Abstract
Mutual diffusion coefficients of benzene in supercritical carbon dioxide are determined at 313.15 K from 8 to 20 MPa using the Taylor dispersion method. A 10 m diffusion tube was oriented in a horizontal position. A UV detector was used to determine solute concentration profiles. We find that the diffusion coefficients have maxima depending on injection volumes and appear to approach zero for 5.7 and 13.1 μl injection volumes near the critical pressure of carbon dioxide, although their values decrease monotonically with pressure for 0.7 and 1.0 μl injection volumes. Based on irreversible thermodynamics, calculation from an equation of state reveals qualitatively anomalous behavior. Below 8 MPa, the decay in concentration distribution due to fluctuation in the critical region is immeasurable with UV due to intense light scattering but can be measured with a flame ionization detector.
