title: Formation and emission of large furans and oxygenated hydrocarbons from flames.
abstract: 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 carbon- and 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.
authors.affiliation: Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550;
authors.forename: K Olof
authors.initials: KO
authors.lastname: Johansson
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109;
authors.forename: Tyler
authors.initials: T
authors.lastname: Dillstrom
authors.affiliation: Department of Materials Science & Engineering, Stanford University, Stanford, CA 94305;
authors.forename: Matteo
authors.initials: M
authors.lastname: Monti
authors.affiliation: Materials Physics, Sandia National Laboratories, Livermore, CA 94550;
authors.forename: Farid
authors.initials: F
authors.lastname: El Gabaly
authors.affiliation: Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550;
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Campbell
authors.affiliation: Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550;
authors.forename: Paul E
authors.initials: PE
authors.lastname: Schrader
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; Department of Chemistry, University of California, Berkeley, CA 94720;
authors.forename: Denisia M
authors.initials: DM
authors.lastname: Popolan-Vaida
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
authors.forename: Nicole K
authors.initials: NK
authors.lastname: Richards-Henderson
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Wilson
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109; Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109; Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109; Biophysics Program, University of Michigan, Ann Arbor, MI 48109 avioli@umich.edu hamiche@sandia.gov.
authors.forename: Angela
authors.initials: A
authors.lastname: Violi
authors.affiliation: Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550; avioli@umich.edu hamiche@sandia.gov.
authors.forename: Hope A
authors.initials: HA
authors.lastname: Michelsen
mesh_terms: D000336:Aerosols / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D002244:Carbon / Q000032:analysis; D019295:Computational Biology / Q000379:methods; D005390:Fires; D005663:Furans / Q000737:chemistry*; D006838:Hydrocarbons / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D056951:Photoelectron Spectroscopy / Q000379:methods; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis; D012906:Smoke / Q000032:analysis; D053260:Soot / Q000032:analysis
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D005663:Furans; D006838:Hydrocarbons; D011084:Polycyclic Aromatic Hydrocarbons; D012906:Smoke; D053260:Soot; D002244:Carbon; D010100:Oxygen
keywords: black carbon; furans; organic carbon; oxygenated hydrocarbons; soot