Effect of the Cl/Br Molar Ratio of a CaCl₂−CaBr₂ Mixture Used as an Ammonia Storage Material

Abstract

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).

A non-invasive microwave method for assessing solid-state ammonia storage

“…As the saturated (large cation) complex is expected to increase in stability with Table 1 Saturated ammonia content of two CaI2 samples, each of mass 1 g, at different ammonia flow rates of (a) 5 cm 3 /min and (b) 10 cm 3 /min. anion size [5] and the metal has not changed an 8:1 ratio might be more expected and indeed an 8:1 ratio has been reported by Weatman and Liu [14,15]. Here we calculate a stoichiometry between 7 and 8 in Table 1.…”

Simulation study for adsorption-induced structural transition in stacked-layer porous coordination polymers: Equilibrium and hysteretic adsorption behaviors

“…The adsorption-induced structural transition was also experimentally observed for the other host/guest systems such as montmorillonite clay/water, [29][30][31][32][33] zeolites/aromatics, 34,35 alkali earth halides/ammonia, [36][37][38] and anthracenebisresorcinol crystal/ethyl acetate. 39 However, the microscopic mechanism of the adsorption-induced structural transition remains to be fully understood.…”

Ammonia Absorption into Alkaline Earth Metal Halide Mixtures as an Ammonia Storage Material

“…In that case, we can select Br-rich material of a CaCl 2 -CaBr 2 mixture. 21 However, in this study, we just discussed the applicability of this material from the data obtained under our conditions. The PSA method for ammonia storage is assumed to be operated between 60-80 kPa (absorption cycle) and 10 kPa (desorption cycle) at 298 K. Among this cycle, just the coordination of 2 to 4 (or 6) NH 3 is used.…”

“…The effect of the Cl/Br ratio in the CaCl 2 -CaBr 2 halide mixture on ammonia absorption is disclosed in detail. 21…”