A photochemical reactor for studies of atmospheric chemistry

Nilsson, Erik; Eskebjerg, Carsten; Johnson, Matthew S.

doi:10.1016/j.atmosenv.2009.02.034

Cited by 53 publications

(39 citation statements)

References 17 publications

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“…7,8 These reactors have many different designs that result in different advantages and limitations for quantitative experimental verification and improvement of atmospheric photochemical models.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Radical Chemistry in an Oxidation Flow Reactor: Radical Formation and Recycling, Sensitivities, and the OH Exposure Estimation Equation

Palm²,

Ortega³

et al. 2015

J. Phys. Chem. A

165

203

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Oxidation flow reactors (OFRs) containing low-pressure mercury (Hg) lamps that emit UV light at both 185 and 254 nm ("OFR185") to generate OH radicals and O3 are used in many areas of atmospheric science and in pollution control devices. The widely used potential aerosol mass (PAM) OFR was designed for studies on the formation and oxidation of secondary organic aerosols (SOA), allowing for a wide range of oxidant exposures and short experiment duration with reduced wall loss effects. Although fundamental photochemical and kinetic data applicable to these reactors are available, the radical chemistry and its sensitivities have not been modeled in detail before; thus, experimental verification of our understanding of this chemistry has been very limited. To better understand the chemistry in the OFR185, a model has been developed to simulate the formation, recycling, and destruction of radicals and to allow the quantification of OH exposure (OHexp) in the reactor and its sensitivities. The model outputs of OHexp were evaluated against laboratory calibration experiments by estimating OHexp from trace gas removal and were shown to agree within a factor of 2. A sensitivity study was performed to characterize the dependence of the OHexp, HO2/OH ratio, and O3 and H2O2 output concentrations on reactor parameters. OHexp is strongly affected by the UV photon flux, absolute humidity, reactor residence time, and the OH reactivity (OHR) of the sampled air, and more weakly by pressure and temperature. OHexp can be strongly suppressed by high OHR, especially under low UV light conditions. A OHexp estimation equation as a function of easily measurable quantities was shown to reproduce model results within 10% (average absolute value of the relative errors) over the whole operating range of the reactor. OHexp from the estimation equation was compared with measurements in several field campaigns and shows agreement within a factor of 3. The improved understanding of the OFR185 and quantification of OHexp resulting from this work further establish the usefulness of such reactors for research studies, especially where quantifying the oxidation exposure is important.

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Section: Introductionmentioning

confidence: 99%

Modeling the Radical Chemistry in an Oxidation Flow Reactor: Radical Formation and Recycling, Sensitivities, and the OH Exposure Estimation Equation

Palm²,

Ortega³

et al. 2015

J. Phys. Chem. A

165

203

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“…The experiments were performed in the photoreactor at CCAR (Copenhagen Center for Atmospheric Research). It consists of a 101 L quartz cylinder white‐cell surrounded by UV lamps (Waldmann F85/100 UV6 lamps, wavelength region 280–360 nm; and Philips TUV 55W HO, wavelength peak at 253.7 nm) and interfaced with a Bruker IFS 66v/s Fourier transform infrared (FTIR) spectrometer . In the present work, an analytical path length of either 43.45 or 56.12 m was used.…”

Section: Methodsmentioning

confidence: 99%

Atmospheric chemistry ofn‐CH₃(CH₂)_xCN (x = 0–3): Kinetics and mechanisms

Andersen

Kyte

Andersen

et al. 2018

Int J of Chemical Kinetics

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Smog chamber/Fourier transform infrared (FTIR) techniques were used to measure the kinetics of the reaction of n‐CH3(CH2)xCN (x = 0–3) with Cl atoms and OH radicals: k(CH3CN + Cl) = (1.04 ± 0.25) × 10−14, k(CH3CH2CN + Cl) = (9.20 ± 3.95) × 10−13, k(CH3(CH2)2CN + Cl) = (2.03 ± 0.23) × 10−11, k(CH3(CH2)3CN + Cl) = (6.70 ± 0.67) × 10−11, k(CH3CN + OH) = (4.07 ± 1.21) × 10−14, k(CH3CH2CN + OH) = (1.24 ± 0.27) × 10−13, k(CH3(CH2)2CN + OH) = (4.63 ± 0.99) × 10−13, and k(CH3(CH2)3CN + OH) = (1.58 ± 0.38) × 10−12 cm3 molecule−1 s−1 at a total pressure of 700 Torr of air or N2 diluents at 296 ± 2 K. The atmospheric oxidation of alkyl nitriles proceeds through hydrogen abstraction leading to several carbonyl containing primary oxidation products. HC(O)CN, NCC(O)OONO2, ClC(O)OONO2, and HCN were identified as the main oxidation products from CH3CN, whereas CH3CH2CN gives the products HC(O)CN, CH3C(O)CN, NCC(O)OONO2, and HCN. The oxidation of n‐CH3(CH2)xCN (x = 2–3) leads to a range of oxygenated primary products. Based on the measured OH radical rate constants, the atmospheric lifetimes of n‐CH3(CH2)xCN (x = 0–3) were estimated to be 284, 93, 25, and 7 days for x = 0,1, 2, and 3, respectively.

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“…The photochemical reactor consists of a 101‐dm 3 quartz chamber interfaced with a Bruker (Karlsruhe, Germany) IFS 66v/s FTIR spectrometer . The chlorine atoms were produced in situ by photolysis of molecular chlorine (Air Liquide, Denmark):

\begin{matrix} true \\ right {Cl}_{2} + h v (λ < 400 nm) \to 2 Cl \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

Atmospheric Chemistry of CH₃CH₂OCH₃: Kinetics and Mechanism of Reactions with Cl Atoms and OH Radicals

Andersen

Svendsen

Østerstrøm

et al. 2016

Int J of Chemical Kinetics

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The atmospheric chemistry of methyl ethyl ether, CH3CH2OCH3, was examined using FT‐IR/relative‐rate methods. Hydroxyl radical and chlorine atom rate coefficients of k(CH3CH2OCH3+OH) = (7.53 ± 2.86) × 10−12 cm3 molecule−1 s−1 and k(CH3CH2OCH3+Cl) = (2.35 ± 0.43) × 10−10 cm3 molecule−1 s−1 were determined (297 ± 2 K). The Cl rate coefficient determined here is 30% lower than the previous literature value. The atmospheric lifetime for CH3CH2OCH3 is approximately 2 days. The chlorine atom–initiated oxidation of CH3CH2OCH3 gives CH3C(O)H (9 ± 2%), CH3CH2OC(O)H (29 ± 7%), CH3OC(O)H (19 ± 7%), and CH3C(O)OCH3 (17 ± 7%). The IR absorption cross section for CH3CH2OCH3 is (7.97 ± 0.40) × 10−17 cm molecule−1 (1000–3100 cm−1). CH3CH2OCH3 has a negligible impact on the radiative forcing of climate.

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A photochemical reactor for studies of atmospheric chemistry

Cited by 53 publications

References 17 publications

Modeling the Radical Chemistry in an Oxidation Flow Reactor: Radical Formation and Recycling, Sensitivities, and the OH Exposure Estimation Equation

Modeling the Radical Chemistry in an Oxidation Flow Reactor: Radical Formation and Recycling, Sensitivities, and the OH Exposure Estimation Equation

Atmospheric chemistry ofn‐CH₃(CH₂)_xCN (x = 0–3): Kinetics and mechanisms

Atmospheric Chemistry of CH₃CH₂OCH₃: Kinetics and Mechanism of Reactions with Cl Atoms and OH Radicals

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A photochemical reactor for studies of atmospheric chemistry

Cited by 53 publications

References 17 publications

Modeling the Radical Chemistry in an Oxidation Flow Reactor: Radical Formation and Recycling, Sensitivities, and the OH Exposure Estimation Equation

Modeling the Radical Chemistry in an Oxidation Flow Reactor: Radical Formation and Recycling, Sensitivities, and the OH Exposure Estimation Equation

Atmospheric chemistry ofn‐CH3(CH2)xCN (x = 0–3): Kinetics and mechanisms

Atmospheric Chemistry of CH3CH2OCH3: Kinetics and Mechanism of Reactions with Cl Atoms and OH Radicals

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Product

Resources

About

Atmospheric chemistry ofn‐CH₃(CH₂)_xCN (x = 0–3): Kinetics and mechanisms

Atmospheric Chemistry of CH₃CH₂OCH₃: Kinetics and Mechanism of Reactions with Cl Atoms and OH Radicals