The Sulfur Catalyzed Recombination of Atomic Oxygen in a CO/O<sub>2</sub>/Ar Flame

Smith, Owen; Wang, Shie-Ning; Tseregounis, Spyros I.; Westbrook, Charles K.

doi:10.1080/00102208308923623

Cited by 34 publications

(40 citation statements)

References 23 publications

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“…7,23,43 The flame results have consistently been interpreted in terms of a fast rate constant for the SO 3 + O reaction (2). On the basis of a more accurate value of k 4 , the authors 12 recently reanalyzed the results of Smith and co-workers 21,22 and Merryman and Levy 20 to obtain a value of k′ 2 ) 7.8 × 10 11 exp(-3065/T) cm 3 /(mol s), in support of the earlier estimates. The flame interpretations 12,[20][21][22] were all based on the assumption that the SO 3 level resulted from a balance between formation by SO 2 + O(+M) (4) and consumption by SO 3 + O (2), i.e., that the SO 3 + H and SO 3 + OH reactions could be disregarded due to a high O/H ratio in these flames.…”

Section: Modeling Results and Discussionmentioning

confidence: 99%

“…10,16,17 The rate constant for the reaction between SO 3 and O (2) has not been measured directly and reported data vary by several orders of magnitude. Indirect determinations have been reported on the basis of results from laminar premixed flames [18][19][20][21][22] and, for the reverse step, from reactor experiments. 10,23 A recent re-interpretation of selected flame results, 12 based on a more accurate value of k 4 , indicates a fairly high rate constant for reaction SO 3 + O h SO 2 + O 2 , in agreement with earlier evaluations, [20][21][22] and a fast reaction is also supported by other experiments.…”

Section: Introductionmentioning

confidence: 99%

“…Indirect determinations have been reported on the basis of results from laminar premixed flames [18][19][20][21][22] and, for the reverse step, from reactor experiments. 10,23 A recent re-interpretation of selected flame results, 12 based on a more accurate value of k 4 , indicates a fairly high rate constant for reaction SO 3 + O h SO 2 + O 2 , in agreement with earlier evaluations, [20][21][22] and a fast reaction is also supported by other experiments. 18,19,23 In conflict with these results, Alzueta et al 10 recommend a very low rate constant, which indicates that the reaction is insignificant under most conditions of interest.…”

Section: Introductionmentioning

confidence: 99%

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Reactions of SO₃ with the O/H Radical Pool under Combustion Conditions

Hindiyarti

Glarborg²,

Marshall

2007

J. Phys. Chem. A

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The reactions of SO 3 with H, O, and OH radicals have been investigated by ab initio calculations. For the SO 3 + H reaction (1), the lowest energy pathway involves initial formation of HSO 3 and rearrangement to HOSO 2 , followed by dissociation to OH + SO 2 . The reaction is fast, with k 1 ) 8.4 × 10 9 T 1.22 exp(-13.9 kJ mol -1 /RT) cm 3 mol -1 s -1 (700-2000 K). The SO 3 + O f SO 2 + O 2 reaction (2) may proceed on both the triplet and singlet surfaces, but due to a high barrier the reaction is predicted to be slow. The rate constant can be described as k 2 ) 2.8 × 10 4 T 2.57 exp(-122.3 kJ mol -1 /RT) cm 3 mol -1 s -1 for T > 1000 K. The SO 3 + OH reaction to form SO 2 + HO 2 (3) proceeds by direct abstraction but is comparatively slow, with k 3 ) 4.8 × 10 4 T 2.46 exp(-114.1 kJ mol -1 /RT) cm 3 mol -1 s -1 (800-2000 K). The revised rate constants and detailed reaction mechanism are consistent with experimental data from batch reactors, flow reactors, and laminar flames on oxidation of SO 2 to SO 3 . The SO 3 + O reaction is found to be insignificant during most conditions of interest; even in lean flames, SO 3 + H is the major consumption reaction for SO 3 .

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Section: Modeling Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reactions of SO₃ with the O/H Radical Pool under Combustion Conditions

Hindiyarti

Glarborg²,

Marshall

2007

J. Phys. Chem. A

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“…In addition, the more accurate value available for k 1 allows for a reassessment of the rate constant for the reaction SO 3 + O f SO 2 + O 2 (R2) obtained from flame measurements. [12][13][14] …”

Section: Introductionmentioning

confidence: 99%

“…4,5 Flow reactor studies of SO 2 oxidation under post-flame conditions 5,7 indicate fractional conversions of SO 2 to SO 3 of the order of a few percent. According to these studies, SO 3 formation occurs primarily through the reaction Direct measurements are available for this reaction in the 300-800 K range 8,9 and for the reverse reaction, thermal dissociation of SO 3 , in the temperature range of 1700-2500 K. 10 Indirect determinations are available from flames [12][13][14] and shock tube experiments. 15 The rate constant increases with temperature at lower temperatures, peaks at around 750 K, and drops off as the temperature increases further.…”

Section: Introductionmentioning

confidence: 99%

Thermal Dissociation of SO₃ at 1000−1400 K

et al. 2006

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The thermal dissociation of SO 3 has been studied for the first time in the 1000-1400 K range. The experiments were conducted in a laminar flow reactor at atmospheric pressure, with nitrogen as the bath gas. On the basis of the flow reactor data, a rate constant for SO 3 + N 2 f SO 2 + O + N 2 (R1b) of 5.7 × 10 17 exp(-40000/T) cm 3 /(mol s) is derived for the temperature range 1273-1348 K. The estimated uncertainty is a factor of 2. The rate constant corresponds to a value of the reverse reaction of k 1 ≈ 1.8 × 10 15 cm 6 mol -2 s -1 . The reaction is in the falloff region under the investigated conditions. The temperature and pressure dependence of SO 2 + O (+N 2 ) was estimated from the extrapolation of low temperature results for the reaction, together with an estimated broadening parameter and the high-pressure limit determined recently by Naidoo, Goumri, and Marshall (Proc. Combust. Inst. 2005, 30, 1219-1225. The theoretical rate constant is in good agreement with the experimental results. The improved accuracy in k 1 allows a reassessment of the rate constant for SO 3 + O f SO 2 + O 2 (R2) based on the data of Smith, Tseregounis, and Wang (Int. J. Chem. Kinet. 1982, 14, 679-697), who conducted experiments on a low-pressure CO/O 2 /Ar flame doped with SO 2 . At the location in the flame where the net SO 3 formation rate is zero,A value of 6.9 × 10 10 cm 3 mol -1 s -1 is obtained for k 2 at 1269 K with an uncertainty a factor of 3. A recommended rate constant k 2 ) 7.8 × 10 11 exp(-3065/T) cm 3 mol -1 s -1 is consistent with other flame results as well as the present flow reactor data.

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Kinetic modeling of the CO/H2O/O2/NO/SO2 system: Implications for high-pressure fall-off in the SO2 + O(+M) = SO3(+M) reaction

Mueller

Yetter

Dryer

2000

Int. J. Chem. Kinet.

113

100

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Flow reactor experiments were performed to study moist CO oxidation in the presence of trace quantities of NO (0-400 ppm) and SO 2 (0-1300 ppm) at pressures and temperatures ranging from 0.5-10.0 atm and 950-1040 K, respectively. Reaction profile measurements of CO, CO 2 , O 2 , NO, NO 2 , SO 2 , and temperature were used to further develop and validate a detailed chemical kinetic reaction mechanism in a manner consistent with previous studies of the CO/H 2 /O 2 /NO X and CO/H 2 O/N 2 O systems. In particular, the experimental data indicate that the spin-forbidden dissociation-recombination reaction between SO 2 and Oatoms is in the fall-off regime at pressures above 1 atm. The inclusion of a pressure-dependent rate constant for this reaction, using a high-pressure limit determined from modeling the consumption of SO 2 in a N 2 O/SO 2 /N 2 mixture at 10.0 atm and 1000 K, brings model predictions into much better agreement with experimentally measured CO profiles over the entire pressure range. Kinetic coupling of NO X and SO X chemistry via the radical pool significantly reduces the ability of SO 2 to inhibit oxidative processes. Measurements of SO 2 indicate fractional conversions of SO 2 to SO 3 on the order of a few percent, in good agreement with previous measurements at atmospheric pressure. Modeling results suggest that, at low pressures, SO 3 formation occurs primarily through SO 2 ϩ O(ϩM) ϭ SO 3 (ϩM), but at higher pressures where the fractional conversion of NO to NO 2 increases, SO 3 formation via SO 2 ϩ NO 2 ϭ SO 3 ϩ NO becomes important. For the conditions explored in this study, the primary consumption pathways for SO 3 appear to be SO 3 ϩ HO 2 ϭ HOSO 2 ϩ O 2 and SO 3 ϩ H ϭ SO 2 ϩ OH. Further study of these reactions would increase the confidence with which model predictions of SO 3 can be viewed.

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The Sulfur Catalyzed Recombination of Atomic Oxygen in a CO/O₂/Ar Flame

Cited by 34 publications

References 23 publications

Reactions of SO₃ with the O/H Radical Pool under Combustion Conditions

Reactions of SO₃ with the O/H Radical Pool under Combustion Conditions

Thermal Dissociation of SO₃ at 1000−1400 K

Kinetic modeling of the CO/H2O/O2/NO/SO2 system: Implications for high-pressure fall-off in the SO2 + O(+M) = SO3(+M) reaction

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The Sulfur Catalyzed Recombination of Atomic Oxygen in a CO/O2/Ar Flame

Cited by 34 publications

References 23 publications

Reactions of SO3 with the O/H Radical Pool under Combustion Conditions

Reactions of SO3 with the O/H Radical Pool under Combustion Conditions

Thermal Dissociation of SO3 at 1000−1400 K

Kinetic modeling of the CO/H2O/O2/NO/SO2 system: Implications for high-pressure fall-off in the SO2 + O(+M) = SO3(+M) reaction

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The Sulfur Catalyzed Recombination of Atomic Oxygen in a CO/O₂/Ar Flame

Reactions of SO₃ with the O/H Radical Pool under Combustion Conditions

Reactions of SO₃ with the O/H Radical Pool under Combustion Conditions

Thermal Dissociation of SO₃ at 1000−1400 K