H 4 EDTA- and (NH 4 ) 2 SiF 6 -liquid phase dealuminated Y zeolites (EDY and FDY) and hydrothermally dealuminated Y zeolites (USY) were treated with an aqueous solution of KOH. The products were characterized by using XRD, n.m.r., FT i.r., SEM, and fast atom bombardment mass spectroscopy (FABMS) techniques. A decrease of Si/Al ratios was observed in the basic solution-treated samples. The results clearly show that dissolution of the surface of EDY and removal of silicon atoms from the framework lattice of FDY occurs during basic solution treatment. Realumination of ultrastable Y zeolite (USY) takes place through reinsertion of aluminum into the framework vacancies formed during hydrothermal treatment of NH 4 NaY or formed during a basic solution treatment of USY.

KOH solution treatment causes dissolution of surface zeolites and removal of silicon atoms from framework lattices, while realumination of ultrastable Y zeolites occurs through reinsertion of aluminum into framework vacancies.

Structural evolution of dealuminated Y zeolites during KOH solution treatment

Key Takeaway: KOH solution treatment causes dissolution of surface zeolites and removal of silicon atoms from framework lattices, while realumination of ultrastable Y zeolites occurs through reinsertion of aluminum into framework vacancies.