Carbon nanotubes (CNTs) were synthesized by catalytic decomposition of 20% methane in hydrogen over Co–Mo/MgO catalysts at 1000 ◦C. The catalysts were prepared by a modified sol–gel method, using sorbitol, ethylenediamine tetraacetic acid (EDTA), tartaric acid and citric acid as organic additives. The specific surface area (SSA) of the catalysts changes with the organic additives in the order of sorbitol > EDTA > citric acid > tartaric acid. As a result the crystallite size, dispersion of Co–Mo and hence the quality of the carbon nanotubes change with the organic additive. Up to 180 wt% yield of high quality single-wall carbon nanotubes (SWNTs) with inner-wall diameter close to 1.0–1.2 nm are obtained on the catalyst prepared in the presence of sorbitol.

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