Fundamental study of de-solventing polymer solutions with supercritical CO₂

Partition coefficients of n-hexane between poly-butadiene (PB) and supercritical CO₂ phases at infinite dilution were measured using supercritical fluid chromatography (SFC) at various temperatures and pressures. The supercritical fluid Chromatograph used was equipped with a packed column and flame ionization detector (FID) and methane was chosen as a marker component which can be considered to have small interaction with the sample polymer at the experimental conditions. The packed column was prepared with support material (chromosorb; 30-60 mesh) coated with PB. The partition coefficients were determined from retention volume data. The obtained partition coefficients changed as a function of fluid density and temperature. It should be noted that at infinitely dilute state the partition coefficient showed fairly high values, indicating the probability of removing n-hexane from PB using CO₂. The equation of state proposed by Sanchez et al. [I.C. Sanchez, R.H. Lacombe, An elementary molecular therory of classical fluids. Pure fluids, J. Phys. Chem. 80 (1976) 2352.] was used to correlate the data, whose parameters were determined from the p-V-T data measured in this study. Good agreement between the experimental and calculated partition coefficient was obtained by optimizing the equation parameters.