Section 7.4 described the development in Canada [S8] of a catalyst for the deuterium exchange reaction between hydrogen and liquid water that is not inactivated when submerged in water.

Availability of this catalyst has led to interest in its possible use in dual-temperature water-hydrogen exchange processes. With liquid-water feed and recirculated hydrogen gas, this catalyst could be used in a dual-temperature process similar in principal to the GS process, with a schematic flow sheet like Fig. 1325. With ammonia synthesis-gas feed and recirculated water, this catalyst could be used in a dual-temperature process similar to the ammonia-hydrogen process flow scheme of Fig. 13.37, provided that impurities in synthesis-gas feed that would poison the catalyst can be recovered sufficiently completely.

Miller and Rae [M7] have suggested process conditions for a dual-temperature process using this catalyst at 69 atm pressure and temperatures of 50°C for the cold tower and 170°C for the hot. These conditions have been used to estimate optimum flow rates and numbers of theoretical stages for dual-temperature water-hydrogen processes using these two flow schemes. The results are tabulated in Table 13.28 and compared with similar data for the other dual-temperature processes discussed previously.

With water feed, the water-hydrogen exchange process has the advantages of lower gas and liquid flow rates and fewer stages than the water-hydrogen sulfide process. Utility requirements would also be smaller. Disadvantages of the hydrogen process are the higher pressure and the need to use large volumes of an expensive catalyst. If the catalyst were sufficiently active and not too expensive, the hydrogen process might be economically attractive.

With synthesis-gas feed, the water-synthesis-gas exchange process appears to be at a dis­advantage relative to the ammonia and methylamine exchange processes because the water pro­cess has the highest flow rates and the largest number of stages.