Hierarchical Zeolite Y with Full Crystallinity: Formation Mechanism and Catalytic Cracking Performance

Hierarchical zeolite Y with high mesoporosity, integrate crystallinity, and hydrothermal stability is desired urgently for heavy oil conversion. Here, an approach combining steam treatment, acid treatment, and alkaline treatment approachs is reported for fabricating hierarchical zeolite Y with high mesoporosity and extraordinarily high crystallinity. A robust zeolite precursor with good crystallinity was prepared first through an acid pretreatment step using fluorosilicic and hydrochloric acids, in which the zeolite crystal could be healed by the migration of Si into the skeleton. Moreover, it was deduced that the formation of hierarchical zeolite Y with extraordinarily high crystallinity was closely related to the unique desilication mechanism. The obtained hierarchical zeolite Y showed remarkable catalytic activities, high selectivity of liquid products, and low selectivity of bottom oil in the conversion of heavy oil.