Supercritical Fluids: Kinetic Solvent Effect and the Correlation of Solid-Fluid Equilibria
Ellison, Timothy Kirk
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Permalink
https://hdl.handle.net/2142/69766
Description
Title
Supercritical Fluids: Kinetic Solvent Effect and the Correlation of Solid-Fluid Equilibria
Author(s)
Ellison, Timothy Kirk
Issue Date
1986
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, General
Engineering, Chemical
Abstract
Kinetic data for the dimerization of cyclopentadiene at 373, 378, 388, and 398 K in a supercritical propane solvent at pressures from 42 to 136 bar are presented. Data are presented for the cracking of dicyclopentadiene in supercritical butane at 433 K in the pressure range of 42-169 bar. Both reactions were studied in a supercritical chromatograph packed with Porasil A. The dimerization slows with increasing density whereas the cracking reaction is complicated by the dimerization of the product and appears to approach equilibrium. The dimerization results were analyzed in terms of transition state theory using the Peng-Robinson equation. The slowing of the dimerization and the implications of this result for the general case of a reactive system in a supercritical solvent are discussed in terms of the relative sizes and energies of the reactive solutes and the fluid solvent.
Binary supercritical mixture solubilities and partial molal volumes for a variety of solutes in carbon dioxide, ethane, ethylene, fluoroform, and sulfur hexafluoride solvents were correlated using perturbed-hard-sphere equations (Augmented van der Waals and Carnahan Starling van der Waals) and a cubic equation-of-state (Peng-Robinson). The overall correlations were fair (20-30%). When an equal number of equivalent adjustable parameters were used for both models, the accuracies were roughly equivalent. Although a preliminary predictive method for solubilities that uses the solute heat of sublimation is presented for the hard-sphere equations, the inability of these equations to represent isothermal compressibilities hints that prediction using these equations when no data are available is somewhat unreliable. Although the cubic is less accurate for correlation than the hard-sphere equations, it can at least reproduce the correct qualitative representation for all solution behavior examined.
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