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, r(i) and q(i). The slope of r(i) and q(i) 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 (H-E) 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 r(i) and q(i) parameters enables prediction of the VLE at various temperatures and leads to reasonable values of H-E. The necessary input reduces to one set of isothermal VLE data. One set of UNIQUAC interaction parameters u(ij) is sufficient for representation of VLE in a wide range of temperature and to obtain a reasonable prediction of H-E. (C) 2001 Published by Elsevier Science B.V.