Investigation of the Synergistic Aromatization Effect During the Co-Pyrolysis of Wheat Straw and Polystyrene Modulated by an HZSM-5 Catalyst

To achieve the high-value utilization of agricultural and plastic wastes, the catalytic co-pyrolysis behavior of wheat straw (WS) and polystyrene (PS) was systematically investigated using HZSM-5 zeolite as a catalyst. The results revealed that oxygenates and aliphatic hydrocarbons derived from WS pyrolysis were efficiently converted into aromatics over the HZSM-5 catalyst, increasing the yield of monocyclic aromatic hydrocarbons (MAHs) from 7.8% to 30.3%. A significant synergistic effect was observed at a WS:PS ratio of 60:40, where the yield of BTX (benzene, toluene, and xylene) reached 41.1%, exceeding the levels achieved from the catalytic pyrolysis of either WS or PS alone. This synergy originates from the reconstruction of reaction pathways: the hydrogen-rich environment generated by PS promoted hydrodeoxygenation of biomass, which suppressed CO2 formation (−16%) and enhanced carbon atom utilization; meanwhile, HZSM-5 facilitated dealkylation and alkyl transfer reactions, leading to an increase in benzene production (+12%). Moreover, elevating the catalytic temperature helped to inhibit the formation of polycyclic aromatic hydrocarbons (PAHs) and further increased the MAH yield. These findings provide a valuable reference and experimental basis for the synergistic conversion of waste materials into high-value-added aromatics.