Catalytic reactions in a membrane reactor configuration

Microporous silica membranes operate on a molecular sieving principle and are usually tailored to separate H2 from other, larger, gases. Hence their incorporation into membrane reactor technology is most suited to those reactions that either consume or produce H2 and especially, given their thermal stability, for those reactions involving H2 that occur at temperatures up to 800°C. This section explores the membrane reactor performance of several of the catalytic reactions where silica-based membranes have been effectively demonstrated at the research level. 

There are three main industrial processes for the production of H2 namely steam reforming (SR), partial oxidation (POX) and autothermal reforming (ATR). All three methods transform a hydrocarbon source into synthesis gas (syngas), a mixture of H2, CO and CO2, before further reaction 

SR converts hydrocarbons into syngas through the addition of steam and heat (Kolb, 2008). The main reactions that take place are the strongly endothermic reforming Reaction [9.9] and [9.10] and the moderately exothermic WGS Reaction [9.11]  

The SR process is divided into two sections a high-temperature and pressure section (typically 800-1000°C and 30-40 bar) in which the reforming and WGS reactions occur, followed by an additional (two-step) shift section at lower temperatures (typically 200-400°C) in order to maximize the CO 

2 Cross section of a catalytic membrane (reprinted fromTsuru eta ., 2004). 

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