MOLTEN-SALT FACILITATED TRANSPORT MEMBRANES .2. SEPARATION OF AMMONIA FROM NITROGEN AND HYDROGEN AT HIGH-TEMPERATURES

Immobilized molten salt (IMS) membranes have been prepared and shown to be effective for the separation of NH3 from mixtures with N2 and H2 at the high temperatures encountered in the recycle loop of ammonia synthesis plants. The membranes were prepared by immobilizing molten LiNO3 and ZnCl2, salts which react reversibly with NH3 but not with N2 or H2, in thin porous supports. Ammonia permeabilities of 10(3) to 10(5) barrer and NH3/N2 and NH3/H2 selectivities of at least 1000 were observed at 250-300-degrees-C. The extraordinary NH3 permeability through the ZnCl2 IMS membrane is explained by a carrier-mediated facilitated transport model wherein zinc ammoniate complexes function as mobile carriers.