The catalytic relevance of hydrothermally substituted Zn on the zeolite ZSM-5 during the methanol-to-aromatics process†

The methanol-to-aromatics (MTA) process, catalyzed by both unmodified and metal-loaded zeolite ZSM-5, offers a promising and sustainable approach for producing liquid aromatics directly from renewable feedstocks. However, traditional metal incorporation methods often result in metals being confined to the surface or pores of the zeolite. While this can enhance aromatic selectivity, it tends to negatively impact the catalyst's lifetime. To address this challenge, this study focuses on the impact of incorporating Zn into ZSM-5 using a post-synthetic hydrothermal substitution process, which differs from traditional metal impregnation methods. Our approach successfully integrates Zn directly into the zeolite framework, enhancing aromatic selectivity and extending catalyst lifetime—a counterintuitive result, as higher selectivity typically accelerates catalyst deactivation. We employed advanced characterization techniques, including operando UV-vis diffuse reflectance spectroscopy and solid-state NMR, to gain deeper insights into how the dual-cycle mechanism governs the MTA process. These findings will pave the way for developing upgraded zeolite-based catalytic systems for the valorization of C1 renewable feedstocks in aromatics production.