An update on the carbon-oxygen reaction

Walker, P.L.; Taylor, Raymond L.; Ranish, J.M.

doi:10.1016/0008-6223(91)90210-a

Cited by 165 publications

(87 citation statements)

References 35 publications

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“…Atomic oxygen has a relatively high reaction probability on graphite [102], and a neighboring catalyst dosing atomic oxygen should thus raise the oxygen coverage on the surface of the carbonaceous material [85]. This should benefit the oxidation rate, since the activation energies for desorption of CO and CO 2 from oxidized species in the surface of graphite decrease with increasing oxygen coverage [72,77,78,103,104].…”

mentioning

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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mentioning

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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“…Due to the strong, inplane covalent bonding, the basal plane of graphite, i.e. the flat flake surface, is considered to be comparatively inert [6]. Thus attack by oxygen is only possible at the edge atoms shown in Fig.…”

Section: Theory 21 Classic Solid State Kinetic Expression For Reactimentioning

confidence: 99%

“…(11) and Eq. (6) shows that the term k ASA (T) is equivalent to a specific case of the "aeric reactivity of growth", while the "space function" is given by f ASA ()*ASA 0 /m 0 . Thus Eq.…”

Section: Generalized Expression For Reaction Interface-controlled Reamentioning

confidence: 99%

A generalized solid state kinetic expression for reaction interface-controlled reactivity

2013

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The ICTAC-recommended approach was used to characterize the gasification of high-purity, highly crystalline, large natural graphite flakes in oxygen. The average activation energy was found to be 157.74.2 kJ.mol -1 . The graphite properties and the simple gasification reaction taking place make this an ideal material for the study of reaction interface-controlled reactivity. Based on simple structural and geometrical observations, it was expected that the conversion function would be that of a shrinking disc. However, the experimental conversion function exhibited a behaviour which could not be linked to any of the commonly established reaction models.A factor contributing to this disconnection is the use of an arbitrary scaling procedure in classic solid state kinetics. A more integrated approach has recently been proposed in the literature with the potential for reconciling disparate models into a single comprehensive scheme. A generalization of the classic solid state kinetic expressions for interface-controlled reactivity is proposed which fits into the integrated approach. It is based on fundamental considerations for the subset of reactions in which reactivity is controlled by the reaction interface alone. The fundamental nature of the approach yields an expression for which all the variables are directly measurable, without any assumptions regarding the conversion function.The generalized conversion function will always start at a value of one, making interpretation and direct comparison of any active surface area (ASA) progression possible. Visual observations indicate the growth of defect structures within the macro graphite flakes, leading to an increase in ASA. This leads to a behaviour resembling nucleation and growth, despite the interface-controlled reaction taking place on a disc-shaped solid. The random nature of the oxidized flake microstructure makes it difficult to develop representative analytical models for this behaviour.

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“…50,51) The inorganic elements are located at the edge sites of the carbon layer and at the vacancies between the carbon layers in the graphitic-like carbon building blocks of coke/agricultural blends also known as carbon active sites. [52][53][54] Their location allows them to catalytically enhance oxygen reactivity of neighbouring carbon atoms in the carbon matrix. 52,55) The reactivity of agricultural waste materials also might be influenced by the activation of the -O -groups present in the structure.…”

Section: Effect Of Blending On Gas Phase Reactionmentioning

confidence: 99%

“…[52][53][54] Their location allows them to catalytically enhance oxygen reactivity of neighbouring carbon atoms in the carbon matrix. 52,55) The reactivity of agricultural waste materials also might be influenced by the activation of the -O -groups present in the structure. The cellulose, hemicellulose and lignin (Fig.…”

Section: Effect Of Blending On Gas Phase Reactionmentioning

confidence: 99%

Structural Transformation of Agricultural Waste/Coke Blends and Their Implications during High Temperature Processes

et al. 2011

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With a sharp increase in demand and production, palm oil wastes, (i.e. empty fruit bunches, fibre and shells) are generated, out of which a large amount ends up in landfill. In such a context, alternative solutions are needed to reduce the impact of these agricultural wastes on the environment. The present paper investigates the effect of addition of agricultural waste materials on the combustion behavior of its blends with metallurgical coke (MC). Two types of agricultural waste materials, palm shell and coconut shell, were mixed in different proportion with MC, while the gas phase reactions were studied at 1 200°C in a drop tube furnace (DTF). In the tested conditions, the blends containing agricultural waste materials indicated higher combustion efficiencies compared to MC alone. Carbon structure analysis were performed through 13 CP/MAS NMR spectroscopy showing various groups of carbons present in the agricultural waste samples ranging from aliphatic to aromatic carbons. The morphology of the samples was studied through Scanning Electron Microscope (SEM). SEM provided a qualitative description of the pore structure in the raw samples as well as the changes occurring following the gas phase reactions in the DTF. It was found that the particles derived from the wastes became increasingly deformed and lost their cell lumen. Surface area measurements were found to be in good agreement with the SEM images, supporting the higher combustion efficiency of the blends in comparison to coke alone. The present study suggests that agricultural waste materials have the potential to partially replace MC, as an auxiliary fuel in metallurgical processes.

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An update on the carbon-oxygen reaction

Cited by 165 publications

References 35 publications

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

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

A generalized solid state kinetic expression for reaction interface-controlled reactivity

Structural Transformation of Agricultural Waste/Coke Blends and Their Implications during High Temperature Processes

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