Review on gas-liquid separations in microchannel devices

Separations are indispensable to most chemical processes, regardless of operational scale. In the field of chemical microprocess engineering, separations have so far attracted rather limited attention compared to reactive processes, although increasingly more research is directed towards this area. Microstructured devices offer the opportunity of intensifying transport processes associated with separation operations by providing high ratios of contact areas to volume, short transport distances and high driving force gradients. These attributes have so far been exploited for various microseparations. In this review, we focus on separations where gas and liquid phases are present, and in particular on absorption, stripping and distillation. Two main approaches for contacting the two phases have been employed: continuous and dispersed phase contactors. Removal of components from gas mixtures by absorption and stripping of volatiles from liquid mixtures have been achieved in falling film devices, thin porous plate microcontactors, as well as in dispersed flow systems. Distillation has been performed in microchannel devices, utilizing capillary, centrifugal and gravity forces, vacuum or carrier gas.