Catalytic Pyrolysis of LDPE over Low-Cost Metal-Modified ZSM-5 Zeolites: Performance and Product Distribution
Plastic pollution poses a global environmental challenge, and developing efficient, low-cost pyrolysis catalysts is crucial for resource recovery from plastic waste. This study investigates ex-situ catalytic pyrolysis of low-density polyethylene (LDPE) over ZSM-5 (Si/Al = 25) modified with Zn and Fe at loadings of 5% and 10% via impregnation. Catalysts were characterized by XRD, FT-IR, XPS, SEM, TEM, and BET. TGA was used to assess thermal behavior, and catalytic pyrolysis experiments were conducted in a tube furnace at 450 °C, with product analysis by GC-MS. Results show that metal incorporation preserved the ZSM-5 framework while modifying acid site distribution and surface morphology, enhancing cracking and dehydrogenation. All modified catalysts increased light gasoline-range hydrocarbon yield and reduced heavy fractions compared to non-catalytic runs. Among them, 10% Zn/ZSM-5 exhibited the best performance, boosting light gasoline hydrocarbons to 74.77%, approximately three times that of the non-catalytic case, significantly improving oil quality. This study demonstrates the potential of low-cost metal-modified zeolites for efficient and economical plastic waste pyrolysis.