Effect of polyethylene terephthalate on the catalytic pyrolysis of polystyrene: Investigation of the liquid products

• PS was pyrolyzed with the effect of polyethylene PET using 20% Al-Al₂O₃ catalyst.
• Significant interactions between PS and PET were noted.
• Increasing the composition of PET reduced the yield of liquid products.
• Single ring aromatic hydrocarbons were dominant products.
• Compounds such as styrene, biphenyls and oxygenated compounds were formed.

Safe and environmentally benign treatment and disposal of waste plastics are growing challenges of our society. In this paper, the influence and reactivity of polyethylene terephthalate (PET) on the pyrolysis of polystyrene (PS) is reported. The experiments were performed in a quartz glass reactor to determine the effects of temperature (250–500 °C), reaction time (20–90 min), and feed to catalyst ratio (1:0–1:0.3) using 20% Al-Al₂O₃ catalyst. PS pyrolyzed at a lower temperature than thermogravimetric (TG) pyrolysis in the presence of catalysts. Significant interactions between the polymers were noted based on the composition of liquid product. Increasing the composition of PET reduced the liquid products formed. Many useful compounds such as benzene, styrene, α-methylstyrene, indene, biphenyl, naphthalene, naphthalene derivatives and terphenyls etc. and some oxygenated compounds such as 2-pentanone, 4-hydroxy-4-methyl, acetophenone, 2-buten-1-one, 1-phenyl and 1,2-propanediol, 3-benzyloxy-1,2-diacetyl etc. were identified. Single ring aromatic hydrocarbons (C6–C9 fraction) particularly that of styrene monomer, were dominant products.