Abstract: A series of ZSM-5(core)/SAPO-5 (shell) binary structure zeolite samples were synthesized by hydrothermal synthesis and vapor-phase transport at different crystallization temperatures for different time. Phosphoric acid, pseudoboehmite, and silica sol were used as phosphorus, aluminum, and silicon sources, respectively. Triethylamine was used as template. The zeolite samples were characterized by means ofX-raydiffraction, scanning electron microscopy,X-rayenergy dispersive spectroscopy, Fourier transform infrared spectroscopy, and N2 adsorption. The zeolite samples had binary structure with a ZSM-5 core and a SAPO-5 shell. The crystallinity of the zeolite samples increased as the crystallization temperature was increased and the crystallization time was protracted. Using the vapor-phase transport technique for synthesis of binary structure zeolite could reduce the SAPO-5 particle size and the amount of self-existent SAPO-5 zeolite and improve the distribution of SAPO-5 on the ZSM-5 surface. The experiments of heavy oil cracking showed that the core/shell binary structure zeolite samples were more favorable for the formation of light olefins than the mechanical mixture.

Key words: ZSM-5 zeolite, SAPO-5 zeolite, core/shell binary structure, hydrothermal synthesis method, vapor-phase transport method