Faujasite frameworks

As mentioned above since there is no provision in the placement of the fourth neighbors for the effect of aluminum interactions, the results of this work will over-estimate the tendency of aluminum atoms to avoid each other in the faujasite framework. 

Figure 1. Idealized projection of the building units of the faujasite framework...

Nature of acidic sites. The location of the acidic hydroxyl groups in the faujasite structure has been the subject of numerous investigations and much discussion. The results of adsorption experiments with several molecules led Eberly (170) to conclude that the 3550-cm-1 hydroxyl absorption band represented hydroxyl groups located in the hexagonal prisms of the faujasite framework [(Si sites (171)], where they were relatively inac-... 

Relatively few studies have focused on influence of the acid/base properties of the support on the chemisorption of reactants on supported metal clusters. A NMR study by Tong et al.23 showed that the stretching frequency of CO chemisorbed on zeolite supported Pt particles correlates with the surface local density of states (LDOS) of the Pt. The LDOS also showed a correlation with the faujasite framework acidity, but an explanation of this correlation is lacking. Several infrared studies on similar supported Pt catalysts show that the mode of CO... 

Figure 5. Possible tetrahedral environments of a silicon atom (marked with a cross) in the faujasite framework. First-order tetrahedral neighbours are separated from the second-order neighbours by the dotted line. Open circles denote silicon, closed circle aluminium arrows indicate Si(OAl) sites. The number of such sites eliminated by substituting the centred silicon by an aluminium is indicated under each diagram.

Fig. 5. Faujasite framework and cation siting. (Roman numerals indicate cation sites arabic numbers show oxygen-atom numbering scheme.)...

If the twin boundaries constitute true mirror planes, it can be shown that, across these planes Loewenstein1s rule must be contravened. If, however, the mirror planes merely reflect the tetrahedral sites of the faujasitic framework and not the actual tenants of such sites Loewenstein s rule need not be... 

Double 6-ring arrangements considered for the formation of a faujasite framework. Shown in the figure are the number of Al-0-Si-0-Al pairs across 4-rings ( ) and across 6-rings (5 ) for each D6R moiety as well as the 3-neighbor distributions... 

For R = 13/11, sodalite cage X missing one A1 atom is used, corresponding to a faujasite framework formed from m3 and 6R sub-units in the ratio 3 1. For compositions R = 14/10,... 

B. Beagley, J. O. Titiloye, Modeling the Similarities and Differences between the Sodalite Cages (Beta-Cages) in the Generic Materials - Sodalite, Zeolites of Type-A, and Zeolites with Faujasite Frameworks Struct. Chem. 1992, 3, 429-448. 

In the faujasite framework there are also four crystallographically distinct oxygens. The experimental proton occupation in H-faujasite is 8 2 4 for the... 

Figure 2 A portion of the faujasite framework. Each vertex represents either a sdicon or an aluminum site, each line represents a bridging oxygen. The opening into the supercage is approximately 8 A in diameter it consists of 12 metal sites and 12 bridging oxygens...

The silicon-substituted aluminium phosphate SAPO-37 has a faujasite framework structure and shows a sharp tetrahedral and octahedral Al resonance, with an underlying broad tetrahedral resonance (Fyfe et al. 1995). By using Al—> P and Al Si TEDOR experiments, Fyfe et al. (1995) have shown that the main Si environment in SAPO-37 is Si[4Al], and have been able to identify the environments of the... 

Figure 6.9 The Na+ sites in the faujasite framework structure. Reproduced with permission from [17], Copyright (1980) Chemical Journal of Chinese Universities...

J. Dwyer and K. Karim, The Incorporation of Heteroatoms into Faujasitic Framework by Secondary Synthesis Using Aqueous Fluoride Complexes. J. Chem. Soc., Chem. Commun., 1991, 905-906. 

Relation Between the Aluminum Content of the Faujasite Framework and the Isomerization and Disproportionation of m -Xylene... 

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