Measurements of binary diffusion coefficient for platinum(II) acetylacetonate in high temperature supercritical carbon dioxide by the chromatographic impulse response method

Infinite dilution binary diffusion coefficients D12 and retention factors k for platinum(II) acetylacetonate in high temperature supercritical carbon dioxide (scCO2), at temperatures from (323.3–454.2) K and pressures from (11.0–25.0) MPa, were measured by the chromatographic impulse response method. Although diffusion coefficients for various compounds up to 353 K in scCO2 reported in the literature were well represented by the hydrodynamic equation, the present data deviated more from the equation as the CO2 viscosity decreased. The deviating D12 data corresponded to the gas-like scCO2 region whose conditions were situated below the density fluctuation ridge line on the pressure (or density) − temperature phase diagram, as observed for Cr(acac)3 measured in the authors’ previous study. All the present D12 data and those previously measured below 343 K over the entire region from gas-like to liquid-like scCO2 were well represented by the Schmidt number correlation over the temperature range from 308.2 K to 454.2 K with an average relative deviation (ARD) of 6.5% for 109 measurement conditions. The retention factors measured in the present study were correlated with CO2 density, with temperature dependent constants having an ARD of 4.4% for 47 measurement conditions.