Diffusion of Ethanol in Supercritical Carbon Dioxide—Investigation of scCO2-Cosolvent Mixtures Used in Pharmaceutical Applications

Abstract

Diffusion coefficients, D, for ethanol in supercritical carbon dioxide (scCO2) were measured in the temperature range 306.15–331.15 K and along the 10.5MPa isobar, using the Taylor dispersion technique. The obtained diffusivities ranged from 1.49 10􀀀8 to 2.98 10􀀀8 m2 s􀀀1, an order of magnitude higher than in usual liquids. The dependence of D on temperature and solvent density was examined. Various correlation models based in the hydrodynamic theory were assessed to estimate the diffusion coefficients, with reasonable results obtained for theWilke–Chang and Lai–Tan models.