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We dedicate this to honor the 60 th birthday of Prof. Christoph Janiak for outstanding networking activities and great research.Knowledge on phase equilibria is of crucial importance in designing industrial processes. However, modeling phase equilibria in liquid-liquid two-phase systems (LLTPS) containing electrolytes is still a challenge for electrolyte thermodynamic models and modeling still requires a lot of experimental input data. Further, modeling electrolyte solutions requires accounting for different physical effects in the electrolyte theory, especially the change of the dielectric properties of the medium at different compositions and the related change of solvation free energy of the dissolved ions. In a previous work, the Born term was altered by combining it with a concentration-dependent dielectric constant within the framework of electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT), and hence called 'ePC-SAFT advanced'. In the present work, ePC-SAFT advanced was validated against liquid-liquid equilibria (LLE) of LLTPS water + organic solvents + alkali halides as well as aqueous two-phase systems containing the phase formers poly (propylene glycol) and an ionic liquid. All the ePC-SAFT parameters were used as published in the literature, and each binary interaction parameter between ion-solvent was set to zero. ePC-SAFT advanced allowed quantitatively predicting the salt effect on LLTPS without adjusting binary interaction parameters, while classical ePC-SAFT or meaningless mixing rules for the dielectric constant term failed in predicting the phase behavior of the LLTPS.

The study of chemical reactions in multiple liquid phase systems is becoming more and more relevant in industry and academia. The ability to predict combined chemical and phase equilibria is interesting from a scientific point of view but is also crucial to design innovative separation processes. In this work, an algorithm to perform the combined chemical and liquid–liquid phase equilibrium calculation was implemented in the PC-SAFT framework in order to predict the thermodynamic equilibrium behavior of two multicomponent esterification systems. Esterification reactions involve hydrophobic reacting agents and water, which might cause liquid–liquid phase separation along the reaction coordinate, especially if long-chain alcoholic reactants are used. As test systems, the two quaternary esterification systems starting from the reactants acetic acid + 1-pentanol and from the reactants acetic acid + 1-hexanol were chosen. It is known that both quaternary systems exhibit composition regions of overlapped chemical and liquid–liquid equilibrium. To the best of our knowledge, this is the first time that PC-SAFT was used to calculate simultaneous chemical and liquid–liquid equilibria. All the binary subsystems were studied prior to evaluating the predictive capability of PC-SAFT toward the simultaneous chemical equilibria and phase equilibria. Overall, PC-SAFT proved its excellent capabilities toward predicting chemical equilibrium composition in the homogeneous composition range of the investigated systems as well as liquid–liquid phase behavior. This study highlights the potential of a physical sound model to perform thermodynamic-based modeling of chemical reacting systems undergoing liquid–liquid phase separation.

Proton activity, which is usually expressed as pH value, is among the most important properties in the design of chemical and biochemical processes as it determines the dissociation of species...

Aqueous and non-aqueous electrolyte solutions are ubiquitous in chemical and biochemical applications, especially in innovative processes, and they play a major role in geochemistry, environmental science, and numerous other scientific fields. Despite the obvious importance of electrolyte systems, research success on electrolyte thermodynamics is still behind all of the advances on non-electrolyte thermodynamics. After decades of research, several issues of thermodynamic models for electrolytes remain the object of discussion in the thermodynamic community. Still today, only a few simulation packages offer a general approach to calculate phase equilibria of electrolyte systems in a broad application range regarding the kind of salts and solvent, the number of phases, and the number of non-ionic or ionic species involved. In this work, the general background and the assumptions behind the equilibrium conditions of multiphase electrolyte systems with distributed ions are reviewed. A general methodology is proposed, which can be used to determine the number of liquid phases and their composition at equilibrium of any electrolyte system independent of the number of components. The algorithm was implemented in a FORTRAN routine using the equation of state “ePC-SAFT advanced” (Bülow, M.; Ascani, M.; Held, C. ePC-SAFT advanced-Part I: Physical meaning of including a concentration-dependent dielectric constant in the born term and in the Debye–Hückel theory. Fluid Phase Equilib. 2021, 535, 112967) to estimate the fugacity of each species. The algorithm was successfully tested against experimental data using case studies including three-phase liquid–liquid–liquid equilibria with two ionic species and two-phase liquid–liquid equilibria with three ionic species.

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Osmolytes are well-known biocatalyst stabilisers as they promote the folded state of proteins, and a stabilised biocatalyst might also improve reaction kinetics. In this work, the influence of four osmolytes...