Manufacture of b-Oriented ZSM-5/Silicalite-1 Core/Shell Structured Zeolite Catalyst

Abstract

A b-oriented MFI shell was formed on the ZSM-5 crystal by pretreating the core using ammonia prior to the hydrothermal synthesis in tetrapropyl ammonium hydroxide medium. The effect of surface structure of the core material on synthesis of MFI/MFI zeolite was investigated. The surface Si-OH groups and amorphous aluminate may play an important role in forming the b-oriented coating. The shell composition changed from high-silica ZSM-5 to silicalite-1 after twice coating synthesis, while the shell coverage increased from 85% to 99%. In toluene methylation, the silicalite-1 shell not only prevented the deactivation of the catalyst, but also enhanced para-selectivity up to 61%.

Keywords:

• oriented shell
• MFI
• pretreatment
• para-selectivity

Acknowledgment

Yaxin Zhou and Weiyi Tong contributed equally to this work.

Funding

The authors gratefully acknowledge the support of the National 973 Program Grant No. 2009CB623501 and SINOPEC contract Grants.