Dehydrocracking of n‐Octane to Light Olefins Over Sn‐Containing HZSM‐5 Composite Zeolite

Achieving a high propylene‐to‐ethylene ratio alongside an increased yield of light olefins constitutes a primary challenge in the catalytic cracking process for light olefin production. Herein, a Sn‐containing HZSM‐5 composite zeolite catalyst was constructed via secondary hydrothermal treatment, and the structure–performance relationship in the catalytic cracking of n‐octane was systematically investigated. Through atom‐planting, Sn is introduced onto zeolite supports, where it interacts with silanol nests and is incorporated into the zeolite framework in a tetrahedrally coordinated manner (Sn(IV)), thereby generating strong Lewis acid sites (LAS). These strong LAS substantially promote the dehydrocracking of n‐octane and increase the contribution of bimolecular cracking pathways, which consequently facilitates formation of propylene. Notably, the secondary hydrothermal treatment induces crystallization of new HZSM‐5 zeolite onto the Sn‐containing HZSM‐5, thereby introducing additional Brønsted acid sites (BAS) into the catalyst. The resulting Sn‐containing HZSM‐5 composite zeolite enables synergistic BAS–LAS catalysis in the dehydrocracking of n‐octane, substantially boosting the production of ethylene and propylene.