Study on the Mechanism and Kinetics of Waste Polypropylene Cracking Oxidation over the Mn₂O₃/HY Catalyst by TG-MS and in Situ FTIR

The low temperature and high efficiency cracking oxidation of organic solid waste over the bifunctional catalyst with both acidity and oxidizing property is an environmentally attractive technology. In this study, the reaction mechanism and kinetics behavior of waste polypropylene (PP) during catalytic cracking oxidation processes were investigated utilizing thermo-gravimetry (TG), differential scanning calorimetry, TG-mass spectrometric, and in situ Fourier transform infrared (in situ FTIR) spectroscopy. PP was cracked into low-molecular weight organic substances (ester, ketone, etc.) over acid sites, which were further oxidized to CO2 and H2O over oxygen vacancy in the Mn2O3/HY catalyst. The kinetics of catalytic cracking oxidation of pure PP and PP over different model catalysts was analyzed by Gauss-Peak function and the distributed activation energy model (DAEM). The catalytic oxygenation apparent activation energy (E) values of pure PP and PP over Mn2O3, HY, and Mn2O3/HY catalysts were 130-190 kJ/mol, 200-618, 108-228, and 41-99 kJ/mol, respectively. DAEM expressed appropriately the various changing trends of E in the reaction process. This theoretical basis of the catalytic cracking oxidation process of polymers would provide a reference for the design and optimization of the reactor and application upgrade of engineering.