expected because of the self-association of methyl methanoates, which decreases as the chain length/molar mass of alkyl methanoates increases. The consideration of autoassociation in methanoates, presented in this paper as an empirical relationship for its characterization as a function of number of carbon atoms of alkyl methanoate, was included as a specific term in the UNIFAC model that gave excellent results in the predictions of H^E, with mean differences smaller than 2%. In the Nitta model the association in methanoates was considered employing different forms of molecular interactions but the results were not so good.