The Application of Zeolites of Predetermined Permeability to the “Water Gas Shift Reaction”

Abstract

A flow sheet is presented for the isolation of pure hydrogen from the gas mixture generated by the well known water-gas shift reaction Separation of the resulting gas mixture is performed on three modified selective zeolite beds. In the first trap the small amount of unreacted water is absorbed by a zeolite with a controlled porosity; CO₂ cannot be absorbed because of steric hindrance due to its kinetic diameter of 0.330 nm. However, it is absorbed in a second trap almost selectively with respect to CO. The latter is finally separated from H₂ in a low temperature third trap. By applying a highly integrated flow pattern with extended recycling of regeneration process streams to the reactor, the only gaseous waste stream generated is CO₂. It is anticipated that this process will demonstrate a high degree of reliability and efficiency with low secondary waste generation even for highly tritiated water, since the zeolites can be prepared with pore sizes “on request” and without hydrogen atoms in their structures avoiding therefore any isotopic exchange with tritium. The preparation of these zeolites as well as other materials is described.