Overview and introduction to zeolite chemistry

Zeolite membranes form the most recent branch of the inorganic membrane field for which characterised and properly described real microporous zeolite 

Zeolites are porous crystalline materials with a complex crystallographic structure. The characteristics of the void (pore) network is completely determined by the crystallographic space group and the composition. 

It is appropriate here to treat structural characteristics of zeolites. A brief summary has been given in the Chapter 9, Section 9.4.1 in which a typical structure is illustrated by Fig. 9.19 for MFI type (ZSM5, siHcalite) zeolites, being almost exclusively used for defect-free membrane s)mthesis. For a more detailed discussion the reader is referred to the works of Breck [92] and of van Bekkum et al. [93]. 

As shown by Jansen [95] on some support materials zeolite crystals are formed in a thin gel layer present on the support, on other supports this gel layer is not observed and a different crystal morphology, or even structure, can be formed. 

The subsequent events present in the course of the zeolite synthesis reaction (after Jansen [94]) 

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