Carbon nanotubes (CNTs) 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/Al3O3 catalyst was used in a range of temperatures from 600 to 800 degrees C. Multiwall carbon nanotubes of 20 nm in diameter and length on the order of micrometers were obtained. Higher yields were observed at 650 degrees C, where no prior catalyst reduction was necessary. Transmission electron microscopy, X-ray diffraction, and Raman spectrometry show a higher crystalline quality at 750 degrees C, although the balance yield quality indicates that 650 degrees C 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.