Structural comparison of partially dehydrated partially Co2+-exchanged zeolites X (FAU, Si/Al = 1.40) and Y (FAU, Si/Al = 1.70)

• Published in: Journal of porous materials 2016, Vol.23 (1), p.95-105
• Main Authors: Seo, Sung Man, Ko, Seong Oon, Lim, Woo Taik
• Format: Article
• Language: English
• Subjects: Aluminum; Catalysis; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Cobalt; Dehydration; Diffraction; Physical Chemistry; Silicon; Single crystals; Synchrotron radiation; Unit cell; X-ray diffraction; Yttrium; Zeolites
• ISSN: 1380-2224; 1573-4854
• DOI: 10.1007/s10934-015-0059-x

The structures of partially dehydrated and partially Co 2+ -exchanged zeolites X (Si/Al = 1.40) and Y (Si/Al = 1.70) were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd 3 ¯ m and were refined to the final error indices R 1 / wR 2  = 0.0773/0.2152 and 0.0683/0.2184, respectively. Their unit-cell formulas are |Co 26.1 Na 21 (H 3 O) 7.1 (H 2 O) 14.2 |[Si 112 Al 80 O 384 ]-FAU ( a  = 24.7892(2) Å) and |Co 29.3 Na 6.2 (H 3 O) 5.9 (H 2 O) 5.9 |[Si 121 Al 71 O 384 ]-FAU ( a  = 24.7346(2) Å), respectively. In the structure of Co 2+ -X, Co 2+ ions occupy sites I′, II′, II, and III′; the Na + ions are at sites I′ and II. In the structure of Co 2+ -Y, Co 2+ ions occupy sites I′, II′, II, and III′; the Na + ions are at site I′. Because of the low pH of the Co 2+ exchange solution, some H 3 O + ions are observed in both structures. The number of Co 2+ ions in zeolite was increased slightly as Si/Al ratio increased, and Na + content and the unit cell constant of the framework were decreased.