The solubility of commercial and synthesized silica gels in a solution of Tetra-Ethyl-Ammonium-Hydroxide (TEAOH) was investigated at room temperature. The state of parent silica frameworks was characterized by BET and SEM. The structural defects were identified both by the Q n group analysis in 29 Si MAS NMR and IR spectroscopic investigation. It was found that the dissolution rate of the samples shows a tendency for growing up with an increasing BET surface.

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Microporous zeolites Na-Y and K-Y were converted into the NaNH 4 -Y and KNH 4 -Y modifications by ion exchange being active in dealumination. Removal of framework aluminium and silicon is accompanied by formation of secondary mesopores. Internal mesopores are formed in the centre of zeolite crystals and external pores at their surface. Formation of mesopores changes the sorption behaviour. 2189Residual alkali metal cations as Na + or K + stabilise, however, the framework ϵSi-O-Alϵ bonds. Because of inhomogeneous distribution of sodium ions, in NaNH 4 -Y less internal but more external mesopores are formed. Potassium ions of KNH 4 -Y are more homogeneous distributed over the framework why a more balanced formation of secondary pores takes place.