Types of Membrane and Reactor Configurations

1 Types of Membrane and Reactor Configurations - Membrane reactors may be classified by the geometry and materials of the membrane, and by the configuration of the reactor. 

The materials of membrane construction can be classified as either dense or porous. Dense metal materials include palladium membranes that are semiperme-able to hydrogen, and silver membranes that are semipermeable to oxygen. The low permeation rates for silver membranes have led to the more recent use of solid oxide electrolyte dense membranes such as modified zirconias and perovs-kites, which have higher O2 permeation rates at high temperatures.  

Some materials have been investigated to obtain fundamental information regarding transport mechanisms. Anodic aluminas were studied by Tsotsis and 

The most active areas of development for membrane materials are currently synthesis of supported thin Aims, and pore modification. The complete selectivity to one species provided by dense membranes is very attractive, but is accompanied by low permeation rates if the membrane is composed entirely of the dense material. To maintain structural stability, thinner dense films must be supported by materials that are strong but that offer no additional resistance to permeation. Similar principles apply to the use of microporous materials with high permselectivities or molecular sieving effects. Some examples of these developments are supported Pd films on porous aluminas,or on porous stainless steel, and supported zeolite films. Pore modification has been used to deposit materials inside mesoporous materials, an example being the deposition of SiOa films in porous glass. 

Classification of membrane reactors with catalysts is based on the location of the catalyst. The notation introduced by Tsotsis et al. has been widely adopted, and will be used here. Table 1 gives a list of the acronyms used in this paper. 

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