Zeolite aluminosilicate

Zeolite A [1318-02-1] Zeolite (aluminosilicate) Zeolite catalysts Zeolite L Zeolites... 

Zeolites Aluminosilicates containing a (SiAl) 02 matrix with a negative charge which is balanced by the presence of cations in the cavities. The cations are easily exchanged, and water and gases can be selectively absorbed into the cavities. Zeolites are also used to remove molecules of specific sizes by absorption into the pores. 

Redox Behavior of Zeolite Aluminosilicates and the Nature of the Sites Responsible for the Electron-Transfer Activity... 

One approach (4) is to calculate, for a certain zeolite structure, the Madelung and polarization energies for fixed lattice positions. The heat of formation due to ionic bonding is calculated both for the zeolitic aluminosilicate with varying amount of aluminum and... 

On the Relative Stabilities of Zeolitic Aluminosilicates, Studies in Surf. Sci. and Catal. 1988, 32, 317. 

Several classes of inorganic open-framework structures have been synthesized and characterized in the past several years. While zeolitic aluminosilicates constitute the best-known class of open-framework structures,4 metal phosphates have been gaining considerable importance, and a variety of metal phosphates with open architectures have been reported in the past decade.5 The open-framework phosphates are generally synthesized under hydrothermal conditions in the presence of organic... 

Solid catalysts such as zeolite (aluminosilicate), heteropolyacids and their alkali or alkaline earth metal salts on a metal oxide support and basic resins have been used as catalysts to manufacture polysulfides. 

Crystallization of Zeolitic Aluminosilicates in the System LizO-NazO-AhCh-SiCh-HzO at 100° C... 

It appears that the first solid-state NMR study using Si NMR on a clay was performed in 1980 by Lippmaa and coworkers )7]. This work showed that the now commonly observed Si(OSi)4 peaks in zeolitic aluminosilicates are clearly resolved in clays (talc) also. 

Barrie and Klinowski [109] discussed ordering in the magnesium alumi-nophosphate network on the basis of aluminum and phosphorus NMR. MgAPO-20 crystallizes in a structure similar to naturally occurring mineral sodalite, with Mg, P, and Al occupying the tetrahedral sites. Barrie and Klinowski postulated that the alternation of the Mg and Al in the tetrahedral sites adjacent to phosphorus creates a situation similar to that in zeolitic aluminosilicates and that the phosphorus spectrum can be interpreted in terms of P(0-A1) where n ranges from 0 through 4 (Fig. 20). 

Ooms G, R A van Santen, C J J Den Ouden, R A Jackson and C R A Catlow 1988. Relative Stabilities of Zeolitic Aluminosilicates. Journal of Physical Chemistry 92 4462-4465. 

The diversity of the inclusion of molecules of any type into host lattices which are distinctly inorganic is now becoming apparent [31], Apart from the oxidic zeolites, aluminosilicates and derivatives with other tetrahedral sites, there are the layered silicates and minerals, pillared clays and numerous other intercalation and inclusion systems, including graphite, metal sulfides and metal cyanides [23, 32, 33]. 

The suggestions of band assignments to framework vibrations advanced in Refs. [112,114] were based on earlier IR investigations of silica and non-zeolitic aluminosilicate frameworks [238, 239]. These assignments are illustrated in Fig. 11. 

The diversity of ordered porous solids increases at an astonishing rate, particularly among the readily crystallised MOFs, and continues to olfer novel materials properties. There is no obvious barrier to the synthesis of a myriad of new zeolite, zeotype or hybrid structures. Challenges remain, however. For zeolitic aluminosilicates, the 10 A pore size restriction remains an important barrier, and an enantiomerically pure zeolite is still out of reach. For nonsilicate crystalline microporous solids, thermal and hydrothermal stability, rather than framework geometry, limit their applicability, since fully crystalline germanates and carboxylates with pores in the mesoporous range now exist, and these solids have enormous specific surface areas. In these hybrid solids the ability to choose chirality in the building units indicates that it will be possible to prepare these in chiral form the first examples have already been prepared. 

Fig. 5.11 High resolution transnussion electron microscopy (HRTEM) images of (a) magnetite NP encapsulated in silica (b) magnetite NPs embedded in a zeolitic (aluminosilicate) matrix (c) Fe NPs encapsulated in silica (energyfiltering TEM, EFTEM, color map) (d) magnetite NP encapsulated in graphite (Reprinted with permission from Arruebo et al. [228]. Copyright 2009 Elsevier)...

The term molecular sieve refers to the fact that their empty spaces are so small that they allow the passage of small molecules only, such as CH4, CO, N2 or CO2. Typical molecular sieves are dehydrated zeolites, aluminosilicates whose structure (with around 130 variations) is formed by a three-dimensional framework of [SiOJ and [AIO4], coordination tetrahedra, interconnected by oxygen bridges. In this spatial structure, there are interconnected cages and channels with diameters from around 0.3 to 1 nm (Fig. 4.6), either empty or containing weakly bound cations. 

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