A new modification of the UNIQUAC equation including temperature dependent parameters

The UNIQUAC equation was modified by introduction of a linear temperature dependence of the volume and surface area parameters, ri and qi. The slope of ri and qi functions were found to be the same for hydrocarbons and pyridine. The modified equation was used for prediction of vapor–liquid equilibria (VLE) in binary mixtures of hydrocarbons and pyridine with hydrocarbons as well as for the prediction of the excess enthalpy (HE) in binary mixtures formed by pyridine with aliphatic alkanes. The results obtained were compared with predictions by UNIFAC and further with UNIQUAC equation and its modification involving temperature dependant coordination number z. The proposed temperature dependence of the ri and qi parameters enables prediction of the VLE at various temperatures and leads to reasonable values of HE. The necessary input reduces to one set of isothermal VLE data. One set of UNIQUAC interaction parameters uij is sufficient for representation of VLE in a wide range of temperature and to obtain a reasonable prediction of HE.