Sulphurous negative ions in a fuel-rich, CH4–O2 flame with OCS additive

1983 ◽  
Vol 61 (8) ◽  
pp. 1703-1711 ◽  
Author(s):  
John M. Goodings ◽  
Kamal Elguindi ◽  
Diethard K. Bohme
Keyword(s):  
Reaction Zone ◽  
Atmospheric Pressure ◽  
Negative Ions ◽  
Ion Concentration ◽  
Quadrupole Mass ◽  
Ion Chemistry ◽  
Naturally Occurring ◽  
Pressure Profiles ◽  
Ion Profiles ◽  
Carbonyl Sulphide

Sulphurous negative ions S • SH • SO • SO2/S2• SO3• HSO3• SO4• and HSO4 were observed when 0.2% of carbonyl sulphide (OCS) was added to a conical, laminar, premixed. fuel-rich (equivalence ratio [Formula: see text]) CH4–O2 flame burning at atmospheric pressure. Profiles were obtained of ion concentration vs. distance along the flame axis by sampling the flame through a pinhole into a quadrupole mass spectrometer. Some of the ion signals observed in the flame reaction zone are very large, particularly that for HSO4. None of the sulphurous ions detected contain carbon. Of those listed above, only S−,•SH, • SO • and SO2 persist downstream through the burnt gas. The sulphurous ions are formed by chemical ionization processes of neutral sulphurous intermediates reacting with the naturally-occurring ions present in any hydrocarbon flame. The ion chemistry is discussed, as is the underlying neutral chemistry of sulphur relevant to the flame environment. The ion profiles show the rapidity with which OCS is oxidized through SH and SO to SO2 even within the reaction zone of this fuel-rich flame. No evidence was obtained for the presence of sulphuric or sulphurous acids, and the presence of S2: was not confirmed.

Ion chemistry of second-row transition metals in hydrocarbon flames: cations and anions of Y, Zr, Nb, and Mo

1995 ◽  
Vol 73 (12) ◽  
pp. 2263-2271 ◽  
Author(s):  
Christine C.Y. Chow ◽  
John M. Goodings
Keyword(s):  
Transition Metals ◽  
Gas Phase ◽  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Ion Concentration ◽  
Oxidation States ◽  
Metallic Ions ◽  
Ion Chemistry ◽  
Hydrocarbon Flames

A pair of laminar, premixed, CH4–O2 flames above 2000 K at atmospheric pressure, one fuel-rich (FR) and the other fuel-lean (FL), were doped with ~10−6 mol fraction of the second-row transition metals Y, Zr, Nb, and Mo. Since these hydrocarbon flames contain natural ionization, metallic ions were produced in the flames by the chemical ionization (CI) of metallic neutral species, primarily by H3O+ and OH− as CI sources. Both positive and negative ions of the metals were observed as profiles of ion concentration versus distance along the flame axis by sampling the flames through a nozzle into a mass spectrometer. For yttrium, the observed ions include the YO+•nH2O (n = 0–3) series, and Y(OH)4−. With zirconium, they include the ZrO(OH)+•nH2O (n = 0–2) series, and ZrO(OH)3−. Those observed with niobium were the cations Nb(OH)3+ and Nb(OH)4+, and the single anion NbO2(OH)2−. For molybdenum, they include the cations MoO(OH)2+ and MoO(OH)3+, and the anions MoO3− and MoO3(OH)−. Not every ion was observed in each flame; the FL flame tended to favour the ions in higher oxidation states. Also, flame ions in higher oxidation states were emphasized for these second-row transition metals compared with their first-row counterparts. Some ions written as members of hydrate series may have structures different from those of simple hydrates; e.g., YO+•H2O = Y(OH)2+ and ZrO(OH)+•H2O = Zr(OH)3+, etc. The ion chemistry for the production of these ions by CI in flames is discussed in detail. Keywords: transition metals, ions, flame, gas phase, negative ions.

Hydrocarbon ions in fuel-rich, CH4–C2H2–O2 flames as a probe for the initiation of soot: interpretation of the ion chemistry

1982 ◽  
Vol 60 (22) ◽  
pp. 2766-2776 ◽  
Author(s):  
John M. Goodings ◽  
Scott D. Tanner ◽  
Diethard K. Bohme
Keyword(s):  
Charge Transfer ◽  
Proton Transfer ◽  
Reaction Zone ◽  
Negative Ions ◽  
Negative Ion ◽  
Ion Chemistry ◽  
Soot Precursors ◽  
Ion Profiles ◽  
Three Body ◽  
Positive Ion

The ion chemistry is discussed for fuel-rich, nearly sooting, methane–oxygen flames at atmospheric pressure with added acetylene. Different types of ion–molecule reactions, both positive and negative, which can contribute through chemical ionization (CI) processes are summarized including their dependence on temperature, pressure, and equivalence ratio [Formula: see text]. Extensive data were presented previously involving ion concentration profiles measured with a mass spectrometer as a function of distance along the axis of conical flames. An understanding of the dominant CI processes provides insight into the early chemical stage of soot formation associated with the flame reaction zone. The negative ion profiles show moderately unsaturated hydrocarbon ions upstream formed by proton transfer followed by progressive dehydrogenation; the highly unsaturated, carbonaceous ions observed downstream appear to arise by two- and three-body electron attachment, charge transfer, and H-atom stripping. The negative hydrocarbon ions can all be explained in terms of polyacetylene derivatives. The same build-up of carbonaceous species downstream is evident from the positive ion profiles. A major role is ascribed to proton transfer reactions with lesser contributions from charge transfer and ion–molecule condensation; three-body association is probably insignificant. Experiments with added acetylene indicate extensive fuel pyrolysis early in the reaction zone. There is no evidence that an ionic mechanism is dominant in forming soot precursors compared with neutral condensation reactions. Because of complexities in the positive ion chemistry, the negative ions appear to provide the more straightforward probe of the underlying neutral chemistry.

Sulphur cation chemistry in a fuel-rich, CH4–O2 flame with OCS additive

1986 ◽  
Vol 64 (9) ◽  
pp. 1733-1742 ◽  
Author(s):  
Nicholas S. Karellas ◽  
John M. Goodings
Keyword(s):  
Reaction Zone ◽  
Atmospheric Pressure ◽  
Mass Spectra ◽  
Mass Range ◽  
Major Product ◽  
Premixed Flame ◽  
Ion Concentration ◽  
Concentration Profiles ◽  
Ion Chemistry ◽  
Ion Molecule Reactions

A fuel-rich, methane–oxygen, premixed flame at atmospheric pressure was doped with 0.2 mol% of OCS. More than 40 different sulphurous cations were observed in the mass range < 100 u by sampling the flame into a flame-ion mass spectrometer. Ion concentration profiles along the flame axis are presented, together with mass spectra at fixed points in the flame. In the reaction zone, primary sulphur ions CHxS+ (x = 1, 3, 5) undergo extensive ion–molecule reactions (association and condensation) with CH4/CH3, C2H2, and OCS to form a considerable variety of secondary sulphurous cations. Just downstream of the reaction zone, the ion chemistry is somewhat different; it appears to be dominated by reactions of primary sulphur ions including HxS+ (x = 0–3) with C2H2 present as an intermediate. A few ions (HxS+, OS+, S2+) persist throughout the burnt gas region in equilibrium with the natural flame ions CHO+ and H3O+. These sulphurous cation signals show the evolution of the sulphur chemistry, both ionic and neutral, through the flame reaction zone into the burnt gas downstream where H2S, not SO2, is the major product in fuel-rich combustion.

Hydrocarbon ions in fuel-rich, CH4–C2H2–O2 flames as a probe for the initiation of soot: an experimental approach

1981 ◽  
Vol 59 (12) ◽  
pp. 1760-1770 ◽  
Author(s):  
Scott D. Tanner ◽  
John M. Goodings ◽  
Diethard K. Bohme
Keyword(s):  
Reaction Zone ◽  
Soot Formation ◽  
Unsaturated Hydrocarbon ◽  
Ion Concentration ◽  
Negative Ion ◽  
Ion Chemistry ◽  
Positive Ions ◽  
Total Ionization ◽  
Ion Profiles ◽  
Positive Ion

The natural hydrocarbon ions CnHx± (n ≥ 2, x ≥ 0) present in premixed, fuel-rich, nearly sooting, CH4–C2H2–O2 flames at atmospheric pressure were studied as a probe of the early chemical stages of soot formation. Ion concentration profiles were measured mass-spectrometrically along the flame axis through the reaction zone into the burnt gas downstream. Total ionization profiles were examined for their dependence on both temperature and equivalence ratio, [Formula: see text] Families of individual CnHx− negative ion profiles exhibit concentration peaks in three distinct regions; predominantly oxygenated ions occur upstream, giving way to moderately unsaturated hydrocarbon ions near the end of the reaction zone, leading to highly unsaturated carbonaceous ions further downstream. The concentrations of the downstream ions alternate with the parity of n, the even-n species being larger. Series of CnHx+ positive ion profiles, for a given n, show profile peak positions which move steadily downstream with decreasing x, indicative of progressive dehydrogenation. The positive ion chemistry of these series is essentially independent of n. As [Formula: see text] is increased at constant temperature towards the sooting point, the concentrations of CnHx± ions increase while those of the oxygenated ions decrease; the positive ions show a relative enhancement of species having high values of n.

Comparative sulphur cation chemistry in a hydrocarbon flame with H2S, OCS, and SO2 additives

1986 ◽  
Vol 64 (12) ◽  
pp. 2412-2417 ◽  
Author(s):  
Nicholas S. Karellas ◽  
John M. Goodings
Keyword(s):  
Reaction Zone ◽  
Atmospheric Pressure ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Mass Range ◽  
Total Ionization ◽  
Ion Recombination ◽  
Diffusion Mass ◽  
Oxygen Flame

A fuel-rich, conical, premixed, methane–oxygen flame at atmospheric pressure was doped separately with 0.2 mol% of H2S, OCS, and SO2 to probe the chemistry of sulphur at its source during combustion. These three additives represent a broad range of fuel-sulphur contaminants since they occur early, intermediate, and late in the sulphur oxidation sequence. A wide variety of sulphurous cations, formed by chemical ionization reactions, is observed for each additive by sampling the flame into a mass spectrometer. The total ionization profile measured along the flame axis is enhanced in the reaction zone when a sulphur additive is present; the mechanism involves the formation of sulphurous negative ions which reduces the rates of cation loss by electron–ion recombination and ambipolar diffusion. Mass spectra measured in the mass range 10–110 u at fixed points on the flame axis are very similar for all three additives, and are not helpful in the identification of the additive. However, the general presence of sulphur is evident from large signals measured near the reaction zone at five principal mass numbers; namely, 45 u (CHS+), 47 u (CH3S+), 58 u (C2H2S+), 59 u (C2H3S+), and 69 u (C3HS+) related to CS, thioformaldehyde, thioketene, and C3S.

Flame-ion probe of the reaction zone in a CH4–O2–Ar flame with added HCN, NH3 and NO

1981 ◽  
Vol 59 (12) ◽  
pp. 1810-1818 ◽  
Author(s):  
John M. Goodings ◽  
Gary B. De Brou ◽  
Diethard K. Bohme
Keyword(s):  
Reaction Zone ◽  
Atmospheric Pressure ◽  
Protonated Form ◽  
Good Evidence ◽  
Ion Concentration ◽  
Bimolecular Reactions ◽  
Hydrocarbon Flames ◽  
Ion Probe ◽  
Increased Sensitivity ◽  
N Compounds

The addition of 0.3% of the fuel-nitrogen (fuel-N) compounds HCN, NH3, or NO to a premixed, fuel-rich, CH4–O2–Ar flame burning at atmospheric pressure demonstrated the rapid interconversion of nitrogenous intermediates in the reaction zone. The nitrogenous species (HCN/CN, HNCO/NCO, NH3, NH2, NH, NO, NO2) were observed as ions (CN−, H2CN+, NCO−, H2NCO+, NH4+, NH3+, NH2+, NO+, NO2−, and hydrate ions) formed in chemical ionization processes discussed previously (1). The ions were sampled directly into a flame-ion mass spectrometer which had sufficient spatial resolution for the measurement of ion concentration profiles through the reaction zone. The study bears on Fenimore's suggestion for the formation of "prompt NO" in fuel-rich hydrocarbon flames. These additive results were compared with previous results involving nitrogenous species present in a similar CH4–O2 flame doped with 10% N2. The increased sensitivity of the additive approach confirmed many of the mass assignments and mechanisms involved in the N2 study. Reasonably good evidence was obtained for the elusive intermediate HNCO (and possibly isomeric HCNO as well) in protonated form, and also formamide, NH2CHO, which had not been detected previously. Similarities in profile peak positions and magnitudes observed for many ions, irrespective of the nature of the fuel-N additive, indicated that the nitrogenous species were linked by a network of fast bimolecular reactions, many of which appeared to be balanced in the reaction zone.

Sulphur anion chemistry in hydrocarbon flames with H2S, OCS, and SO2 additives

1986 ◽  
Vol 64 (4) ◽  
pp. 689-694 ◽  
Author(s):  
John M. Goodings ◽  
Diethard K. Bohme ◽  
Kamal Elguindi ◽  
Arnold Fox
Keyword(s):  
Rate Constants ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Negative Ions ◽  
Ion Concentration ◽  
Concentration Profiles ◽  
Hydrocarbon Flame ◽  
Flowing Afterglow ◽  
Hydrocarbon Flames ◽  
Oxygen Flame

A premixed, fuel-rich, methane–oxygen flame at atmospheric pressure was doped separately with 0.2 mol% of H2S, OCS, and SO2 to probe the behaviour of fuel sulphur during combustion. These three additives represent compounds occurring early, intermediate, and late in the oxidation sequence of fuel sulphur. They are chemically ionized in the reaction zone of a hydrocarbon flame to give large signals of sulphurous negative ions. Those detected include S−, SH−, SO− (uncertain), SO2− (S2−), SO3−, HSO3−, CH3O−•SO2, SO4− (S2O2−, S3−), and HSO4−. Ion concentration profiles of these ions were measured along the conical flame axis by sampling the flame into a mass spectrometer. The shapes of the profiles are insensitive to the nature of the additive, but their relative magnitudes are indicative of the additive's position in the sulphur oxidation sequence. For each additive, the very large HSO4− signal has analytical implications as an indicator for total fuel sulphur. The sulphurous anion chemistry is discussed for each additive in terms of roughly twenty ion (electron)-molecule reactions of six basic types, whose rate constants were known previously, or were measured at room temperature using the York flowing afterglow apparatus.

scholarly journals Propagation of radiosonde pressure sensor errors to ozonesonde measurements

2014 ◽  
Vol 7 (1) ◽  
pp. 65-79 ◽  
Author(s):  
R. M. Stauffer ◽  
G. A. Morris ◽  
A. M. Thompson ◽  
E. Joseph ◽  
G. J. R. Coetzee ◽  
...  
Keyword(s):  
Pressure Sensor ◽  
Atmospheric Pressure ◽  
Pressure Profile ◽  
Mixing Ratio ◽  
Concentration Cell ◽  
Pressure Profiles ◽  
Dependent Variables ◽  
Sensor Errors ◽  
Subsequent Addition ◽  
Total Column

Abstract. Several previous studies highlight pressure (or equivalently, pressure altitude) discrepancies between the radiosonde pressure sensor and that derived from a GPS flown with the radiosonde. The offsets vary during the ascent both in absolute and percent pressure differences. To investigate this problem further, a total of 731 radiosonde/ozonesonde launches from the Southern Hemisphere subtropics to northern mid-latitudes are considered, with launches between 2005 and 2013 from both longer term and campaign-based intensive stations. Five series of radiosondes from two manufacturers (International Met Systems: iMet, iMet-P, iMet-S, and Vaisala: RS80-15N and RS92-SGP) are analyzed to determine the magnitude of the pressure offset. Additionally, electrochemical concentration cell (ECC) ozonesondes from three manufacturers (Science Pump Corporation; SPC and ENSCI/Droplet Measurement Technologies; DMT) are analyzed to quantify the effects these offsets have on the calculation of ECC ozone (O3) mixing ratio profiles (O3MR) from the ozonesonde-measured partial pressure. Approximately half of all offsets are > ±0.6 hPa in the free troposphere, with nearly a third > ±1.0 hPa at 26 km, where the 1.0 hPa error represents ~ 5% of the total atmospheric pressure. Pressure offsets have negligible effects on O3MR below 20 km (96% of launches lie within ±5% O3MR error at 20 km). Ozone mixing ratio errors above 10 hPa (~ 30 km), can approach greater than ±10% (> 25% of launches that reach 30 km exceed this threshold). These errors cause disagreement between the integrated ozonesonde-only column O3 from the GPS and radiosonde pressure profile by an average of +6.5 DU. Comparisons of total column O3 between the GPS and radiosonde pressure profiles yield average differences of +1.1 DU when the O3 is integrated to burst with addition of the McPeters and Labow (2012) above-burst O3 column climatology. Total column differences are reduced to an average of −0.5 DU when the O3 profile is integrated to 10 hPa with subsequent addition of the O3 climatology above 10 hPa. The RS92 radiosondes are superior in performance compared to other radiosondes, with average 26 km errors of −0.12 hPa or +0.61% O3MR error. iMet-P radiosondes had average 26 km errors of −1.95 hPa or +8.75 % O3MR error. Based on our analysis, we suggest that ozonesondes always be coupled with a GPS-enabled radiosonde and that pressure-dependent variables, such as O3MR, be recalculated/reprocessed using the GPS-measured altitude, especially when 26 km pressure offsets exceed ±1.0 hPa/±5%.

scholarly journals A numerical model of the ionosphere, including the E-region above EISCAT

1996 ◽  
Vol 14 (2) ◽  
pp. 191-200 ◽  
Author(s):  
P.-Y. Diloy ◽  
A. Robineau ◽  
J. Lilensten ◽  
P.-L. Blelly ◽  
J. Fontanari
Keyword(s):  
Electric Field ◽  
Fluid Model ◽  
Molecular Ions ◽  
Ion Concentration ◽  
Topside Ionosphere ◽  
Ion Chemistry ◽  
Vhf Radar ◽  
Theoretical Predictions ◽  
Consistent Manner ◽  
E Region

Abstract. It has been previously demonstrated that a two-ion (O+ and H+) 8-moment time-dependent fluid model was able to reproduce correctly the ionospheric structure in the altitude range probed by the EISCAT-VHF radar. In the present study, the model is extended down to the E-region where molecular ion chemistry (NO+ and O+2, essentially) prevails over transport; EISCAT-UHF observations confirmed previous theoretical predictions that during events of intense E×B induced convection drifts, molecular ions (mainly NO+) predominate over O+ ions up to altitudes of 300 km. In addition to this extension of the model down to the E-region, the ionization and heating resulting from both solar insolation and particle precipitation is now taken into account in a consistent manner through a complete kinetic transport code. The effects of E×B induced convection drifts on the E- and F-region are presented: the balance between O+ and NO+ ions is drastically affected; the electric field acts to deplete the O+ ion concentration. The [NO+]/[O+] transition altitude varies from 190 km to 320 km as the perpendicular electric field increases from 0 to 100 mV m-1. An interesting additional by-product of the model is that it also predicts the presence of a noticeable fraction of N+ ions in the topside ionosphere in good agreement with Retarding Ion Mass Spectrometer measurements onboard Dynamic Explorer.

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