(305c) Understanding the Impact of Supercritical CO2 on the Hydrocracking of Polyethylene into Liquid Alkanes over Zeolite-Based Catalysts

This study investigates the use of Ruthenium/Zeolite catalysts for the depolymerization of polyolefins using hydrogenolysis in a hydrogen and CO₂ atmosphere, addressing plastic waste challenges. The addition of CO₂ into the reaction atmosphere addresses several limitations of previous works performing hydrogenolysis of polyolefins, namely mass transfer limitations due to the high viscosity of polymer melts. The ability of CO₂ to act as a plasticizer reduces the viscosity of the melt, thus improving the mass transfer properties within the reaction media. Our experimental approach aimed to investigate the effects of hydrogen pressure, CO₂ pressure, zeolite support type, and reaction temperature. We were able to demonstrate that the addition of CO₂ into the reaction media positively affected the reaction kinetics by increasing the conversion of the plastic. Relative to H₂ only reactions, reactions with both H₂ and CO₂ had 22% higher conversion for 8hrs at 200^oC. As well, the presence of CO₂ shifted the reaction products towards lower carbon number products. H₂ and CO₂ pressures were varied from 10-40bar, for 4-16hrs, at 200-275C. H-BEA, HY, and mesoporous HY were loaded with 5% Ru and tested under the previously mentioned conditions. These findings contribute to the development of sustainable plastic waste management, offering insights for designing efficient catalyst systems to convert polyolefins into valuable chemical feedstocks.