Thermodynamics of alkanone plus aromatic hydrocarbon mixtures

Linear alkanone or cyclohexanone + aromatic hydrocarbon mixtures have been studied using DISQUAC and the Kirkwood-Buff formalism. The aromatic compounds considered are: benzene, toluene, 1,4-dimethylbenzene, 1,2,4-trimethylbenzene and ethylbenzene. Vapour-liquid equilibria (VLE), molar excess Gibbs energies, G(m)(E), molar excess enthalpies, H-m(E), and isobaric molar excess heat capacities, C-pm(E), of the binary systems studied are well represented by DISQUAC. There is a good agreement between experimental H-m(E) of related ternary mixtures, and DISQUAC predictions obtained by means of binary interaction parameters only DISQUAC improves very meaningfully UNIFAC results on H-m(E), C-pm(E), properties which are closely related to the molecular structure of the mixture components. The enthalpy (H-int(CO-S)) of the ketone-aromatic hydrocarbon interactions has been evaluated. These interactions become weaker when the alkanone size increases in mixtures with a given aromatic hydrocarbon, or when the aliphatic surface of the alkylbenzene is increased in systems with a given ketone. Steric effects are more relevant in 1,4-dimethylbenzene mixtures than in those with ethylbenzene. The application of the Kirkwood-Buff formalism to mixtures including toluene or ethylbenzene shows that orientational effects, related to ketone-ketone interactions, exist in solutions with the shorter 2-alkanones. Such effects are weakened when the chain length of the 2-alkanone increases. The opposite behaviour is observed when increasing the aliphatic surface of the alkylbenzene in systems with a given 2-alkanone. The cyclohexanone + benzene mixture shows a structure close to random mixing. (C) 2012 Elsevier B.V. All rights reserved.