Master of Science in Chemical Engineering (MSChE)
Carbon nanotubes are seamless cylindrical tubes, consisting of carbon atoms arranged in a regular hexagonal structure. It is considered as the ultimate engineering material because of its unique and distinct electronic, mechanical and material characteristics. The discovery of these materials pioneered the nanotechnology revolution, which encompasses a broad and multidisciplinary spectrum, including nanomaterials, nanobiotechnology, and nanoelectronics. Hundreds of published articles of laboratory scale and pilot plant processes were reviewed that describe potential synthesis and post–synthesis purification methods for large scale production of carbon nanotubes. The main production technologies include electric arc discharge, laser vaporization, and catalytic chemical vapor deposition. These production technologies were evaluated based on criteria such as operating conditions, continuous processes, feedstock source, yield, catalyst and product selectivity. Based on these criteria, two catalytic chemical vapor deposition production technologies were identified, and used as a basis for the conceptual design and development of two, 5,000 metric tons per year carbon nanotube production plants. The production technologies selected are the high–pressure carbon monoxide (HiPCO) process, and the cobalt–molybdenum catalyst (CoMoCAT) process. The HiPCO production technology is a gas–phase homogeneous process that employs a floating catalyst approach, whereby the growth catalyst is formed in situ during the production process. Carbon nanotubes are produced from the disproportionation of carbon monoxide over catalytic iron nanoparticles at 1,323 K and 450 psia. In the HiPCO process, a multi–step purification approach, involving oxidation, acid treatment and filtration, was used to remove amorphous carbon and residual iron impurities from the final carbon nanotube product. The CoMoCAT production technology is a heterogeneous process involving growth on supported catalysts. Carbon nanotubes are produced by the catalytic decomposition of carbon monoxide on silica supported, Co–Mo bimetallic catalyst particles, at 1,223 K and 150 psia. The silica supports, residual cobalt and molybdenum particles, and amorphous carbon are removed from the final carbon nanotube product by silica leaching, froth flotation, acid treatment and filtration purification processes. Economic and profitability analysis showed a positive net present value (NPV) of $609 million and $753 million for the HiPCO and CoMoCAT processes respectively. The rate of return (ROR) on investment, based on an economic life of ten years, was calculated to be 37.4% and 48.2% for the HiPCO and CoMoCAT processes respectively. These results showed the scalability, economic feasibility and viability of the proposed HiPCO and CoMoCAT technologies with a design capacity of 5,000 metric tons per year of carbon nanotubes. Hence, the route to multi tons production of high purity carbon nanotubes at affordable prices would soon be a reality.
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Agboola, Adedeji Ebenezer, "Development and model formulation of scalable carbon nanotube processes: HiPCO and CoMoCAT process models" (2005). LSU Master's Theses. 1635.
Ralph W Pike