In this work, the Catalytic Chemical Vapor Deposition (CCVD) technique was used to synthesize carbon nanotubes (CNT). Natural gas (NG) was employed as a carbon source for the growing of CNT, while magnesium oxide was used as a catalyst support for the nanotubes synthesis. Two systems were utilized. The Fe-Mo/MgO system was obtained by the impregnation technique through the dispersion of iron oxide, which is the catalyst, over magnesia (with molybdenum additions). This system was tested intending to optimize the parameters for the production of single-walled carbon nanotubes (SWCNT). Moreover, Mg1-x Fe (x) MoO4, which was prepared by the combustion synthesis method, was tested to produce multi-walled carbon nanotubes (MWCNT). The Fe-Mo/MgO tests were carried out under H-2/GN and Ar/GN atmospheres at 950 degrees C, whereas the Mg1-x Fe (x) MoO4 was submitted to 1,000 degrees C under H-2/GN atmosphere. The Fe-Mo/MgO catalyst produced better results regarding number of CNT and their diameters under Ar/NG atmospheres than under H-2/NG atmospheres. The system Mg1-x Fe (x) MoO4 produced MWCNT according to the expectations.