Catalysis of graphitisation

Marsh, H.; Warburton, A.P.

doi:10.1002/jctb.5010200409

Cited by 183 publications

(77 citation statements)

References 66 publications

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“…3 and 4); this is also consistent with other premixed flame experiments performed with the same fuel-air combination [21][22][23]. This can be explained in terms of the steep increase in C 2 hydrocarbons in the postcombustion gases that react with the catalyst and undergo graphitization [37] to produce surface carbon. When the rate of production of surface carbon (either through the graphitization of hydrocarbons or the disproportionation and hydrogenation of carbon monoxide) is greater than the diffusion rate of this surface carbon into the catalyst particle, the active surface area of the catalyst sites get deactivated.…”

Section: Discussionsupporting

confidence: 88%

Chemical kinetic considerations for postflame synthesis of carbon nanotubes in premixed flames using a support catalyst

Gopinath

Gore

2007

Combustion and Flame

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Multiwalled carbon nanotubes (MWCNTs) on a grid supported cobalt nanocatalyst were grown, by exposing it to combustion gases from ethylene/air rich premixed flames. Ten equivalence ratios (φ) were investigated, as follows: 1.37, 1.44, 1.47, 1.50, 1.55, 1.57, 1.62, 1.75, 1.82, and 1.91. MWCNT growth could be observed for the range of equivalence ratios between 1.45 and 1.75, with the best yield restricted to the range 1.5-1.6. A one-dimensional premixed flame code with a postflame heat loss model, including detailed chemistry, was used to estimate the gas phase chemical composition that favors MWCNT growth. The results of the calculations show that the mixture, including the water gas shift reaction, is not even in partial chemical equilibrium. Therefore, past discussions of compositional parameters that relate to optimum carbon nanotube (CNT) growth are revised to include chemical kinetic effects. Specifically, rapid departures of the water gas shift reaction from partial equilibrium and changes in mole fraction ratios of unburned C 2 hydrocarbons to hydrogen correlate well with experimentally observed CNT yields.

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Section: Discussionsupporting

confidence: 88%

Chemical kinetic considerations for postflame synthesis of carbon nanotubes in premixed flames using a support catalyst

Gopinath

Gore

2007

Combustion and Flame

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“…The formation of this type of deposit could be due to the release of localised stresses caused by graphite precipitation within the bulk metal. This kind of internal graphite precipitation has been reported to be found in the transition metals Ni, Co and Fe [21,22]. The appearance of these graphite particle clusters supports the hypothesis of Zeng and Natesan [21] that internal graphite precipitation plays an important role in the dusting of nickel.…”

Section: Discussionsupporting

confidence: 70%

Alloying with copper to reduce metal dusting of nickel

Zhang

Cole

Young

2005

Materials & Corrosion

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Copper is thought to be noncatalytic to carbon deposition from gas atmospheres, and owing to its extremely low solubility for carbon, inert to the metal dusting reaction. Thus, the addition of copper to nickel, which forms a near perfect solid solution, may be able to suppress or greatly retard the metal dusting of the alloy, without the need for a protective oxide scale on the surface.The dusting behaviour of Ni-Cu alloys containing up to 50 wt% Cu, along with pure Cu, was investigated in a 68%CO-31%H 2 -1%H 2 O gas mixture (a C : 19) at 680 8C for up to 150 h. Surface analysis showed that two types of carbon deposits, graphite particle clusters and filaments, were observed on pure Ni and Ni-Cu alloys with Cu contents of up to 5 wt%. Alloys with more than 10 wt% Cu showed very little coking, forming filaments only. SEM and TEM analyses revealed metal particles encapsulated by graphite shells within the graphite particle clusters, and metal particles at filament tips or embedded along their lengths. A kinetic investigation showed that alloy dusting rates decreased significantly with increasing copper levels up to 10 wt%. At copper concentrations of more than 20 wt%, the rate of metal dusting was negligible. Although pure copper is not catalytic to carbon formation, scattered carbon nanotubes were observed on its surface. The effect of copper on alloy dusting rates is attributed to a dilution effect.

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“…Finally, the influence of the inherent metallic species of the BCNFs (Al, Ni, Co) in the graphitization cannot be ruled out, particularly, considering that Al, Ni and Co have been used previously as catalysts for the graphitization of different carbon materials [15,33]. However, no apparent improvement of the graphitic three-dimensional order of the materials prepared was observed in this work by using BCNFs with higher inherent metal content, such as for example BCNF1-7 instead of BCNF1-6 (Tables 1-3).…”

Section: Influence Of Bcnfs Compositionmentioning

confidence: 99%

“…Nickel catalysts supported on SiO 2 , Al 2 O 3 , TiO 2 or MgO were used in this decomposition process, thus leading to CNFs containing different metals which have been traditionally employed as graphitization catalysts of carbon materials [15]. As indicated by X-ray diffraction (XRD), Raman spectroscopy and high-resolution transmission electron microscopy (TEM), graphitic nanomaterials with high degree of crystallinity were prepared from these methane-derived CNFs at temperatures above 2400 ºC, mainly because of the catalytic effect of the metal-containing species (namely Ni and Si).…”

Section: Introductionmentioning

confidence: 99%

Graphitic nanomaterials from biogas-derived carbon nanofibers

Cuesta

Cameán

Ramos

et al. 2016

Fuel Processing Technology

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Carbon nanofibers with different microstructure and elemental composition that were produced in the catalytic decomposition of synthetic biogas mixtures, in a rotary-bed reactor using nickel and nickel-cobalt catalysts at 600 ºC and 700 ºC, were heat treated in the temperature interval 2600-2800 ºC to explore their ability to graphitize. The influence of treatment temperature as well as carbon nanofibers composition, particularly metallic species, on the structural and textural properties of the materials prepared is discussed. Graphitic nanomaterials with great development of the three-dimensional structure (d 002 ~ 0.3360 nm, L c ~ 48 nm, L a ~ > 100 nm) and low porosity (S BET ~ 20 m 2 g -1 ) have been achieved. Because of the catalytic effect of silicon in the presence of inherent nickel and cobalt metals, more structurally ordered materials were obtained from the carbon nanofibers by adding silica. Based on the results of this work, the utilization of biogasderived carbon nanofibers for the production of synthetic nanographite to be used in different applications, such as electrode material in energy storage devices in which both high degree of graphitic order and small surface area are required, appears feasible.

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Catalysis of graphitisation

Cited by 183 publications

References 66 publications

Chemical kinetic considerations for postflame synthesis of carbon nanotubes in premixed flames using a support catalyst

Chemical kinetic considerations for postflame synthesis of carbon nanotubes in premixed flames using a support catalyst

Alloying with copper to reduce metal dusting of nickel

Graphitic nanomaterials from biogas-derived carbon nanofibers

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