The Synthesis of Core-Shell Encapsulated Metal Catalysts for Conversion of Methanol to Aromatics

Abstract

A core-shell encapsulated metal catalyst was prepared, and its catalytic performance in the methanol-to-aromatics (MTA) reaction was investigated. This study introduces a simple secondary hydrothermal synthesis method based on the traditional preparation of HZSM-5 catalyst resulting in a nanoparticle with HZSM-5 catalyst encapsulating 2Gd%/S-1 with hollow and hierarchical pores (2Gd%/S-1@HZSM-5). This catalyst offers several advantages. First, the inner silicalite-1 layer shields the aluminum species within the HZSM-5 framework, thus passivating some of the strong acid sites on the catalyst surface. This in turn inhibits continuous reactions that result from the overly acidic surfaces. The 2Gd%/S-1@HZSM-5 catalyst demonstrates high selectivity for aromatics (59.4%), particularly BTX (benzene, toluene, and xylene), in the methanol-to-aromatics reaction (MTA). This selectivity arises from the catalyst's suitable acidity and optimized porous system. Importantly, the selectivity for C9+ aromatics is low, thus indicating effective inhibition of continuous reactions of BTX products on the catalyst surface due to low pH. Furthermore, the hydrothermal stability of the 2Gd%/S-1@HZSM-5 catalyst is significantly higher. Therefore, this method holds promise for the widespread development

of novel catalysts with hollow layered porous systems, tunable pH, and high hydrothermal stability.