Dense ceramic membrane reactors types

Abstract Dense ceramic membrane reactors are made from composite oxides, usually having perovskite or fluorite structure with appreciable mixed ionic (oxygen ion and/or proton) and electronic conductivity. They combine the oxygen or hydrogen separation process with the catalytic reactions into a single step at elevated temperatures (>700°C), leading to significantly improved yields, simplified production processes and reduced capital costs. This chapter mainly describes the principles of various types of dense ceramic membrane reactors, and the fabrication of the membranes and membrane reactors. 

It is well known that dense ceramic membranes made of the mixture of ionic and electron conductors are permeable to oxygen at elevated temperatures. For example, perovskite-type oxides (e.g., La-Sr-Fe-Co, Sr-Fe-Co, and Ba-Sr-Co-Fe-based mixed oxide systems) are good oxygen-permeable ceramics. Figure 2.11 depicts a conceptual design of an oxygen membrane reactor equipped with an OPM. A detail of the ceramic membrane wall... 

There are three main types of dense ceramic membranes disk/flat sheet, tubular, and hollow fibers. The disk/flat sheet membranes are applied mostly in research work because they can be fabricated easily in laboratories with a small amount of membrane material. Comparatively, the hollow fiber membranes can provide the largest membrane area per volume but low mechanical strength, while the tubular membranes possess a satisfactory specific membrane area, high mechanical strength, and are easy to assemble in membrane reactors. Dense ceramic MRs can be constructed and operated in either packed bed MR or catalytic MR configurations. 

Figure 5.37 Effect of reaction pressureon methane conversion for methane steam reforming in membrane reactors with different types of membranes reaction temperature 500°C S/C ratio 3 A, thermodynamic equilibrium , conversion in a membrane reactor with porous ceramic membrane 0, methane conversion in a membrane reactor with dense palladium membrane [406].

Organic membrane reactions are best carried out in reactors made of inorganic membranes, such as from palladium, alumina, or ceramics. A recent trend has been to develop polymeric-inorganic composite-type membranes formed by the deposition of a thin dense polymeric film on an inorganic support. Another class of membranes under development for organic synthesis is the liquid membrane. The permselective barrier in this type of membrane is a liquid phase, often containing a dissolved carrier or transporter which selectively reacts with a specific permeate to enhance its transport rate through the membrane. 

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