Hollow Y zeolite single crystals: synthesis, characterization and activity in the hydroisomerization of n-hexadecane

Hollow Y zeolite single crystals have been obtained from a conventional NaY zeolite following a three-step process involving a severe dealumination of the zeolite with silicon tetrachloride (step #1), followed by an acid washing under mild conditions (step #2) and finally a selective dissolution of the crystals core in the presence of protective Al species (step #3). Crystals are characterized by the presence of a regular internal cavity with 0.1-0.2 nm thick microporous walls. They contain a relatively low framework Al content but significant amounts of extraframework Al oxide species mainly located on the external surface of the crystals. Hollow crystals have been mixed with a Pt-supported alumina binder and used as catalysts in the hydroisomerization of n-hexadecane. Compared to the corresponding bulk crystals obtained after step #2, their higher activity has been attributed to a better efficiency, directly resulting from the presence of the cavity.