Properties, Preparation and Application of Zeolites

The next commercially successful synthetic zeolite introduced in the early 1960's was a large pore mordenite (Fig. 2) with ratio Si/Al ≈ 5. The improvement in thermal, hydrothermal, and acid stability coupled with its specific structural and compositional characteristics resulted in application of mordenite as an adsorbent and hydrocarbon conversion catalyst . Type L zeolites (Fig. 3), discovered in the early 50's by D. W. Breck and N. A. Acara with a Si/Al = 3.0 have unique framework topology. They were adapted as commercial catalysts in selective hydrocarbon conversion reactions.

Synthesis of Mordenite Type Zeolite - Download PDF

Keywords: Zeolite, zeolithes, chemistry, mineralogy, properties, database, structure

Natural Zeolite Structural and ion-exchange properties - Format: PDF

Zeolite molecular sieves have found extensive applications in ion-exchange, separation and catalytic processes, particularly in the chemical and petroleum industries. Currently, the state-of-the-art in synthesis of high-silica zeolites involves the use of complex organic molecules to direct the formation of zeolitic materials with novel pore structures. While efforts towards preparation of new zeolites using organic molecules as structure-directing agents continues, synthesis of calcium and other alkaline-earth zeolites has not received much attention since the inception of the systematic investigation of zeolite synthesis some 35 years ago. Of the approximate 50 natural zeolites discovered to date, over 20% have eluded synthesis and another 10% have proven exceedingly difficult to synthesize at typical hydrothermal conditions. The overwhelming majority of these zeolites are calcium-dominant. The difficulty encountered in the synthesis of these alkaline-earth zeolites is in direct contrast to their natural occurrence as alteration products of volcanic glasses. Thus, the objective of this work is developing practical methodolgies for the synthesis of alkaline-earth zeolites.

Database of Zeolite Structures - IZA Structure Commission

The properties of the porous materials depend both on the pore structures and the chemistry of the framework. The continuously increasing demands for materials with highly specific chemical and physical properties as zeolites have inspired scientists to make new porous materials with unique structures .

Lecture notes, structure, synthesis, structural investigations, applications, atlas of zeolite types

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Zeolites have the ability to act as catalysts for chemical reactions which take place within the internal cavities. Essentially, zeolites have two properties which make them particularly suitable as starting materials for the preparation of catalysts :

Synthesis, characterization and properties of zeolite films and membranes. Dissertation, 2001. Lulea University

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Zeolites find and increasing application in production of petrochemicals, often replacing environmentally unfriendly catalysts. Zeolite catalysts typically yield fewer impurities, have higher capacity, give greater unit efficiency, and afford higher selectivity. Unlike the more hazardous acid catalysts that have been used in the past, e.g., solid phosphoric acid, hydrofluoric acid, etc., zeolites are non-hazardous and regenerable.

This property can be fine tuned by variating the structure by changing the size and number of cations around the pores.

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The naturally occurring zeolites are an important group of minerals for industrial and other purposes . The discovery in 1957 of largedeposits of relatively high purity zeolite minerals in volcanic tuffs in the western United States and in a number of other countries represents the beginning of the commercial natural zeolite era. Prior to that time there was no recognized indication that zeolite minerals with properties useful as molecular sieve materials occurred in large deposits. Commercialization of the natural zeolites chabazite, erionite, and mordenite as molecular sieve zeolites commenced in 1962 with their introduction as new adsorbent materials with improved stability characteristics. The applications of clinoptiolite in radioactive waste recovery and in waste water treatment during the same period of the 60's were based not only on superior stability characteristics but also high cation exchange selectivity for cesium, strontium, and for ammonium ion.

Recently, zeolite powders for external use have found application as deodorants, antimycotic agents and wound dressings.

Zeolites and Catalysis: Synthesis, ..

In the case of shape-selective catalysis in zeolites, the combination of both properties exploited to control the selectivity of catalytically conducted reactions.