Vapor-liquid equilibria

Author

Vincent De Paul Brown, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

6-30-1957

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering

First Advisor

Edward G. Scheibel

Second Advisor

C. L. Mantell

Third Advisor

Joseph Joffe

Abstract

The thesis was undertaken for the purpose of testing available experimental vapor-liquid equilibrium data for thermodynamic consistency, with a view to finding an intercorrelation of the activity coefficient-concentration curves, for different groups of systems, as a function of the intercepts. It was hoped that a correlation using molar volumes, parachor volumes, or molecular weights would be developed which could be explained on the basis of hydrogen bonding.

The Redlich and Kister^{1 equations were used to smooth the experimental data and to obtain values for the constants B, C and D. Redlich and Kister state that these constants serve as a natural and convenient classification of various systems. The present investigation sought to determine whether such a grouping based on these constants would correspond to the classification of organic compounds based on their ability to form or to break hydrogen bonds, as outlined by Ewell, Harrison and Berg.2}

Systems of aromatic-alcohols, paraffin-alcohols, and paraffin-aromatics were studied. It was assumed that the energy of the hydrogen bonds is constant and could be expressed as a function of the energy per unit volume holding the liquid together. The theory requires the energy of a polar compound to be the same from all paraffins, while the energy of the paraffins from the same polar compound would vary linearly with the volume of the paraffin.

It developed that the quantitative relationship between the correlations was not according to the predictions of the hydrogen bond theory--assuming that the paraffin compounds do not form hydrogen bonds with themselves or other molecules.

The aromatic-alcohol systems had partial molal excess free energy values higher than those of the paraffin-alcohol mixtures, contrary to the theory, and two systems of methylcyclohexane-alcohols, instead of lying between the aromatic-alcohols and the paraffin-alcohols, indicating a gradual transition, were actually similar to aromatic-alcohols. It is possible that the assumption is in error, or factors other than hydrogen bonding contribute to the deviation of the systems from ideality.

Equations developed from the empirical correlation of the published data used in the thesis, are offered for the prediction of Redlich and Kister constants for the aromatic-alcohol, paraffin-alcohol and paraffin-aromatic systems.

Recommended Citation

Brown, Vincent De Paul, "Vapor-liquid equilibria" (1957). Theses. 2516.
https://digitalcommons.njit.edu/theses/2516