Performance comparison and sustainability assessment of mesoporous FAU zeolites for the plastic upcycling

This study investigates the influence of hierarchical modification of zeolites, synthesized via top-down (surfactant-templating via basic solution of CTAB) and bottom-up (use of organosilane, TPOAC) approaches, on the hydrocracking of linear and branched chain plastics. Unlike traditional comparisons exclusively based on catalytic performance, this study further provides an insight into the simultaneous comparison of conversion with environmental and economic benefits. Overall, top-down hierarchical zeolites (CT-HY) showed higher conversions than bottom-up modified (ST-HY) and HY zeolites for the hydrocracking of virgin HDPE and mixed post-consumer plastic waste, suggesting that improved textural properties play a dominant role for the hydrocracking of plastics. Interestingly, while conversion increases progressively with mesoporosity when branched plastics are present, a plateau in conversion is reached after a certain mesoporosity development for linear-chain plastics. However, product quality improves steadily with the increase in mesoporosity in both cases. A 27 % higher Pareto front optimisation score was obtained for the prolonged treated top-down hierarchical HY zeolite (CT-HY-2) than HY when processing mixed post-consumer plastic waste. Finally, the sustainability assessment showed the benefits of top-down hierarchically modified Y zeolites as compared to previous literature, with both zeolites showing high productivity of middle distillates (6.96–8.35 g C5-C18 g cat −1 h −1 ). Overall, the present study shows the contribution of mesoporosity in hierarchical zeolites to the upcycling of different types of plastic chains. Similarly, the demonstration of sustainability assessment helps to optimise the physiochemical properties of hierarchical zeolites and reaction conditions for improved catalytic results and provides decision makers a standardised approach when studying industrial-scale processes. • Performed the hierarchical modification of zeolites via top-down and bottom-up methods • Compared the catalytic activity for hydrocracking of virgin and post-consumer plastics • Used Pareto front optimisation-led approach to compare the activity of various zeolites • Top-down hierarchically modified zeolites showed high Pareto front optimisation score. • Sustainability assessment showed the economic and environmental benefits of CT-HY samples.