Use of monomer fraction data in the parametrization of association theories

Georgios M. Kontogeorgis, Ioannis Tsivintzelis, Nicolas von Solms, Andreas Grenner, David Bøgh, Michael Frost, Anders Knage-Rasmussen, Ioannis G. Economou

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Abstract

Association theories such as the CPA (cubic-plus-association), NRHB (non-random hydrogen bonding) equations of state and the various variants of SAFT (statistical associating fluid theory) have been extensively applied to phase equilibrium calculations. Such models can also be used for estimating the monomer fraction of hydrogen bonding compounds and their mixtures. Monomer fraction data are obtained from spectroscopic measurements and they are available for a few compounds such as pure water and alcohols as well as for some alcohol-alkane and similar mixtures. These data are useful for an understanding of the capabilities and limitations of association models. The purpose of this work is two-fold: (i) to compare the performance of three models, CPA, NRHB and sPC-SAFT, in predicting the monomer fraction of water, alcohols and mixtures of alcohol-inert compounds and (ii) to investigate whether "improved" model parameters can be obtained if monomer fraction data are included in the parameter estimation together with vapor pressures and liquid densities. The expression "improved" implies parameters which can represent several pure compound properties as well as monomer fraction data for pure compounds and mixtures. The accuracy of experimental monomer fraction data is discussed, as well as the role of monomer fraction data in clarifying which association scheme should be used in these equations of state. The results reveal that the investigated association models (CPA, sPC-SAFT and NRHB) can predict, at least qualitatively correct, monomer fractions of associating compounds and mixtures. Only, small differences are observed between the models. In addition, it has been shown that, using a suitable association scheme, a single set of parameters can describe satisfactorily vapor pressures, liquid densities and monomer fractions of water and alcohols. The 4C scheme is the best choice for water, while for methanol there is small difference between the 2B and 3B association schemes.

Original languageEnglish
Pages (from-to)219-229
Number of pages11
JournalFluid Phase Equilibria
Volume296
Issue number2
DOIs
Publication statusPublished - 1 Sep 2010

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Keywords

  • Association theories
  • CPA
  • Methanol
  • Monomer fraction
  • NRHB
  • PC-SAFT
  • Water

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Kontogeorgis, G. M., Tsivintzelis, I., von Solms, N., Grenner, A., Bøgh, D., Frost, M., Knage-Rasmussen, A., & Economou, I. G. (2010). Use of monomer fraction data in the parametrization of association theories. Fluid Phase Equilibria, 296(2), 219-229. https://doi.org/10.1016/j.fluid.2010.05.028