Chabazitic group

The phenomenon of polytypism is by no means limited to the chabazite group. Stacking faults also are likely to occur in most of the other... 

In the faujasite group of zeolites, the T-O bend occurs at 450-475 cm-1 in Cl, also near 450 in the phillipsite group zeolites (B and W), at a lower frequency, near 430 cm 1. A distinct two- to three-band T-O bend structure between 410 and 450 cm-1 is characteristic of the chabazite group of structures. 

Fig. 2.11 Different types of linkages of tetrahedra in the secondary building units of framework structures of zeolite groups, a, c, d Analcime group, b Heulandite and Moidenite groups, e Phillipsite group, f Pentasil and g Chabazite group [8]. Variation in channel shapes and dimensions of common zeolites, h Analcime—8R, i CUnoptilolite—8R and j Faujasite—12R [8]...

Commercially significant zeolites include the synthetic zeolites type A (LTA), X (FAU), Y (FAU), L (LTL), mordenite (MOR), ZSM-5 (MFI), beta ( BEA/BEC), MCM-22 (MTW), zeolites E (EDI) andW (MER) and the natural zeolites mordenite (MOR), chabazite (CHA), erionite (ERl) and clinoptiloUte (HEU). Details of the structures of some of these are given in this section. Tables in each section lists the type material (the common name for the material for which the three letter code was established), the chemical formula representative of the unit cell contents for the type material, the space group and lattice parameters, the pore structure and known mineral and synthetic forms. 

This hypothesis does not agree with the HRMAS Si-NMR results of Bodart et al. [3], who found that the Al atoms in chabazite are distributed statistically. However, the low resolution of the Si-NMR spectra and the superimposition of different Si(nAl) lines for zeolites of the chabasite group with two independent T sites make these results uncertain. 

The combined results of EXAFS and Mossbauer effect spectroscopies have been used to deduce the oxidation state and local structure of iron in iron containing Na, K- and H-chabazites. In the mineral Na,K(Fe) chabazite iron is found to be present as oxo- or hydroxo-bridged Fe(III) oligimers, while in the H-chabazite it is found to be present as Fe(III) ions bridged by oxo- or hydroxo-groups to the zeolite frameworks... 

A number of templates having the trimethylammonium group attached to a cyclohexane ring (and derivatives thereof) produce the high silica chabazite, SSZ-13. The rate of conversion of Cubic P to SSZ-13 increases as the nonpolar group increases in size up to C group. 

Chabazite, gmelinite, levynite and erionite form a group of porous crystals which exhibit certain similarities. Structures have previously been proposed for the anionic frameworks of chabazite,5 gmelinite and erionite. A structure is now proposed for levynite. On the basis of the crystallographic data, dilfusion anisotropy and molecular sieve behaviour of the four types of framework have been examined and the channel systems described and compared. 

Rozanska et al. compared plane wave LDA and GGA calculations for the chemisorption of propylene in chabazite.282 They concluded that allowing zeolite atoms to relax upon chemisorption made a significant impact on the computed results, but relaxation of the zeolite s unit cell shape and volume had considerably less effect. The same group performed plane wave GGA calculations for the chemisorption of isobutene in three different zeolites, chabazite, ZSM-22 (TON), and mordenite.283... 

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