Catalytic synthesis of carbon nanotubes by methane decomposition

Abstract

The unique properties of carbon nanotubes have shown high potential for a wide range of applications. However, the carbon nanotubes are not in commercial market since they still can be produced in a small scale, causing the very high cost of this material. The production of carbon nanotubes by heterogeneous catalytic reaction is the most promising technique to commercially produce this material. Therefore, it is necessary to find a selective catalyst, feed gas, and reaction condition that preferentially produce high selectivity of carbon nanotubes. In this study, the families of Co-Mo, Fe-Mo catalysts on magnesium oxide have been systematically studied in order to find the catalsts for carbon nanotubes production by methane decomposition. Furtermore, fed gas composition and operating temperature have also been investigated for the carbon nanotubes production. The carbon products have been characterized by TGA, TEM and Raman spectroscopy. Among the studied catalysts, only Fe:Mo (2:1 molar ratio) can produce signle-wall carbon nanotubes, while others yield multi-wall carbon nanotubes. When compare with the carbon products from CO disproportionation by Co-Mo/SiO2 catalyst, the total amount of deposited carbon is higher, but the selectivity towards single-wall carbon nanotube is much lower. Moreover, the effect of reaction temperature in the range 700-1000 C was further investigated with Co:Mo (1:1 mole ratio) catalysts.