Carbon Nanotubes: Understanding through Synthesis, Catalyst Design, and Kinetics

Abstract

This work focuses on carbon nanotube synthesis and hydrogen generation from catalytic decomposition of either ethylene or methane in both the presence and absence of cofed molecules through modification of the catalyst structure. Through identification and modification of the lamellar clay vermiculite as a catalyst support, carbon nanotube yields were significantly increased. This work has broad applications in the generation of high yield nanotubes that inherently require less purification and are therefore less expensive to produce. The processability of these nanotubes in a ball mill is discussed for the application of incorporation into polymer composites. The feasibility of carbon nanotube synthesis as a method of hydrogen production and carbon sequestration increases with the use of methane as a feedstock. This work therefore presents the efforts in designing and understanding a catalyst for catalytic methane decomposition. In evaluation of this catalyst, a unique mechanism of catalyst evolution is identified and shown to apply to the family of tested catalysts. The efficacy of cofeeds, specifically water and hydrogen, are evaluated and discussed, indicating that it is important to be cognizant of the extent of conversion at which the nanotubes are grown. Finally, the feasibility of carbon nanotube gasification is presented as a means of studying the carbon nanotube synthesis reaction from an alternative angle. This work led to the study of the generation of larger C2+ molecules from nanotubes, potentially paving the way for conversion of low value hydrocarbons to carbon nanotubes as an intermediate in production of other desired hydrocarbon products.