Pore-Structure\nEngineering of Hierarchical β\nZeolites for the Enhanced Hydrocracking of Waste Plastics to Liquid\nFuels

Hydrocracking of plastics over bifunctional hierarchical\nzeolites\nis promising for the upcycling of plastics into value-added products.\nHowever, the exact role of their acidic and textural properties toward\nthe catalytic activity remains unclear. Herein, we modified the structure\nof a β zeolite via dealumination and desilication routes, resulting\nin hierarchical zeolites. The parent and hierarchical modified β\nzeolite samples were loaded with Ni and studied for the hydrocracking\nof virgin HDPE. In comparison to the parent and dealuminated β\nzeolite, desilicated β zeolite showed a higher conversion of\n87.8% with 66.7% of the products in the gasoline range, owing to its\nsignificantly high textural properties. The conversion and selectivity\nof gasoline-range hydrocarbons over the desilicated zeolite were further\nimproved to 95.9 and 69.2%, respectively, by Ni addition. To unlock\nthe structure–activity correlation of the various zeolite samples,\nthe role of different activity-driven factors was studied, resulting\nin an empirical relationship that aligns with the observed conversions\nover different zeolite samples. Moreover, it was observed that it\nis possible to achieve high selectivity of iso-paraffins in gasoline-range\nhydrocarbons via the optimization of the balance between metal-acid\nsites on bifunctional hierarchical zeolites. Furthermore, both Ni-loaded\nhierarchical β zeolites showed good stability and the ability\nto be regenerated under cyclic runs. The best-performing Ni-loaded\ndesilicated β zeolite was also maintained over various postconsumer\nwaste plastics (conversion = 85–95%) and when using a mixture\nof postconsumer waste plastics (88.4%). A life cycle assessment and\na comparison with the recent literature also demonstrated the advantages\nof the proposed hierarchical modification routes in achieving high\ngasoline productivity (6.6–7.6 g<sub>gasoline</sub>/g<sub>cat</sub>·h) and less environmental impact. Overall, these findings highlight\nthe role of improved textural properties of noble-metal-free, easily\nmodifiable, and environmentally friendly bifunctional hierarchical\nβ zeolites for the enhanced conversion of waste plastics into\nliquid fuels.