Rational design of Core-Shell ZSM-5@Beta zeolite for selective production of C8–C15 aromatics toward sustainable aviation fuel precursors

Abstract

Zeolite catalysis plays a crucial role in the synthesis of sustainable aviation fuel (SAF). Currently, the conversion of biomass into jet fuel components faces dual challenges: a broad carbon number distribution of products and rapid catalyst deactivation. Conventional ZSM-5, limited by its single pore structure and non-uniform acid site distribution, struggles to balance reaction activity and stability. To address this, this study proposes three strategies for the synergistic modulation of structure and acidity, achieving multi-level structural optimization of ZSM-5 through hydrothermal recrystallization, citric acid modification, and Beta zeolite coating. Recrystallization promotes the migration of framework aluminum and enhances crystallinity, optimizing the Brønsted/Lewis acid ratio. Moderate citric acid modification enables surface dealumination and acid site reconstruction, expanding the pore structure and improving diffusion performance. Coating with a Beta shell via a sol–gel method constructs a core–shell system with hierarchical pores and gradient acidity. In the alkylation of benzene with olefins to produce C8–C15 aromatics, all three types of catalysts exhibited excellent performance. Specifically, N-ZSM-5_RC36h, N-ZSM-5(2.0 M), and Z5@B3 achieved benzene conversions of 43.6%, 40.3%, and 45.0%, and C8–C15 aromatic selectivities of 86.4%, 85.3%, and 91.0%, respectively. The results demonstrate that precise regulation of the Brønsted/Lewis acid ratio, combined with the synergistic effect of hierarchical pore structures, significantly enhances both reaction activity and product selectivity. This study highlights the critical role of multi-level structural control in optimizing acid site matching and mass transfer, providing new catalyst design insights for the targeted synthesis of efficient SAF precursors.