Nanoplatelet Mordenite Zeolite with a Controlled Aspect Ratio: Implications for the Alkylation of Benzene with Benzyl Alcohol

Abstract

Modulating the anisotropic growth rate of zeolites to tailor their physicochemical properties holds significant promise across various fields, such as catalysis and adsorption. However, achieving this objective using commercially available small molecules remains a fascinating yet challenging task in zeolite crystallization, particularly for zeolites with a strong growth orientation. Herein, we demonstrate the synthesis of well-faceted nanoplatelet mordenite (MOR) zeolite with a thickness of 80 nm along the (100) direction in a low alkaline gel system utilizing tetraethylammonium hydroxide (TEAOH) and hexamethylenimine (HMI) as dual templates. Time-resolved analysis of precursor evolution reveals the unique crystallization pathway of in situ crystal transformation induced by the exchange of structuredirecting agents. The dissolved species maintain some "memory" of MCM-56 due to the strong interaction between the silanol groups and HMI, which inhibits the attachment of incoming building units to the MOR phase and benefits the formation of nanoplatelet MOR. A comprehensive investigation into key factors influencing nanoplatelet MOR zeolite formation demonstrated that metastable MCM-56 and the crystallization rate play pivotal roles. Moreover, fine-tuning the crystallization rate allows customization of the crystal size and aspect ratio for nanoplatelet MOR zeolite. The catalytic performance of the nanoplatelet MOR zeolite in the alkylation of benzene with benzyl alcohol is enhanced compared to its bulk counterpart.