Liquid-liquid extraction using combined hydrophilic-hydrophobic emulsion templated macroporous polymer micromixer-settlers

Abstract

Continuous liquid-liquid extraction and separation of 4-aminoacetophenone, a product of the hydrogenation of 4-nitroacetophenone, was performed within emulsion templated macroporous polymer (polyHIPE) extraction units combined with a miniaturized gravity-based settler. PolyHIPEs with interconnected and tailorable macroporous structures are effective micromixers allowing to mix fluids in both axial and radial directions. We fabricated extraction units by combining hydrophilic and hydrophobic polyHIPEs, which improved the extraction efficiency by inverting the liquid/liquid dispersion type from oil/water to water/oil (or vice versa) during the extraction. The dispersion type is governed by the wettability of the porous medium. The extraction efficiency of our combined polyHIPE micromixer reached 98%, while that of control experiments performed using a blank tube or commercial Kenics® static mixer was 78%. The overall volumetric mass transfer coefficient kLa in polyHIPE micromixer-settlers was significantly higher 0.011 s−1 reaching interfacial areas a of 17900 m2/m3, much larger compared to a blank tube (kLa = 0.0035 s−1 and a = 5700 m2/m3) and static mixer (kLa = 0.0041 s−1 and a = 6800 m2/m3). PolyHIPE micromixer-settlers could be potentially useful to intensify continuous L-L extractions.