Zeolite materials

Base exchange The property of the trading of cations shown by certain in- soluble namrally occurring materials (zeolites) and developed to a high degree of specificity and efficiency in synthetic resin adsorbents. 

Synthesis of Porous Materials Zeolites, Clays, and Nanostructures, edited by Mario L. Occelli and Henri Kessler Methane and Its Derivatives, Sunggyu Lee... 

In a sorption pump, the gas is trapped within the adsorbing material (zeolites or active charcoal) called molecular sieve. Zeolites are porous aluminium silicates which adsorb large amount of gas when cooled to low temperature (usually 77K). The pump is filled with zeolite and put in a bucket containing liquid nitrogen (see Fig. 1.11). 

Sudhakar Reddy, J., Dicko, A., and Sayari, A., in Synthesis of Porous Materials Zeolites, Clays and Nanostructures (M. Occelli and H. Kessler, Eds.), p. 405-415. Marcel Dekker, New York, 1997. 

AEL (n defines a number indicating a specific material) zeolite structure types aluminophosphate eleven (A1P04-11)... 

Four different methods to store hydrogen are currently available compressed gas, liquid hydrogen, metal hydrides and sorption on different porous materials (carbon materials, zeolites, metal organic frameworks, etc).2-4... 

Key words microporous materials, zeolites, electron microscopy, structure determination... 

Chapman, D.M., and Roe, A.L. (1990) Synthesis, characterization and crystal chemistry of microporous titanium-silicate materials. Zeolites, 10, 730. 

Synthetic zeolites and other molecular sieves are important products to a number of companies in the catalysis and adsorption areas and numerous applications, both emerging and well-established, are encouraging the industrial synthesis of the materials. There are currently no more than a few dozen crystalline microporous structures that are widely manufactured for commercial use, in comparison to the hundreds of structures that have been made in the laboratory. See Chapter 2 for details on zeolite structures. The highest volume zeolites manufactured are two of the earliest-discovered materials zeolite A (used extensively as ion exchangers in powdered laundry detergents) and zeolite Y (used in catalytic cracking of gas oil). 

M.J., and Valencia Valencia, S. (2006) Microporous crystalline zeolite material, zeolite ITQ-28, production method thereof and use of same. US patent application US 2006/0286029. 

The second part of the book covers zeolite adsorptive separation, adsorption mechanisms, zeolite membranes and mixed matrix membranes in Chapters 5-11. Chapter 5 summarizes the literature and reports adsorptive separation work on specific separation applications organized around the types of molecular species being separated. A series of tables provide groupings for (i) aromatics and derivatives, (ii) non-aromatic hydrocarbons, (iii) carbohydrates and organic acids, (iv) fine chemical and pharmaceuticals, (v) trace impurities removed from bulk materials. Zeolite adsorptive separation mechanisms are theorized in Chapter 6. 

Zeolites and related ordered clay—associated materials have been suggested to be involved in the initial primeval synthesis of basic elements of life—are also being involved in the synthesis of a number of polymeric and nonpolymeric materials. Zeolites come in a variety of forms and different shapes and sizes with researchers associating the particular size and shape with a particular desired synthesis. This is somewhat akin to the considerations that are made in effectively employing crown phase transfer agents and related materials. 

Synthesis of Porous Materials Zeolites, Clays, and Nanostructures,... 

Porous oxide catalytic materials are commonly subdivided into microporous (pore diameter <2nm) and mesoporous (2-50 nm) materials. Zeolites are aluminosilicates with pore sizes in the range of 0.3-1.2 nm. Their high acidic strength, which is the consequence of the presence of aluminium atoms in the framework, combined with a high surface area and small pore-size distribution, has made them valuable in applications such as shape-selective catalysis and separation technology. The introduction of redox-active heteroatoms has broadened the applicability of crystalline microporous materials towards reactions other than acid-catalysed ones. 

In the case of silica materials, zeolites and related materials, and mesoporous molecular sieves (MMS), the spectrum in the middle IR region, that is, 250 to 4000cm"1 can be classified in three regions ... 

NaY zeolite with a Si/Al ratio of 2. 7 was used as the starting material, zeolite... 

Intercalation Chemistry loiuc Conductors Phosphorus Inorganic Chemistry Porous Inorganic Materials Zeolites. 

The parallel bundle analysis of Figure 2 furnishes the results presented in Figure 5. The key to this analysis is the recognition that whatever the distribution of pore sizes is for each category of porosity (intra-particle, inter-pellet and intra-pellet) the actual amounts of pore volumes are integrals of those distributions. These take values specified by the density of the solid materials (zeolite, plus silica/alumina support) and the pore volumes per gm indicated by the porosimeter results in Figure 2. Thus the final penetration for the powder is the sum of inter-particle and intra-particle and intra-particle porosity. By the same token, the final penetration for the pellet comprises the sum of the intra-particle volume added to the intra-pellet and inter-pellet volumes. 

The 10-membered ring zeolites (ZSM-22 and ZSM-23) were kindly provided by Prof. Martens (COK, KULeuven). Both of the zeolites have unidimensional pore structures without any intersection. The crystals are needle-like shaped for both materials. Zeolite ZSM-22 (belonging to the TON fhmily) has free pore dimensions of 0.44 X 0.55 nm and zeolite ZSM-23 (MTT fiimily) has free pore diameters of 0.45 X 0.42 nm. The framework structures are sketched in Figure 2. The low coverage adsorption properties were determined with the pulse chromatographic technique. The details of the experimental method are discussed elsewhere. The Henry constant was determined from the first moment of the response curve on the TCD detector alter injection of an alkane trace. Adsorption enthalpy and entropy were obtained by fitting the temperature dependence of the Henry constant to the van t Hoff equation. 

Numerous studies have established the wide scope of inclusion chemistry that is possible with inorganic solids. From layered hosts such as FeOCl and nanoporous membranes to zeolite molecular sieves, very different dimensions are accessible for the encapsulation of conjugated, potentially conducting materials. Zeolites are distinct hosts because they offer well-defined, crystalline pore systems at molecular dimensions, with sizes in mesoporous systems now reaching even beyond the molecular scale. 

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