Synthesis of core–shell structured HZSM-5@silicalite-1 catalyst for production of light aromatics from catalytic pyrolysis of torrefied poplar wood

Abstract

Catalytic fast pyrolysis (CFP) of torrefied poplar wood was investigated to enhance light aromatics production using a core-shell hierarchical HZSM-5@Silicalite-1 catalyst. In this work, torrefaction deoxygenation pretreatment (TDP) significantly reduced oxygen content in poplar wood, with optimal deoxygenation achieved at 260 ºC, yielding torrefied solid product with enhanced pyrolysis reactivity. The core-shell hierarchical HZSM-5@Silicalite-1 catalyst was synthesized via epitaxial growth and characterized by BET, NH₃-TPD, SEM, and TEM, exhibited a micro-mesoporous structure that suppressed external coking and prolonged intermediate diffusion, thereby improving aromatics selectivity. CFP systematic optimization revealed that the yield of BTX (5.56 × 10⁸ a.u./mg) and total aromatics (3.15 × 10⁸ a.u./mg) were maximized with a catalyst-to-feedstock ratio of 4:1 and CFP temperature of 800 ºC, due to the intensified devolatilization, low mass transfer resistance, and efficient Brønsted acid catalysis for the deoxygenation/aromatization of pyrolysis intermediates. This study demonstrated that coupling moderate torrefaction with tailored core-shell catalysts synergistically could enhance the production of BTX, offering a viable strategy for upgrading biomass-derived biofuels.