Hierarchization of USY Zeolite by NH4OH. A Postsynthetic Process Investigated by NMR and XRD
| Autor: | Bert F. Sels, Pierre Jacobs, Christine E. A. Kirschhock, Joost Van Aelst, Kristof Houthoofd, Sreeprasanth Pulinthanathu Sree, Francis Taulelle, An Philippaerts, Elena Gobechiya, Mohamed Haouas, Johan A. Martens |
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| Rok vydání: | 2014 |
| Předmět: |
Aqueous solution
Chemistry Analytical chemistry Surfaces Coatings and Films Electronic Optical and Magnetic Materials Silanol chemistry.chemical_compound Crystallinity General Energy Heteronuclear molecule Magic angle spinning Physical and Theoretical Chemistry Mesoporous material Zeolite Two-dimensional nuclear magnetic resonance spectroscopy |
| Zdroj: | The Journal of Physical Chemistry C. 118:22573-22582 |
| ISSN: | 1932-7455 1932-7447 |
| DOI: | 10.1021/jp5058594 |
| Popis: | © 2014 American Chemical Society. Ammonia treatment of USY zeolite has led to a new hierarchical material. The local and global structural changes during the transformation have been monitored by XRD and by 1H, 29Si, and 27Al solid-state NMR. A wealth of 1D and 2D NMR protocols were applied, including 1H DQ-SQ (double-quantum-single-quantum), 27Al MQMAS (multiple-quantum magic angle spinning), 29Si MAS (magic angle spinning) and CPMAS (cross-polarization magic angle spinning), and 1H-29Si HETCOR (heteronuclear correlation). The effects of aqueous ammonia treatment, different thermal post-treatments, and rehydration were studied. An increasing loss of crystallinity was observed upon increasing duration of ammonia treatment. Under the experimental conditions, a few percent of silica was lost into solution and no loss of aluminum was observed. However, increasing numbers of silanol groups were detected. The progressive transformation induces formation of mesopores, reduction of the fraction of the sample exhibiting Bragg crystallinity, and apparition of a dense, amorphous aluminosilicate phase. The latter contains ammonium ions and strongly bound water, both of which are resistant to thermal decomposition up to 350 °C. After about 24 h of treatment, the zeolite fraction is completely transformed into the amorphous phase. At intermediate stages, a complex hierarchical material is obtained with mesopores and zeolitic micropores next to a dense amorphous aluminosilicate, containing ammonium ions, highly structured water, and silanol nests. ispartof: Journal of Physical Chemistry C vol:118 issue:39 pages:22573-22582 status: published |
| Databáze: | OpenAIRE |
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