Thermocatalytic conversion of polyethylene in molten salts as a route for the valorization of plastic waste

The accumulation of single-use polyethylene waste presents a major challenge to the recovery of value from end- of-life plastic. Herein, we demonstrate a molten salt-assisted thermocatalytic process using ZnCl2 for the upcycling of high-density polyethylene (HDPE) into value-added hydrocarbons and carbonaceous products under relatively mild conditions (reaction temperature of 400◦C). The molten ZnCl2 serves as both a heat transfer medium and a Lewis acid catalyst, enabling efficient depolymerization and product selectivity control. While negligible polymer conversion was measured in conventional pyrolysis at 400◦C, when the process was performed in a stirred batch reactor in the presence of molten ZnCl2, HDPE was converted to liquid hydrocarbons in the range C6-C20 with 40% w/w yield, a carbonaceous solid residue having H/C 0.45 with 27% w/w yield, and a gas phase composed of H2 and volatile hydrocarbons with 33% w/w yield, with no evidence of wax formation. This study highlights the potential of molten ZnCl2 as process medium for the valorization of plastic waste.