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Structure-Based Generalizations of Eos Interaction Parameters for Predicting Vapor-Liquid Equilibria of Asymmetric Mixtures

Khaled A. M. Gasem, A. Kasturirangan, R. L. Godavarthy, and S. S. Robinson, Jr. Oklahoma State University, 423 Engineering North, Stillwater, OK 74078

The proper design, operation and optimization of coal conversion and utilization processes depend heavily on knowledge of phase behavior of the asymmetric mixtures encountered in these processes. Further, solubility of light gases such as hydrogen and nitrogen affects the rates of reaction, mass transfer and selectivity of the Fischer-Tropcsh synthesis. Although experimental techniques have been developed for measuring vapor-liquid equilibrium data of asymmetric mixtures, experimental measurements are often time consuming and expensive. As such, reliable generalized equilibrium models have been sought for a priori prediction of VLE phase behavior of targeted systems.

In the present work, we evaluate the efficacy of structure-based generalization of equation-of-state (EOS) binary interaction parameters. Specifically, we have developed Quantitative Structure Property Relationships (QSPR) models for the a priori predictions of the Peng-Robinson EOS binary interaction parameters. The QSPR generalized parameters provide reliable phase behavior predictions for the binary asymmetric mixtures involving methane, ethane, carbon dioxide, hydrogen, nitrogen and carbon monoxide in n-paraffins (C4- C44), cylcoparaffins, and aromatics.

Generalizations with absolute average deviation of 5% in bubble point pressure were obtained for the conformal exponent of the EOS interaction parameters using the QSPR methodology. In addition the nature of the solute solvent interactions were clearly elucidated.