Microwave-assisted catalytic decomposition of polyetherimide with a focus on hydrogen and high-value hydrocarbons production

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This study investigates the microwave-assisted catalytic pyrolysis of polyetherimide (PEI). Activated carbon (AC), petroleum coke, graphite, silicon carbide, and AC-supported oxides (Fe₃O₄, Fe₂O₃, Al₂O₃, and ZnO) were chosen as microwave absorbers and/or catalysts to determine the impact of microwave absorber/catalyst type on the decomposition. Experiments were conducted at a microwave power of 400 W, which corresponded to an average bulk temperature of 400 °C, for 10 min in an argon atmosphere. No PEI remained intact after the treatments and the products were in the gas, liquid, wax, and solid phases, with the gas phase being the dominant fraction. Decomposition with the AC–Fe₃O₄ catalyst resulted in the highest gas yield and hydrogen production of up to 20 mmol g⁻¹ PEI, corresponding to 76% of the hydrogen content of PEI. Decomposition without metal oxides produced more wax, whereas metal oxides shifted the product distribution toward gases and/or aromatic condensates (notably toluene), depending on the oxide. The catalysts were deactivated by carbon deposition, degradation of the carbon support and/or reduction of metal oxide species. These results demonstrate that microwave-assisted catalytic pyrolysis of PEI enables hydrogen generation and the recovery of aromatic hydrocarbons (e.g., toluene, styrene, and naphthalene), highlighting its potential as a chemical recycling route for high-performance thermoplastics.