Kinetics and fuel properties of the oil obtained from the pyrolysis of polypropylene over cobalt oxide

Abstract

In this study pyrolysis of polypropylene (PP) was performed with and without cobalt oxide from 355 to 445 °C in inert conditions in an indigenously manufactured furnace. No oil was produced from non-catalytic reaction; however, the catalytic reaction resulted in production of oil in sufficient quantity. Optimum conditions for the maximum oil yield were explored and 100 min reaction time, 430 °C temperature and 5% of catalyst in continuous flow of nitrogen were observed as the most appropriate conditions for maximum oil production. Gas chromatography-mass spectrometry (GC-MS) of the obtained oil was performed for determining the composition of the oil. Moreover, fuel properties of the oil were examined and found comparable with commercial fuel. Furthermore, thermal degradation of polypropylene with and without cobalt oxide catalyst was performed in a thermobalance under nitrogen environment in the temperature ranging from 30 to 600 °C at temperature programmed rate of 5, 10, 15 and 20 °C/min. Using Kissinger-Akahira-Sunnose (KAS) kinetic model, the average activation energy (Ea) of non-catalytic reaction was found to be 83.14 kJ/mol, while in the presence of cobalt oxide the average Ea was observed as 63.55 kJ/mol. It was observed from the comparison of both the results that use of cobalt oxide has not only reduced Ea but also resulted in the production of oil having resemblance with fuel grade oil. Hence, cobalt oxide was found to be an efficient catalyst for the conversion of polypropylene into valuable products and the study performed on model polypropylene can be extended to polypropylene waste on industrial scale.