Microchannels biphasic flow

Figure 3.33 Biphasic flow in microchannel for narrow RTD (a) schematic illustration and (b) monochrome snapshot of slug flow. (Adapted from Ref. [21] with permission from Elsevier.)...

In a macroscale channel, gravitational force has an effect on the flow pattern of a biphasic system consequently, the flow pattern varies between vertical and horizontal channels. However, in a microchannel, the gravity effect is dominated by the viscous forces that are expressed by the ratio of gravity force and the surface tension using the Bond number (Bo) as expressed in Equation 4.5 where Ap is the density difference between two immiscible liquids, g is acceleration due to gravity, dh is the channel dimension and ct the surface tension. 

Lipase catalyzed synthesis of isoamyl acetate in n-heptane/buffer using acetic acid as acyl donor enhanced reaction rates in microreactor compared to batch model simulations achieved by numerical solution of nonlinear systems provided a good fit to experimental data Technique relies on segmented-flow biphasic system crude cell lysate allowed for enatio-selective synthesis of cyanohydrins in microchannels. The reaction rate and selectivity only achieved in larger batch mode with intense shaking (stable emulsion formed). 

Applications of microreactors to biphasic catalytic reactions constitute a topac of interest. The benefits of having an exceedingly high surface-to-volume ratio and efficient mass-transfer in microchannels have led many researchers to study continuous flow systems using microreactors for catalytic reactions. The excellent mass transfer characteristics within and between the catalyst carrier phase and reaction medium, together with the minimal catalytic pore diffusion resistances at the micrometer scale, make such biphasic catalysis an attractive alternative to conventional catalysis operation (Wieflmeier, 1996 Rahman et al., 2006). 

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