Effect of Solutes on the Viscosity of Supercritical Solutions

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• 作者：Andrew P. Abbott ; Eric G. Hope ; Donna J. Palmer
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：July 19, 2007
• 年：2007
• 卷：111
• 期：28
• 页码：8114 - 8118
• 全文大小：68K
• 年卷期：v.111,no.28(July 19, 2007)
• ISSN：1520-5207

文摘

This study shows that solutes can impart significant structure to supercritical solutions, resulting in unexpectedlyhigh solution viscosity at pressures close to the critical value. The viscosity passes through a minimum as thepressure is increased, and this is accounted for by a solvation of the solutes leading to a decrease in solute-solute interactions. At high pressure, the solution viscosity is similar to that of the pure solvent as solvent-solvent interactions dominate. The increase in relative viscosity is modeled using a modified Dole-Jonesequation, and it is shown that the change in relative viscosity is related to the volume fraction occupied bythe solute. A general model is presented for simple solutes whereby the viscosity of a supercritical solutioncan be calculated from the molecular volume of the solute and the viscosity of the pure fluid. The higher thanexpected viscosity observed at low pressures is used to explain the variation of reaction rate constant withpressure.