High yield of multiwalled carbon nanotubes from the decomposition of acetylene on Co/MgO catalyst

Abstract

A new catalytic method of carbon nanotubes synthesis, by the decomposition of acetylene at 600 °C over particles of CoxMg(1−x)O solid solution, gives high yield of carbon nanotubes. CoMgO catalyst have been prepared from Co nitrate hexahydrate, Mg nitrate hexahydrate and citric acid dissolved in water solution then gently evaporated to solid solution and finally calcinated under N2 during 5 hours at 700 °C. The influence of different parameters on the quality and quantity of the produced nanotubes was investigated such as the nature of support, reaction time and velocity of hydrocarbon along the catalyst. Separation of the nanotubes from the catalyst particles was carried out by 12 mol.l−1 hydrochloric acid treatments at 110 °C during 12 hours. The quality of the nanotubes production was characterized by scanning electron microscopy (SEM) and the nanotexture was investigated by transmission electron microscopy (TEM). The standard external diameters obtained, range between 10–20 nm. Presented method is an easy, effective and selective way to produce nanotubes without existence of amorphous carbon, acetylene black or any others carbon forms; as a consequence without heavy purification process in comparison to syntheses using Co supported on silica or zeolite. Even yields are much higher, from 20 mg of such efficient catalyst, 80 mg entangled nanotubes are obtained, with more than 95% of purity.