A Predictive Equation for the Tracer Diffusion of Various Solutes in Gases, Supercritical Fluids, and Liquids

Abstract

A predictive equation for the infinitely dilute diffusion coefficients of various solutes in gaseous and liquid phases is proposed. The expressions proposed previously for the tracer diffusion in binary hard sphere fluids are examined critically and a new expression, based on the molecular dynamics simulations of Alder et al. (1974), obtained. The obtained expression is extended first to a Lennard-Jones fluid and then, by introducing a coupling factor, to a real fluid. The molecular diameter and energy parameters used in the equation are calculated with generalized correlations and simple combining rules. The coupling factor is correlated with the acentric factor. The derived equation is tested against a large number of experimental data: 1443 points for 120 systems, including the diffusions of various solutes in gases, supercritical fluids, and liquids. Excellent predictions were obtained: the total absolute average deviation is only 8.42%. For most systems, the predicted errors are comparable to the experimental uncertainties.

Accurate hydrodynamic models for the prediction of tracer diffusivities in supercritical carbon dioxide

“…This is consistent with our findings, since the D 12 values of n-alkanes were frequently overestimated by the hydrodynamic correlations. For this reason, dedicated constants are proposed for the particular case of these solutes, similarly to previous works [79,80].…”

Application of the corresponding states principle to the diffusion in CO2

“…21 for D AB taking the experimental values of only one solute, several predictive equations have been tested and their average absolute deviations (AAD) are listed in Table 5. The first 14 are based on the hydrodynamic model of Stokes–Einstein4 and the following 12 are based on the Rough–Hard–Sphere model 59–61. Equation 14 can also be considered a particular case of this last theory.…”

Solubilities and diffusion coefficients of high boiling compounds in supercritical carbon dioxide

“…Funazukuri et al (1991) and Funazukuri (1996) (Liu and Ruckenstein, 1997b;Liu et al, 1997;Yu, 1997, 1998).…”