Placement of Catalyst Relative to Membrane

Where and how the catalyst is placed in the membrane reactor can have significant impact not only on the reaction conversion but also in some cases, the yield or selectivity. There are three primary modes of placing the catalyst (1) A bed of catalyst particles or pellets in a packed or fluidized state is physically separated but confined by the membrane as part of the reactor wall (2) The catalyst in e form of particles or monolithic layers is attached to the membrane surface or inside the membrane pores and (3) The membrane is inherently catalytic. Membranes operated in the first mode are sometimes referred to as the (catalytically) passive membranes. The other two modes of operation are associated with the so called (catalytically) active membranes. In most of the inorganic membrane reactor studies, it is assumed that the catalyst is distributed uniformly inside the catalyst pellets or membrane pores. As will be pointed out later, this assumption may lead to erroneous results. 

The above issues will be described individually as follows. 

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