Synthesis of a ZSM-5 (core)/SAPO-11 (shell) composite zeolite and its catalytic performance in the methylation of naphthalene with methanol.

In the present work, a ZSM-5 (core)/SAPO-11 (shell) composite was prepared by the hydrothermal method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), temperature programmed desorption of ammonia (NH-TPD), and other characterization techniques. The catalytic performance of ZSM-5/SAPO-11 for the methylation of naphthalene with methanol was also studied. For comparison, the mechanical mixture was prepared through the blending of ZSM-5 and SAPO-11. The experimental results showed ZSM-5/SAPO-11 has been prepared with good crystallization, and exhibited a core-shell structure, with the ZSM-5 phase as the core and the SAPO-11 phase as the shell. The pore size of ZSM-5/SAPO-11 was between that of ZSM-5 and SAPO-11, and it had fewer acid sites than ZSM-5 and the mechanical mixture but more acid sites than SAPO-11. The excellent catalytic performance of ZSM-5/SAPO-11 was due to suitable pore size and acidity. The formation mechanism of the ZSM-5/SAPO-11 composite zeolite was also discussed.