Direct upcycling of mixed plastic waste into liquid alkanes

Abstract

Direct upcycling of waste mixed plastics into single-purpose, value-added products is a highly desirable goal. However, the significant variations in the physical and chemical properties of different plastics, as well as the mutual poisoning effects between components, may hinder the activation and cleavage of various chemical bonds within mixed plastics under mild conditions. Here, we report for the first time the direct hydrogenolysis of mixed plastics comprising polyolefins and oxygen-containing plastics into liquid alkanes under solvent-free conditions at 250 °C on Ru/CeO2 + Re/CeO2 blend catalysts. The mixed plastics require no pretreatment, and the resulting liquid alkanes can be used as transportation fuel without the need for complex separation processes. This eliminates the challenge of separating different product types during the process. Compared to conventional Ru catalysts, the unique performance of the Ru/CeO2 + Re/CeO2 arises from its effective elimination of poisoning effects by oxygen-containing species and its significantly enhanced ability to cleave C-C and C-O bonds. Overall, unlike conventional single-plastic conversion pathways, this process offers a sustainable and cost-effective solution for the direct recycling of mixed plastic waste, thereby providing a viable approach for advancing a circular plastics economy.