NER: Feasibility Study on High Yield Thermal Plasma Synthesis of Carbon Nanotubes and Other Nanocrystalline Forms of Carbon

Drexel University, Philadelphia PA

Investigators

Abstract

The feasibility of synthesizing carbon nanotubes and other high-value forms of carbon will be studied using a lab-scale, nominally atmospheric pressure, induction-coupled plasma [ICP] reactor. The rationale for this work was the discovery of nanotubes in carbonaceous residues produced during the gasification of polymers for monomer recovery from waste, but under conditions minimizing solids formation. In this work, the ICP will be used to decompose solid polymeric and low molecular weight gaseous hydrocarbon precursors [methane, propane and ethylene] under conditions maximizing carbon recovery. Organometallic catalysts [Fe, Ni and Co-bearing], previously shown to nucleate and enhance nanotube formation and growth, will be injected into the feed stream prior to injection into the hot [~10,000 k] plasma region to produce conditions favoring nanotube formation. Several hydrocarbon precursors and catalysts will be studied in an experimental matrix determining the influence of key process variables such as plasma power, process gas flows, precursor feed rate, quenching gas flows and reactor pressure on product yield and composition. Solid products will be analyzed by electron microscopy and chemical solubility techniques to determine the yield of nanotubes, their type(s) and any associated by-products. ICP's are flexible, capable of operating under neutral, oxidizing or reducing conditions, and of accepting gaseous, liquid or solid feeds. Furthermore, ICP reactors are readily scalable. While the lab-scale system to be used in this work will feed solids at ~ 5 gm/min, potentially yielding up to 5.8 kg of solids/day, industrial systems rated in the 600 kW to 1MW power range have already been developed. If successful, this work offers the possibility of large-scale production of carbon nanotubes at significantly lower cost than existing furnace, arc and laser-ablation techniques. This would enable more of the applications proposed for C-nanotubeshydrogen storage, composite reinforcement, therapeutics delivery etc., to be developed.