Physical separation, catalyst incorporation

In this case, the membrane compartmentalizes the reactor and functions for separation but is not involved directly in the catalytic reaction (called an inert membrane ). The catalyst pellets are usually packed or fluidized on the inert membrane (Figure 1.12(a)), which acts as an extractor for fractionation of products and/or as a distributor for controlled addition of reactants. This incorporation of catalyst is most popular in practical use and can easily be operated. Since the catalyst is physically separated from the membrane, the separation fimction of the membrane and the activity of the catalyst can be modulated independently. Catalysts are generally placed on the separation layer... 

In order to improve the catalytic activity and selectivity of the membrane reactor, a catalyst has to be used. A simple way is to place the catalyst pellets on/next to the membrane, as shown in Fig. 7.9a. The membrane mainly functions as either a product extractor or a reactant distributor, although it also plays some role in the reaction.The reaction selectivity is mainly determined by the catalyst. This incorporation mode is most popular in practical use and is easily operated. Since the catalyst is physically separated from the membrane, only the separation function of the membrane needs to be controlled. The high selectivity of the dense ceramic membranes leads to highly attractive results (pure Hj extraction in dehydrogenation reactions and direct use of air in partial oxidation reaction). But the permeability of the membrane has to be improved as high as possible. 

The effectiveness of metal deposition can be impeded in the presence of other ionic species, organic or neutral species and also when relevant ionic species are in low concentrations. To improve the efficiency a combined, or integrated , approach to metal recycling can be used which incorporates other chemical and physical separation processes in conjunction with electrodeposition. This approach is used in the recycling of batteries and metal catalysts. 

Separation of enantiomers by physical or chemical methods requires the use of a chiral material, reagent, or catalyst. Both natural materials, such as polysaccharides and proteins, and solids that have been synthetically modified to incorporate chiral structures have been developed for use in separation of enantiomers by HPLC. The use of a chiral stationary phase makes the interactions between the two enantiomers with the adsorbent nonidentical and thus establishes a different rate of elution through the column. The interactions typically include hydrogen bonding, dipolar interactions, and n-n interactions. These attractive interactions may be disturbed by steric repulsions, and frequently the basis of enantioselectivity is a better steric fit for one of the two enantiomers. ... 

The preparation of heterogeneous catalysts is a complex operation that can incorporate many unit operations. The operation involves the formation of the catalyst precursor, separation, and purification, posttreatment, and forming. These operations can be carried out in many ways. All of these operations affect the physical and chemical properties of the final catalysts, which affect the performance in industrial use. Last, the economics of the process that uses the catalyst will be affected and is the ultimate driving force. 

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