Use of the Reaction to Improve Driving Force

1 Use of the Reaction to Improve Driving Force - We have seen that for product-removal membranes to be viable they must have high permselectivity for one species. This usually means that the permeation rate will be too low. One idea to overcome this problem is to conduct a reaction on the permeate side to decrease the partial pressure of the permeate. This also has the potential to produce a useful product. 

They also noted that hydrogen on the surface of the membrane emerges as dissociated atoms, and they found that the expression, rate oc po, / h, fitted their data better. This expression corresponds to the limiting step O2 + 2H 20H -I-. This result warns us that the kinetics obtained on conventional catalysts may not hold for catalytically-active membranes. 

Kinetics were determined directly on the catalyst bed, packed with Pd on AI2O3. Note that the Pd film was on the permeate side and could catalyse the hydrogen oxidation reaction in addition to permeating hydrogen. The authors found a higher conversion when a reactive sweep gas was used, but not as high as their model predicted. They attributed this discrepancy to the formation of a PdO 

2 Use of the Reaction to Modify the Membrane and Improve Driving Force -The use of dense oxide membranes to feed O2 to partial oxidation reactions is limited by the need for high temperatures to obtain reasonable permeation rates. The potential exists for selectivity gains and the control of heat effects. One application where dense membranes have a clear role to play is in methane activation. In particular, the partial oxidation of methane to syngas. 

The use of a dense membrane reactor has been studied experimentally by the group at Argonne/Amoco and by the group at WPI both theoretically and experimentally.  

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