Insights into structure–performance relationship in the catalytic cracking of high density polyethylene

Zeolite is considered a promising catalyst for plastic cracking because of its well-defined acid sites, high product selectivity, and outstanding stability. The relationship between zeolite structure and catalytic performance is still not well understood. Therefore, on either as prepared or purposely modified ZSM-5 zeolites, we made a systematic investigation of how acid density and pore structure affect catalytic performance in this work. Our results demonstrate that Brønsted acid site density had profound impact on the catalyst lifetime and aromatic selectivity. The relationship between Brønsted acid site density and catalyst lifetime displays a tendency that catalyst lifetime declines with acid site density at the beginning, then rises up, instead of a linear correlation. Also, the increase of mesoporosity extends the catalyst lifetime to some extent. This information can give us a better understanding of how to design higher-performance catalysts for chemical upcycling of waste plastics.