OH-initiated oxidation of benzene

The present work represents a continuation of part I of this series of papers, in which we investigated the phenol yields in the OH-initiated oxidation of benzene under conditions of low to moderate concentrations of NOx, to elevated NOx levels. The products of the OH-initiated oxidation of benzene in 700–760 Torr of N2/O2 diluent at 297 ± 4 K were investigated in 3 different photochemical reaction chambers. In situ spectroscopic techniques were employed for the detection of products, and the initial concentrations of benzene, NOx, and O2 were widely varied (by factors of 6300, 1500, and 13, respectively). In contrast to results from previous studies, a pronounced dependence of the product distribution on the NOx concentration was observed. The phenol yield decreases from approximately 50–60% in the presence of low concentrations ( 10 000 ppb) NOx concentrations. In the presence of high concentrations of NOx, the phenol yield increases with increasing O2 partial pressure. The rate constant of the reaction of hydroxycyclohexadienyl peroxyl radicals with NO was determined to be (1.7 ± 0.6) × 10−11 cm3 molecule−1 s−1. This reaction leads to the formation of E,E-2,4-hexadienedial as the main identifiable product (29 ± 16%). The reaction of the hydroxycyclohexadienyl radical with NO2 gave phenol (5.9 ± 3.4%) and E,E-2,4-hexadienedial (3.4 ± 1.9%), no other products could be identified. The residual FTIR product spectra indicate the formation of unknown nitrates or other nitrogen-containing species in high yield. The results from the present work also show that experimental studies aimed at establishing/verifying chemical mechanisms for aromatic hydrocarbons must be performed using NOx levels which are representative of those found in the atmosphere.

[1]  Roger Atkinson,et al.  Formation of ring-retaining products from the OH radical-initiated reactions of benzene and toluene , 1989 .

[2]  I. Barnes,et al.  New results on the atmospheric photooxidation of simple alkylbenzenes , 1998 .

[3]  I. Barnes,et al.  KINETIC STUDY OF THE GAS-PHASE PHOTOLYSIS AND OH RADICAL REACTION OF E, Z-AND E, E-2,4-HEXADIENEDIAL , 1999 .

[4]  S. M. Aschmann,et al.  Alkyl Nitrate, Hydroxyalkyl Nitrate, and Hydroxycarbonyl Formation from the NOx−Air Photooxidations of C5−C8 n-Alkanes , 2001 .

[5]  R. Zellner,et al.  A cw UV laser absorption study of the reactions of the hydroxy-cyclohexadienyl radical with NO2 and NO , 1985 .

[6]  Stephen D. Piccot,et al.  A global inventory of volatile organic compound emissions from anthropogenic sources , 1992 .

[7]  R. Kamens,et al.  Characterization of secondary aerosol from the photooxidation of toluene in the presence of NOx and 1-propene. , 2001, Environmental science & technology.

[8]  Atmospheric photodissociation lifetimes for nitromethane, methyl nitrite, and methyl nitrate , 1980 .

[9]  Ulrich Platt,et al.  Primary and Secondary Glyoxal Formation from Aromatics: Experimental Evidence for the Bicycloalkyl−Radical Pathway from Benzene, Toluene, and p-Xylene , 2001 .

[10]  H. Akimoto,et al.  Photochemical Oxidation of Benzene, Toluene, and Ethylbenzene Initiated by OH Radicals in the Gas Phase , 1978 .

[11]  A. Mellouki,et al.  Kinetics of OH radical reactions with a series of ethers , 1995 .

[12]  M. Kurylo,et al.  The gas phase reactions of hydroxyl radicals with a series of aliphatic ethers over the temperature range 240–440 K , 1987 .

[13]  D. Stocker,et al.  Further studies of the temperature dependence of the rate coefficients for the reactions of OH with a series of ethers under simulated atmospheric conditions , 1993 .

[14]  M. Sigrist.  Air monitoring by spectroscopic techniques , 1994 .

[15]  J. Milford,et al.  Reactivity estimates for aromatic compounds. Part 2. Uncertainty in incremental reactivities , 2000 .

[16]  S. Leggett,et al.  Forecast distributions of species and their atmospheric reactivities for the U.K. VOC emission inventory , 1996 .

[17]  J. Milford,et al.  Reactivity estimates for aromatic compounds. Part 1. Uncertainty in chamber-derived parameters , 2000 .

[18]  Jack G. Calvert,et al.  The mechanisms of atmospheric oxidation of aromatic hydrocarbons , 2002 .

[19]  D. Stocker,et al.  THE TEMPERATURE DEPENDENCE OF THE OH RADICAL REACTIONS WITH SOME AROMATIC COMPOUNDS UNDER SIMULATED TROPOSPHERIC CONDITIONS , 1995 .

[20]  H. Akimoto,et al.  Design and characterization of the evacuable and bakable photochemical smog chamber , 1979 .

[21]  Ian Barnes,et al.  Gas-phase absorption cross sections of 24 monocyclic aromatic hydrocarbons in the UV and IR spectral ranges , 1999 .

[22]  John H. Seinfeld,et al.  Atmospheric Photochemical Oxidation of Benzene: Benzene + OH and the Benzene−OH Adduct (Hydroxyl-2,4-cyclohexadienyl) + O2 , 1996 .

[23]  F. Kirchner,et al.  A new mechanism for regional atmospheric chemistry modeling , 1997 .

[24]  I. Barnes,et al.  Rate coefficients for the gas-phase reaction of OH radicals with selected dihydroxybenzenes and benzoquinones , 2000 .

[25]  I. Barnes,et al.  Kinetic and mechanistic study of the atmospheric chemistry of muconaldehydes. , 1995, Environmental science & technology.

[26]  U. Platt,et al.  UV-absorption cross sections of a series of monocyclic aromatic compounds , 1997 .

[27]  R. Koch.  Comment on “UV Spectrum and Kinetics of Hydroxycyclohexadienyl Radicals” , 1997 .

[28]  W. Carter,et al.  Major atmospheric sink for phenol and the cresols. Reaction with the nitrate radical , 1981 .

[29]  P. Pagsberg,et al.  UV spectrum and kinetics of hydroxycyclohexadienyl radicals , 1996 .

[30]  J. H. Seinfeld,et al.  The Atmospheric Aerosol-Forming Potential of Whole Gasoline Vapor , 1997, Science.

[31]  H. Herrmann,et al.  On the formation of benzene oxide/oxepin in the gas-phase reaction of OH radicals with benzene , 1999 .

[32]  M. C. Dodge,et al.  Chemical oxidant mechanisms for air quality modeling: critical review , 2000 .

[33]  T. Kleindienst,et al.  Primary Product Distributions from the Reaction of OH with m-, p-Xylene, 1,2,4- and 1,3,5-Trimethylbenzene , 1999 .

[34]  U. Platt,et al.  Numerical analysis and estimation of the statistical error of differential optical absorption spectroscopy measurements with least-squares methods. , 1996, Applied optics.

[35]  Ian Barnes,et al.  Atmospheric Oxidation of Toluene in a Large-Volume Outdoor Photoreactor: In Situ Determination of Ring-Retaining Product Yields , 1998 .

[36]  S. Paulson,et al.  ON THE UNCERTAINTIES IN THE RATE COEFFICIENTS FOR OH REACTIONS WITH HYDROCARBONS, AND THE RATE COEFFICIENTS OF THE 1,3,5-TRIMETHYLBENZENE AND M-XYLENE REACTIONS WITH OH RADICALS IN THE GAS PHASE , 1998 .

[37]  T. Kleindienst,et al.  Primary Product Distribution from the Reaction of Hydroxyl Radicals with Toluene at ppb NOX Mixing Ratios , 1998 .

[38]  T. Wallington,et al.  Kinetics of the reaction of OH radicals with a series of ethers under simulated atmospheric conditions at 295 K , 1989 .

[39]  J. Yu,et al.  Atmospheric photooxidation of alkylbenzenes—II. Evidence of formation of epoxide intermediates , 1997 .

[40]  In-situ Measurements of Tropospheric Hydroxyl Radicals by Folded Long-Path Laser Absorption During the Field Campaign POPCORN , 1998 .

[41]  I. Barnes,et al.  ATMOSPHERIC CHEMISTRY OF BENZENE OXIDE/OXEPIN , 1997 .

[42]  Roger Atkinson,et al.  Gas-Phase Tropospheric Chemistry of Volatile Organic Compounds: 1. Alkanes and Alkenes , 1997 .

[43]  Ulrich Platt,et al.  Correction of the oxygen interference with UV spectroscopic (DOAS) measurements of monocyclic aromatic hydrocarbons in the atmosphere , 1998 .

[44]  P. Pagsberg.  Reply to Comment on “UV Spectrum and Kinetics of Hydroxycyclohexadienyl Radicals” , 1997 .

[45]  J. Mellqvist,et al.  DOAS for flue gas monitoring—II. Deviations from the Beer-Lambert law for the U.V./visible absorption spectra of NO, NO2, SO2 and NH3 , 1996 .