Volumetric and derivative properties under pressure for the system 1-propanol + toluene: A discussion of PC-SAFT and SAFT-VR

Abstract

The density of the asymmetrical binary system 1-propanol + toluene has been measured (882 points) for nine different compositions including the pure compounds at seven isotherms in the range 293.15–353.15 K and 14 isobars up to 65 MPa with a vibrating-tube densimeter, the experimental uncertainty is estimated to be ±0.5 kg m −3. The isothermal compressibility, the isobaric thermal expansivity, and the excess molar volume have been derived. As a function of the composition, the isobaric thermal expansivity shows a non-monotonical behavior involving a maximum, whereas the excess molar volume reveals a complex sigmoid behavior. These results can be interpreted as due to changes in the molecular free-volume, disruption of the order molecular structure, and the breaking or formation of molecular interactions. Without using any binary interaction parameters or taking into account that electron donor–acceptor type of interactions exists between 1-propanol and toluene, PC-SAFT and SAFT-VR predict the density of this binary system within the considered temperature and pressure ranges with an overall AAD less than 0.5%. A satisfactory description of the azeotropic VLE behavior of the binary system is also found, whereas the derived properties, especially the isothermal compressibility, are not satisfactorily predicted.