Abstract
Diffusion in liquids is a very important phenomenon in all mass transfer operations. Although there are many correlations available to predict diffusivities in liquids, almost all of these are developed from data at ambient or close to ambient conditions. There is a severe lack of data on diffusion coefficients at high temperatures and pressures. Consequently, theoretical treatments are also lacking for diffusivity at high temperatures. In this study, a Taylor dispersion apparatus was constructed for measuring diffusion coefficients in liquids at temperatures between 298 and 573 K and pressures between atmospheric and 3500 kPa. Because the diffusion coefficients are known to be a strong function of molar volume and viscosity, the apparatus was designed to measure the viscosity and density of the liquids, also. The diffusion coefficients of hydrogen, carbon monoxide, carbon dioxide, octane, decane, dodecane, tetradecane, and hexadecane were measured in the solvents heptane, dodecane, and hexadecane between 298 and 567 K and at 1400 and 3450 kPa. The density and viscosity of dodecane and hexadecane were also measured at all conditions. These data are the first for these systems at temperatures above 343 K, and represents a significant extension of the high temperature data base for diffusion coefficients. A rough hard sphere kinetic theory approach has been developed to analyze the data and develop a predictive equation. Some of the other theoretical treatments have been shown to be less desirable due to the difficulty in predicting the necessary parameters or to the failure of the basic assumptions of the theory. Methods for estimating the parameters needed to predict the diffusivity from the rough hard sphere theory have been provided, and the resulting equations have been shown to work better than previously available predictive equations. In addition, the theory given in this study also predicts other diffusivities given in the literature for chemically similar systems. This study provides the first systematic effort to generalize the rough hard sphere theory for an important class of compounds.
Matthews, Michael Anthony (1986). Diffusion coefficients at infinite dilution in n-alkane solvents at temperatures to 573 K and pressures to 3.5 MPa. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -24183.