Activation of zeolite Ω

• Published in: Applied catalysis 1988-08, Vol.42 (1), p.105-120
• Main Authors: Massiani, Pascale, Chauvin, Brigitte, Fajula, François, Figueras, François, Gueguen, Claude
• Format: Article
• Language: English
• ISSN: 0166-9834
• DOI: 10.1016/S0166-9834(00)80079-2

29Si and 27Al magic angle spinning NMR spectroscopy, X-ray diffraction, porosity measurements, chemical analysis and infrared spectroscopy of the framework and hydroxyl regions were used to study the changes in properties of zeolite Ω which occurred upon thermal activation. Calcination in the presence of dry air at 500°C and self-steaming at 600°C resulted in 25% and 50% of framework dealumination respectively. The dislodged species contained aluminium in tetrahedral and octahedral configurations. The former were characterized by an 27Al NMR signal at 30 ppm and an IR band at 3575 cm t-1. Most of these species could be removed by acid leaching with dilute nitric acid. Activated zeolite Ω possessed acid sites which were stronger than those of Y type zeolites; some of them were not accessible to ammonia. In the parent material, aluminium was incorporated preferentially in the six-membered rings of the gmelinite cages. Dealumination affected selectively the sites located in the four-membered rings.