Atmospheric-pressure growth of multi-walled carbon nanotubes over Ni–Fe nanosheets supported on α-Al2O3 foam

Abstract

A novel Ni–Fe nanosheets catalyst supported on α-Al2O3 foam ceramic was synthesized by a hydrothermal method and used to obtain multi-walled carbon nanotubes (MWNTs) via the propane partial oxidation. Catalytic performance tests were carried out at 600 °C and atmospheric pressure using a fixed-bed reactor. The synthesized catalysts and carbon materials were analyzed using various characterization methods. According to the field emission scanning electron microscope (FESEM) results, the catalyst morphology was a 3D grid structure consisting of nanosheets 800 nm length and 80 nm width. Additionally, the quantity and quality of the carbon nanotubes were greatly influenced by different oxygen-to-propane molar ratios, defined as the equivalence ratio ϕ (ϕ = 1.5, 1.78, 2). Transmission electron microscope (TEM) images showed that carbon nanotubes over all catalysts were MWNTs. In addition, the thermogravimetric analysis and Raman data showed that a high yield of MWNTs was obtained at ϕ = 1.78, but the accumulated MWNTs at ϕ = 1.5 exhibited a higher degree of graphitization (ID/IG = 0.89) compared with the other two equivalence ratios.