Compressed CO ₂ -Assisted Catalytic Hydrocracking of Polyethylene over Ru-Loaded Zeolites

Although several chemical processes have been developed to convert waste polyolefins, their long carbon chain and high viscosity when molten result in transport-limiting kinetics. In this work, the potential of compressed CO2 as a reaction medium was evaluated for the catalytic hydrocracking of polyethylene (PE) into hydrocarbon fuels using Ru-loaded zeolites. The results showed that the addition of compressed CO2 (3 MPa H2 + P CO2 = 6 MPa) to the catalytic hydrocracking of PE led to a relative increase of 27% and 64% in PE conversion and liquid product yield, respectively, compared to the H2-only control reaction (3 MPa H2 pressure) using a 5 wt % Ru/H-β catalyst at 200 °C for 4 h. Similar trends were observed with a 5 wt % Ru/H-Y catalyst. However, the presence of compressed CO2 did not enhance the hydrocracking performance when a less viscous substrate (i.e., n-hexadecane), relative to the PE melt, was used at 200 °C for 1 h with 5 wt % Ru/H-Y. These results demonstrate the potential of compressed CO2 as a reaction medium to enhance the chemical transformation (e.g., hydrocracking and hydrogenolysis) of highly viscous molten plastic wastes.