Research on MWCNT growth process through on-line intermittent monitoring in a fluidized bed reactor

Abstract

Carbon nanotubes (CNTs) have been extensively investigated in the past two to three decades owing to their superior properties. Most people focus on studying the role of catalyst, reaction temperature, partial pressure, and carbon source in the growth of CNTs. However, research on the effect of different reaction times on the growth process of multiwall CNTs (MWCNTs) remains insufficient. Here, through on-line intermittent monitoring technology, we studied the growth process of MWCNTs on Fe–Co–Mo/Al2O3 catalyst at high temperature using propylene decomposition to solid carbon and gaseous hydrogen in a self-made fluidized bed reactor proposed in the previous study that utilized the effect of cone angle instead of the role of distributor. A parametric systematic study on the effect of intermittent time (5–60 ​min) on the MWCNT morphology, quality, quantity, and particle properties was performed by using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. It was found that the carbon source conversion rate decreased at a lower linear rate of 0.15, the MWCNT yield increased at a higher linear rate of 1.45, the lowest ash content reached 2.04% at 60 ​min, and the mean diameter remained at 12.5 nm. A formula with empirical coefficient and time dependence was proposed to predict the carbon source conversion rate.