Enhanced electron-ion recombination in hydrocarbon flames by metallic additives in relation to soot suppression

Goodings, John M.; Graham, Sheila M.; Karellas, Nicholas S.

doi:10.1016/0168-1176(86)87025-2

Cited by 4 publications

(2 citation statements)

References 8 publications

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“…Known thermothemetal, the A+ ions disappear by relatively slow, three-body, chemical data for the metals, their compounds, and associated atomic recombination cations are assembled in Table 1. [3] A + + e -+ M -+ A + M Downstream in the burnt gas with metal absent, the ion signal is overwhelminghly H30+ and its first hydrate, H30+.H20 (1, where M is a third body. For Fe, Co, Ni, and Cu, the atomic ion 7), most of which is formed on sampling (1 3).…”

Section: ] H 3 0 + + E --+ H + H + O H ( O R H + H 2 0 )mentioning

confidence: 99%

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Ion chemistry of transition metals in hydrocarbon flames. I. Cations of Fe, Co, Ni, Cu, and Zn

Tran¹,

Karellas²,

Goodings³

1988

Can. J. Chem.

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A fuel-rich, premixed, conical, methane-oxygen flame at 2200 K and atmospheric pressure is doped with approximately 1 ppm of the transition metals Fe, Co, Ni, Cu, and Zn. Metallic ions of these metals and their compounds formed by chemical ionization reactions with H 3 0 + are observed by sampling the flame through a nozzle into a quadrupole mass spectrometer. Concentration profiles of individual and total cations are measured as a function of distance along the flame axis, and also mass spectra at a fixed point in the burnt gas. For a given metal A, the mass spectra are dominated by the atomic ion A+ with smaller amounts of the molecular ions AH+, AOH', A(OH)H+, A(oH)~H+, and ACO+ and their hydrates. The spectra for Fe, Co, Ni, and Cu are very similar, but no ions are observed for Zn. The ion chemistry is dominated by proton transfer reactions from H 3 0 + to A and to the metallic compounds AO, AOH, and A(OH)2 which exist in the flame. In addition, A+ can be formed from the reaction of H 3 0 + with A by a charge transfer process. Also, some ions are formed by three-body association and free radical stripping reactions. The chemistry is discussed in detail to explain the relative magnitudes of the ion signals observed. In particular, when the atomic A+ ion is dominant, its concentration can reach a superequilibrium level early in the burnt-gas region before it slowly decays downstream; the phenomenon is similar to the free radical overshoot which occurs in hydrogen flames. [Traduit par la revue] Introduction We recently had occasion to consider the ion chemistry of alkali and alkaline earth metals in a premixed, fuel-rich, CH4-C2H2-O2 flame (I). This arose in the context of soot suppression by metallic additives involving an ionic mechanism (2, 3). We have now extended these studies to include chemical ionization (CI) processes for the first row of ten transition metals, Sc to Zn (atomic numbers 2 1-30). The last five including Fe, Co, Ni, Cu, and Zn are described here; the first five including Sc, Ti, V, Cr, and Mn present some different features, and are the subject of a second paper.A premixed, fuel-rich, CH4-O2 flame doped with metallic additive is sampled into a mass spectrometer to ascertain what metallic cations are present and where in the flame they occur. The interest in the problem stems from the considerable variety of oxidation states known for these metals, and the bond formation and structural configurations which they may exhibit at high temperature.Basically two mass-spectrometric flame studies involving cations of some of these transition metals have appeared in the past. In hydrogen flames, Hayhurst and Telford (4) observed ions for Cr, Mn, Fe, and Cu, and also other metals, in the course of measuring rate constants attributed to the charge transfer reaction

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Section: ] H 3 0 + + E --+ H + H + O H ( O R H + H 2 0 )mentioning

confidence: 99%

“…This arose in the context of soot suppression by metallic additives involving an ionic mechanism (2,3). We have now extended these studies to include chemical ionization (CI) processes for the first row of ten transition metals, Sc to Zn (atomic numbers 2 1-30).…”

Section: Introductionmentioning

confidence: 99%

Ion chemistry of transition metals in hydrocarbon flames. I. Cations of Fe, Co, Ni, Cu, and Zn

Tran¹,

Karellas²,

Goodings³

1988

Can. J. Chem.

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The dissociative recombination of molecular ions

Brian

1990

Physics Reports

296

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Investigation of the initial reactions of the Calcote mechanism for soot formation

Egsgaard

1996

J. Am. Soc. Mass Spectrom.

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The first three reactions of the Calcote mechanism for soot formation, that is, C3H 3 (+) +C2H2→C5H 5 (+) , C5H 5 (+) →C5H 3 (+) H2, and C5H 3 (+) +C2H2→C7H 5 (+) , have been studied based on chemi-ions withdrawn directly from a premixed methane-oxygen flame by supersonic molecular beam sampling. The first reaction is reversible and involves the formation of a specific encounter complex sensitive to pressure and ion kinetic energy. The second reaction appears to require large amounts of internal energy in the C5H 5 (+) ion to proceed. The third reaction is reversible; however, in contrast to the initiating reaction, the C5H 3 (+) ion formed from the [C7H 5 (+) ]* complex exhibits a much lower reactivity. The conclusions are based on ion-molecule reactions as well as collision activation mass spectrometry of isolated chemi-ions. In addition, the product distributions as functions of pressure and ion kinetic energy were studied.

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Enhanced electron-ion recombination in hydrocarbon flames by metallic additives in relation to soot suppression

Cited by 4 publications

References 8 publications

Ion chemistry of transition metals in hydrocarbon flames. I. Cations of Fe, Co, Ni, Cu, and Zn

Ion chemistry of transition metals in hydrocarbon flames. I. Cations of Fe, Co, Ni, Cu, and Zn

The dissociative recombination of molecular ions

Investigation of the initial reactions of the Calcote mechanism for soot formation

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