Here is a link to a 3 year old essay of mine about how membrane reactors work and how you can use them to get past the normal limits of thermodynamics. The words are good, as is the example application, but I think I can write a shorter version now. Also, sorry to say, when I wrote the essay I was just beginning to make membrane reactors; my designs have gotten simpler since.
At left, for example, is a more modern, high pressure membrane reactor design. A common size is 72 tube reactor assembly; high pressure. The area around the shell is used for heat transfer. Normally the reactor would sit with this end up, and the tube area filled or half-filled with catalyst, e.g. for the water gas shift reaction, CO + H2O –> CO2 + H2 or for the methanol reforming CH3OH + H2O –> 3H2 + CO2, or ammonia cracking 2NH3 –> N2 + 3H2. According to normal thermodynamics, the extent of reaction for these reactions will be negatively affected by pressure (WGS is unaffected). Separation of the hydrogen generally requires high pressure and a separate step or two. This setup combines the steps of reaction with separation, give you ultra high purity, and avoids the normal limitations of thermodynamics.
Once equilibrium is reached in a normal reactor, your only option to drive the reaction isby adjusting the temperature. For the WGS, you have to operate at low temperatures, 250- 300 °C, if you want high conversion, and you have to cool externally to remove the heat of reaction. In a membrane reactor, you can operate in your preferred temperature ranges and you don’t have to work so hard to remove, or add heat. Typically with a MR, you want to operate at high reactor pressures, and you want to extract hydrogen at a lower pressure. The pressure difference between the reacting gas and the extracted hydrogen allows you to achieve high reaction extents (high conversions) at any temperature. The extent is higher because you are continuously removing product – H2 in this case.
Here’s where we sell membrane reactors; we also sell catalyst and tubes.