Physicochemical Transport Phenomena

It is preferable if the reactions in RD columns are catalyzed by heterogeneous catalysts because they are easily kept in the reactor and they allow hybrid RD columns combining reactive and non-reactive sections. Fig. 5.25 illustrates a column randomly packed with supported ion exchangers in rings. Such a heterogeneous cat- 

The directions of the mass and energy fluxes between the phases cannot be predicted because of the influence of convection in axial column direction, and due to the fact that multicomponent mass-transport phenomena may result in uphill transport [30]. There are three types of transport resistances present in the considered three-phase (vapor/liquid/solid) process 

If supported macroreticular ion exchangers are used as catalysts, the intrapartide transport processes can be decomposed into gel phase diffusion and macropore diffusion [31]. For a combination of the two mechanisms special catalyst models were proposed [32]. 

Furthermore, it should be mentioned that for structured packing additional mass-transport resistances may exist between the catalyst particles in the structured wire gauzes of the packing. So far, relatively little is known about these interparticle resistances. However, they may play a major role in RD operations since a 

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The electroosmotic mobility and bulk EOF velocity are sensitive to the physicochemical properties of the solution and channel walls. Because electroosmosis is a surface-driven phenomenon, EOF fluid transport is characterized by plug flow. Except in the thin EDL, there is no shear in the fluid flow and so the velocity profile is flat. At the same time, the individual species charged permanently or spontaneously in the bulk fluid also undergo electric forces. 

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