Cation distribution in K,H-L zeolite prepared through ion-exchange with TMA ion
✍ Scribed by T. Ohgushi; T. Matsuo; H. Satoh; T. Matsumoto
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 846 KB
- Volume
- 117
- Category
- Article
- ISSN
- 1387-1811
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✦ Synopsis
Structural analyses of hydrated K 9 -L and K 7.5 H 1.5 -L zeolites were carried out by measurements of X-ray powder diffraction patterns and Rietveld refinements, and distributions of potassium ion in the zeolites were investigated. K 7.5 H 1.5 -L was obtained by heating K 7.5 TMA 1.5 -L at 773 K in air, which was prepared through an ion-exchange of K 9 -L with TMA ion. In both K 9 -L and K 7.5 H 1.5 -L, potassium ion located only on sites B, D and E. The number of potassium ion on site D was the most remarkably different between K 9 -L and K 7.5 H 1.5 -L, that is, its number was 4.08 per unit cell (puc) in K 9 -L and 3.00 puc in K 7.5 H 1.5 -L. It was found from this result that TMA ion preferentially exchanges with potassium ion on site D. The potassium ion on site E also reduced to 2.52 puc in K 7.5 H 1.5 -L from 2.94 puc in K 9 -L. It was considered that the reduction arose in the ion-exchange between K + /E and the hydrogen ion (just) after converting to K,H-L from K 7.5 TMA 1.5 -L by heating, because TMA ion cannot access site E at all due to the location of site E and its ion size, but hydrogen ion can. All the nearest interatomic distance between a potassium ion and a framework oxygen showed the tendency which becomes longer in K 7.5 H 1.5 -L than K 9 -L. The results suggest that the Coulmbic attraction between the potassium ion and a negative chare of framework (AlO À 4 ) becomes weaker in K 7.5 H 1.5 -L than K 9 -L.