Hollow structures by controlled desilication of beta zeolite nanocrystals

The present work examines the different parameters that affect desilication of nanometric Beta zeolite crystals in alkaline solutions. The influences of different synthesis parameters such as the nature of the zeolite (size of the crystals, composition), the alkalinity, the temperature and the amount of added Al species on the morphology and properties of hollow structures are discussed. Addition of sodium aluminate to the alkaline solution protects the surface from desilication and favors dissolution at the center of the crystals, leading to the formation of hollow structures. The size, morphology and crystallinity of those structures depend mainly on zeolite composition, treatment temperature and alkalinity of the solution. If hollow structures are totally amorphous when desilication is carried out under stirring, their crystallinity and thermal stability are significantly improved in the presence of tetraethyammonium (TEA+) cations.