Role of azeotropy in true-boiling-point distillation of complex mixtures of aliphatics, aromatics and 1-butanol

In true-boiling-point (TBP) distillation, the complex mixture is assumed to be separated into its components according to their boiling points. Plotting the head temperature of the column versus the mass fraction distilled, the TBP curve is obtained. Usually, the TBP curve may be considered to be an integral distribution function with respect to the normal boiling-point temperature characterizing the composition of the complex mixture. However, if there are azeotropes, this assumption is no longer correct. revious paper, we studied the role of azeotropy for mixtures consisting of an aliphatic petroleum fraction and of alcohols both experimentally and by continuous thermodynamics. We verified the TBP curve to be essentially influenced by azeotropy. Particularly, azeotropic influence is expressed by the occurrence of a temperature jump in the TBP curve. etroleum fractions often contain large amounts of aromatics. Therefore, in this paper, we expand the investigation of azeotropic effects to more complex mixtures consisting of aliphatics, aromatics and of 1-butanol. We show how to calculate TBP curves, and corresponding to that, we present experimental data. For the calculation, continuous thermodynamics is applied. In this, both the aliphatics and the aromatics are described by continuous distributions functions except for toluene which is treated as a separate component. The calculated TBP curves agree reasonably well with the measured data.