Optimization of carbon nanotubes synthesis via pyrolysis over Ni/Al₂O₃ using response surface methodology

Abstract

Owing to the rapid expansion of preparing a low-cost and pure carbon nanotubes (CNTs) from large available raw materials as cheap carbon precursors and catalyst depositions via chemical vapor deposition process, Algerian condensate gas over Ni/Al₂O₃ was used in this study. Response surface methodology was utilized to assess and optimize the preparation parameters. Synthesis of CNTs was studied as a function of three independent parameters: catalyst/condensate-gas weight ratio (5–10 wt %), synthesis time (30-120 min) and temperature (700–1000 °C). Optimum conditions for the CNTS-synthesis were found to be 5%, 112 min and 1000 °C, for catalyst/condensate gas mass ratio, synthesis time and temperature, respectively. Under these conditions, Raman spectrum indicates high values of (IG/ID), which means high-quality CNTs. Examination by SEM and HRTEM revealed that the CNTs grown under optimum conditions had diameters of 10 nm. The carbon yield predicted at the optimum process conditions was 81.76%. Conclusively, the pure and uniformed CNTs can be produced with high yield by the conversion of available-cheap resources via CVD-method. This method is practical, realistic, feasible in industrial scale and thus can reduces the cost manufacture of CNTs, which may help increase the impact of these remarkable materials in many fields.

Keywords:

• condensate gas pyrolysis
• carbon nanotubes
• Ni/Al₂O₃ catalyst
• response surface methodology