Electrolysis and Steam-Hydrogen Exchange

The variation of this equilibrium constant with temperature is given in Table 13.16. 

The exchange reaction proceeds at a ne gible rate unless catalyzed, and the only catalysts available until recently lost activity in the presence of liquid water. It was therefore necessary to use a gas-phase catalytic reactor, as described in the previous example. 

The maximum recovery of deuterium possible with such a cascade is achieved by increasing the number of stages indefinitely and reducing the reflux ratio of depleted hydrogen to product heavy water until the depleted hydrogen is in deuterium exchange equilibrium with feed. The deuterium recovery r is given by 

Therefore, the maximum recovery of deuterium obtainable by steam-hydrogen exchange at 80°Cis 

This is more than twice the maximum recovery attainable economically by electrolysis alone. The deuterium content of depleted hydrogen in equilibrium with natural steam is 

---