Catalytic pyrolysis of FeAlOx and medical plastic waste: kinetic, slag conversion, and gas emission patterns

The globally substantial increase in medical waste stream and types renders efficient disposal and circularity strategies imperative. Currently, most medical waste disposed of is predominantly plastic materials. A promising approach for its recycling efficiency involves using catalytic pyrolysis to transform plastic waste into reusable pyrolysis oil. This study aimed to characterize gas products and bottom slag of the catalytic pyrolysis of medical waste infusion tubes (PVC) via thermogravimetric (TG) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) analyses. As s bimetallic catalyst known for its exceptional ability as a carbon carrier that can turn carbon into CO at high pyrolysis temperatures, FeAlOx was synthesized and characterized. The addition of 50% (wt) FeAlOx yielded the lowest activation energy (Eα = 108.11kJ/mol). The catalyst facilitated the breaking of the C-Cl bond in PVC, increasing HCl and light hydrocarbon gases, such as CH4. Prolonged pyrolysis residence times reduced chlorine remnants in the bottom slag, increased its alumina content, and achieved a stable slag composition. The reaction model with varying catalyst additions was dynamically evolved as follows: F1.6→F2→F2.2→F1.5 in the first stage and F2.3→F2.8→F4.8→F2 in the second stage, thus achieving an optimal kinetic and thermodynamic ratio of 5:5. The addition of the catalyst reduced not only the energy consumption and complexity of the two pyrolysis stages of PVC but also the production of pollutants, thus improving the circularity. This study provides actionable insights into the potential of the catalyst-assisted pyrolysis as an effective method for the circular management of medical waste.