Diffusion Coefficients of Ethers in Supercritical Carbon Dioxide

The Taylor−Aris tracer response method was applied to measure binary diffusion coefficients, D 12, in supercritical carbon dioxide under quasi-infinite-dilution conditions, by means of the Giddings and Seager chromatographic technique. Diethyl ether, diisopropyl ether, and tetrahydrofuran have been studied at 40, 50, and 60 °C in the pressure range 80−160 atm. The resulting binary diffusion coefficients are on the order of 10 - 4 cm 2 /s. The influence of molecular weight, temperature, pressure, carbon dioxide density, and viscosity on the D 12 values is extensively examined. The applicability of the Wilke−Chang and Tyn−Calus hydrodynamic correlations, the free-volume diffusion model of Dymond, the Catchpole and King correlation, and the Lennard-Jones model of Liu−Silva−Macedo is also evaluated.