Advertisement

International Journal of Thermophysics

, Volume 11, Issue 1, pp 119–132 | Cite as

An FTIR spectroscopic study of hydrogen-bonding competition in entrainer-cosolvent mixtures

  • J. M. Walsh
  • M. L. Greenfield
  • G. D. Ikonomou
  • M. D. Donohue
Article

Abstract

In chemical separation processes such as supercritical extraction the use of an entrainer cosolvent can dramatically improve selectivity and yield. Ideally, in an extraction process, an entrainer cosolvent should complex with only the desired solute, pulling it from the feed. But not all cosolvents are entrainers, and a cosolvent that is effective in one application may not be effective in others. Often, competing hydrogen bonding interactions limit the effectiveness of an entrainer cosolvent. In this paper FTIR spectroscopy is used to study hydrogen bonding competition in solute/solvent/entrainer cosolvent mixtures. The extent of hydrogen bonding is determined from analysis of hydrogen-bonded and non-hydrogen-bonded infrared absorption peaks. Since these peaks overlap, curvefitting and Fourier self-deconvolution techniques are used to resolve them. Concentrations of monomeric and hydrogen-bonded species are modeled using the associated perturbed anisotropic chain theory (APACT). Using APACT it is shown that the equilibrium constant, derived from activities, can be written as the product of a temperature-dependent term and the ratio of concentrations: K=(RT)vIIC i vi . This gives a statistical mechanical basis for the empirical observation that for hydrogen-bonding equilibria, the ratio of concentrations is approximately equal to the ratio of activities.

Key words

entrainer FTIR hydrogen bonding supercritical 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    D. K. Joshi and J. M. Prausnitz, AIChE J. 30:522 (1984).Google Scholar
  2. 2.
    J. M. Walsh, G. D. Ikonomou, and M. D. Donohue, Fluid Phase Equil. 33:295 (1987).Google Scholar
  3. 3.
    J. A. Hyatt, J. Org. Chem. 49:5097 (1984).Google Scholar
  4. 4.
    M. J. Kamlet, J. M. Abboud, M. H. Abraham, and R. W. Taft, J. Org. Chem. 48:2877 (1983).Google Scholar
  5. 5.
    E. D. Becker, Spectrochim. Acta 17:436 (1961).Google Scholar
  6. 6.
    M. D. Donohue, and J. M. Prausnitz, AIChE J. 24:849 (1975).Google Scholar
  7. 7.
    P. J. Flory, J. Am. Chem. Soc. 87:1833 (1965).Google Scholar
  8. 8.
    I. Prigogine, The Molecular Theory of Solutions (North-Holland, Amsterdam, 1957).Google Scholar
  9. 9.
    G. D. Ikonomou and M. D. Donohue, AIChE J. 32(10):1716 (1986).Google Scholar

Copyright information

© Plenum Publishing Corporation 1990

Authors and Affiliations

  • J. M. Walsh
    • 1
  • M. L. Greenfield
    • 1
  • G. D. Ikonomou
    • 1
  • M. D. Donohue
    • 1
  1. 1.Department of Chemical EngineeringThe Johns Hopkins UniversityBaltimoreUSA

Personalised recommendations