Thermodynamics of alkanone + 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 values 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.