Catalytic co-pyrolysis of waste coconut fibers and polystyrene using Py-GC-MS: Effect of temperatures and catalyst loading on pyrolytic hot vapours

This present study investigates the catalytic co-pyrolysis of waste coconut shells (CNS) and polystyrene (PS) using Py-GC-MS to evaluate the effect of temperature and catalyst loading on pyrolytic vapour products. CNS was characterised by 75.51 % volatile matter, 14 % fixed carbon, 5.6 % moisture content, 4.86 % ash, 49 % carbon, and 18.32 MJ kg⁻¹ higher heating value, while PS exhibited 99 % volatile matter, 92 % carbon, and 40.52 MJ kg⁻¹ energy content. Co-pyrolysis was conducted at 450, 550, and 650 °C with varied PS (10–30 wt%) and ZSM-5 catalyst loadings (10–30 wt%). Pyrolysis of CNS alone at 650 °C produced 10.49 % hydrocarbons, 30.34 % acids, and 16.52 % phenols, while PS produced up to 95.61 % hydrocarbons at 550 °C. When blended, 30 % PS with CNS yielded up to 64 % hydrocarbons and 14 % acids at 650 °C, highlighting the synergistic effect. Catalyst addition significantly improved hydrocarbon yields: at 10 wt% ZSM-5 and 650 °C, hydrocarbon yield reached 33 %, with decreased acid and phenol content, enhancing oil quality. FTIR confirmed the presence of hydroxyl, carbonyl, and aromatic groups, whereas TGA confirmed thermal decomposition stages of CNS and PS. The highest conversion efficiency was observed at 650 °C with 30 wt% PS and 10 wt% ZSM-5, driven by cracking, decarboxylation, and aromatisation reactions. The study demonstrates that integrating waste plastics with biomass and ZSM-5 in co-pyrolysis enhances hydrocarbon-rich oil production while mitigating environmental issues from biomass burning and plastic waste. This process presents a sustainable pathway for converting lignocellulosic and polymeric waste into renewable fuel.