Illustrative examples of zeolite membrane synthesis and processing

2 Illustrative Examples of Zeolite Membrane Synthesis and Processing 

The obtained gas permeation and separation properties of the clay supported MFI films were, however, rather low. This was ascribed to the low porosity of the clay support. 

Geus et al. concluded that to obtain total, continuous coverage of porous supports a relatively large layer thickness should be necessary. The minimal layer thickness is expected to be correlated to the maximal pore size of the porous support and on the smoothness of the support top face. 

Gas permeation values can be increased by decreasing the layer thickness. Therefore Vroon et al. [82-84,97,98] selected in situ synthesis conditions to obtain very small MFI crystals from which thin layers could be grown. 

Mesoporous y-alumina and titania supporting layers were severely attacked by the precursor solution (with high alkalinity) and could not be used. Macro-porous a-alumina supports (pore diameter 0.16 pm, porosity = 46%) could however be successfully applied. 

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