Estudio cinético de la descomposición térmica de plásticos de polietileno tereftalato (PET) reciclado

Abstract

The objective of the present investigation was to determine the kinetic parameters of the thermal decomposition of recycled polyethylene terephthalate (RPT) plastics. The samples were characterized by infrared spectroscopy and analyzed by thermogravimetry, with heating rates of 5, 10 and 15 degrees Celsius min-1, in a nitrogen atmosphere. They were used the isoconversional kinetic methods of Friedman, Kissinger-Akahira-Sunose and Flynn-WallOzawa that allow modeling the reaction mechanism during thermal cracking of RPT waste. The results indicate conformations of the oxyethylene, carboxyl and ester groups; which during the pyrolysis of RPT, result in the formation of oligomers. Thermal degradation of recycled RPT occurs between 400 to 470 degrees Celsius and with a maximum degradation temperature of 427 degrees Celsius. With the kinetic modeling of Friedman and Kissinger-Akahira-Sunose, an activation energy of 223.34 kJmol-1 and a pre-exponential factor of 1.29 x 10e16 and 2.76 x 10e15 s-1 were determined respectively; While, with the Flynn-Wall-Ozawa kinetic model, an activation energy of 249.26 kJmol-1 and a pre-exponential factor of 1.46 x 10e19 s-1 was determined. Statistical analysis of variance showed with 95% confidence that the theoretical models fit the experimental model correctly. The kinetic study shows the need for an adequate kinetic model based on the adjustment of the calculated data based on the experimental data, prior to implementation in a pilot or industrial scale reactor. It is recommended to perform an in situ gaseous emission detection of polyethylene terephthalate pyrolysis by coupling a mass spectrometer to the thermobalance to identify and quantify the products generated during the thermal degradation process.