Kinetic and thermodynamic insights into the catalytic pyrolysis of PP with Fe/Ni catalysts

Pyrolysis is an effective strategy for recycling plastic waste and mitigating environmental pollution. This study investigated the kinetic and thermodynamic behaviors of polypropylene pyrolysis and catalytic pyrolysis with HY zeolite, Fe-modified HY zeolite, Ni-modified HY zeolite, and Fe-Ni-modified HY zeolite catalysts through thermogravimetric experiments at heating rates of 4, 6, and 8 ^oC/min. The results showed that HY zeolite, Fe-modified HY zeolite, Ni-modified HY zeolite, and Fe-Ni-modified HY zeolite catalysts reduced the onset temperature of polypropylene pyrolysis from 343.67 °C to 305.19, 282.34, 274.95, and 259.87 °C, respectively. The incorporation of Fe, Ni, or Fe-Ni into HY zeolite reduced carbon deposition. The effect of these catalysts on the activation energy of polypropylene pyrolysis, was more accurately captured by the FRD method, showing higher R² values and better precision than the OFW method. Polypropylene pyrolysis, and catalytic pyrolysis with HY zeolite, Fe-modified HY zeolite, Ni-modified HY zeolite, and Fe-Ni-modified HY zeolite had activation energies of 297.68, 44.41, 188.19, 362.94, and 195.55 kJ/mol. HY zeolite significantly reduced activation energy by promoting chain cracking via acidic sites. Fe and Ni incorporation increased activation energy due to enhanced dehydrogenation, while Fe-Ni loading raised activation energy, promoting dehydrogenation and facilitating aromatics production.