Low-temperature diesel-induced depolymerization of waste polyethylene

Abstract

Plastic waste poses a significant threat to the environment due to its slow degradation and low recyclability. In recent years, thermochemical and biological processes for turning plastic waste into useful fuel and chemicals have been developed, but multiple processing steps and susceptibility to contaminants have so far prevented their widespread deployment. This study reports the diesel-induced depolymerization process for low density polythene (LDPE) at a low temperature to produce easily separable liquid and solid products. The produced liquid stream can be utilized as an alternative fuel, due to its chemical compatibility with diesel. The LDPE was dissolved in diesel at a range of temperatures (80–165 °C), reaction times (0.5–10 h), and ratios of LDPE to diesel under inert atmosphere. It was found that the LDPE/diesel weight ratio was the most significant process variable, with up to 95 wt% of the LDPE being converted into liquid phase and blended with the diesel fuel. The temperature at which the dissolution took place also played a role in the LDPE conversion; a higher temperature led to a greater degree of LDPE dissolution. The solubility of LDPE was not significantly affected by the reaction time. The dissolution of LDPE in diesel fuel led to a rise in the kinematic as well as the dynamic viscosity. The resulting liquid diesel/LDPE mixture also exhibited an increased high heating value (HHV). The measured HHV was 45.2439 MJ/kg for pure diesel, 45.5247 MJ/kg for diesel mixed with LDPE at 135 °C, and 45.9247 MJ/kg for diesel mixed with LDPE at 165 °C.