Abstract
Zeolite BEA with SiO2/Al2O3 ratios ranging from 30 to 740 were crystallized at 413 and 453 K by the dry gel conversion technique. The particle size of the products increased with increasing SiO2/Al2O3 ratio as well as with increasing crystallization temperature. In as-synthesized BEA, the TEA+ ions interacting with Si-O- decomposed between 473 and 673 K and those interacting with Al-O- were cleaved between 673 and 798 K. During their elimination, the TEA+ ions interacting with Al-O- underwent higher degradation than those interacting with Si-O-. Chemical compositions showed the least influence on the fractions of decomposition product during the elimination between 473 and 673 K. The framework of H-BEA and NH4-BEA zeolites with SiO2/Al2O3 ratios ranging from 400 to 740 were stable even at 1373 K, whereas H-BEA with SiO2/Al2O3 = 30 was stable only up to 1173 K and became amorphous when calcined at 1373 K. After calcination at 1373 K, Na-BEA with SiO2/Al2O3 = 400 and 730 were transformed to tridymite (dense phase) whereas that with SiO2/Al2O3 = 30 became amorphous. The elimination of Na+ ions is necessary to have a BEA remain stable above 1173 K.
Original language | English |
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Pages (from-to) | 305-313 |
Number of pages | 9 |
Journal | Microporous and Mesoporous Materials |
Volume | 21 |
Issue number | 4-6 |
DOIs | |
Publication status | Published - 1998 May |
Keywords
- Crystallization
- Dry gel conversion
- High silica zeolite
- Interaction of TEA ions with zeolite
- Thermal stability
- Zeolite BEA (beta)
ASJC Scopus subject areas
- Chemistry(all)
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials