The flow of two immiscible fluids was investigated in rectangular glass microchannels with equivalent diameters of 269 and 400 m. Deionised water, dyed toluene and hexane were selected as probe fluids. Flow patterns were obtained for Y-and T-junction of two micro-channels and monitored by a photo-camera. Volumetric velocities of water and organic phase varied between 1 and 6 ml/h. The formation mechanism of slug and parallel flow was studied and the mass transfer performances of two flow patterns were compared. The shape of the interface between the immiscible liquids was controlled by a competition between the viscous forces and the local interfacial tension. The flow patterns could be correlated with the mean Capillary and Reynolds numbers. The mass transfer coefficients for parallel and slug flow were determined using instantaneous neutralisation (acid-base) reaction. The two flow patterns showed the same global volumetric mass transfer coefficients in the range of 0. 2-0. 5 s −1 , being affected mainly by the base concentration in water for parallel flow and by the linear velocity in the case of the slug flow.

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This review addresses the catalytic reactions performed in microstructured reactors, which are more and more recognized in recent years as a novel approach for chemistry and chemical process industry. They are particularly suited for highly exothermic and fast reactions allowing temperature control and isothermal operation. A brief evaluation of the advantages for gas-phase, liquid-phase, and gas-liquid-solid reactions carried out in miniaturized devices is discussed. Alternative designs to achieve microstructured fluid patterns, besides microfabrication, are also described. #

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The performance of microstructured reactors (or microchannels) for mass-transfer-controlled liquid–liquid reactions depends on flow regimes that define the specific interfacial area for the mass transfer. In the present work, experiments were carried out to investigate the two phase-flow regimes and the mass transfer at relatively high throughput for a single microchannel (of 1–18 mL/min) in five generic microchannel designs (with and without structured internal surfaces), using a nonreacting water–acetone–toluene system. When the flow results were analyzed collectively in all microchannels, six different flow regimes such as slug, slug-drop, deformed interface, parallel/annular, slug-dispersed, and dispersed flow were observed. The mass-transfer comparison shows that the microchannel with structured internal surfaces shows better performance, because it creates a very fine dispersion, providing high interfacial area, compared to other microchannels. Finally, the mass-transfer data were correlated, which can be used for a priori predictions of mass-transfer rates in microchannels.