Chitosan-Templated Synthesis of Anticoking Hierarchical Zeolite for Enhanced Monoaromatics Production in Biomass and Plastics Copyrolysis

Catalytic copyrolysis of biomass and plastics offers a significant pathway for upcycling solid waste into high-value chemicals. However, traditional HZSM-5 zeolites suffer from rapid deactivation due to mismatched pore architectures that trap bulky intermediates and promote excessive coke formation. This study introduces an innovative and eco-friendly synthesis approach that employed chitosan as a multifunctional green template for in situ secondary MFI growth during the alkaline treatment of HZSM-5, yielding hierarchical zeolites with balanced micromesoporous structures and tunable acid site distributions. A comprehensive parametric optimization was undertaken to evaluate various factors including chitosan loadings, temperatures, feedstock-to-catalyst ratios, atmospheres, and different biomass/plastic combinations. The optimized catalyst, featuring a 25% chitosan loading (designated as 0.25C@A-HZ ), demonstrated exceptional performance in the catalytic copyrolysis of corn stover and high-density polyethylene in a 1:1 ratio at 550 °C under a nitrogen atmosphere, achieving a monoaromatic hydrocarbons content of 94.5% while reducing coke deposition by approximately 45% compared to pristine HZSM-5. This superior efficacy was attributed to improved mass transfer of bulky intermediates within the hierarchical pores and synergistic hydrogen transfer, promoting deoxygenation and Diels–Alder aromatization while inhibiting polymerization pathways. Furthermore, this synergy alleviated micropore blockage and mitigated strong acid site deactivation, favoring the accumulation of softer, less oxygenated coke species. These findings contribute to the advancement of anticoking zeolite design for the valorization of waste into high-value chemicals.