Intergrowth MFI Zeolite with Inverse Al Zoning and Predominant Sinusoidal Channels for Highly Selective Production of Styrene

Abstract

ZSM-5 zeolites with accessible micropore architecture and tunable acid–base sites are important shape-selective catalysts. However, the presence of exposed straight channels and the external acid–base sites of conventional ZSM-5 has a negative impact on shape selectivity. Herein, we report on the direct synthesis of an intergrowth ZSM-5 zeolite mimicking the mortise–tenon joints. It can be revealed by various methods that the mortise–tenon ZSM-5 shows an inverse Al gradient from the surface to the core of the zeolite. More importantly, the sinusoidal channels predominantly opened to their external surfaces are constructed. The shape-selective capability of the ZSM-5 zeolite has been fully exploited due to the intrinsic inert external surface and unique sinusoidal channel features, thereby resulting in high styrene selectivity (>90%) and good catalytic stability (>100 h) in the toluene side-chain alkylation reaction. In addition, in situ DRIFTS confirms that this intergrowth ZSM-5 contributes to the formation of more active intermediates of HCOO* and H₃CO*, which is another reason responsible for the superior performance.