As the only carbon-containing and abundant renewable resource, biomass provides a sustainable route for the production of fuels and chemicals. The catalytic conversion of biomass pyrolysis volatiles into chemicals, such as light aromatics (LAs), serves as an effective strategy for ensuring energy security and achieving “carbon neutrality” goals. Zn-modified ZSM-5 (Zn/ZSM-5) shows great potential for enhancing LAs yield during the pyrolysis process. Therefore, starting from the spent catalyst, the key factors causing catalyst deactivation are explored, so as to guide the optimization of Zn/ZSM-5 in terms of mass transfer capacity and active site regulation, with the aim of enhancing the catalytic yield while delaying the deactivation of the catalyst. By regulating the dispersion of Zn active sites within the channels, a hierarchical ZSM-5 zeolite with well-dispersed Zn species was constructed. By leveraging the synergistic advantages of acidity regulation and hierarchical pore structures, a tandem system featuring coupled acid-metal active sites was constructed using core-shell structured Zn/ZSM-5 nano-zeolites.
To address the problem of easy coking at the active sites on impregnated Zn/ZSM-5 catalysts, acidity modulation was performed on in-situ synthesized Zn-doped zeolites. In-situ doping was employed to alter the introduction method of Zn active sites. Specifically, the intrinsic acidity of the catalyst was weakened by synthesizing 0.7Zn(DS) (a Zn-doped catalyst with a SiO₂/Al₂O₃ ratio of 100) to weaken the acidity of the parent ZSM-5, while the external acidity was reconstructed by constructing a core-shell structure featuring Zn/ZSM-5 coating a high SiO₂/Al₂O₃ ratio ZSM-5 core (ZnZ5@yZ5(z)). By integrating the spatial configuration of core-shell catalysts with the mass transfer advantages of hierarchical nano-zeolites, a Zn active site-embedded zeolite with a Zn/SiO₂ core and a Nano-Z5 shell (xZnSiO₂@Z5) was designed. The LAs yield of the 1/3ZnSiO₂@Z5 catalyst reached the highest at 145.7 mg/g, with the coke deposition yield reduced to 3.9 wt.%. The synergistic regulation of active sites and pore structures enables the preservation of effective active sites and achieves excellent catalyst stability.

Biomass pyrolysis; Volatiles; Catalytic reforming; Light aromatics; Zn-modified ZSM-5