Zeolite application

Al-rich aluminosilicate Hydrophilic Polar High-cation exchange capacity Relatively low chemical, thermal and hydrothermal stability Catalytic activity Relatively low acid strength in H form Moderately high basic strength in cationic form (Cs+) 

Defect-free pure silicate Strictly hydrophobic Highly apolar No cation exchange ability No catalytic activity No acidity, no basicity Very high chemical, thermal and hydrothermal stability 

Heteroatom-substituted Specific catalytic properties, depending on the type 

Zeolites find widespread commercial applications and new opportunities emerge as new structures and compositions are attained. In terms of bulk quantities, synthetic zeolites are most commonly sold as cation exchangers builders) in the detergent industry zeolites are able to soften water 

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Sauer, J., 1998, Zeolites Applications of Computational Methods in Encyclopedia of Computational Chemistry, Schleyer, P. v. R. (Editor-in-Chief), Wiley, Chichester. 

Control of the multitude of pathways which feed molecules can take is the primary objective of aU catalyst and process developments. The work covered in this chapter focuses primarily on describing the approaches in material and catalysis development which have led to major advances in zeolite application in hydrocarbon conversion. The breaking and formation of carbon-carbon and carbon-hydrogen bonds constitute the majority of the chemical transformations involved here with the less prevalent, but very important, breaking of carbon bonds with sulfur, nitrogen and oxygen taking place in parallel. 

Post-synthesis methods (pore-size engineering) allow an existing shape-selectivity effect to be intensified, and also a new one to be established. However, normally not only the pore size will be influenced by most of these methods, but also the catalytic activity. Vansant [104] gives a classification of post-synthesis modification methods which covers the entire range of zeolite applications (gas separation, gas purification, encapsulation of gases and catalysis). 

All these aspects were thoroughly discussed by lecturers and participants during the round table organized during the Poitiers School on The Future Trends in Zeolite Applications . Special emphasis was placed on the role played by the sites at the external surface (pockets, etc.) or at the pore mouth, by mesopores, extraframework aluminum species, as well as by the polarity of reactant and product molecules. Other important topics dealt with the remarkable catalytic properties of BEA zeolites for fine chemical synthesis, the potential of mesoporous molecular sieves, zeolitic membranes and the role of combinatorial catalysis in the development of zeolite catalysts. It is our hope that the fruits of these discussions will appear in the literature or even better as new and environmentally friendly products or processes. 

Three-dimensional cationic lanthanide hydroxide frameworks structures have been prepared by using amino acids or other types of bridging ligands [56, 74]. These materials possess nanosized pores that are occupied by water and counterions from the original synthesis. These materials may find zeolitic applications such as their uses for anion exchange or occlusion and activation of electron-rich substrates. 

Among pore-opening vibrations of zeolite structures, those resulting in fluctuations of window aperture are of great importance for the majority of zeolite applications, because the window openings dictate the molecular sieving... 

J. Fraissard, T. Ito and L.C. De Menorval, Nuclear Magnetic Resonance study of Xenon adsorbed on zeolites and metal-zeolites. Application to catalyst research, in Proceedings 8th International Conference on Catalysis, Berlin, 1984, pp. 25-35. 

With zeolites application of electron tomography has provided unique information on the nature of mcsoporcs that have been obtained by secondary treatments or the use of carbon templates. 

Invention and application of synthetic zeolites 11,2> have led to a most peculiar process of innovation in chemical industry, initiated by the prospects of the three main fields of zeolite application as cation exchanger, molecular sieves and catalysts. In all these case the relevant processes in the adsorbate-adsorbent system are inevitably accompanied by a succession of transport phenomena, maintaining the molecular exchange between the active sites and the surrounding fluid. The investigation of mass transfer in zeolitic adsorbate-adsorbent systems has become therefore a major objective of both fundamental research and industrial application. 

Cost calculations showed that the expenses for zeolite application are in the same range as for coconut shell-based activated carbon and carbonaceous resin (Ambersorb) since material costs are similar. However, the estimated bed life for zeolites is up to six times longer than for activated carbon and the estimated adsorbent usage rate is only 25% [54]. Moreover, zeolites are thermally stable which implies an easier and faster regeneration [57]. 

Type one substitution has low relevance from the point of view of zeolite applications. 

New developments are to be expected from the recent growth of knowledge in traditional areas of zeolite applications and from the recent progress which has been made with such systems in material science. The use of zeolitic materials as hosts for specific chemical entities and their application in SUPRAMOLECULAR chemistry and catalysis looks particularly promising. 

During the Chernobyl disaster thirty to forty times the radioactivity of the atomic bombs dropped on Hiroshima and Nagasaki were released. The main radioactive isotopes from the Chernobyl accident were Cs, Cs, Sr, and Sr. The details of zeolite applications at Chernobyl remain rather obscure because of a secrecy problem still remaining after disintegration of the former Soviet Union. About 500,000 tons of zeolite rocks, mainly containing clinoptilolite, were processed at various deposits in Ukraine, Georgia, and Russia specifically for use at Chernobyl [65]. The majority of the zeolites was used for the construction of protective barriers and for agricultural applications in polluted areas. 

The purpose of zeolite application in this field is slow-release fertilization or a combination of ion-exchange and mineral dissolution reactions. Mainly K- or NHj-saturated clinoptilolites... 

Zeolite could selectively adsorb A -nitrosamines in the solution of methylene chloride or water, and the equilibrium data were fitted to Freundlich-type isotherms. Textural and acid-basic properties of zeolite determined their adsorption capacity. The extraordinary adsorption properties of NaA zeolite for iV-nitrosamines is inferred that the adsorbates inert the channel with the group -N=N-0. Larger amount of A-nitrosamines was adsorbed on ZSM-5 zeolite in water instead in methylene chloride, due to the hydrophobicity of the zeolite. Application of zeolite to remove A-nitrosamines from beer seems successful. Up to 100% of the worst carcinogenic compounds could thus be removed with 1.4 g/L of zeolite which was proven to be better adsorbent than silica or alumina. On Na 3 zeolite and MCM-41 mesoporous material A-nitrosodimethylamine decomposed above 573 K and the liberated NOx could be detected even at 773 K during the TPSR process, indicating the strong adsorption of A-nitrosamines on molecular sieves that makes zeolite become the functional materials for environmental protection. 

Natrolite, applications Natrolite, ion exchange Natrolite, lattice vibrations Natural zeolites, Antarctica Natural zeolites applications PL-2... 

Also, whereas medium-pore zeolites, e.g. MFI-t5q)es (ZSM-5), have only limited application in refinery hydrocracking (e.g. selective de-waxing applications), due to their inability to process large, bulky molecules, not only are these zeolites applicable to the linear paraffinic nature of F-T wax but may even be of advantage in limiting the extent of branching possible and so serve to maintain molecular linearity and its associated high cetane number properties. 

Han W, Kwan SM, Yeung KL. Zeolite applications in fuel eeUs Water management and proton conductivity. Chem Eng JW12 187 367-371. 

Corma gave a comprehensive review on zeolite applications. He has discussed practically all commercial oil refining and petrochemical processes in which zeolites are used. FCC was the first commercial use of zeolites. It is still the most important one. Three important properties make zeolites the catalysts of choice in most applications. These are high concentrations of acid sites which may be tailored to almost any particular need, high thermal and hydrothermal stability, and high selectivity and (sometimes) high shape selectivity. 

From the time of the mixing of the starting materials to the moment of zeolite application, seve processes may occur all of which may contribute to the formation of the final product. In the majority of zeolite formation processes, the synthesis involves the formation of a gel phase. Investigations of the precrystalline gel phase have shown that the chemical composition of this phase resembles the composition of the final zeolite structure (Zhdanov 1971). As such, zeolite X could, for instance, be directly synthesized by treatment of the solid, precrystalline phase of the initid reaction mixture (Breck 1974). Formation of the alumino-silica gel thus must play a crucial role in zeolite synthesis. 

The currents chapter summarizes the basic synthesis, characterizations, and applications of zeolites including medical application. It is evident from the discussion that zeolites have a great potential in numerous application. Not only zeolites are very cheap and naturally occurring but also they can easily be synthesized. The ease of handling of the zeolites attracts more and more industries and academic scientist toward finding the new applications of the zeolites. The medical field needs to be more explore as far as zeolites applications are concerned. 

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