Hierarchical porous hollow HZSM-5 catalyst for waste plastic upcycling to aromatics oil via synergistic optimization of pore structure and acidic sites

During plastic catalytic pyrolysis, HZSM-5 faces challenges such as limited mass transfer and low active site utilization, resulting in poor aromatization and anti-deactivation performance. To address these challenges, a hollow HZSM-5 catalyst with a hierarchical micro- meso -macroporous structure was designed in this work. The structure–activity relationship of hollow HZSM-5 was then systematically explored, focusing on the influence of pore structure and acidic sites on catalytic performance. The hollow HZSM-5 catalyst without metal loading exhibited outstanding catalytic performance in the catalytic pyrolysis of plastics, with high selectivity of 95.79% for aromatic hydrocarbons (AHs) and 83.08% for monocyclic aromatic hydrocarbons (MAHs). More importantly, hollow HZSM-5 delivered outstanding stability with an initial performance retention of 95.75% after five cycles and achieved selectivity of AHs exceeding 86% for various polyolefin plastics. The excellent catalytic performance was attributed to the synergistic optimization of pore structure and acidic sites. On the one hand, the hierarchical porous structure significantly enhanced mass transfer, thereby improving the anti-deactivation performance and active site utilization of the catalyst. On the other hand, acidity enhanced by desilication efficiently promoted the aromatization of plastics. This work highlighted the importance of rational catalyst design in achieving efficient and stable catalytic pyrolysis of plastics toward valuable chemical products.