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

This paper presents an interpretation on the behaviour of mixtures containi ng alkyl methanoates with n-alkanes from a structural point of view. New ex perimental 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 quan tities higher than expected because of the self-association of methyl metha noates, 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 fu nction of number of carbon atoms of alkyl methanoate, was included as a spe cific term in the UNIFAC model that gave excellent results in the predictio ns of H-E, with mean differences smaller than 2%. In the Nitta model the as sociation in methanoates was considered employing different forms of molecu lar interactions but the results were not so good.