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.