Sodalite hydrate

Trapping or encapsulation represents a second situation wherein guests are introduced at high temperature and at high pressure of the guest. Crystals are chilled, and then the pressure is released. The host lattice is permanent, and the windows are small. Examples are sodalite hydrate, cancrinite hydrate, and analcite. 

Isotypes sodalite hydrate or Zhdanov G (48, 49), TMA-sodalite (2), tugtupite (15)... 

Strong Bases Zeolites upon reaction with strong bases change into different species. For example, zeolite A when reacted with NaOH gives zeolite P and further reaction gives sodalite hydrate. 

The distribution of cations in a hydrated zeolite is mainly controlled by their sizes and can be described by a statistical model. In the dehydrated state, most of the cations are located on the intraframework sites their occupancies are governed by mutual repulsions and cation—framework interactions [1]. By which, the environments of the framework silicon atoms and their corresponding ssi NMR spectra are affected [2,3]. The chemical shift and lineshape of Si NMR have been found to depend on the nature and the distribution of cations in the small sodalite and double hexagonal prism (D6R) cavities of the dehydrated Y zeolites [3] The irreversible migration of La3 ions from the supercages to the small sodalite and/or D6R cavities by... 

Cation Siting in Linde A. At the time this work was completed, x-ray studies on hydrated NaA (3, 4) and hydrated KA (5) had shown that 8 of the 12 exchangeable cations per unit cell are firmly bound to the zeolite framework and would therefore be expected to have the major influence on the lattice vibrations. These cations are sited in front of the sodalite... 

Figures 3 and 4 show plausible sodalite unit and large cavity structures which are consistent with the structural parameters determined for hydrated Bag-A.

Figure 4. A stereoview of the sodalite unit of hydrated Bat-A. Ba1 ions are coordinated to 3 framework oxide ions, 0(3), and probably to some unlocated water molecules. Ellipsoids of 20% probability are used.

Figure 4. UV-visible spectra showing the progression from the isolated AgBr molecule to the isolated Ag4Br cluster and to the extended (Ag4Br)n supralattice inside hydrated sodalite (8-2n-p)Na,2nAg,(2-p)Br-SOD. (a) p = 1.7, n = 0.05 (b) p = 1.7, n = 4 (c) p = 0, n = 4.

The pretreatment temperature of the sample submitted to xenon adsorption and NMR experiments was low enough (393 K) to prevent any hydrolysis. Evacuation to KT4 ton ( 1 ton = 133.322 Pa) for 15 h at this temperature ensures the elimination of most of the water of hydration. Moreover, Gdddon et al. (79) showed that when NaY is less than 15% hydrated the remaining water molecules are in the sodalite cages. Such a small amount of water cannot affect xenon adsorption, which occurs only in the supercages. 

Sodium-23 MASNMR measurements have been used to examine the extent to which this method can be used to determine the cation distribution in hydrated and dehydrated Y-zeolites. Results have been obtained on Na-Y and series of partially exchanged (NH, Na)-Y, (Ca,Na)-Y and (La,Na)-Y zeolites which demonstrate that the sodium cations in the supercages can be distinguished from those in the smaller sodalite cages and hexagonal prisms. For the hydrated Y zeolites, spectral simulation with symmetric lines allows the cation distribution to be determined quantitatively. 

---