Zeolite Structure Types

W. M. Meier and D. H. Olson, Mtlas of Zeolite Structure Types, Juris Dmck and Vedag AG, Zurich, 1978. 

Zeolite, or more properly, faujasite, is the key ingredient of the FCC catalyst. It provides product selectivity and much of the catalytic activity. The catalyst s performance largely depends on the nature and quality of the zeolite. Understanding the zeolite structure, types, cracking mechanism, and properties is essential in choosing the right catalyst to produce the desired yields. 

Meier, W. M. Olson, D. H. Atlas of Zeolite Structure Types. Butterworth-Heinemann London, 1992. 

Meier, W.M. Olson, D.H. "Atlas of Zeolite Structure Types" Structure Commission of the Inti. Zeolite Assn., Polycrystal Book Service, Pittsburgh, PA, 1978. 

The connectivity (topology) of the zeolite framework is characteristic for a given zeolite type, whereas the composition of the framework and the type of extra-framework species can vary. Each zeolite structure type is denoted by a three-letter code [4], As an example, Faujasite-type zeolites have the structure type FAU. The pores and cages of the different zeolites are thus formed by modifications of the TO4 connectivity of the zeolite framework. 

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

Overall the period since the 1980s can be described as a period of explosion in the discovery of new compositions and structures of molecular sieves. This can perhaps be seen most vividly by comparing the numbers of structure types contained in the various editions of the Atlas of Zeolite Structure Types [4]. The first edition (1978) contained 38 structure types, the second edition (1987) 64, the third edition (1992) 85 and the most recent edition (2007) 176. Thus 112 new structure types have been discovered since 1978. However, the reader should be cautioned that a significant number of the structure types included in the Atlas are not truly microporous or molecular sieve materials (i.e., they are not stable for the removal of as-synthesized guest species, typically water or organic templates) and therefore carmot reversibly adsorb molecules or carry out catalytic reactions. Unfortunately, the Atlas gives only limited information on the stability of the structures described. 

The IZA has several established Commissions. The Structure Commission formed in 1977 has published four editions of the Atlas of Zeolite Structure Types (1978, 1987, 1992, 1996) and two subsequent editions in the Atlas of Zeolite Framework Types (2001, 2007). An up-to-date version is maintained on the World Wide Web at the IZA Structure Commission web site (http //www.iza-structure.org). Subsequently commissions were established in catalysis (1998), synthesis (1992), ordered mesoporous materials (2001) and natural zeolites (2001). The synthesis commission published a volume, Verified Syntheses of Zeolitic Materials , in 1998, with a second revised edition in 2001 (http //www.iza-structure.org). 

Faujasites of the X and Y type are the most frequently studied zeolite structure type for this reachon. Because the key step in the reachon is a hydride hansfer, zeolites with low Si02/Al203 ratios are favored. The other preferred characteristic is a large pore opening and hence a low diffusion barrier to product diffusion. These details and others were reviewed recently by Feller et al. [50] (Table 12.8). 

The constraint index test revisited anomalies based upon new zeolite structure types. Micropor. Mesopor. Mater., 35-36, 31 5. 

W.M. Meier, D.H. Olson, and Ch. Baerlocher, in Atlas of Zeolite Structure Types , 4th revised edition, Elsevier, Amsterdam, 1996. 

The section on crystallization comprises zeolite synthesis, kinetics and mechanism of formation, stability relationships, recrystallization processes as well as the genesis of natural zeolites. Recent advances in this field have been surveyed, and some new perspectives have been outlined in the review by E. M. Flanigen. Most of the studies in this field are still empirical because of the complexity of the systems involved. Considerable progress has been made, however, towards a better understanding of the processes and mechanisms governing zeolite crystallization. It is not unreasonable to expect that conditions for synthesizing new zeolite structure types can eventually be predicted. 

Figure 9.6 Topologies of zeolite structure types, (a) Sodalite (b) Linde type A (c) faujasite (zeolite X and Y) (d) AlP04-5 and (e) ZSM-5. The vertices represent the positions of AI04 or Si()4 letrahedra while straight lines represent Si-O-Si or Si-O-Al linkages. (Reproduced with permission from [5]).

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