Behavior of cesium cation in zeolite Y (FAU, Si/Al = 1.56) and their single-crystal structures, |Cs75−xNax|[Si117Al75O384]-FAU (x = 35 and 54)

To study the tendency of Cs + exchange into zeolite Y (Si/Al = 1.56) dependence on Cs + and Na + concentration of aqueous solution during exchange, two single-crystals of fully dehydrated, Cs + -and Na + -exchanged zeolites Y were prepared by the flow method using a mixed ion-exchange solution whose CsNO 3 :NaNO 3 mol ratios were 1:1 (crystal 1) and 1:100 (crystal 2), respectively, with a total concentration of 0.1 M, followed by vacuum dehydration at 723 K. Their crystals were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd 3 ¯ m , respectively, and were refined to the final error indices R 1 / wR 2 = 0.084/0.248 and 0.088/0.274 for crystals 1 and 2, respectively. In the structure of |Cs 40 Na 35 |[Si 117 Al 75 O 384 ]-FAU (crystal 1), 40 Cs + ions per unit cell occupy five different equipoints; 3, 3, 14, 9, and 11 are at sites I, II′, II, IIIa and IIIb, respectively, whereas, the remaining 35 Na + ions occupy three different sites: 9, 11, and 15 are at sites I, I′, and II, respectively. In the structure of |Cs 21 Na 54 |[Si 117 Al 75 O 384 ]-FAU (crystal 2), 21 Cs + ions per unit cell occupy three equipoints; 4, 6, and 11 are at sites II, IIIa, and IIIb, respectively. The residual 54 Na + ions per unit cell are found at three different sites; 6, 20 and 28 are at sites I, I′, and II, respectively. The degrees of ion exchange are 53 and 28 % for crystals 1and 2, respectively. This result shows that the degree of Cs + exchange decreased sharply by decreasing the initial Cs + concentration and increasing the initial Na + concentration in given ion-exchange solution.