Publication

Perspective for Extended Group-Contribution Methods for the Prediction of Activity Coefficients Accounting for Sterical Effects. Linking UNIFAC and the Group Vector Space Method

Martin Grasemann
2008
Journal Articles

Abstract

Group contribution methods for the calculation of an activity coefficient such as UNIFAC (universal factorial activity coefficient) currently do not take into account sterical effects. Consequently one of the major deficiencies of such methods is their inability to resolve isomeric systems and their often insufficient accuracy for systems including molecules of very different size. In this paper an approach is presented by which sterical information can be implemented into those methods by means of a modified group vector space (GVS) procedure. (Wen, X.; Qiang, Y. Group Vector Space method for estimating melting and boiling points of organic compounds. Ind. Eng. Chem. Res. 2002,41, 5534-5537.) Exemplary calculations with UNIFAC/GVS underline the potential of this new approach resulting in a perspective for substantially improved group contributions methods with a wider range of applicability and even more reliable predictive performance.

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https://infoscience.epfl.ch/entities/publication/2c77e7cf-1bea-4419-8e4c-36210d592297

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Martin Grasemann
2008
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/2c77e7cf-1bea-4419-8e4c-36210d592297

About this result

Related concepts (32)

Activity coefficient

In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. In an ideal mixture, the microscopic interactions between each pair of chemical species are the same (or macroscopically equivalent, the enthalpy change of solution and volume variation in mixing is zero) and, as a result, properties of the mixtures can be expressed directly in terms of simple concentrations or partial pressures of the substances present e.g. Raoult's law.

Partition coefficient

In the physical sciences, a partition coefficient (P) or distribution coefficient (D) is the ratio of concentrations of a compound in a mixture of two immiscible solvents at equilibrium. This ratio is therefore a comparison of the solubilities of the solute in these two liquids. The partition coefficient generally refers to the concentration ratio of un-ionized species of compound, whereas the distribution coefficient refers to the concentration ratio of all species of the compound (ionized plus un-ionized).

Boiling point

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding environmental pressure. A liquid in a partial vacuum, i.e., under a lower pressure, has a lower boiling point than when that liquid is at atmospheric pressure. Because of this, water boils at under standard pressure at sea level, but at at altitude.

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Perspective for Extended Group-Contribution Methods for the Prediction of Activity Coefficients Accounting for Sterical Effects. Linking UNIFAC and the Group Vector Space Method

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