An investigation into the crystallization of low-silica X zeolite
- 370 Downloads
The crystallization of low-silica X (LSX) zeolite with FAU topology was examined under hydrothermal synthesis conditions. PXRD was employed to follow the evolution of the long-range ordering of the gel. Raman spectra provided information on various ring and cage species existing in the gel. 27Al and 29Si solid-state NMR spectroscopy was utilized to monitor the change in local environment of tetrahedral sites. The results indicate that an amorphous aluminosilicate phase was formed immediately upon mixing different reactive species. Hydrothermal treatment led to the formation of sodalite-cage like species and the species with larger cavities, joint four-member rings (4Rs) and branched 4Rs, which are the structural building units of the FAU framework. These units were assembled into the crystalline structure of LSX zeolite. 23Na and 39K solid-state NMR results show that the transformation process was accompanied by the changes of the local structure of hydrated Na+ and K+ ions. The two types of cations may work synergistically to template the crystallization of LSX zeolite.
KeywordsZeolites Faujasite Crystallization Hydrothermal synthesis Solid-state NMR Raman spectroscopy
Y. H. thanks the Natural Science and Engineering Research Council of Canada for a Discovery grant. Access to the 900 MHz NMR spectrometer was provided by the Canadian National Ultrahigh Field NMR Facility for Solids (http://nmr900.ca). We thank Dr. V. Terskikh for acquiring 39K NMR spectra and Mr. P. He for 39K spectral simulation. We also thank Prof. Yang Song for the access of a Raman spectrometer. This work was funded by the Natural Science and Engineering Research Council of Canada (2012).
Conflict of interest
The authors declare that they have no conflict of interest.
- 4.Ch. Baerlocher, L.B. McCusker, Database of zeolite structures. http://www.iza-structure.org/databases/
- 9.A.F. Ojo, F.R. Fitch, M. Bülow, C.S. Gittleman, S.R. Jale, US Patent 6596256 (2003)Google Scholar
- 10.R.T. Yang, N.D. Hutson, US Patent 6780806 (2004)Google Scholar
- 18.US Patent, 6, 264, 881Google Scholar
- 29.P. Khemthong, J. Wittayakun, S. Prayoonpokarach, Suranaree J. Sci. Technol. 14, 367 (2007)Google Scholar
- 41.K. Eichele, R.E. Wasylishen, v. 1.19.15 edn. (2009)Google Scholar
- 52.P. Bodart, J.B. Nagy, Z. Gabelica, E.G. Derouane, J. Chim. Phys. 83, 777 (1986)Google Scholar