Supercritical catalytic cracking of n-decane over microwave-synthesized hierarchical core–shell nano-Beta@SBA-15 composite zeolite

Abstract

Catalytic cracking of endothermic hydrocarbon fuels offers a promising regenerative cooling strategy for hypersonic propulsion systems, yet conventional microporous zeolite catalysts suffer from severe diffusion limitations and rapid coke deposition under supercritical conditions. This study develops a hierarchical core–shell Beta@SBA-15 composite zeolite via a microwave synthesis method, integrating microporous nano zeolite Beta as the catalytic core with ordered mesoporous SBA-15 as the transport shell. Comprehensive characterization confirms the core–shell structure and the intimate integration of both components. Such core–shell catalyst exhibits 14.9% higher acidity-normalized activity than nano zeolite Beta. Its exceptional enhanced stability and reduced coke formation were also demonstrated, with only 25.39% conversion loss over 15 hour time-on-stream tests compared to 47.45% for nano zeolite Beta, while substantially reducing coke deposition from 6.3% to 3.8%. These results are attributed to the core–shell structure, where the mesoporous shell improves active site accessibility, facilitates rapid product and coke precursor removal, and effectively mitigates diffusion limitations in catalytic processes. These findings reveal the structure–performance correlation of microporous core-ordered mesoporous shell zeolite catalysts, offering insights for hydrocarbon conversion under extreme conditions.