Application of rough hard sphere theory to diffusion in supercritical fluidst

Abstract

The limiting mutual diffusion coefficients of benzene and carbon tetrachloride were measured in subcritical and supercritical carbon dioxide at 298 and 309 K in the pressure range 8.96 – 26.0 MPa using the Taylor dispersion technique. The rough hard sphere theory was used for interpretation of the data obtained in this study as well as the data in the literature for limiting and self-diffusion coefficients. The theory represents the data successfully for pure fluids with a density-independent coupling parameter. The effective hard sphere diameters extracted from the data match closely with the diameters calculated by other methods. The same functional dependence of the self-diffusion coefficients on molar volume was also observed for limiting mutual diffusion coefficients determined in this work and for naphthalene data in the literature. Hence, a correlation based on the rough hard sphere theory was developed for prediction of diffusivities in sub- and supercritical carbon dioxide. The correlation reproduces the data with an average absolute deviation of 7.68%.