Chitosan-assisted reassembled hierarchical HZSM-5 for selective production of monocyclic aromatics in catalytic co-pyrolysis of biomass and plastic

Biomass presents significant potential as an alternative template agent for assisting zeolites in developing new pore structure during recrystallization to enhance their catalytic performance. In this study, a new hierarchical HZSM-5 was synthesized through the in-situ reassembly of alkali-treated HZSM-5 with chitosan as an assisting agent. The impact of chitosan dosage on the catalytic performance of the hierarchical HZSM-5, as well as the influences of temperature, catalyst dosage, and corn stover (CS) to high-density polyethylene (HDPE) mass ratio on the content and selectivity of monocyclic aromatic hydrocarbons (MAHs) during the catalytic co-pyrolysis process, were thoroughly investigated. The results indicated that chitosan exhibited great potential as a template in the reassembly of hierarchical HZSM-5 during NaOH treatment, promoting the formation of weak acid sites and micro-mesoporous structures. Compared to the parent HZSM-5, the chitosan-assistant reassembled hierarchical HZSM-5 significantly enhanced the production of MAHs and inhibited the formation of polycyclic aromatic hydrocarbons (PAHs). The highest carbon yield of MAHs reached 36.9 % at 550 °C with a chitosan dosage of 15 %. Furthermore, the chitosan-modified HZSM-5 notably enhanced the synergistic production of MAHs by 38.2 %, while preventing the formation of PAHs and coke. This study contributes insights into the sustainable synthesis of hierarchical HZSM-5 for improved production of high-value products in the co-pyrolysis of biomass and waste plastics.