Polyethylene upcycling to aromatics by pulse pressurized catalytic pyrolysis

To address the challenging issues of waste plastic pollution and petroleum shortage, we report herein a pulse pressurized catalytic pyrolysis process where polyethylene is continuously converted into aromatics using HZSM-5 catalyst incorporated with hydrated SiO₂. Pressurization improves the activity of single-pulse pyrolysis of polyethylene by 14.42%. In contrast to the linear decrease of BTEXS relative yield with a K value of - 0.23 under non-pressurized conditions, pressurization results in a notable stability in the latter stage, characterized by a K value of only - 0.063. Comprehensive catalyst characterization demonstrates that pressurization promotes the release of water from hydrated SiO₂, enabling HZSM-5 to effectively undergo dealumination and obtain suitable acidity and pore structure, and ultimately enhancing the resistance to carbon deposition. In summary, pressurization improves both pyrolysis activity and catalysis stability, offering a promising strategy for the high-value utilization of waste plastics.