Selective Permeation of Ammonia and Carbon Dioxide by Novel Membranes

Experimental results are presented on membranes of novel composition which selectively permeate ammonia and carbon dioxide from mixtures containing hydrogen. The CO2-selective membrane, which consists of a thin liquid film of the salt hydrate tetramethylammonium fluoride tetrahydrate, exhibits a CO2 permeance of 4-1 × 10−5 cm3/cm2·s·cmHg with selectivity, α(CO2/H2), ranging from 360-30. The NH3-selective membrane, poly(vinylammonium thiocyanate), displays a high NH3 permeance, 5−20 × 10−5 cm3/cm2·s·cmHg, with α(NH3/N2) as high as 3600 and α(NH3/H2) as high as 6000. Such membranes, which retain H2 at pressure in the feed stream, may offer new opportunities in the design of separation processes.