Application of the Cell Method to the Statistical Thermodynamics of Solutions

Prediction of Excess Enthalpy Using Volume-Translated Peng–Robinson Equation of State

In this work volume-translated Peng–Robinson group contribution equation of state was used to calculate excess enthalpies. Four model systems were selected with the purpose to compare experimental and predicted enthalpy values at different temperatures. After the calculations were performed in Matlab software, results were verified with free software tool of Dortmunder Datenbank (DDB). In a next step, the mixing process and interaction forces were described on the basis of the sign and course of enthalpy values. The endothermic behavior of three systems could be well predicted, while for the most polar system, predictions were less precise. Furthermore, the discrepancy between experimental data from the literature and predicted values was discussed to evaluate the accuracy of the selected model. Lowest mean deviations (<75 J/mol and <15% at all temperatures) could be stated for alkane/benzene mixtures, while highest deviations could be again observed for the most polar mixture. Although the magnitude of deviations was in agreement with the literature, it could be shown that the selected temperature is of major importance for the quality of predictions. Furthermore, a review of different literature values for the n-hexane/benzene system could reveal that the reliability of experimental data has to be carefully checked.

The rehabilitation of irreversible processes and dissipative structures' 50th anniversary

In 2017, Ilya Prigogine would have been 100 years of age. As for any human being, this centenary is a notable event. For him, as a scientist, 2017 was also above all the 50th anniversary of dissipative structures It was indeed in 1967 that for the first time he used this denomination at the occasion of an important scientific event and in publications. The attribution of this qualification for self-organized behaviours of matter only possible far from equilibrium coincided with the outcome of a research effort of more than 25 years. Centred in thermodynamics and statistical physics on the role played by irreversible processes in the physical evolution of matter, the aim of this research is clear from the outset of his scientific career. With visionary personal intuition and iron-willed determination, it was pursued. The road to success had been long and sinuous, but finally it led to what he called the rehabilitation of irreversible processes The progresses that stand out as major landmarks of this endeavour that imposed a U-turn with respect to conceptions of classical physics deeply rooted since the nineteenth century will be described. This article is part of the theme issue 'Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (Part 1)'.

Effect of Water Adsorption on Cation-Surface Interaction Energy in the Na-Mordenite of 5.5 : 1 Si/Al Ratio

The mobility of the Na+cations localized at the inner surface of the studied mordenite zeolite depends on the material surface properties. In this work, we show that the activation energy,ΔEhop, relating to the Na+cation hopping displacement is associated to the surface potential and therefore can be used to get a better insight into the zeolite surface properties. Indeed, when molecules as water are adsorbed at the surface, they modify the surface potential energy and hence influence the value ofΔEhop. If the adsorbed molecules are polar they directly interact with the cations which become more mobile. The more theΔEhopvalue is, the less the amount of adsorbed water molecules is. Alterations of theΔEhopvalue with respect to the amount of adsorbed water molecules are interpreted using the Dubinin model which is based on simple adsorption principle.

Cluster integrals and statistical mechanics of solutions

A formally convergent method for calculating the thermodynamic properties of solutions containing molecules not widely different in size and interaction energies is developed using the cluster-integral approach of the theory of imperfect gases. The potential energy of the actual solution is referred to the potential energy of a suitably chosen ‘reference liquid’; the correction terms which are required to give the correct energy for the solution give rise to cluster integrals which contain distribution functions of the reference liquid as factors in the integrand. Even if all the cluster integrals are neglected a useful result may be obtained. The first cluster integral, corresponding to the second virial coefficient in the theory of imperfect gases, is comparatively easy to evaluate. This approach provides a unified and formally exact basis for existing approximate theories of solutions, as well as a method for obtaining more accurate results.