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 p rocess was carried out in a stainless steel column, filled with inert packi ng, wetted by the polymer. Three representative polymer fractions (degree o f 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 u sed for evaluation of process parameters, applying a model that considers t he 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 ver y pronounced, but the active contact area is strongly reduced, supposedly a s a result of solvent-rich phase channeling. After the transient initial pe riod, the overall mass-transfer coefficient is controlled by the component diffusivity in the polymer-rich phase.