High Quality and Maximizing the Production of CNTs from the Pyrolysis of Waste Polypropylene

Abstract Thermal decomposition of plastics by pyrolysis into oil is a successful way of treating wastes. Nevertheless, the production of carbon nanotubes (CNTs) from wastes improves the feasibility of the waste management process. An experimental setup was developed to study the influence of different heating rates on the produced oil by pyrolysis of waste polypropylene (WPP), and the influence of using foamed nickel on the produced CNTs as a function of operating temperature and heating rate. Different heating rates of 5, 10, and 20 °C/min were examined, as well as the different carbon vapor deposition (CVD) temperatures of 600, 700, and 800 °C were studied. It has been found that increasing the heating rate from 5 to 20 °C/min increases the oil yield from 59.3 to 71%, but on the other hand it decreases the quality of the oil. It has been also found that increasing the heating rate decreases the quality of CNTs, i.e., uniform CNTs with small diameter and small wall thickness, and as well as the quantity. The physical properties of the produced CNTs have been improved by increasing the CVD temperature; however, the quantity of CNTs decreased. The highest yield of CNTs produced was 43.12% at the lowest CVD temperature and heating rate examined, i.e., 600 and 5 °C/min, respectively. The optimum heating rate and CVD temperature for the pyrolysis of waste polypropylene to achieve the highest quality of CNTs with moderate production of 39.34%, is the lowest heating rate examined, i.e., 5 °C/min, with a moderate CVD temperature of 700 °C.