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

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 supported on carbon (Ru/C). Reactivity studies on a model n-octadecane substrate showed that Ru/C catalysts are highly active and selective for the hydrogenolysis of C(sp(3))-C(sp(3)) bonds at temperatures ranging from 200 to 250 degrees C. Under optimal conditions of 200 degrees C in 20 bar H-2, polyethylene (average M-w similar to 4000 Da) was converted into liquid n-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 (C-1-C-6). At 250 degrees C, nearly stoichiometric yields of CH4 were obtained from polyethylene over the catalyst. The hydrogenolysis of long chain, low-density polyethylene (LDPE) and a postconsumer LDPE plastic bottle to produce C-7-C-45 alkanes was also achieved over Ru/C, demonstrating the feasibility of this reaction for the valorization of realistic postconsumer plastic waste. By identifying Ru-based catalysts as a class of active materials for the hydrogenolysis of polyethylene, this study elucidates promising avenues for the valorization of plastic waste under mild conditions.

Automated summary

Chemical upcycling of waste polyolefins via hydrogenolysis using Ru/C catalysts demonstrates high activity and selectivity in the conversion of polyethylene into liquid alkanes and light alkane gases under mild conditions. The study also shows the feasibility of producing C-7-C-45 alkanes from long chain, low-density polyethylene and postconsumer LDPE plastic bottles, providing promising pathways for plastic waste valorization using Ru-based catalysts.