CaCo₃ supported Co‐Fe catalysts for carbon nanotube synthesis in fluidized bed reactors

Abstract

in Wiley InterScience (www.interscience.wiley.com).The synthesis of carbon nanotubes (CNTs) on a cobalt-iron (Co-Fe) catalyst supported on a calcium carbonate (CaCO 3 ) substrate, contained within a fluidized bed was investigated for the first time. CaCO 3 supported catalysts, prepared using traditional wet impregnation techniques result in a soft and sticky powder requiring special arrangements to ensure satisfactory fluidization. A modified method developed using citric acid complex resulted in CaCO 3 supported catalysts that can be classically fluidized without special arrangements. The issue of Fe 31 (aq) hydrolysis above its critical pH of ;3.5 was also addressed. A carbon yield consistently greater than 10 times the weight of the catalyst metal loading was obtained. Thermogravimetric analysis coupled with mass spectrometry showed a single peak centered on 5758C, with no peaks below 4008C, indicating that an insignificant quantity of amorphous carbon was present. Transmission electron microscopy verified that the products contained a large proportion of CNTs.

The synthesis of carbon nanomaterials using chlorinated hydrocarbons over a Fe-Co/CaCO3 catalyst

“…These peaks are assigned to the presence of small amounts of graphitic materials. 64,65 Further evaluation of the thermographs obtained from chlorinated benzenes, revealed that the CNTs contained residues even after purification in 30 % HNO 3 for 30 min (~21 %, 6 % and 10 % for CB, DCB and TCB (Table 2)). An attempt was made to further purify the materials generated from CB by stirring the product in 30 % HNO 3 for 2 h and 3 h (Supplementary Fig.…”

Optimizing the synthesis of cobalt-based catalysts for the selective growth of multiwalled carbon nanotubes under industrially relevant conditions

“…Various oxides can be used as support or as structural promoter to enhance the dispersion of the active phase such as Co nanoparticles and to improve the yield of CNTs [12][13][14][15][16]. The catalytic system for CNT synthesis can be considered as sacrificial catalyst, where both the active phase and the oxidic components remain in the product as impurities.…”

Kinetic model of carbon nanotube production from carbon dioxide in a floating catalytic chemical vapour deposition reactor

“…The choice of calcium carbonate was based on the good quality, high yield and high purity materials obtained from its use as a support. 19 The catalyst was prepared by a modied wet impregnation technique 20 by mixing a predetermined amount of iron nitrate and citric acid in approximately 1 : 1 molar ratio in deionized water. Ammonia solution was added in drops until a neutral pH was reached.…”