Chemical Recycling of Post-Consumer Polystyrene by Thermal Pyrolysis: High-Yield Recovery of Aromatic Hydrocarbons for Circular Plastic Economy

This study evaluates the non-catalytic thermal pyrolysis of post-consumer polystyrene (PS) in a laboratory-scale batch fixed-bed reactor to recover aromatic-rich liquid products. The PS feedstock was characterized by thermogravimetric analysis (TGA) and micro-Raman spectroscopy to assess its thermal behavior and chemical homogeneity. In addition, the main TGA degradation region was analyzed using Coats–Redfern, Horowitz–Metzger, and Broido kinetic models, yielding apparent activation energies of 269.18, 288.83, and 280.69 kJ mol−1, respectively. Pyrolysis experiments were performed at final temperatures of 400, 450, and 500 °C and heating rates of 10 and 20 °C min−1 under continuous N2 flow. The maximum liquid yield reached 95.2wt% at 500 °C and 20 °C min−1, while the estimated gaseous fraction decreased to approximately 2.0wt%. ANOVA confirmed that final temperature was the dominant factor controlling liquid recovery, contributing approximately 83% of the model variability, whereas heating rate had a secondary but significant effect. GC–MS analysis showed that the pyrolysis oil was mainly composed of aromatic hydrocarbons, including styrene, toluene, and ethylbenzene, with increasing temperature promoting the redistribution of the liquid fraction toward lighter monoaromatic compounds. These results indicate that non-catalytic fixed-bed pyrolysis is a promising route for converting post-consumer PS into aromatic-rich liquid products. However, the recovered oil should be considered a complex mixture rather than a purified monomer stream, and further gas-phase characterization, downstream purification, energy-balance evaluation, life-cycle assessment, and techno-economic analysis are required before definitive claims regarding industrial circularity or environmental performance can be established.