Zeolite Framework Type Codes

Web of Science and around 1000 zeolite related patents per year can be found under the same Topic search in the Derwent Innovation Index . The number of new Zeolite Framework Type Codes (FTCs, see below) also grows fast, with an average of over 7 FTCs per year for the last 12 years. This chapter tries to cover a vast portion of zeolite science at an intermediate level, with a focus on and more in-depth coverage of zeolite synthesis. The chapter is organised in, perhaps, a less usual way, since the general sections on structural and compositional chemistry and applications go before the more specific sections on synthesis. We think the early sections will show that the vast richness of current zeolite science and applications heavily rehes on an enormous synthetic effort that we will try to summarise and rationalise in the later sections. 

The three-letter framework-type codes, recognized by the IUPAC Commission on Zeolite Nomenclature, have been used to organize the entries in this publication. The powder diffraction data and simulated patterns for the reference structures are listed alphabetically according to the respective framework type code. An index of material names, and associated three-letter codes, is included in the companion volume, the Atlas of Zeolite Framework Types (Baerlocher, McCusker and Olson (2007)). 

The reported zeolite minerals are 61 instead of 57 as referred to in the text. This is due to the fact that, for historical and opportunity reasons, different names have been saved for the isostructural couples clinoplilolile-heulandite and harmotome-phillipsite and for the isostructural triplet analcime-pollucite-wairakite. As regards the 3-letter framework-type codes, see [27]. 

GIS). A three letter code (e.g. GIS) is assigned to confirmed framework types by the Structure Commission of the International Zeolite Association according to rules set up by an 1UPAC Commission on Zeolite Nomenclature [3,4]. The codes are normally derived from the name of the zeolite or type material , e.g. FAU from the mineral faujasite, LTA from Linde Type A, and MFI from ZSM-5 (Zeolite Socony Mobil - five). Information pertinent to these framework types is published in the Atlas of Zeolite Framework Types [5] and on the internet at http //www.iza-strncture.org/databases/. As new codes are approved, they arc announced on the IZA Structure Commission s WWW pages (http //www.iza-structure.org/) and included in the internet version of the Atlas. As of January 2005, 161 zeolite framework types had been confirmed by the Structure Commission. In this chapter, all references to materials whose framework types are known will be accompanied by the appropriate three letter code in boldface type. 

As mentioned at the beginning of this chapter, essential structural information for all zeolite framework types to which the Structure Commission has assigned a three-letter code is... 

Source Web of Science (papers) and Derwent Innovation Index (patents), October 2008, used with permission. The inset shows the number of Framework Type Codes (FTCs) collected in the different editions of the Atlas of Zeolite Framework Types plus the number of FTCs already approved by the Structure Commission of the International Zeolite Association in November 2008 (http //www.iza-structure.org/)... 

Figure 5.2 The structure of zeolites is built from AB4 tetrahedra (bottom left and middle) sharing all vertices once and only once with neighbouring tetrahedra (top left) to yield a (4 2)-3D net in which connection between 4-connected nodes (A, light grey) occurs through 2-connected nodes (B, dark grey). Thus, the composition of the framework is AB2. In the structure of Si02-ZSM-12 (top right), A=Si, B=0 and the connectivity of tetrahedra is defined by the M l W Framework Type Code, a (4 2)-3D net shown at the bottom right...

Considering only frameworks made up entirely of tetrahedral comer-sharing TO4 species, full details of all the structure types are collected, refereed and published by the Structure Commission of the International Zeolite Association. The most recent publication indicates that around 170 framework types (each of which is given a unique three-letter code) have been unambiguously identified and both hardcopy publications (in particular the so-called Atlas of Zeolite Framework Types ) and the continuously updated structural summary on the web site (www.iza-structure.org) are indispensable resources for the researcher in this field. 

The Atlas of Zeolite Framework Types contains 168 topological distinct tetrahedral T04 frameworks where T may be Si, Al, P, Ga, B, Be etc. The compiled fiamework types, characterized by Framework Type Codes consisting of three capital letters, do not depend on the composition, distribution of the various T atoms, cell dimensions or S5munetry. Their frameworks exhibit such a diversity of four-connected three-dimensional nets that finite and infinite component units were introduced to describe their topologies. 

Based on such variations in the framework of zeolites, a structure code has been assigned to each one of them, for the sake of simplicity in their identification. In fact, as many as 191 types of structure codes (i.e.. Framework Type Code, FTC) have been proposed by the Structure Commission of the International Zeolite Association (IZA-SC) [5]. It is notable that several zeolites exhibit similarities in their structures which can be grouped together to form a iso-structural group of zeolites. Table 2.9 represents details of the common groups based on the type of structure of zeohtes [8]. 

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. 

Zeolites are now defined as solids that possess a framework of tetrahedra which are all corner-sharing and include a degree of opermess such as channels or cavities. Each framework type is issued a unique three letter code by the Structure Commission of the International Zeolite Association. " At the end of February 2007, there were 176 framework types. This definition does not specify atom types. 

Configurationally biased Monte Carlo techniques [63-65] have made it possible to compute adsorption isotherms for linear and branched hydrocarbons in the micropores of a siliceous zeolite framework. Apart from Monte Carlo techniques, docking techniques [69] have also been implemented in some available computer codes. Docking techniques are convenient techniques that determine, by simulated annealing and subsequent freezing techniques, local energy minima of adsorbed molecules based on Lennard-Jones-or Buckingham-type interaction potentials. 

Nowadays, the term zeolite includes all microporous solids based on silica and exhibiting crystalline walls, as well as materials where a fraction of Si atoms has been substituted by another element, T, such as a trivalent (T = Al, Fe, B, Ga,. ..) or a tctravalent (T = Ti, Ge,...) metal. Crystalline microporous phosphates are known as zeotypes or as related microporous solids (14, 54). At present, there are 179 confirmed zeoHtc framework types. For the structure types, three-letter codes are used, which were adopted from the name of the first material reported with a specific stmcturc. As an example, FAU is given for the structure of faujasite and its synthetic equivalents X and Y, and MFl for the stracture of ZSM-5 or silicalite-1 (105). Figure 9.11 shows prominent examples of zeolite firameworks, for example, FAU, LTA, and MFI types (pentasil). 

Zeolites are crystalline microporous materials with uniform pore sizes (<2nm) that find a wide range of applications in many industrially important adsorption, separation, and catalytic processes [89-92]. Traditionally, the term zeolite refers to a crystalline aluminosilicate or silica polymorph based on corner-sharing TO (T = Si and Al) tetrahedra forming a three-dimensional network with uniformly sized pores of molecular dimensions (Figure 3.9). Each material is assigned a three-letter framework structure code by the International Zeolite Association (IZA) [93]. Framework types do not depend on composition, distribution of T-atoms, cell dimensions, or symmetry [1]. 

---