Suppressing Hydrogen Transfer and Aromatization Reactions Enables Efficient Photothermal Recycling of Polyethylene into Platform Olefins

The recycling of polyethylene (PE) into highly selective platform olefins holds great promise as a potential closed-loop recycling route that minimizes dependence on the petrochemical industries, whereas the selectivity of olefins is mainly limited by two side reactions: hydrogen transfer and aromatization. Herein, we present a photothermal recycling pathway that effectively converts various types of PE into highly selective olefins using ZnCrO_x/HZSM-5 composite catalyst, with efficaciously suppressing both side reactions. The inclusion of ZnCrO_x modifies catalyst acidity to inhibit the hydrogen transfer reaction, while jointly establishing an intra-catalyst spatial temperature gradient through distinct photothermal responses between ZnCrO_x and HZSM-5 whereby the endothermic aromatization can be suppressed. This strategy achieves an impressive selectivity of 75.4% for C₂-C₅ hydrocarbons, with 84.7% of them being C₂-C₅ olefins, in the photothermal recycling of low-density PE (LDPE) under atmospheric pressure using Xe lamp irradiation. Further, the demonstrated universality across various PE feedstocks (e.g., high-density PE and commercial LDPE bags) and concentrated sunlight operation highlights a solar-powered plastic-to-olefin platform with industrial viability.