Kinetics of carbon nanotubes growth on a Ni–Mg–Al catalyst by CCVD of methane: Influence of catalyst deactivation

In this work, we present the application of a phenomenological kinetic model to the analysis of experimental results obtained with a LDH-based Ni–Mg–Al catalyst during the CCVD of methane. This model takes into account all the main stages implicated in CNT growth: methane decomposition, metal surface carburization, carbon diffusion, CNT nucleation and growth. The main causes of growth cessation, catalyst deactivation and steric hindrance have also been considered. The effect of the main operational variables, reduction (activation) and reaction temperatures and feed composition (hydrogen and methane composition), have been studied. The model fits very well the data obtained with the studied catalyst at the different operating conditions. As a consequence of the application of the model to the kinetic results, we can describe the influence of the operating conditions on each of the individual stages involved in the CNT formation.