NH ₃ Permeation Performance of ZnCl ₂ -Immobilized Molten Salt Membranes at Elevated Pressures

Advanced membrane technologies are promising for improving the efficiency and sustainability of energy-intensive chemical processes. In the Haber–Bosch process, membranes can reduce reliance on condensation and refrigeration units, lowering energy use and CO2 emissions. Inorganic NH3-permeable membranes provide better thermal stability than polymeric membranes for high-temperature applications. Recent studies show that ZnCl2-immobilized molten salt (IMS) membranes achieve NH3/N2 and NH3/H2 selectivities over 107 at ∼300 °C. Previous research focused only on atmospheric pressure for total feed pressure. This study uniquely explores the NH3 separation properties of ZnCl2 IMS membranes under high-pressure conditions. The IMS membrane was prepared by forming a molten ZnCl2 in and above the pores of stainless-steel wire mesh supports. Characterization via TG-DTG-DSC techniques revealed that ZnCl2 could be used for IMS membranes between 310 and 400 °C without experiencing extreme thermal degradation. NH3 permeation tests were carried out on the IMS membrane using feed gas of NH3/N2 mixtures at pressures up to 450 kPa and helium sweep gas in the permeate at the same pressures. By maintaining equal total pressure at the retentate and permeate side, the IMS membrane exhibited an NH3 permeance of ∼400 GPU at a total feed pressure of 450 kPa with NH3/N2 mixtures.