Complete Li+ exchange into zeolite X (FAU, Si/Al = 1.09) from undried methanol solution

Abstract

Complete exchange of Li+ into zeolite Na-X, |Na92|[Si100Al92O384]-FAU, was accomplished using undried methanol solvent (water concentration 0.02 M). A crystal of Na-X was treated with 0.1 M LiNO3 in the solvent at 333 K, followed by vacuum dehydration at 673 K and 1 × 10−6 Torr for 2 days. Its structure was determined by single-crystal synchrotron X-ray diffraction techniques, in the cubic space group \( Fd\overline{3} \) at 100(1) K. The 92 Li+ ions per unit cell are found at three different crystallographic sites. The 32 Li+ ions occupy at site I’ in the sodalite cavity: these Li+ ions are recessed 0.28 A into the sodalite cavity from their 3-oxygens plane [Li–O = 1.903(5) A and O–Li–O = 117.8(3)°]. Another 32 Li+ ions are found at site II in the supercage, being recessed 0.26 A into the supercage [Li–O = 1.968(5) A and O–Li–O = 118.3(3)°]. The remaining 28 Li+ ions are located at site III in the supercage [Li–O = 2.00(8) A].