Flow Simulations Including Iron Nanoparticle Nucleation, Growth and Evaporation for Floating Catalyst CNT Production

Filip K A Gökstorp,Matthew P Juniper

doi:10.3390/catal10121383

Abstract

We use a computational fluid dynamics model coupled with a particle dynamics model to simulate how catalyst nanoparticles nucleate, grow and evaporate over the length of a floating catalyst reactor. We focus on the influence of the flowrate in the reactor and the ferrocene mass fraction on the production of the catalyst nanoparticles. In the downstream region of the reactor, where the majority of CNT growth occurs, we find that, as either the flowrate or the ferrocene mass fraction increases, the particle mass fraction profile changes, with the mass fraction peak shifting away from the centreline. This displacement away from the centreline of the mass fraction peak may explain why the CNTs form a hollow, sock-like, aerogel at the downstream end of the reactor.

Highlights

In the floating catalyst chemical vapour deposition (FC-CVD) process, pioneered by Li et al [1], carbon nanotubes (CNTs) are continuously produced in a heated reactor
We develop a model capable of simulating the nucleation, growth and evaporation of catalyst nanoparticles in a reactor for the production of carbon nanotubes
We looked at three different measurements of the particles: (a) particle mass fraction; (b) average particle diameter; and (c) total particle surface area

Summary

Introduction

In the floating catalyst chemical vapour deposition (FC-CVD) process, pioneered by Li et al [1], carbon nanotubes (CNTs) are continuously produced in a heated reactor. The working fluid in the reactor contains a carrier gas (typically hydrogen) mixed with a carbon source (typically methane), an iron source (typically ferrocene) and a sulphur source (typically thiophene). Hydrogen is the dominant species accounting for the majority of the total mass of the mixed fluid in the reactor. Ferrocene and thiophene account for 0.5% and 3% of the total fluid mass, respectively. Methane accounts for approximately 20% of the total mass, if present. The iron source decomposes into iron vapour, which forms iron nanoparticles. The iron particles form the catalyst surface on which carbon nanotubes grow, promoted by the sulphur

Methods

Results

Conclusion