A novel binary-molecular sieve composite, namely Y/MCM-41, was synthesized from NaY gel by an in-situ two-step hydrothermal crystallization process, and the crystallization parameters were optimized. Fa-J curve and relative crystallinity methods were employed to deteimine the amounts of the constituent parts of Y and MCM-41 in the composite. The product was characterized by XRD, MAS-NMR, SEM, XPS, IR, N2 adsorption/desorption and thermal treatment methods. It indicated that Y/MCM-41 was different from the mechanical mixture of MCM-41 and Y. The composite has a narrow, relatively disordered pore structure, a thicker and partially crystalline wall, and a higher stability. And it showed that the Y zeolite was enwrapped by the MCM- 41.1, 3,5-triisopropylbenzene was employed as a model compound to detect the cracking activity of the composite molecular sieve, and a higher conversion was observed by using Y/MCM-41 catalyst than that of the mechanical mixture catalyst.

Key words: MOLECULAR SIEVE, HYDRO-THERMAL REACTION, CATAROLE PROCESS, CATALYTIC ACTIVITY, XRD, MS, NMR, XRD, IR