Growth of ZSM-5 crystals within hollow β-zeolite

A zeolite composite composed of ZSM-5 and β-zeolites has been synthesized by a procedure of the nucleation and crystallization of ZSM-5 zeolite in the hollow β-zeolite. The property of β-zeolite crystals with aluminum-poor interior and aluminum-rich outer rim results in silicon extraction favorably in the aluminum-poor bulk rather than the aluminum-rich external surface. Subsequently, alkaline treatment of β-zeolite crystals during the second-step synthesis leads to a preferential dissolution of the aluminum-poor center and the formation of hollow β-zeolite crystals. ZSM-5 zeolite crystals are therefore embedded and grown within the hollow β-zeolite. The catalytic activities of Co-Hβ, Co-HZSM-5 and Co-HZSM-5/BEA are investigated during the reaction of methane catalytic reduction NO in the presence of O2.