[en] Carbon nanotubes (CNTs), which are in high demand were synthesized over 18Co:12Mo:70MgO catalyst at temperatures 500-1000⁰C from C₂H₂ decomposition. It was observed that the yield of CNTs sharply increased with increasing temperature up to 725⁰C and then decreased with further increase of temperature. The diameter of CNTs showed a decreasing tendency with increasing growth temperature. The quadruple mass spectroscopy (QMS) study on the species generated from the decomposition of C₂H₂ identified the formation of C and C₂ species, the ingredient of CNT formation along with other species. From the XRD analysis of catalyst surface, and XRD, SEM and Raman analysis of the CNTs, it was concluded that Co particles released from Co₃O₄, and CoMoO₄ and CoO-MgO participated in CNTs growth. Mo played no active role in growing CNTs. The Co particles acted as the transporting medium of carbon to grow CNTs. The CNTs were grown by tip growth mode and they were multi-walled. (authors)