Study on ammonia transport and separation in Aquivion® perfluoro sulfonated acid membranes

The present study reports the results of a series of sorption and permeation tests of pure ammonia as well as nitrogen and hydrogen carried out on Aquivion C87-05 (short-side chain perfluoro sulfonic acid ionomer). Such material is indeed of interest for possible applications in sustainable processes for ammonia production, either as base material for polymer electrolyte membranes in low-temperature electrochemical ammonia synthesis or as a membrane for effective product separation. NH3, N2, and H2 permeation tests are performed at different temperatures (20, 35, and 50 ◦C) and both in dry and humid conditions (R.H. up to 80%), aiming to assess the influence of these parameters on the resulting permeabilities, while ammonia sorption is inspected at the same temperatures, and pressures up to near saturation conditions. Pure ammonia permeability reached outstanding values around 7000 Barrer in dry Aquivion membranes, revealing an increasing trend with upstream pressure, while it decreased with temperature. The same behavior is recorded for NH3 solubility, indicating that sorption drives the ammonia transport through the membrane. The obtained separation performances are found to be significantly better than those of other polymeric membranes proposed for the same separations, as compared to a permeability-selectivity plot.