Solid–liquid equilibria of binary mixtures of alcohols and aromatic hydrocarbons: experimental methods and modeling analysis

The increasing use of heavy and non-conventional crude oils deals with complex multicomponent phase behavior; hence, studying solid–liquid equilibrium is essential. Dealing with solid phases and their subsequent issues is becoming more common in fuel production processes. In these terms, solvent-based processes in hydrocarbon streams are of particular concern, and the use of alcohols as solvents is widely recommended in the literature because of their low hazardousness. Therefore, determining the solid–liquid phase behavior of mixtures containing solvents and fuel representative molecules is interesting in the hydrocarbon industry. This work studied the solid–liquid equilibria of binary systems containing 1-hexanol and 1-decanol as alcohols, p-xylene, o-xylene, and 1-methylnaphthalene as fuel molecules. Two-phase diagram determination methods were employed: a DSC-based with an integration method and the conventional DSC method. The phase diagrams showed that all the systems studied presented a eutectic behavior. Moreover, solid–solid transitions were found among all the systems, mainly due to pure compound crystallization. The activity coefficients of the systems indicated a strong non-ideal behavior of the mixtures. Moreover, a comparison was addressed between the experimental solid–liquid equilibria and data predicted by the UNIFAC and the modified UNIFAC (Dortmund) models. The second model resulted in better estimations of the systems studied. Finally, the activity coefficients were predicted by the modified UNIFAC (Dortmund) and the COSMO-RS models, observing that, in general, both models undercalculate the values, but the latter showed a better fit.