Ammonia adsorption isotherm on ion exchanged Y-zeolites (Na-Y, H-Y, Co-Y, Cu-Y, K-Y, Rb-Y, and Cs-Y) was investigated to asses the potential for use in ammonia separation and storage, by measuring the adsorption isotherm at 323 to 473 K and below 1 atm.Ammonia adsorption on Y-zeolite was increased by exchanging the cation with transition metal ions due to the increase in the number of ammonia adsorption sites with ammine complex formation, but was decreased by exchanging with alkali metal ions due to the decreased electrostatic attraction between ammonia and the zeolite surface. Irreversible ammonia adsorption sites on the ion exchanged Y-zeolite were classified into 3 types by IR (infrared) and TPD (temperature programmed desorption) techniques; M(OH) + (M: divalent cation), H + , and M + (M: alkali metal ion Na + , K + , Rb + , Cs + ). The first type of site bonds by ammine complex formation, the second type of site bonds by ammonium ion formation, and the third type of sites bonds by ammonia adsorption with electrostatic attraction.Cu 2+ exchanged Y-zeolite provided the best ammonia separation (4.92 mmol g −1 ) with the temperature swing adsorption method (323-473 K, 40 kPa).

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The behavior of ammonia absorption and desorption was studied for CaCl2−CaBr2 halide mixtures with various molar ratios prepared via the aqueous solution method. The CaCl2−CaBr2 halide mixture was revealed to form solid solutions in any molar contents. Ammonia absorption abruptly increased at some pressure, forming the ammine complex, and the (step) pressures were different for the samples with different molar contents. The step pressure decreased when the Cl/Br ratio was decreased for both absorption and desorption cycles. All samples absorbed ammonia irreversibly, up to two molecules of ammonia coordination. Three samplesCaCl1.33Br0.67, CaClBr, and CaCl0.67Br1.33proved to separate a great deal of ammonia at pressures of 60−10 kPa at 298 K. These samples are promising candidates for ammonia storage material to be used for pressure swing separation in a new ammonia synthesis process. Especially, CaCl1.33Br0.67 treated at 523 K showed the best separation capacity (27.1 mmol/g).