The Polymer Society of Korea

Abstract

The chemical recycling of waste tires remains challenging due to the robustness of vulcanized, multi-component rubber networks and their high filler content. We demonstrate that cooperative Pd-Ru isomerization-metathesis (ISOMET) catalysis selectively depolymerizes waste tires into well-defined C5-C6 cycloalkenes under mild conditions. Eight tires from major manufacturers were divided into representative sections to correlate composition with reactivity, showing that sidewalls exhibit the highest depolymerization efficiency. ISOMET promotes cross-metathesis between rubber components, leading to the formation of 1-methylcyclopentene, a product inaccessible from single-polymer systems. Alkene isomerization controls double-bond spacing, favoring low-strain cyclic products. Alcoholysis pretreatment enhances catalyst accessibility and increases yields to 48 wt%. This work establishes ISOMET as a selective platform for upcycling vulcanized waste tires into valuable molecular feedstocks.