Structural Effects on Adsorption of Atmospheric Gases in Mixed Li,Ag–X-Zeolite

Sil®er is known to strongly affect the adsorpti®e properties of zeolites. In the synthesis ( ) of mixed Li,Ag low-silica X-type LSX zeolite, adding ®ery small amounts of sil®er and specific dehydration conditions results in a sorbent with enhanced adsorpti®e characteristics for air separation. The location of the extraframework sil®er in relation to the aluminosilicate framework is of primary importance for elucidating the effect of sil®er cations on the adsorpti®e characteristics of the zeolite. In this work, mixed Li,Ag ion-exchanged zeolites were synthesized and treated to promote the formation of intracrystalline sil®er clusters. These samples were structurally characterized using Riet®eld refinement of neutron powder diffraction data. Structural characterization re®ealed the presence of cations in a no®el site II in mixed Li,Ag ] LSX zeolites that were ®acuumdehydrated at 4508C. Cations in this site II are more interacti®e with the atmospheric sorbates of interest than sil®er at the con®entional site II location. Vacuum dehydration at 4508C induced thermal migration of Ag q from site II to site II and gi®es rise to the superior properties for air separation.