Measurement and correlation of the diffusion coefficients of chromium(III) acetylacetonate at infinite dilution in supercritical carbon dioxide and in liquid ethanol

Highlights: • The diffusion coefficients in supercritical state and in liquid state were measured. • The effects of temperature, pressure and viscosity on diffusivity were investigated. • The diffusion activation energies were presented. • Good agreement between experimental data and the correlation was obtained. - Abstract: The diffusion coefficients of chromium(III) acetylacetonate (Cr(acac)₃) were measured at infinite dilution in supercritical carbon dioxide and in liquid ethanol. The diffusion measurements in supercritical carbon dioxide were carried out at five different temperatures varying from T = (308.15 to 343.15) K and at pressures up to 40.00 MPa by using the chromatographic impulse response (CIR) method. And the measurements in liquid ethanol were also made by the Taylor dispersion method at five temperatures in the range from T = (299.15 to 333.15) K and 0.10 MPa. The determined diffusion activation energies in supercritical carbon dioxide were E_a = (22.9–11.2) kJ·mol⁻¹ at p = (13.00–35.00) MPa, respectively, and that in liquid ethanol was 15.9 kJ·mol⁻¹ at 0.10 MPa. All the diffusion coefficients of Cr(acac)₃ in supercritical and in liquid states can be correlated by the hydrodynamic equation as a function of temperature and fluid viscosity with average absolute relative deviation (AARD) of 4.6% over a wide viscosity range from η = (3.036·10⁻⁵ to 1.113·10⁻³) Pa·s for 85 data points.