SEMINAR

Polyolefins, including polyethylene (PE) and polypropylene (PP), are among the most common single-use plastics consumed worldwide, and are also among the most pervasive in landfills and the environment. In this presentation I will show two avenues for the chemical recycling of polyolefin waste into hydrocarbons that involve the selective cleavage of C-C bonds in the plastic backbone. Our initial studies identified Ru-based catalysts as highly active for the hydrogenolysis of C-C bonds in PE and PP under relatively mild conditions (200-250ºC, 20-40 bar H₂, 2-16 h). Despite their high activity, one of the remaining challenges with Ru-catalyzed hydrogenolysis over supports such as carbon is the production of methane, resulting from cleavage of terminal C-C bonds. First, I’ll show that supporting Ru nanoparticles on a Brønsted-acidic support improves selectivity by promoting a bifunctional acid/metal-catalyzed hydrocracking mechanism that suppresses methane formation. Operando EXAFS with model polyolefin hydrogenolysis revealed that the support affects the reducibility of the nanoparticles. Next, we used this mechanistic insight to encapsulate cobalt nanoparticles in different zeolite topologies, ultimately showing that a 5 wt% Co-ZSM catalysts converts PE and PP into mainly C3 and C4 hydrocarbons with a selectivity >80 % under mild conditions.