Using simultaneous DSC/TG to analyze the kinetics of polyethylene degradation—catalytic cracking using HY and HZSM-5 zeolites

Abstract

High-density polyethylene (HDPE) was cracked over HZSM-5 and HY zeolites and the reaction was followed using simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) and was compared with the degradation of the same material in the absence of an added catalyst. The products obtained in the degradation reaction were analyzed by gas chromatography. The simultaneous use of the signals from the TG and DSC allowed an accurate description of the thermal and catalytic degradation of the polymer by application of a novel kinetic model that correlates the two signals that are measured. The kinetic parameters were estimated by fitting this model to the experimental data obtained by TG and DSC. For both zeolites, the polymer degradation takes place at lower temperatures when compared with pure thermal degradation. It was also observed that the two zeolites have a distinct influence on the product distribution.

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

“…When the conversion rate was 0.1–0.45, the E value showed a gradual growth trend from 100 to 330 kJ/mol. It was inferred that E could be gradually increased because of the weakly strong chemical bond in PP catalyzed by the acidic site of the HY catalyst . In the conversion rate of 0.45–0.8, the values of E were increased from 140 to 220 kJ/mol.…”

“…Moreover, the peaks of CO 2 and H 2 O were obviously weak during the whole cracking process. It could be inferred that the catalytic cracking oxidation degree of PP was relatively low without the action of catalysts, which was in good agreement with the results of TG and TG–MS analysis. Figure b shows that the peak strength of CO 2 in the oxygen-cracking products of PP + Mn 2 O 3 was significantly enhanced implying the formation of hydrogen peroxide early at 250 °C.…”

“…It was inferred that E could be gradually increased because of the weakly strong chemical bond in PP catalyzed by the acidic site of the HY catalyst. 37 In the conversion rate of 0.45−0.8, the values of E were increased from 140 to 220 kJ/mol. This process was the occurrence of oxidation reaction, and the oxidation reaction gradually transitions from easy to difficult, resulting in a gradual increase of E values.…”

Thermal decomposition of fire-retarded high-impact polystyrene and high-impact polystyrene/ethylene–vinyl acetate blend nanocomposites followed by thermal analysis

“…According to the DSC results presented in Table 3, the degradation process of fire-retarded samples is less endothermic due to the dehydration of polymer and polymer oxidation reactions, which are exothermic reactions. As it is known, 22 the heat flow signal contains three different components: the heat required to increase the temperature of the sample, the heat required to vaporize the sample molecules that can go into the gas phase and the heat required to break the polymer bonds. The first and second terms are easily computed because the former should be proportional to the mass of the material at any given time, whereas the latter should be proportional to the change in mass.…”