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Pure Appl. Chem., 2011, Vol. 83, No. 6, pp. 1221-1242

Published online 2011-01-05

Toward a COSMO equation-of-state model of fluids and their mixtures

Costas Panayiotou

Department of Chemical Engineering, University of Thessaloniki, 54124 Thessaloniki, Greece

Abstract: The basic objective of this work is the development of an approximate, yet coherent and consistent equation-of-state model of fluids, which will benefit from recent developments in the successful COnductor-like Screening MOdel (COSMO)-type group-contribution models with their quantum-mechanical description of fluids. The development is done within our recent non-random hydrogen-bonding (NRHB) equation-of-state framework. In contrast to NRHB, the new model will not need any new parameters for the strong specific interactions, such as hydrogen bonds, since they will be provided by its COSMO component and the associated quantum-chemistry calculations. The bridge between COSMO and NRHB is the non-randomness factors as calculated by the quasi-chemical treatment of the non-random distribution of molecular entities in the system. Analytical expressions are provided for all basic thermodynamic quantities, including expressions for the cavitation and charging components of the solvation Gibbs energy. The new equation-of-state model is tested against experimental data for vapor pressures, heats of vaporization, and liquid densities of pure fluids and on phase equilibria of mixtures. The strength and perspectives of the new model are critically discussed.