Reaction of carbon with oxidizing gases: The role of unpaired electrons

Harker, H.; Gallagher, J.T.; Parkin, A.

doi:10.1016/0008-6223(66)90053-4

Cited by 29 publications

(7 citation statements)

References 10 publications

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“…In contrast, further studies by Harker et al (1966) indicated that the number of unpaired electrons on a carbon is not directly related to its reactivity with 02(g). The investigators did find a relationship between the number of unpaired electrons and the ability of a carbon to adsorb NO(g), however.…”

Section: Influence Of Unpaired Electrons On Irreversible Adsorptionmentioning

confidence: 86%

Irreversible adsorption of phenolic compounds by activated carbons

Grant¹,

King²

1988

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Section: Influence Of Unpaired Electrons On Irreversible Adsorptionmentioning

confidence: 86%

Irreversible adsorption of phenolic compounds by activated carbons

Grant¹,

King²

1988

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“…The initial absorption appears, on the basis of magnetic susceptibility, infrared, and thermal studies, to involve the addition of nitric oxide in an "N-down" configuration.5•6 Another study casts doubt on the notion that the sites reactive toward nitric oxide addition could be spin centers. 4 It also appeared that more highly heattreated carbons gave nitric oxide surface complexes of lower thermal stability. 4 This suggests that addition to aromatic ring structures is involved and that the number of resonance structures affects the stability of the NO adduct.…”

Section: Introductionmentioning

confidence: 99%

“…4 It also appeared that more highly heattreated carbons gave nitric oxide surface complexes of lower thermal stability. 4 This suggests that addition to aromatic ring structures is involved and that the number of resonance structures affects the stability of the NO adduct. In summary, it appears that the literature implies that radical addition processes occur on the surface of carbons, involving the paramagnetic nitric oxide (which is essentially free radical in nature).…”

Section: Introductionmentioning

confidence: 99%

Chemisorption of nitric oxide on char. 1. Reversible nitric oxide sorption

Teng¹,

Suuberg²

1993

J. Phys. Chem.

106

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The process of chemisorption of nitric oxide (NO) on a carbon derived from phenol-formaldehyde resin has been studied at temperatures between 323 and 473 K and at N O partial pressures between 2.02 and 10.1 kPa. The process of chemisorption can be split into two separate pathways-one a reversible chemisorptive pathway forming nitric oxide surface complexes C ( N 0 ) and the other an irreversible chemisorptive pathway yielding N2 and carbon surface oxides C ( 0 ) and C(02). The enthalpy of formation of C ( N 0 ) is between 42 and 46 W/mol exothermic. The reversible pathway is governed by isotherms that are linear in NO partial pressure, within the range of pressures studied here. This same process, however, appears to be kinetically second order with respect to N O partial pressure, suggesting a possible role of NO dimer as an intermediate in the process. IatradUcti0nThe reactions of nitric oxide with carbons have been considered as offering interesting possibilities for reduction of NO emissions from combustion systems. Some of the relevant literature on these reactions has been reviewed in a paper on the global kinetics of the gasification reaction.'s2 The first step of the process, involving the chemisorption of NO on the carbon surface, has been separately con~idered.~ The literature on chemisorption and/or physisorption of NO on carbons is l i m i t~d .~-~~ Most of these studies acknowledge that if temperatures are kept low (Le., well below ambient) mainly physisorption occurs.*J0 It is generally agreed that chemisorption occurs to a significant extent at temperatures above ambient. The chemisorption is generally accompanied by formation of surface oxides and release of N2.The actual mechanism of the chemisorption processes is not yet established in any detail.One study has reported that the chemisorption of nitric oxide affects the spin-resonance absorption of charcoal in a manner similar to oxygen; there is an increase of ESR absorption linewidth with increasing extent of absorption on a cleaned carbon surface.I2 The difference is that oxygen adsorbed at room temperature can be desorbed by evacuation, whereas nitric oxide cannot. The initial absorption appears, on the basis of magnetic susceptibility, infrared, and thermal studies, to involve the addition of nitric oxide in an "N-down" config~ration.~,~ Another study casts doubt on the notion that the sites reactive toward nitric oxide addition could be spin center^.^ It also appeared that more highly heattreated carbons gave nitric oxide surface complexes of lower thermal stability.' This suggests that addition to aromatic ring structures is involved and that the number of resonance structures affects the stability of the NO adduct. In summary, it appears that the literature implies that radical addition processes occur on the surface of carbons, involving the paramagnetic nitric oxide (which is essentially free radical in nature). These addition processes appear to affect the ESR spectra but do not destroy the measurable free radicals in carbons (which ar...

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“…Therefore, the production of C0_ might be associated with the oxygen-free radical reaction. The other products may arise by independent mechanisms (Harker et al, 1966).…”

Section: Free Radical Character Of Carbonmentioning

confidence: 99%

“…Two identical 1 cm diameter columns were packed with 1.6 g of F-400 inactive otherwise. It is also known that some radicals are formed from carbonizing organic materials in absence of oxygen (Harker et, al., 1966).…”

Section: Effect Of Surface Oxygenmentioning

confidence: 99%

Effects of Activated Carbon on Reactions of Free and Combined Chlorine With Phenols

Βουδριασ¹

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Reaction of carbon with oxidizing gases: The role of unpaired electrons

Cited by 29 publications

References 10 publications

Irreversible adsorption of phenolic compounds by activated carbons

Irreversible adsorption of phenolic compounds by activated carbons

Chemisorption of nitric oxide on char. 1. Reversible nitric oxide sorption

Effects of Activated Carbon on Reactions of Free and Combined Chlorine With Phenols

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