Preparation and performance evaluation of asphalt modifier from catalytic pyrolysis of waste plastics using Ni modified HZSM-5

Pyrolysis technique can effectively convert waste plastics into high-performance asphalt modifiers, improving the asphalt pavement performance, thus achieving the resourceful utilization of waste plastics as building materials. Selecting Polypropylene (PP) and polystyrene (PS) as raw materials, pyrolysis experiments were conducted to explore their synergistic interaction. Using Thermogravimetric analysis (TGA), tube furnace, and gas chromatography-mass spectrometry (GCMS), the effects of plastics mixing ratio and Ni loading in HZSM-5 on the pyrolysis products and heavy oil composition were investigated. Based on the optimal heavy oil, the high and low temperature performance and aging resistance of the heavy oil modified asphalt were quantitatively evaluated. The results showed that the PP/PS co-pyrolysis exhibited higher conversion efficiency, with a 1:3 ratio maximizing liquid yield at 74.26 %. Ni-modified HZSM-5 effectively boosted the production of aromatic hydrocarbons in heavy oil while inhibiting the generation of phenols, acids, organosilicons and other non-hydrocarbon byproducts. The optimal Ni loading was 10 wt%, which maximized aromatic hydrocarbon content at 81.36 % within 90.6 % polycyclic aromatic hydrocarbons (PAHs), achieving the best modulation of pyrolysis heavy oil components. The addition of heavy oil significantly improved the high-temperature stability and aging resistance of asphalt, though impairing low-temperature cracking resistance. The optimal oil content was 6 wt%, making the softening point increased by 10.3°C. This advancement promoted the conversion of waste plastic heavy oil into high-performance asphalt modifiers to avoid difficult combustion, providing theoretical support and technical guidance for its high-value application in the asphalt pavement field.