Structural and Functional Effects in Solutions With Pure and Entrainer-Doped Supercritical Solvents
Van Alsten, John Gregg
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https://hdl.handle.net/2142/69767
Description
Title
Structural and Functional Effects in Solutions With Pure and Entrainer-Doped Supercritical Solvents
Author(s)
Van Alsten, John Gregg
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)
Engineering, Chemical
Abstract
The structural dependence of the solubility of nonvolatile compounds in compressed supercritical fluids has been investigated. Within pure, nonpolar supercritical solvents the predominant factor determining solubility is the volatility of the solute at the solution temperature. Of secondary importance is the effect of solute size, with larger solutes showing greater solubility enhancements, as defined by the dimensionless enhancement factor. Little influence of the solute polarity is observed. These factors are shown to make pure supercritical fluids poor separation solvents for solute mixtures of solids with similar sizes and volatilities.
Solubilities of six solid solutes were measured in supercritical carbon dioxide which had been doped with small quantities of methanol or acetone. These "entrainer-doped" solvents gave large increases in the solvent loading and, in contrast to pure fluids, this increase was sensitive to the solute structure. The mechanism for the observed increases is unclear, but may include such phenomena as hydrogen bonding and dipolar coupling. An entrainer doped fluid was also shown to be superior to a pure solvent in selectivity, offering potential for improved performance as a separation solvent.
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