A facile route for tailoring mesoporous silica-alumina with short-range faujasite zeolite structure

A mesoporous amorphous silica-alumina (MSA) material with enhanced acidity, higher surface area and pore volume was synthesized through alkaline treatment of high Si/Al ratio zeolite Y in the presence of the structure directing agent CTAB. The effect of alkaline concentration, treatment temperature and reaction duration on zeolite dissolution, mesoporosity formation, textural properties and acidity was systemically investigated. The alkaline treatment initially caused partial dissolution of the zeolite. The resulting undissolved zeolite fragments and dissolved silicon and aluminum species then interacted with CTAB micelles, assembling into mesophases where the zeolite basic building blocks are still remained and serve as the wall of the mesophases. At low NaOH solution concentration, the formation of the mesophase was restricted due to limited zeolite dissolution and low alkalinity. The low alkalinity was insufficient to continuously dissolve the Si and Al species from the amorphized zeolite, and to effectively transfer these species to SDA micelles for mesophase assembly. In contrast, a higher NaOH concentration improves the dissolution of Si and Al species from the zeolite, facilitating their mobilization and incorporation into CTAB micelles, thereby promoting the formation of more mesophases. This facile route enables controlled tailoring of silica-alumina mesostructures with short-range zeolitic walls, offering improved hydrocracking catalyst supports with tunable acidity and stability.