Difussion Coefficients of Bromobenzenes in Supercritical Carbon Dioxide

Diffusion in supercritical fluid is a real important field that is in expansion. During recent years, supercritical fluid extraction and supercritical fluid chromatography have received considerable attention as techniques for the separation of non-volatile substances. A Taylor-Aris dispersion apparatus was set up to measure diffusion coefficients in supercritical carbon dioxide. Binary diffusion coefficients were determined for benzene, bromobenzene, and o-dibromobenzene in liquid and supercritical CO₂. The temperature range covered was from 24.5 [^oC] to 40 [^oC] and the pressure ranged from 12 [MPa] to 30 [MPa]. The uncertainty of the measurement, as showed by of the mean absolute deviation, was estimated at about ±6 %. The results were free of secondary flow by working in the appropriate velocity range according to the apparatus design. Other sources of errors were carefully taken into account to obtain accurate data. Diffusion coefficients found in this work showed a pressure dependence similar to that in previous works, although their magnitudes were appreciably smaller. Three different methods that predict binary diffusion coefficients are under study to produce a good model based on the prediction of the experimental values obtained.