Chemical species associated with the early stage of soot growth in a laminar premixed ethylene–oxygen–argon flame

Öktem, Berk; Tolocka, Michael P.; Zhao, Bin; Wang, Shuangfeng; Johnston, Murray V.

doi:10.1016/j.combustflame.2005.03.016

Cited by 175 publications

(112 citation statements)

References 38 publications

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“…The majority of the species predicted by SNAPS experienced molecular growth as they evolved in the flame, and furans constituted the largest group of oxygenated species at large distance from the fuel outlet (DFFO), where the flame temperature was around 1,750 K. An important furan-destruction pathway identified in the simulations is CO reactions: CO can open furan rings and abstract the oxygen atom to form CO 2 , leaving the original furan ring as an aliphatic radical side chain. This mechanism may explain the observed aliphatics on the surface of soot particles under some conditions (25,27,31,39).…”

Section: Resultsmentioning

confidence: 95%

Formation and emission of large furans and oxygenated hydrocarbons from flames

Johansson

Dillstrom

Monti

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Many oxygenated hydrocarbon species formed during combustion, such as furans, are highly toxic and detrimental to human health and the environment. These species may also increase the hygroscopicity of soot and strongly influence the effects of soot on regional and global climate. However, large furans and associated oxygenated species have not previously been observed in flames, and their formation mechanism and interplay with polycyclic aromatic hydrocarbons (PAHs) are poorly understood. We report on a synergistic computational and experimental effort that elucidates the formation of oxygen-embedded compounds, such as furans and other oxygenated hydrocarbons, during the combustion of hydrocarbon fuels. We used ab initio and probabilistic computational techniques to identify low-barrier reaction mechanisms for the formation of large furans and other oxygenated hydrocarbons. We used vacuum-UV photoionization aerosol mass spectrometry and X-ray photoelectron spectroscopy to confirm these predictions. We show that furans are produced in the high-temperature regions of hydrocarbon flames, where they remarkably survive and become the main functional group of oxygenates that incorporate into incipient soot. In controlled flame studies, we discovered ∼100 oxygenated species previously unaccounted for. We found that large alcohols and enols act as precursors to furans, leading to incorporation of oxygen into the carbon skeletons of PAHs. Our results depart dramatically from the crude chemistry of carbonand oxygen-containing molecules previously considered in hydrocarbon formation and oxidation models and spearhead the emerging understanding of the oxidation chemistry that is critical, for example, to control emissions of toxic and carcinogenic combustion by-products, which also greatly affect global warming.furans | oxygenated hydrocarbons | soot | organic carbon | black carbon

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Section: Resultsmentioning

confidence: 95%

Formation and emission of large furans and oxygenated hydrocarbons from flames

Johansson

Dillstrom

Monti

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…[28][29][30][31][32][33][34][35][36] Figure 1a and c show aerosol mass spectra of soot extracted from the premixed flame at a height above the burner (HAB) of 6 and 10 mm, respectively. The sampling line used for extraction of the samples yielding the signals presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…[28][29][30][31][32][33][34][35][36] Explicit evidence suggesting the presence or absence of particular isomers is, however, lacking. Some studies have presented results, beyond just molecular masses, that are consistent with the generation of stabilomer species during combustion and pyrolysis of carbonaceous fuels.…”

Section: Schuetz Andmentioning

confidence: 99%

Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

et al. 2017

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We present a critical evaluation of photoionization efficiency (PIE) measurements coupled with aerosol mass spectrometry for the identification of condensed soot-precursor species extracted from a premixed atmospheric-pressure ethylene/oxygen/nitrogen flame. Definitive identification of isomers by any means is complicated by the large number of potential isomers at masses likely to comprise particles at flame temperatures. This problem is compounded using PIE measurements by the similarity in ionization energies and PIE-curve shapes among many of these isomers. Nevertheless, PIE analysis can provide important chemical information. For example, our PIE curves show that neither pyrene nor fluoranthene alone can describe the signal from C16H10 isomers and that coronene alone cannot describe the PIE signal from C24H12 species.A linear combination of the reference PIE curves for pyrene and fluoranthene yields good agreement with flame-PIE curves measured at 202 u, which is consistent with pyrene and fluoranthene being the two major C16H10 isomers in the flame samples, but does not provide definite proof. The suggested ratio between fluoranthene and pyrene depends on the sampling conditions. We calculated the values of the adiabatic-ionization energy (AIE) of twenty-four C16H10 isomers. Despite the small number of isomers considered, the calculations show that the differences in AIEs between several of the isomers can be smaller than the average thermal energy at room temperature. The calculations also show that PIE analysis can sometimes be used to separate hydrocarbon species into those that contain mainly aromatic rings and those that contain significant aliphatic content for species sizes investigated in this study. Our calculations suggest an inverse relationship between AIE and the number of aromatic rings. We have demonstrated that further characterization of precursors can be facilitated by measurements that test species volatility.3

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“…The relatively compact, high temperature (>2200°C), and lean flame (air:fuel ratio ) 17.1:1 or ∼3% excess oxygen in the flue gas) the ROB burner produces probably inhibits the formation of coarse cenospheres, and the semivolatile organic condensates needed for further particle growth. Methods of air-fuel premixing and fuel atomization, stoichiometric ratios, and fuel batches and grades vary among different fossil fuel combustion sources, affecting flame characteristics and ultimately the size of the particles emitted (24).…”

Section: Resultsmentioning

confidence: 99%

Physical and Chemical Characterization of Residential Oil Boiler Emissions

Hays

Beck

Barfield

et al. 2008

Environ. Sci. Technol.

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The toxicity of emissions from the combustion of home heating oil coupled with the regional proximity and seasonal use of residential oil boilers (ROB) is an important public health concern. Yet scant physical and chemical information about the emissions from this source is available for climate and air quality modeling and for improving our understanding of aerosolrelated human health effects. The gas-and particle-phase emissions from an active ROB firing distillate fuel oil (commonly known as diesel fuel) were evaluated to address this deficiency. Ion chromatography of impactor samples showed that the ultrafine ROB aerosol emissions were ∼45% (w/w) sulfate. Gas chromatography-mass spectrometry detected various n-alkanes at trace levels, sometimes in accumulation mode particles, and out of phase with the size distributions of aerosol mass and sulfate. The carbonaceous matter in the ROB aerosol was primarily light-adsorbing elemental carbon. Gas chromatography-atomic emission spectroscopy measured a previously unrecognized organosulfur compound group in the ROB aerosol emissions. High-resolution transmission electron microscopy of ROB soot indicated the presence of a highly ordered primary particle nanostructure embedded in larger aggregates. Organic gas emissions were measured using EPA Methods TO-15 and TO-11A. The ROB emitted volatile oxygenates (8 mg/(kg of oil burned)) and olefins (5 mg/(kg of oil burned)) mostly unrelated to the base fuel composition. In the final analysis, the ROB tested was a source of numerous hazardous air pollutants as defined in the Clean Air Act Amendments. Approximations conducted using emissions data from the ROB tests show relatively low contributions to a regionallevel anthropogenic emissions inventory for volitile organic compounds, PM 2.5 , and SO 2 mass.

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Chemical species associated with the early stage of soot growth in a laminar premixed ethylene–oxygen–argon flame

Cited by 175 publications

References 38 publications

Formation and emission of large furans and oxygenated hydrocarbons from flames

Formation and emission of large furans and oxygenated hydrocarbons from flames

Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

Physical and Chemical Characterization of Residential Oil Boiler Emissions

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