Poly(ethylene glycol)nonylphenyl ether extraction with supercritical carbon dioxide in a packed column

A semibatch extraction of poly(ethylene glycol)nonylphenyl ether (PEG-NPE) with supercritical carbon dioxide was studied at 20,0 MPa, and 323 K. The process was carried out in a stainless steel column, filled with inert packing, wetted by the polymer. Three representative polymer fractions (degree of polymerisation 40, 50, and 60) and the total polymer amount at the column exit were monitored for a period of 4 h. Experimental data obtained were used for evaluation of process parameters, applying a model that considers the mass transfer on both phases and the longitudinal mixing in the solvent-rich phase, continuously flowing through the packed column. It was found that for the studied conditions the longitudinal mixing is very pronounced, but the active contact area is strongly reduced, supposedly as a result of solvent-rich phase channeling. After the transient initial period, the overall mass-transfer coefficient is controlled by the component diffusivity in the polymer-rich phase.