Biphasic flow

The more important physical aspects of the flow of gas -containing systems are analyzed for a uni-phase and a biphase flow. Equations are developed for a qualitative description of these systems. 

Figure 4.27 Heck reactions accelerated by biphasic flow system.

As summarized in this chapter, various synthetic protocols have made advantageous use of biphasic liquid-liquid systems in microreactors. Apart from reaction optimization and acceleration of processes, the application of biphasic flow systems has already led to the development and design of novel protocols, and it is expected that this area of research will grow in future. 

P. Guillot, A. Colin, A. S. Utada, and A. Ajdari, Stability of a jet in confined pressure-driven biphasic flows at low Reynolds numbers. Physical Review Letters, 99, 104502, 2007. 

One of the main differences of DAFC with H2/O2 PEM fuel cells is the biphasic flow in the anode exhaust due to the feed of aqueous alcohol and the production of CO2, which is only partially soluble in the liquid. 

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.)...

The polymeric catalytic membrane is utilized for biphasic laminar flow synthesis. Uozumi and coworkers developed membrane-installed microflow devices, in which a self-assembled polymeric Pd nanoparticle membrane was installed, for several important chemical transformations. The polymer membrane was precipitated at the laminar interface between the two parallel flows (Scheme 7.5). There is no doubt that the vast interfacial surface of the catalytic membrane with substrates and reactants in the biphasic flows would improve the rate of chemical transformation. 

The synthesis of 3,3-disubstituted 2-oxindoles by palladium-catalyzed a-arylation/alkylation sequences in a biphasic flow system has been achieved by Buchwald et al. [44]. The reaction sequence consisted of two steps, the arylation followed by the alkylation. The first reaction system contains the substrate and aryl halide in toluene in one solution, the second the pre-catalyst in toluene, and a third solution containing potassium hydroxide and tetrabutyl ammonium bromide (TBAB) (Scheme 8.11). This is then mixed in a packed-bed mixer and heated to 100 °C for arylation. This system is then fed into a second T-piece where the alkyl halide is introduced, further mixing is applied in the second packed-bed reactor for the alkylation. This product mixture is then quenched with monosodium phosphate and extracted with ethyl acetate. The overall reaction proceeded in a 93% yield and could also be stopped at the arylation step by the addition of a switch valve before the alkylation step. Palladium-catalyzed hydrogenations have also been investigated under organic/aqueous biphasic conditions and an enhancement has been observed when using polymeric encapsulation [45]. 

Theory of slow biphasic flows in porous media , Physico-Chemical Hydrodynamics. 4, n 2, pp. 175-185 (1983). 

Biphase flow models Describing how the gas and liquid interact in a porous media... 

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