Fuel oil recovery from waste polybutylene plastic using microwave-assisted pyrolysis

Microwave-assisted pyrolysis of plastics has emerged as a promising technology for sustainable oil recovery, while also addressing environmental pollution. In this study, the microwave-assisted pyrolysis of waste polybutylene was investigated for the first time, focusing on the recovery of fuel oil. The effects of polybutylene size (0 - 2, 2 - 4, 4 - 6, 6 - 8, and 8 - 10 mm), microwave power (500, 550, 600, 650, and 700 W), and pyrolysis temperature (420, 440, 460, 480, and 500 °C) on products distribution, oil composition, and higher heating value (HHV) of the pyrolysis oil were detailed. The results revealed that increasing polybutylene size, microwave power, and pyrolysis temperature initially promoted an increase in oil yield, followed by a subsequent decline. The oil yield was in the range of 58.6–87.1 wt.%, with a HHV range of 44.93–47.07 MJ/kg. The maximum oil yield was achieved at a polybutylene size of 4–6 mm, microwave power of 600 W, and pyrolysis temperature of 480°C, with the corresponding oil exhibiting a HHV of 46.59 MJ/kg. The oil was dominated by alkane (12.52–27.68 area%), alkene (26.01–51.18 area%), alkyne (0.17–2.49 area%), cycloalkane (25.79–51.15 area%), cycloalkene (1.08–6.22 area%), and the carbon numbers mainly distributed in C5-C18 (65.39–80.79 area%). This study provided valuable insights and supporting data for the efficient recovery and sustainable utilization of waste polybutylene via microwave-assisted pyrolysis.