HIGH PRESSURE VAPOR-LIQUID EQUILIBRIUM MEASUREMENTS AND A NEW EQUATION OF STATE: THE SIMPLIFIED - PERTURBED - HARD-CHAIN THEORY

In this research program, experimental high pressure vapor-liquid equilibrium data for binary, ternary, and quaternary mixtures involving supercritical carbon dioxide and model coal compounds were measured. In addition to these measurements, a new equation of state, the Simplified-Perturbed-Hard-Chain theory, was developed and applied to both pure fluids and mixtures.; The objective of experimental phase equilibrium measurements was to investigate the enhancement in solubility of model coal compounds, anisole and benzaldehyde, in dense carbon dioxide using methanol as cosolvent. Since major component of a typical coal mixture is naphthalenes, we studied mixtures of chosen model coal compounds and 1-methylnaphthalene. An equilibrium apparatus, in which both the vapor and liquid phases are circulated, has been built to determine the equilibrium phase compositions and densities.; We measured the phase equilibria of the ternary and quaternary systems and constituent binaries as well as the system carbon dioxide-tetralin, since tetralin is present in significant amounts in liquified coal. Comparison of data for ternary and quaternary systems indicates that, to pressures up to 15 MPa, the solubility of anisole in dense (vapor phase) carbon dioxide is decreased by the addition of methanol as cosolvent. At higher pressures, slight enhancement in solubility of anisole is observed. Similar results are obtained for benzaldehyde.; Along with experimental measurements, a simple analytical equation for chain-like molecules interacting with square-well potential was derived by replacing the complicated attractive term in the Perturbed-Hard-Chain theory (PHCT) of Beret, Donohue, and Prausnitz with a theoretical but simple expression derived by Lee, Lombardo and Sandler. The resulting Simplified-Perturbed-Hard-Chain theory (SPHCT) reproduced both experimental vapor pressure and liquid-density data for a number of fluids over a wide temperature and pressure range with good accuracy.; The three pure-component parameters in the SPHCT have been obtained for several n-alkanes and multipolar fluids. Average errors in predicted vapor pressures and liquid-densities are about 3% and 4% respectively. Mixture calculations indicate that the SPHCT predicts K-factors with reasonable accuracy (about 10% error) without the use of any binary parameters.