Liquefaction of polystyrene(PS) waste plastics in supercritical ethanol and reaction pathway exploration

The correlation between the liquefaction efficiency of polystyrene (PS) with different process parameters was studied using an autoclave. In addition, we also analyze the reaction path of PS liquefaction based on the composition of functional groups and compounds in the liquefied oil. The results showed that the products were dominated by 2–4 cyclic benzenes. PS favored liquefaction to oil at mild temperatures, long residence times, and low solid-to-liquid ratios, with the highest liquefaction efficiency (63.86%) when liquefied at 340 °C for 90 min at a 10% solid-to-liquid ratio. The 1 H NMR spectrum found that 6.0–8.5 ppm is the main resonance peak of chemical shift, indicating that the liquefied oil contains a large amount of aromatic/hetero-aromatic ring functional group-like compounds. The GC-MS analysis results were consistent with the 1 H NMR results. The highest content of compounds in the liquefied oil were benzene derivatives. TG and DTG analysis showed that the pyrolysis of liquefied oil was divided into two stages: light oil and heavy oil, and the boiling range was 60 °C ∼ 400 °C. Analyzed by carbon chain length, the percentage of C1∼C22 in the oil can reach up to 86.51%. Therefore, PS liquefied oil has the potential as a liquid fuel.