Mesostructured bimetallic MFI zeolite for efficient aromatization of light naphtha to BTX aromatics

Diffusion limitations in microporous ZSM-5 zeolites hinder the efficient aromatization of light naphtha into valuable BTX (benzene, toluene, xylenes). In this work, we report the development of a mesostructured bimetallic catalyst through controlled alkaline desilication of ZSM-5 (Z5), followed by the incorporation of 2 wt% La and 1 wt% Zn via wet impregnation. The desilicated zeolite (Z5-AT) exhibited enhanced mesoporosity, improving molecular diffusion and boosting BTX yield from 24 wt% (Z5) to 49 wt%. Further metal modification significantly enhanced performance, with the optimized 2%La-1%Zn/Z5-AT catalyst achieving a BTX yield of 72.7 wt% at 550 °C in a fixed-bed down-flow reactor. Zn incorporation enhances the Lewis-to-Brønsted acid site (L/B) ratio, which accelerates dehydrogenation activity and promotes higher BTX formation. Textural and acidity characterizations confirmed uniform metal dispersion, improved surface area, and a favorable increase in L/B ratio. In-situ pyridine-FTIR and NH₃-TPD analyses revealed synergistic effects between La and Zn, promoting dehydrogenation, acidity tuning, and coke suppression. These results demonstrate the effectiveness of mesostructured bimetallic ZSM-5 in enhancing light naphtha aromatization, with high aromatic selectivity and improved stability.