Metal oxides as catalysts for the oxidation of graphite

McKee, D.W.

doi:10.1016/0008-6223(70)90055-2

Cited by 232 publications

(81 citation statements)

References 8 publications

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“…Iron is known to influence the oxidation behavior of carbon materials because of its catalytic activity. 44,45 Previous experiments have shown that the oxidation temperature of carbon black can be reduced by ¾100°C by adding 1-2% iron particles. 46 Graphitized MWCNTs are more resistant against oxidation than the as-received MWCNTs.…”

Section: Resultsmentioning

confidence: 99%

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Monitoring oxidation of multiwalled carbon nanotubes by Raman spectroscopy

Osswald

Havel

Gogotsi

2007

J Raman Spectroscopy

559

367

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Multiwalled carbon nanotubes (MWCNTs) were oxidized in air and acids while varying the treatment time and/or temperature. The goal of this approach was to create the highest density of carboxyl groups with moderate sample loss, which is necessary for nanocomposite applications. In situ Raman experiments allowed real-time observation of the structural changes in MWCNTs upon oxidation. The ratio of the Raman intensities of the D and G bands was used to estimate the concentration of defects. It was found that while an oxidation for 6 h in H 2 SO 4 /HNO 3 provided the strongest effect, a 'flash oxidation' in air (15 min at 550°C) also leads to an efficient functionalization in a cost-effective and environmentally friendly way. Transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis and electrophoretic mobility analysis were used to study the oxidized nanotubes.

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Section: Resultsmentioning

confidence: 99%

“…This can be explained by the fact that the maximum catalytic effect of iron is reached at ¾1-3 wt.%, while a further increase in the iron concentration does not affect the reaction kinetics. 44,45 This iron can be removed by a subsequent HCl treatment.…”

Section: Resultsmentioning

confidence: 99%

Monitoring oxidation of multiwalled carbon nanotubes by Raman spectroscopy

Osswald

Havel

Gogotsi

2007

J Raman Spectroscopy

559

367

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“…This is presumably especially clear for the employed bulk gold sample, which has a very low surface area (1.1 m 2 /g). Small gold nanoparticles would be expected to bind oxygen more strongly [64] and thus have a more appropriate binding energy and higher activity, as it is also observed in graphite oxidation [91,92]. Among the tested materials, Co 3 O 4 and CeO 2 are the catalysts closest to the optimal oxygen bond strength.…”

Section: Catalytic Oxidation In Tight Contactmentioning

confidence: 99%

“…This could indicate a mechanism, where oxygen is activated on the catalyst and then diffuses to the soot and reacts (a type of spillover phenomenon [99]). For carbon oxidation by Cr 2 O 3 TGA and microscopy experiments [92], IR studies [100], electron microscopy investigations [101] and isotopic labeling experiments [85] have also pointed to a mechanism where oxygen is activated on the catalyst and then diffuses to reactive sites on the carbon surface and reacts. The observation [97,98] that oxygen remains activated when transferred from the catalyst to the soot across a dividing layer of inert material seem most consistent with the activated oxygen species being dissociated atomic oxygen.…”

Section: Catalytic Oxidation In Loose Contactmentioning

confidence: 99%

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Christensen

Grunwaldt

Jensen

2016

Applied Catalysis B: Environmental

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The oxygen bond strength on a catalyst, as measured by the heat of oxygen chemisorption, is observed to be a very important parameter for the activity of the catalyst in soot oxidation. With both intimate contact between soot and catalyst (tight contact) and with the solids stirred loosely together (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation energies for soot oxidation follow linear Brønsted-Evans-Polanyi relationships with the heat of oxygen chemisorption. Among the tested metal or metal oxide catalysts Co 3 O 4 and CeO 2 were nearest to the optimal bond strength in tight contact oxidation, while Cr 2 O 3 was nearest to the optimum in loose contact oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe 2 O 3 and α-Cr 2 O 3 . Guided by an interpolation principle Fe a Cr b O x binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr 2 O x binary oxide catalyst, which exhibited a rate constant at 550 °C that was 2.3 times higher than the one for pure α-Cr 2 O 3 and 29 times higher than the one for pure α-Fe 2 O 3 .

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“…The concentration levels of the gas pollutants can be drastically reduced by increasing the efficiency of the combustion. Both noble metal catalysts (platinum group of metals) [2], and metal oxide catalysts (mainly of alkali and alkaline earth metals) [3] have been studied in coal combustion. It is known that catalyst plays a major role in the reactivity of chars [4].…”

Section: Introductionmentioning

confidence: 99%

Catalytic Combustion of Carbon

Viswanath

Wilson

2017

Eurasian Chem. Tech. J.

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Present day energy needs of mankind are strongly dependent on the combustion of fossil fuels and other carbonaceous materials. The combustion reaction is accompanied by simultaneous production of gaseous pollutants like CO, NO x and SO 2 . In the catalytic combustion, the advantages are two fold: i. The combustion efficiency will be higher and this results in the higher energy realization and ii. The operating temperatures being much lower the emission level of the pollutants also will be greatly reduced. In this study, thermogravimetric analysis (TGA) has been used in following the non-isothermal kinetics of the combustion using two different models. . In the present study an attempt has been made to evaluate from the thermogravimetry, the kinetic parameters for carbon combustion in oxygen and their dependence on the catalyst present in the system. Four different supported systems have been used for the oxidation. Similarly, four different pure carbon materials, differing in their surface areas and crystallinity, have been investigated. For evaluating the catalytic activity, two rate equations have been applied for the isothermal oxidation kinetics of the carbon samples. The catalytic activity on the oxidation of carbon has been observed in the form of lower ignition temperature and a decrease in the energy of activation. The possible role of oxygen spill-over is discussed.

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Metal oxides as catalysts for the oxidation of graphite

Cited by 232 publications

References 8 publications

Monitoring oxidation of multiwalled carbon nanotubes by Raman spectroscopy

Monitoring oxidation of multiwalled carbon nanotubes by Raman spectroscopy

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Catalytic Combustion of Carbon

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