Controlled Defect Engineering and Metal Incorporation in ZSM‐5 Zeolites for Methanol Aromatization With Enhanced Selectivity for C ₈₊ Alkyl Aromatics

ABSTRACT

An efficient, Zn‐functionalized, hierarchically porous ZSM‐5 catalyst has been developed for the sustainable production of aromatics via methanol aromatization, with enhanced selectivity for C ₈₊ aromatics. The catalyst synthesis protocol was carefully designed to promote strong interactions between Zn species and the ZSM‐5 support, thereby enhancing the stabilization of framework‐associated hydroxylated Zn species, potentially including ZnOH ⁺ within the porous, defect‐rich environment of ZSM‐5. The catalyst preparation method consists of sequential steps: desilication‐induced defect generation in the ZSM‐5 framework and incorporation of Zn at defect‐rich sites to compensate for defect‐induced framework distortion, thereby stabilizing Zn species at defect‐associated sites. The catalyst showed significantly improved acidity, Lewis/Bronsted acid ratio, porosity, and higher concentration of framework‐associated metal species compared to a conventionally impregnated ZSM‐5 catalyst. The catalyst with a higher concentration of framework‐associated metal species and improved porosity conferred an enhanced yield of aromatics, especially aviation fuel‐range C ₈₊ aromatics. An exceptional 60.9 C‐mole% yield of liquid hydrocarbons, equivalent to STY of 528 mgg _cat ⁻¹ h ⁻¹ , with aromatics selectivity of ∼96 C‐mole% and C ₈₊ monocyclic aromatics selectivity of ∼77C‐mole% in liquid hydrocarbons could be achieved. The catalyst showed excellent repeatability, recyclability, and stability.