Synthesis of carbon nanotubes by methane decomposition over Co–Mo/Al 2O 3: Process study and optimization using response surface methodology

Abstract

Systematic studies of various process variables on the formation of carbon nanotubes (CNTs) by methane decomposition over a Co–Mo/Al 2O 3 catalyst were performed using a three-level factorial design in response surface methodology. A quadratic polynomial model for carbon yield was developed by multiple-regression analysis. The optimum conditions for CNT production within the experimental ranges were found at a reaction temperature of 761 °C, a methane partial pressure of 0.75 atm and a catalyst weight of 0.4 g. The carbon yield predicted at the optimum process conditions was 607%. Examination by electron microscopy revealed that the CNTs grown under optimum conditions had diameters of 11.8 ± 1.9 nm (average diameter ± standard deviation) and possessed an open-tip morphology.