Lidia M. Casás

Liquid phase behaviour and thermodynamics of acetone+methanol+n-alkane (C9–C12) mixtures

Abstract This paper reports the results of a new experimental study of two-liquid phases equilibria as a function of temperature and one-liquid phase thermodynamic magnitudes (densities, refractive indices and speeds of sound), covering the composition diagrams for the mixtures acetone+methanol+n-alkane (C9–C12). The obtained coexistence curves were very asymmetrical with respect to equimolar alcohol+n-alkane composition, such effect increasing with the length of the aliphatic chain and temperature. A comparative analysis was performed by application of different methods to predict experimental liquid–liquid equilibria (LLE) behaviour and thermodynamics of these ternary mixtures. The obtained experimental results let us know the potential role of the linear aliphatic alkanes as separation agents for heterogeneous modified distillation of the azeotrope acetone+methanol.

Excess molar internal pressures and changes in refractive indices of acetone + methanol + (2-methyl-1-propanol or 3-methyl-1-butanol) at 298.15 K

This study aims at extending the characterisation by refractive index of ternary systems containing potential separation agents for extractive distillation of minimum azeotropes. The systems considered are acetone + methanol + (2-methyl-1-propanol or 3-methyl-1-butanol), which have been studied at 298.15 K and atmospheric pressure for the whole composition diagram. Parameters of polynomial equations, which represent the molar fraction dependence of the refractive index and derived property, are gathered. Based on the variations of the derived values with composition, conclusions about the molecular interactions and their dependence on branched alcohol structure were drawn.

Excess molar volumes of ternary mixtures containing benzene, cyclohexane, 1-pentanol and anisole at 298.15 K

The expansive trend of the cosolvents anisole and 1-pentanol for benzene + cyclohexane binary azeotropic mixture by extractive distillation is analyzed by a volumetric study of the ternary mixtures benzene + 1-pentanol + anisole, cyclohexane + 1-pentanol + anisole and benzene + cyclohexane + anisole at 298.15 K and atmospheric pressure. The results obtained of application of the Peng–Robinson equation of state for estimating excess volumetric values shows the versatility of this model for thermodynamic prediction in complex systems.

New methodology for simultaneous volumetric and calorimetric measurements: Direct determination of αp and Cp for liquids under pressure

A new batch cell has been developed to measure simultaneously both isobaric thermal expansion and isobaric heat capacity from calorimetric measurements. The isobaric thermal expansion is directly proportional to the linear displacement of an inner flexible below and the heat capacity is calculated from the calorimetric signal. The apparatus used was a commercial Setaram C-80 calorimeter and together with this type of vessels can be operated up to 20 MPa and in the temperature range of 303.15-523.15 K, In this work, calibration was carried out using 1-hexanol and subsequently both thermophysical properties were determined for 3-pentanol, 3-ethyl-3-pentanol, and 1-octanol at atmospheric pressure, 5 and 10 MPa, and from 303.15 to 423.15 K in temperature. Finally experimental values were compared with the literature in order to validate this new methodology, which allows a very accurate determination of isobaric thermal expansion and isobaric heat capacity.

Measurement and correlation of liquid–liquid equilibria of methanol + 2-butanone + n-alkanes (C10–C12) ternary mixtures

The experimental liquid–liquid equilibrium (LLE) data of the mixtures methanol +2-butanone + n-alkane (C10–C12) were studied at atmospheric pressure in the temperature range 268.15–298.15 K. The equilibrium compositions were measured by gas chromatography from samples splitted isothermally into a glass-stirred device and phase diagrams are reported at each temperature. The non-random two-liquid and universal quasichemical models were used to correlate the experimental tie-lines. A good fit has been obtained as a function of temperature for all the mixtures. The experimental results have been compared with the values predicted by the UNIFAC group contribution method and its modifications. Such predictions provide, however, a rather unsatisfactory description for the experimental results.