Diffusion coefficients of phenylbutazone in supercritical CO2 and in ethanol

The diffusion coefficients D12 of phenylbutazone at infinite dilution in supercritical CO2 were measured by the chromatographic impulse response (CIR) method. The measurements were carried out over the temperature range from 308.2 to 343.2 K at pressures up to 40.0 MPa. In addition, the D12 data of phenylbutazone at infinite dilution in ethanol were also measured by the Taylor dispersion method at 298.2–333.2 K and at atmospheric pressure. The D12 value of phenylbutazone increased from 4.45 × 10−10 m2 s−1 at 298.2 K and 0.1 MPa in ethanol to about 1.43 × 10−8 m2 s−1 at 343.2 K and 14.0 MPa in supercritical CO2. It was found that all diffusion data of phenylbutazone measured in this study in supercritical CO2 and in ethanol can be satisfactorily represented by the hydrodynamic equation over a wide range of fluid viscosity from supercritical state to liquid state with average absolute relative deviation of 5.4% for 112 data points.

► Brief theoretical background for the CIR and Taylor dispersion methods.
► Effects of wavelength, secondary flow and injected amount on diffusion.
► Diffusion measurements of phenylbutazone in supercritical CO2 by the CIR method.
► Diffusion measurements of phenylbutazone in ethanol by the Taylor dispersion method.
► Predicting all diffusion data measured in this study.