The influence of heat treatment on the properties of the catalyst for the synthesis of carbon nanotubes

Abstract

In this paper, we studied the effect of heat treatment on the texture characteristics of Co-Mo/Al2O3, a catalyst for the synthesis of carbon nanotubes (CNTs). It has been experimentally proved that the heat treatment conditions at the stage of obtaining the metal oxide catalyst have a significant effect not only on its morphology, but also on its activity in the process of synthesis of CNTs. It was found that the implementation of the heat treatment of the starting components in one stage (decomposition) allows to obtain a catalytic system with a specific surface of ~ 14 ? 26 m2/g and a specific yield of ? ~ 5.2 ? 9.4 gС/gcat, and in two stages (decomposition / calcination) - Scat ~ 30 ? 147 m2/g and ? ~ 18.6 ? 30.0 gС/gcat. The smallest degree of defectiveness (ID / G ~ 0.53 ? 0.72) includes CNTs synthesized on a catalyst formed as a result of thermal changes for 10 min at 350 ° C and calcination at 500 °C, the diameter of the nanotubes is 15 ? 19 nm. The use of a metal oxide catalyst during the synthesis of CNTs, which has been calcined at higher temperatures (700 °C and above), leads to an increase in the speed and degree of defectiveness of the resulting nanostructures. Thus, the introduction of an additional heat treatment stage — calcination in the process of obtaining the Co-Mo/ Al2O3 catalyst — makes it possible to flexibly control the quality parameters of not only the formed metal oxide systems, but also the CNTs synthesized on them.