Kinetic study of nitrogen doped carbon nanotubes in a fixed bed

- Nitrogen doping in carbon nanotubes was carried out in a fixed bed reactor with varying parameters.
- A plausible reaction mechanism is proposed and validated using experimental results.
- The kinetic parameters, rate controlling step(s) and overall rate of reaction were determined.
- The amount of nitrogen doping and the structural morphology of doped nanotubes were correlated with synthesis temperature.

Nitrogen doped carbon nanotubes has been synthesized using imidazole and acetylene in a fixed bed reactor by catalytic chemical vapour deposition. Ferrocene was used as a catalyst dispersed on magnesium oxide as a support. Imidazole acted as both carbon and nitrogen source and acetylene was used as an additional carbon source to tune the nitrogen content and increase the productivity. The temperature, flow rate of the reactants, particle size of the support, and height of the boat and partial pressure of acetylene were varied to understand their effect on the rate of formation of nitrogen doped carbon nanotubes. A plausible reaction mechanism was proposed to predict the rate determining step of the reaction and it was found that saturation and supersaturation of the nitrogen doped carbon nanotubes was rate determining. Temperature studies showed surface reaction can be possibly controlling the reaction rate with activation energy of 114 kJ mol−1. Average particle size of >91 µm depicted pore diffusion control. The products have been characterized by electron microscopy, thermogravimetry, Raman spectroscopy, carbon-hydrogen-nitrogen analysis and surface area analysis.