Microwave-assisted pyrolysis of polypropylene plastic for liquid oil production

Abstract

Polypropylene (PP) is one of the most common polymers used in various plastic materials, and its degradation plays a significant role in sustainable environmental development. The objective of this study was to enhance the yield and quality of liquid oil derived from polypropylene plastics through microwave-assisted pyrolysis. The effects of pyrolysis temperature, microwave power, and PP loading on oil products were experimentally analyzed. The results revealed that increasing the pyrolysis temperature from 350 °C to 550 °C led to a rise in the yield of liquid oil from 0.027 to 0.793 g/g and then decreased to 0.657 g/g. With the increase in microwave power from 400 W to 800 W, the oil yield increased from 0.65 to 0.793 g/g and then dropped to 0.22 g/g. Furthermore, increasing the amount of PP from 20 g to 40 g resulted in an increase in oil yield from 0.345 to 0.793 g/g and then decreased to 0.713 g/g. An optimal oil yield was 0.793 g/g when the microwave power, pyrolysis temperature, and PP loading were 500 W, 450 °C, and 30 g respectively, and the oil was rich in cyclanes, alkenes and alkanes (about 97–99.6 area%). Additionally, the liquid oil primarily ranged from C8 to C15 (90.1 area%), indicating that microwave-assisted pyrolysis of polypropylene plastics raises the selectivity of small molecular products.