Design of hollow sphere MCM-22 zeolite with minimal extraframework Al and its enhanced aromatization and regeneration capability

초록

Hollow sphere-type thin MCM-22 zeolite catalysts were developed for enhanced regeneration capability and performance in aromatization reactions. The MWW-type MCM-22 zeolite, known for its distinctive leaf-like structures, was deemed suitable for preparing a hierarchical zeolite catalyst through a templating method. Silica-coated carbon sphere (CS-Si) was used for anchoring zeolitic seeds on it during hydrothermal synthesis. By doing so, the hollow sphere-type morphology of MCM-22 (HS-CAT) seemed more stable and robust than that in our previous study. More interestingly, extraframework or octahedral aluminum species were barely detected, with almost Al was found as tetrahedral aluminum closely related to Brønsted acid sites, as in the case of HS-CAT. To test the catalytic performance and regeneration capability, an aromatization reaction of acetylene experiencing severe coke formation was selected. Thermogravimetric analysis revealed that the coke removal rate of the regenerated HS-CAT was found higher than that of the conventional MCM-22. The improved regeneration features of this catalyst could be attributed to the significantly reduced mass transfer resistance of the hollow and hierarchically porous particles having very thin diffusion length. Considering the performance and the regeneration, important Brønsted acid sites in tetrahedral sites were also identified and quantified in the HS-CAT catalysts. © 2025 The Korean Society of Industrial and Engineering Chemistry.

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