Technical Report 44, c4e-Preprint Series, Cambridge

Authors: Matthew S. Celnik, Richard H. West, Neal M. Morgan, Markus Kraft*, Anna Moisala, John Wen, William H. Green, and Henning Richter

Reference: Technical Report 44, c4e-Preprint Series, Cambridge, 2007

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In this paper we present a simple model for carbon nanotube synthesis in the gas-phase on iron catalyst particles. We include a particle growth model for the catalyst particles and describe nanotube growth processes through carbon monoxide disproportionation and hydrogenation. Models for particle-particle interactions and sintering are also included. Once carbon arrives at a catalyst particle surface it can either dissolve in the particle, until a saturation limit is reached, or form a graphene layer on the particle, or go to form a nanotube. Two models for nanotube inception are considered. The first model allows nanotubes to form once a catalyst particle reaches the saturation condition. The second model only allows nanotubes to form on the collision of two saturated particles. We solve the particle system using a multivariate stochastic solver coupled to the gas-phase iron chemistry using operator splitting. The model is compared to experimental data from a laminar flow reactor and shows promising results under the assumptions made. The model predicts well the nanotube length, and predicts reasonably well the catalyst particle diameter and nanotube diameter of the experimental data. A parameter study is presented in which the carbon monoxide reaction rate constants are varied, as is the fraction of carbon allowed to form nanotubes relative to carbon surface layers. The assumptions of the coagulation and sintering models are also discussed. The model is a first step towards detailed modelling of whole carbon nanotube gas-phase systems, and provides the ground work for future development.

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