Plastic waste has grown at a dramatical rate over recent years, resulting in an emerging global environmental issue of white pollution. However, it also represents a potential and untapped resource for its rich carbon and hydrogen content. This work converts plastic waste into high quality oil by employing supercritical methanol. Polypropylene (PP) was liquefied at the temperature range of 330~400 °C and reacting time of 0~70 min to evaluate the effect of temperature and time on liquefaction. The results show that both increasing temperature and reaction time could promote the PP conversion, thus increasing oil yield. Among parameters tested, conversion rate could achieve as high as 95.2% at 400 °C for 70 min. The oil composition was investigated by GC-MS, exhibiting that the compounds mainly include hydrocarbons and oxygenates. Reaction time leads a slight difference in the oil composition while temperature leads more significant variation. 72.83% and 71.55% of hydrocarbon in oil were obtained at 400 °C for 60 min and at 370 °C, respectively. With temperature and time increasing, long chains were further cracked into short chains and the carbon distribution became more concentrated. These results implied that supercritical methanol could work well as a solvent to liquefy plastic into high quality oil, which provides a feasible way to solve the plastic pollution problem.

Plastic waste;supercritical methanol;Polypropylene;hydrocarbons