Isothermal co-pyrolytic kinetics investigation of polystyrene/polymethyl methacrylate blended Bakelite

The widespread use of Bakelite, polystyrene (PS), and polymethylmethacralate (PMMA) has caused significant pollution, requiring advanced recycling methods. Pyrolysis, co-pyrolysis, and catalytic co-pyrolysis are key for recycling these wastes, necessitating kinetic studies and specific reactor designs of their thermal degradation. Isothermal thermogravimetric analysis at 300, 350, 400, 450, and 500°C was used to study thermal degradation kinetics, based on the non-isothermal degradation zone of Bakelite. The batch pyrolysis of discarded Bakelite and PS/PMMA–Bakelite blends was conducted at 450°C. The thermal decomposition of Bakelite and its blends increases with higher isothermal pyrolytic temperatures. The addition of PS or PMMA to Bakelite substantially accelerates its thermal decomposition. The maximum weight loss of Bakelite, PS–Bakelite, and PMMA–Bakelite are 55%, 96.75%, and 89.51% at 500°C, respectively. The kinetic analysis is crucial for designing specific reactors, utilizing the D₁-diffusion-based method for Bakelite, with an activation energy (Ea) of 17.178 kJ/mol and Arrhenius constant (A) of 0.095 min⁻¹. The A₂- and A₃-Avrami–Erofeyev methods explain the isothermal degradation of PS–Bakelite and PMMA–Bakelite blends, with activation energies of 9.031 and 12.59 kJ/mol, and Arrhenius constants of 0.056 and 0.075 min⁻¹, respectively. The co-pyrolysis of PS–Bakelite yields the highest condensable products (66.76%) and needs the longest reaction time (320 min). The Fourier transform Infrared (FTIR) and gas chromatography–mass spectrometry (GC–MS) analyses confirm the presence of alkanes, cycloalkanes, alkenes, cycloalkenes, aromatic hydrocarbons, and oxygenated compounds in the pyrolytic oils. This study provides unique kinetic parameters and product analyses, showing effects of blending on the decomposition rates and yields valuable compounds, advancing recycling technologies.