Faujasite FAU

Linde type X and Y zeolites are two typical microporous materials with the FAU framework. So far, both low-silica type X and high-silica type Y molecular sieves are 

Unlike X type molecular sieve, the Si/Al ratio of Y type molecular sieve normally falls in the range 1.5-3. The laboratory synthetic method introduced here was developed by D.M. Ginter, A.T. Bell, and C.J. Radke (Ref. [125]). Deionized water, sodium aluminate (Na/Al=1.27, 6.1% H20), sodium hydroxide pellets, and sodium silicate solution (28.7% Si02, 8.9% Na20) were used to prepare the reaction gel with a composition of 4.62 Na20 A1203 10 Si02 180 H20. The detailed procedure for the preparation of 32 g of dry product is described below  

Synthetic forms Beryllophosphate X, Li-LSX, LZ-210, SAPO-37, siliceous Na-Y, zeolite X (Linde X), zeolite Y (Linde Y), zincophospate X 

FAU type zeolites exchanged with many different cations (Na, K, Ba, Cu, Ni, Li, Rb, Sr, Cs, etc.) have been extensively studied. The unit cell contents of hydrated FAU type zeolite can be represented as M,j(H20)y [A Sii92 0384] -FAU, where x is the number of A1 atoms per unit cell and M is a monovalent cation (or one-half of a divalent cation, etc.). The number of A1 atoms per cell can vary from 96 to less than 4 (Si/Al ratios of 1 to more than 50). Zeolite X refers to zeolites with between 96 and 77 A1 atoms per cell (Si/Al ratios between 1 and 1.5) and Zeolite Y refers to zeolites with less than 76 A1 atoms per cell (Si/Al ratios higher than 1.5). 

Pore stmcture One-dimensional 12-ring, one-dimensional eight-ring 

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One of the most popular zeolites for photochemical studies faujasite (FAU) is depicted in Fig. 1. Fig. la is a ball and stick drawing which not only shows the... 

Fig. 1 (a) Ball and stick structure of faujasite (FAU). (b) Conventional stick drawing of faujasite (FAU). 

Faujasite (FAU), 226-227 ball and stick structure of, 226-227, 227/ Fluorescence correlation spectroscopy, 178-181... 

Figure 4.2 Zeolite cages as found in Sodalite (SOD), Zeolite A (LTA), and Faujasites (FAU). (Reprinted from D.

Other framework structures based on zeolites have also been synthesized which contain atoms other than aluminium and silicon, such as boron, gallium, germanium, and phosphorus, which are tetrahedrally coordinated by oxygen. Such compounds are known as zeotypes. Pure aluminium phosphate, commonly called ALPO, and its derivatives, can take the same structural forms as some of the zeolites such as sodalite (SOD), faujasite (FAU), and chabazite (CHA) (e.g., ALPO-20 is isostructural... 

Figure 9 Linkage of chains in (a) piuUipsite (PHI) and Figure 11 Faujasite (FAU) structure emphasizing the linkage of (b) gismondine (GIS) truncated octahedra (/3-cages) via D6R units...

Industrial production of synthetic zeolites gives fine powders (<10pm) in their sodium exchanged form. These materials can be used as synthesized , such as for use as detergents, and Figure 16 is a schematic diagram of the production of zeohte ETA (Na form) for this purpose. The manufacture of the synthetic faujasite (FAU) zeolite Y for catalytic nses follows a similar route. 

Figure 18 The cation sites of the faujasite (FAU) framework (see text for explanation of symbols). (Reprinted with permission from J.V. Smith, Molecular Sieve Zeolites-T, eds. E.M. Flanigen and L.B. Sand, ACS Symp. Ser., 1971, 101, 173. 1971 American Chemical Society)...

The modification of zeolites mainly relies on secondary synthesis methods. The aim of modification is to reprocess the zeolites using suitable techniques to improve the properties and functions such as (1) acidity, (2) thermal and hydrothermal stability, (3) catalytic performance such as redox catalytic and coordination catalytic properties, etc., (4) channel structures, (5) surface properties and microporous frameworks and charge-balancing ions. Modification is also called secondary synthesis and can lead to new properties that cannot be achieved through direct synthesis. Let us consider the case of faujasite (FAU), the main component of the cracking catalyst, and its catalytic performance (represented by the catalytic activity K/K Std for n-hexane cracking). From Table 6.1 it is seen that the secondary synthesis affects the catalytic performance to a considerable degree. 

An error in the cation occupancies for the mineral faujasite (FAU) has been corrected. This correction has changed the diffraction pattern noticeably. 

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