Production of Carbon Nanotubes from Polyethylene Pyrolysis Gas and Effect of Temperature

Abstract

Carbon nanotubes (CNT) were produced by catalytic chemical vapor deposition using, as carbon source, a mixture of hydrocarbons and hydrogen that simulates the effluent gases from pyrolysis of polyethylene (PE). An Fe/Al 3 O 3 catalyst was used in a range of temperatures from 600 ºC to 800 ºC.Multi-wall carbon nanotubes of 20 nm in diameter and length on the order of microns were obtained. Higher yields were observed at 650 ºC, where no prior catalyst reduction was necessary. TEM, XRD and Raman spectrometry show a higher crystalline quality at 750 ºC, although the balance yield-quality indicates that 650 ºC is a satisfactory temperature for producing CNTs at a reasonable cost, since no extra hydrogen is necessary for the process. In addition to this, the effluent gas from the process can be further used for energy production.

Effect of growth temperature and feedstock:catalyst ratio on the production of carbon nanotubes and hydrogen from the pyrolysis of waste plastics

“…The peak at 1589 cm −1 corresponds to the G peak associated with graphitic carbon within the sample, the peak at 1348 cm 1 corresponds with the D peak and is associated with defects within the graphitic lattice; while the G' peak at the Raman shift around wavelength 2709 cm -1 indicates the two photon elastic scattering process, indicating the purity of CNTs. The ratio between the size of the G peak and D peak is a useful way of comparing the quality of the carbon nanotubes obtained in terms of how ordered and graphitic they are [14,50,58,59]. This will enable the purity of the deposits in terms of the carbon nanotubes produced to be evaluated, with a larger G/D ratio indicating a higher purity.…”

“…Whilst they were first produced by Ijima et al by an arc discharge process [10], large scale production favours chemical vapour deposition of hydrocarbon gases such as methane and acetylene. In more recent years a method of producing carbon nanotubes from the pyrolysis of plastics has been demonstrated [11][12][13][14][15][16][17][18][19][20][21].…”

Production of bamboo-type carbon nanotubes doped with nitrogen from polyamide pyrolysis gas

“…The characterization of this catalyst was evaluated in a previous study by transmission electron microscopy (TEM), X-ray fluorescence and scanning electron microscopy (SEM) employing electron dispersion spectroscopy (EDS). Details can be consulted elsewhere [44]. The results showed that the catalyst was satisfactorily synthesized, where Fe was well dispersed over the Al2O3 support, and that the Fe2O3 nanoparticles size distribution was in a range on the order of 2 nm.…”

“…These studies are mainly focused on the production from polyolefins, polypropylene [37][38][39][40][41][42] and polyethylene PE [42][43][44][45]. Other contribution studies the production of CNT from a mixture of waste polymers, more realistic and economically viable, which consists of a majority of polyolefins with small contribution of polystyrene [37,46], polyvinyl chloride [42,46], PET [47], etc.…”

“…The feeding system of the reactor allows the introduction to the sample to the oven once it is already at the setpoint temperature, which assures to reach the final temperature in a few seconds, simulating a continuous reactor. More details about the apparatus can be found elsewhere [44]. Special attention was paid to obtain nitrogen compounds and hydrogen as decomposition products, since they are required for growing BCNTs.…”