High-yield synthesis of multi walled carbon nanotubes using zeolite as a supported iron catalyst: Effect of zeolite textural properties and its morphology

The effect of the textural properties and morphology of zeolite, used as support of iron (Fe), on the quantity and quality of the multi-wall carbon nanotubes (MWNTs) synthesized by catalytic chemical vapor deposition (CCVD) of acetylene was studied. The parent zeolite 4A was modified by various dealumination procedures. In this work, catalyst (Fe) and catalyst support (zeolite) are Fe/zeolite in ratio 1:10, acetylene (C2H2) was used as source of carbon and mixture of N2 and H2 as the carrier gases. Characterization of the carbon nanotubes was carried out using scanning electron microscope (SEM), thermo-gravimetric analysis (TGA), zeta-sizer and Raman spectroscopy. Also, high resolution transmission electron microscope (HRTEM) images and micro-Raman spectra taken right after growth confirmed the formation of high quality MWNTs with a low degree of disorder irrespective of the catalysts used, the degree of dealumination of the zeolite 4A and the textural and morphological characteristics of the zeolitic support. It is detected that the nanotubes have the inner diameter about 5-10 nm and they are highly uniform. As the matter of fact, this special structure guarantees its usage in the world of nano-composites as reinforcement material. The ionexchange and wet impregnation methods were used for supporting the metals on the zeolite 4A samples, with the latter method providing the most effective catalysts for multi walled carbon nanotube (MWCNT) formation.