Synthesis and Catalytic Performance of ZSM-5/MCM-41 Zeolites With Varying Mesopore Size by Surfactant-Directed Recrystallization

ZSM-5/MCM-41 zeolite composites with varying mesopore sizes were prepared through alkali-desilication and surfactant-directed recrystallization with different chain length of alkyltrimethylammonium bromide. XRD and TEM revealed that the composites possessed the characteristics of both ZSM-5 and mesoporous MCM-41 with hexagonal symmetry. N-2-adsorption-desorption, Al-27 MAS NMR, NH3-TPD and in situ FT-IR results suggested that the sizes of the mesopores and the accessibility of acid sites could be affected greatly by the chain length of alkyltrimethylammonium bromide used. Catalytic cracking of n-dodecane over ZSM-5/MCM-41 composites was studied in the form of coatings on the inside of a tubular reactor at 550 A degrees C and 4 MPa. The conversion of n-dodecane increased gradually with increasing the mesopore sizes of ZSM-5/MCM-41 composites, implying a positive effect of the mesopores on the diffusion inside pore channels and the accessibility of acid sites by the reactants.