Conversion of Polyolefin Waste to Liquid Alkanes with Ru-Based Catalysts under Mild Conditions

<p>Chemical upcycling of waste polyolefins via hydrogenolysis offers unique opportunities for selective depolymerization compared to high temperature thermal deconstruction. Here, we demonstrate the hydrogenolysis of polyethylene into liquid alkanes under mild conditions using ruthenium nanoparticles sup-ported on carbon (Ru/C). Reactivity studies on a model <i>n</i>-octadecane substrate showed that Ru/C catalysts are highly active and se-lective for the hydrogenolysis of C(sp³)-C(sp³) bonds at temperatures ranging from 200-250°C. Under optimal conditions of 200°C in 20 bar H2, polyethylene (average Mw ~4,000) was converted into liquid <i>n</i>-alkanes with yields of up to 45% by mass after 16 h using a 5 wt% Ru/C catalyst, with the remaining products comprising light alkane gases (C1-C6). At 250°C, nearly stoichiometric yields of CH4 were obtained from polyethylene over the catalyst. The hy-drogenolysis of long chain, low-density polyethylene (LDPE) and a post-consumer LDPE plastic bottle to produce C7-C45 alkanes was also achieved over Ru/C, demonstrating the feasibility of this reac-tion for the valorization of realistic post-consumer plastic waste. By identifying Ru-based catalysts as a class of active materials for the hydrogenolysis of polyethene, this study opens new avenues for the valorization of plastic waste under mild conditions.<br></p>