Indexed on: 01 Jan '96Published on: 01 Jan '96Published in: Russian Chemical Bulletin
The changes in the structure of highly siliceous Y- and ZSM-5-type zeolites during prolonged aging in air have been RAW by IR spectroscopy. M relatively low (<20) Si/Al ratios, gradual improvement of the zeolite structure is observed, which is related to ordering of the cationic and anionic sublattices. As a rule, this is accompanied by symmetrization of the tetrahedral framework units and decrease of the excessive negative charge of the framework. At higher Si/Al ratios, the zeolitc structure transforms into stable crystalline silica modifications, α-cristobalite (in the case of highly siliceous analogs of Y zeolite) and α-quartz (in the case of ZSM-5-type zeolites).