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Li+- and H+-Exchanged Low-Silica X Zeolite as Selective Nitrogen Adsorbent for Air Separation

“…On the other hand, it was reported that the adsorption amount of nitrogen to Li-LSX changed strangely by the Liexchanged ratio. 6,12,15 In Li-Na-LSX, nitrogen adsorption amount did not increase until the Li-exchanged ratio reached 2/3 of total ion-exchange sites as shown in Figure 4. Yoshida et al 12 explained that the specific adsorption behavior of Li-LSX was concerned with the three types of ion-exchange sites in the FAU structure.…”

“…6,12,15 In Li-Na-LSX, nitrogen adsorption amount did not increase until the Li-exchanged ratio reached 2/3 of total ion-exchange sites as shown in Figure 4. Yoshida et al 12 explained that the specific adsorption behavior of Li-LSX was concerned with the three types of ion-exchange sites in the FAU structure. They suggested that the Li ions are preferentially arranged in a sequential order of site I', site II and site III of FAU structure, and the only Li ions located in site III contributed to adsorption.…”

“…[6][7][8][9][10][11][12][13] However, the higher Liexchange ratio should be required to prepare the Li-LSX with high performance to oxygen producing by P(V)SA. 6,7,12 Compared with the other available cations for selective nitrogen adsorption like Ca, Li source is expensive and it was reported that the Li ions are hard to be exchanged to X zeolite. 14 To reduce the usage of Li ions, many researches, such as introduction of second and/or third cations and Li recovery from waste solution of ion-exchange treatment, were conducted.…”

“…15,16 Yoshida et al reported that the nitrogen adsorption capacities of Liexchanged FAU type zeolites such as LSX, X and Y is related to the location of Li ions in FAU structure. 12,13 In this study, ammonium ions were introduced as second cation. The ammonium ions were transformed into proton by desorption of ammonia with calcinations.…”

“…The influence of proton on the FAU framework structure was similar to that of Li. If the hypothesis 12 about position of Li ions in FAU structure can apply to Li-H-LSX, Li ions located in the site II are also considered to be useful to nitrogen adsorption. Since a lot of expensive materials like lithium chloride should be consumed in order to obtain the highly Li-exchanged LSX, the consumption of lithium materials could be significantly reducible with these results.…”