Pilot Plant Scale Study of the Influence of the Operating Conditions in the Production of Carbon Nanofibers

Abstract

In this paper, the optimization of typical reaction variables for a pilot scale synthesis of carbon nanofibers (CNFs) using a fixed-bed reactor has been carried out to provide a more economically viable large scale production of these materials. Using a Ni/SiO 2 catalyst (10 wt % Ni) and ethylene as the carbon source, the optimum value of temperature, space velocity, and H 2 /C 2 H 4 ratio (v/v) in terms of carbon yield was 600 °C, 10000 h -1 , and 1:4, respectively. The modification of these variables caused a significant change in the type and amount of solid carbon recovered. Carbon product characterization demonstrated that CNFs with mesoporous character, large external surface, and good thermal stability and crystallinity were obtained. Finally, results demonstrated a successful scale-up by a factor of 45 in the pilot plant scale; a CNFs yield of 106 g CNFs /g catalytic metal could be obtained at optimal conditions during a reaction time of 60 min at optimal conditions in the pilot plant scale. For the same reaction conditions, only 80 g CNFs /g catalytic metal were obtained in the laboratory reactor.

Synthesis and characterization of ruthenium supported on carbon nanofibers with different graphitic plane arrangements

“…[22]. In each synthesis run 5 g of catalyst (10% Ni/SiO 2 ) was placed in the centre of the reactor and activated by heating (10 • C min −1 ) in a flow of dry 20% (v/v) H 2 /He at the desired reaction temperature.…”

“…Temperature-programmed decomposition was used to obtain qualitative information about oxygenated groups formed on the surface of the different carbon materials. Analyses were performed on 50 mg samples using a Micromeritics AutoChem 2950 HP apparatus with a flow of 100 mL min −1 helium and then heated (5 • C min −1 ) up to 700 • C. Temperature-programmed reduction (TPR) measurements for the metal catalysis were recorded on a Micromeritics AutoChem 2950 HP apparatus according to the procedure described in [22,24]. The chemisorption measurements were carried out using a dynamic pulse technique with an argon flow of 50 mL min −1 and pulses of H 2 (99.9995% purity) using the same apparatus described for the TPR analysis and the procedure described in Ref.…”

Electrochemical promotion of the CO2 hydrogenation reaction on composite Ni or Ru impregnated carbon nanofiber catalyst-electrodes deposited on YSZ

“…The preparation is based on chemical vapour deposition (CVD) of a H 2 /C 2 H 4 mixture over a Ni/SiO 2 catalyst. After deposition, the CNFs have to be separated from the catalyst particles by repeated dissolution of the support in hydrofluoric acid (70%) [24]. During this treatment the metal component of the catalyst was generally transferred into the waste solution.…”

“…The time constant for electrochemical promotion, , is defined as the time required for a rate increase, r, to 63% of its steady-state value during galvanostatic transient operation. This constant is slightly larger in comparison to porous metal electrodes [22], and may indicate that ions migrate not only through the metal phase but also through the carbon nanofibers, which are electrically conductive [24]. …”

Nano-Scale Au Supported on Carbon Materials for the Low Temperature Water Gas Shift (WGS) Reaction

“…Graphite (supplied by Aldrich) underwent the same treatment with this acid to make their properties comparable. Further details regarding the CNF synthesis are given in a previous work [58].…”