Oil recovery from microwave co-pyrolysis of polystyrene and polypropylene plastic particles for pollution mitigation

Addressing the mounting environmental challenge of non-degradable polymeric waste, the world grapples with escalating production driven by population growth, modernization, and industrialization. Pyrolysis has emerged as a promising and strategic solution for transforming non-degradable polymeric waste into valuable fuels and other chemical products. This study detailed the high-quality oil recovery from microwave co-pyrolysis of polystyrene (PS) and polypropylene (PP) mixtures. The effects of PS/PP ratio (30:0, 10:20, 15:15, 20:10, and 30:0 g), microwave power (400, 500, 600, 700, and 800 W), and pyrolysis temperature (450, 500, 550, 600, and 650 °C) on oil yield and components were studied, and the synergistic effect, higher heating value (HHV) and thermal efficiency were also detailed. The results revealed that the highest oil yield was 93.84 wt% when PS/PP ratio, microwave power, and pyrolysis temperature were adjusted at 20:10 g, 600 W, and 550 °C, respectively. And the maximum higher heating value and thermal efficiency were 45.67 MJ/kg and 56.53%, respectively. The contents of aromatic hydrocarbons, cyclic hydrocarbons, and oxygenated hydrocarbons varied in the ranges of 1.92-58.88 area%, 10.47-41.76 area%, and 5.06-24.36 area%, respectively. The contents of the major carbon numbers were C₈ and C₉, and they varied in 2.51-43.66 area% and 7.31-20.09 area%, respectively. The results presented in this study showed that high-quality oil can be recovered from polystyrene and polypropylene plastics by using microwave irradiation, contributing to cleaner ways for plastics recycling.