Crystallographic studies of fully dehydrated partially Zn~(2+)-exchanged zeolite Y (FAU, Si/AI = 1.56) depending on Zn~(2+) concentration of aqueous solution during exchange

摘要

Four single crystals of fully dehydrated and partially Zn2+-exchanged zeolites Y (Si/Al = 1.56) were prepared by the static ion-exchange method using a mixed ion-exchange solution in which Zn(NO3)(2):NaCl mole ratios were 1:1 (crystal 1), 1:25 (crystal 2), 1:50 (crystal 3), and 1:100 (crystal 4), respectively, with a total concentration of 0.05 M, and followed by vacuum dehydration at 673 K. Their single-crystal structures were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd (3) over barm and refined to the final error indices R-1/wR (2) = 0.0459/0.1454, 0.0449/0.1283, 0.0427/0.1284, and 0.0486/0.1680, respectively. Their unit-cell formulas are vertical bar Zn25Na25 vertical bar[Si117Al75O384]-FAU (crystal 1), vertical bar Zn19.5Na36 vertical bar[Si117Al75O384]-FAU (crystal 2), |Zn19.5Na36 vertical bar[Si117Al75O384]-FAU (crystal 3), and vertical bar Zn7Na61 vertical bar[Si117Al75O384]-FAU (crystal 4), respectively. The degree of Zn2+ exchange decreases from 67 to 19% as the initial concentration of Zn2+ decrease and the initial concentration of Na+ increases in given ion-exchange solutions.