Generating Disk-Shaped MTW Zeolite with Reduced Channel Length Using Polycation Structure-Directing Agent for Hydroisomerization of N-Dodecane

Abstract

The development of hierarchically structured zeolites to mitigate diffusion limitations and improve catalytic performance constitutes a focus of current research. In this study, we present the synthesis of hierarchical disk-shaped MTW zeolite (ZSM-12-P) with shortened channel length using polycation [-C5H9N+C10H10N+C5H9-C3H6-]n[Br−]2n (PDIP) as an organic structure-directing agent (OSDA). The ZSM-12-P zeolite forms disk-shaped structures with thicknesses ranging from 140 to 160 nm and exhibits rotational intergrowth. These structures are composed of interconnected nanocrystalline domains that form mesopores accessible from the outer surface, while the microporous channels extend along the thickness direction. In addition, the polycationic OSDA possesses strong interaction with framework and MTW structure-directing ability, enabling the successful synthesis of the Al-rich ZSM-12-P. Owing to its strong acidity and improved diffusion property, the Pt/HZSM-12-P catalyst demonstrates enhanced catalytic n-dodecane hydroisomerization activity and isomer yield.