Influence of temperature and reaction time on the conversion of polystyrene waste to pyrolysis liquid oil

•Polystyrene comprises 14.7% of municipal solid waste in Saudi Arabia.•The optimum temperature for pyrolysis was 450°C at 75min retention time.•At optimum conditions liquid fuel was 76% by mass of polystyrene.•The liquid fuel had a high energy value of 41.2GJ/t and density (0.92g/cm3).•The liquid fuel had low pour point (−18°C) and freezing point (−64°C). This paper aims to investigate the effect of temperature and reaction time on the yield and quality of liquid oil produced from a pyrolysis process. Polystyrene (PS) type plastic waste was used as a feedstock in a small pilot scale batch pyrolysis reactor. At 400°C with a reaction time of 75min, the gas yield was 8% by mass, the char yield was 16% by mass, while the liquid oil yield was 76% by mass. Raising the temperature to 450°C increased the gas production to 13% by mass, reduced the char production to 6.2% and increased the liquid oil yield to 80.8% by mass. The optimum temperature and reaction time was found to be 450°C and 75min. The liquid oil at optimum conditions had a dynamic viscosity of 1.77mPas, kinematic viscosity of 1.92cSt, a density of 0.92g/cm3, a pour point of −60°C, a freezing point of −64°C, a flash point of 30.2°C and a high heating value (HHV) of 41.6MJ/kg this is similar to conventional diesel. The gas chromatography with mass spectrophotometry (GC–MS) analysis showed that liquid oil contains mainly styrene (48%), toluene (26%) and ethyl-benzene (21%) compounds.