Abstract
Carbon nanotubes (CNTs) have the potential to act as a catalyst support in many sciences and engineering fields due to their outstanding properties. The CNT-coated monolith was synthesized over a highly active Ni catalyst using direct liquid injection chemical vapor deposition (CVD). The aim was to study the optimum condition for synthesizing CNT-coated monoliths. The Taguchi method with L9 (34) orthogonal array design was employed to optimize the experimental conditions of CNT-coated monoliths. The design response was the percentage of carbon yield expressed by the signal-to-noise (S/N) value. The parameters including the mass ratio of Ni to citric acid (Ni:CA) (A), the injection rate of carbon source (B), time of reaction (C), and operating temperature (D) were selected at three levels. The results showed that the optimum conditions for CNT-coated monolith were established at A1B2C1D2 and the most influential parameter was D followed by B, C, and A. The ANOVA analysis showed the design was significant with R-squared and standard deviation of the factorial model equal to 0.9982 and 0.22, respectively. A confirmation test was conducted to confirm the optimum condition with the actual values of the average percentage of carbon yield deviated 1.4% from the predicted ones. The CNT-coated monoliths were characterized by various techniques such as field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy.
Highlights
Carbon plays a dual role as a catalyst or catalyst support for many chemical reactions due to its outstanding properties such as large surface area, high porosity, excellent electron conductivity, and relative chemical inertness [1]
The Taguchi method was employed to investigate the optimum parameters in synthesizing carbon nanotubes (CNTs) on monolith support
The identified optimum condition of the CNT growth on monolith should be performed at 1:1 mass ratio of Ni to CA (A1 ), 5 mL/h injection rate of carbon (B2 ), 30 min reaction time (C1 ), and 700 ◦ C operating temperature (D2 )
Summary
Carbon plays a dual role as a catalyst or catalyst support for many chemical reactions due to its outstanding properties such as large surface area, high porosity, excellent electron conductivity, and relative chemical inertness [1]. Graphene and carbon nanotubes (CNTs) are the most investigated carbon materials which build broad interest in science and engineering. Both these carbon materials present remarkable physical, mechanical, thermal, and optical properties. The graphene is the basic structure of graphite, fullerenes, and CNTs with a planar sheet of sp2 -bonded carbon atoms densely packed in a honeycomb crystal lattice [2]. CNTs are cylindrical in structure consisting of a hexagonal arrangement of hybridized carbon atoms
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