Synthesis of core-shell zeolite composite ZSM-5/Y based on depolymerization of Y zeolite

Composite zeolite with ZSM-5 as shell and polycrystalline Y as core was prepared by using the depolymerized NaY zeolite as the nutrients for the growth of ZSM-5 zeolite. The prepared samples were characterized by XRD, FT-IR, NH3-TPD, SEM and EDS. The catalytic performances of ZSM-5/Y composite zeolites were tested in the cracking of n-heptane and isopropylbenzene, and compared with the corresponding physical mixture. The results revealed that the formation of ZSM-5/Y composite zeolite was a transformation process of Y zeolite into ZSM-5 zeolite. Y zeolite was wrapped by the post-synthesized ZSM-5 zeolite, resulting in the formation of the core-shell composite. The ZSM-5/Y composite showed an outstanding difference from the corresponding physical mixture of pure Y and ZSM-5 zeolites. As compared with the corresponding physical mixture as catalyst, with ZSM-5/Y composite as catalyst a decreased conversion of isopropylbenzene in its catalytic cracking was obtained, while an enhanced conversion of n-heptane as well as an increased selectivity of light hydrocarbon, especially the selectivity of light olefins in n-heptane catalytic cracking was obtained. ©, 2015, Science Press. All right reserved.