UBC Theses and Dissertations

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UBC Theses and Dissertations

Prediction of non-ideal equilibria for separation operations Groves, William Douglas


A rather general expression for the excess Gibbs free energy of a nonionic liquid mixture has been developed in this thesis and the expression has been tested on nine binary mixtures exhibiting a considerable range of nonideal behavior in both vapor-liquid and liquid-liquid equilibria. The basis for the formulation is that of the constant coordination number quasichemical mixture theory of Guggenheim, suitably modified to account for the major effects arising from the nonconstant coordination number situation inherent in a mixture of unequally sized constituents. The development of the geometric aspects of the theory is considerably based on the ideas of Hogendijk for mixtures of random-packed spheres. The generalization of the theory to multicomponent systems is based on the work of Barker on associated mixtures. Because the expression handles a nonconstant coordination number system, it has for brevity been termed the NCZ equation. Although in many cases the proposed equation performed no better than those already available for certain systems, no existing theory was able to deal with all of the nine binaries on which the NCZ expression has been so far tested. The proposed method of formulating the excess Gibbs function has brought to the fore the need for physical chemical measurement of data of a kind not presently available on a large scale, despite the fact that the required parameters are in themselves standard thermodynamic quantities, such as the pure-component free energy of a liquid. The present extension of quasichemical theory is seen as an indication of the basic viability of the quasichemical type of approach for the prediction of the excess properties of liquid mixtures.

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