Effect of crystallization time on physicochemical and catalytic propertiesof ZSM-5 zeolite

The effect of crystallization time on physicochemical properties of ZSM-5 z eolite and its catalytic performance in vapor-phase alkylation of benzene a nd ethylene were investigated. It was found that the first ZSM-5 crystal fo rmed after 70 h and the amorphous phase almost disappeared after 90 h. When the crystallization time was varied from 90 to 150 h, the crystal shape, t he average diameter and the SiO2/Al2O3 molar ratio in bulk of ZSM-5 zeolite remained unchanged. However, the SiO2/Al2O3 molar ratio at the external su rface of the zeolite decreased with the crystallization time. The catalyst crystallized for 90 h showed the best catalytic performance in the vapor-ph ase alkylation of benzene and ethylene to ethylbenzene.