In-situ growth of ZSM-5 zeolite on acid-activated metakaolin

摘要

A series of acid-activated metakaolins overgrown with ZSM-5 crystals have been prepared by in situ crystallization of zeolite ZSM-5 on the acid-activated metakaolins with tetraethylammonium hydroxide (TEAOH) as the templating agent. The acid-activated metakaolin was obtained by first calcining China kaolin at 993 K and then treating the calcined kaolin, metakaolin, with 20 wt% HCl solution at 367 K. The composites synthesized were characterized by XRD, SEM, IR spectra and N2 adsorption. It is found that the relative amount of ZSM-5 in the composite can be controlled by varying the reactant composition and by tuning the crystallization conditions. The results of N2 adsorption indicate that the composites possess a bimodal pore system comprising mesopores inherited from acid-activated metakaolin and microporous structure of zeolite ZSM-5. Furthermore, the catalytic activity of the composite was tested by means of light diesel oil cracking reaction and compared with that of the mechanical mixture composed of ZSM-5 and acid-activated metakaolin. Interestingly, the composite-based catalyst exhibits better catalytic activity than the mechanical mixture.