Selection of Catalyst Placement

The choice of the above three modes of catalyst placement relative to the membrane can significantly affect the reactor performance. From the analysis of catalytically active and passive (inert) membrane reactors [Sun and Khang, 1988], it appears that the critical parameter determining the choice is the reaction residence time. At low residence times, the difference between a catalytically active and a catalytically passive membrane is not significant. However, as the reaction residence time becomes high, the catalytically active membrane shows a higher reaction conversion. 

Although technically more superior to the catalytically passive membranes in reaction performance under certain conditions, the catalyst-mo fied membranes pose a few technical challenges. The first issue is the control of the resulting membrane pore sizes and their distribution. There has been no indication of a robust procedure for incorporating catalysts either only on the membrane surface or in the membrane pores such that the fuial pore size distribution is uniform or can be predicted. The second concern is the physical and chemical stabilities of the catalyst After an extended period of q eration, the catalyst may be physically detached from the membrane or eroded, or catalytically poisoned. It is generally easier to replace or regenerate the catalyst in the catalytically passive mode. 

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