Abstrakt
Ultrastabilization of zeolites is performed by an intense treatment: high-temperature steaming with further acid leaching to obtain a stable and very catalytically active material. This work shows that ultra-stable zeolite Y (USY) possesses small particles of amorphous material located in the porous structure, as detected via (29)Si MAS NMR and STEM.
They are washed out by the chemical treatment with 0.2 M TBAOH without deterioration or modification of the crystal structure of zeolite. Contrarily, the treatment of this zeolite with NaOH-containing solutions, results in major changes in porosity and acidity of the samples.
TBAOH-treated sample showed significantly different NMR spectra of adsorbed (129)Xe, containing two separate signals and powder-like line shapes recorded at low temperatures. It was ascribed to the higher loading of xenon atoms in supercages.
The cleaning of the sample from the debris located in micropores increases the accessible volume in supercages, therefore xenon atoms could occupy the cages in higher quantities. This treatment method could be used for fine-tuning of ultra-stable zeolite Y crystals.