scholarly journals Kinetics of the OH + NO<sub>2</sub> reaction: Rate coefficients (217–333 K, 16–1200 mbar) and fall-off parameters for N<sub>2</sub> and O<sub>2</sub> bath-gases

2019 ◽  
Author(s):  
Damien Amedro ◽  
Arne J. C. Bunkan ◽  
Matias Berasategui ◽  
John N. Crowley
Keyword(s):  
Pressure Range ◽  
Great Influence ◽  
Rate Coefficients ◽  
Atmospheric Conditions ◽  
Collision Efficiency ◽  
Temperature And Pressure ◽  
Photolysis Laser ◽  
Kinetics Of ◽  
Lower Collision

Abstract. The radical terminating, termolecular reaction between OH and NO2 exerts great influence on the NOy / NOx ratio and O3 formation in the atmosphere. Evaluation panels (IUPAC and NASA) recommend rate coefficients for this reaction that disagree by as much as a factor 1.6 at low temperature and pressure. In this work, the title reaction was studied by pulsed laser photolysis-laser induced fluorescence over the pressure range 16–1200 mbar and temperature 217–333 K in N2 bath-gas, with experiments at 295 K (67–333 mbar) for O2. In-situ measurement of NO2 using two optical-absorption set-ups enabled generation of highly precise, accurate rate coefficients in the fall-off pressure range, appropriate for atmospheric conditions. We found, in agreement with previous work, that O2 bath-gas has a lower collision efficiency than N2 with a relative collision efficiency to N2 of 0.74. Using the widely used Troe-type formulation for termolecular reactions we present a new set of parameters with k0(N2) = 2.6 × 10−30 cm6 molecule−2 s−1, k0(O2) = 2.0 × 10−30 cm6 molecule−2 s−1, m = 3.6, k∞ = 6.3 × 10−11 cm3 molecule−1 s−1, Fc = 0.39 and compare our results to previous studies in N2 and O2 bath-gases.

scholarly journals Kinetics of the OH + NO<sub>2</sub> reaction: rate coefficients (217–333 K, 16–1200 mbar) and fall-off parameters for N<sub>2</sub> and O<sub>2</sub> bath gases

2019 ◽  
Vol 19 (16) ◽  
pp. 10643-10657 ◽  
Author(s):  
Damien Amedro ◽  
Arne J. C. Bunkan ◽  
Matias Berasategui ◽  
John N. Crowley
Keyword(s):  
Pressure Range ◽  
Great Influence ◽  
Rate Coefficients ◽  
Atmospheric Conditions ◽  
Collision Efficiency ◽  
Title Reaction ◽  
Temperature And Pressure ◽  
Kinetics Of ◽  
Lower Collision

Abstract. The radical terminating, termolecular reaction between OH and NO2 exerts great influence on the NOy∕NOx ratio and O3 formation in the atmosphere. Evaluation panels (IUPAC and NASA) recommend rate coefficients for this reaction that disagree by as much as a factor of 1.6 at low temperature and pressure. In this work, the title reaction was studied by pulsed laser photolysis and laser-induced fluorescence over the pressure range 16–1200 mbar and temperature range 217–333 K in N2 bath gas, with experiments at 295 K (67–333 mbar) for O2. In situ measurement of NO2 using two optical absorption set-ups enabled generation of highly precise, accurate rate coefficients in the fall-off pressure range, appropriate for atmospheric conditions. We found, in agreement with previous work, that O2 bath gas has a lower collision efficiency than N2 with a relative collision efficiency to N2 of 0.74. Using the Troe-type formulation for termolecular reactions we present a new set of parameters with k0(N2) = 2.6×10-30 cm6 molecule−2 s−1, k0(O2) = 2.0×10-30 cm6 molecule−2 s−1, m=3.6, k∞=6.3×10-11 cm3 molecule−1 s−1, and Fc=0.39 and compare our results to previous studies in N2 and O2 bath gases.

scholarly journals Temperature-(208–318 K) and pressure-(18–696 Torr) dependent rate coefficients for the reaction between OH and HNO<sub>3</sub>

2018 ◽  
Vol 18 (4) ◽  
pp. 2381-2394 ◽  
Author(s):  
Katrin Dulitz ◽  
Damien Amedro ◽  
Terry J. Dillon ◽  
Andrea Pozzer ◽  
John N. Crowley
Keyword(s):  
Cross Sections ◽  
Pressure Dependence ◽  
Low Temperatures ◽  
Room Temperature ◽  
Rate Coefficients ◽  
Title Reaction ◽  
Data Set ◽  
Dependent Rate ◽  
Temperature And Pressure

Abstract. Rate coefficients (k5) for the title reaction were obtained using pulsed laser photolytic generation of OH coupled to its detection by laser-induced fluorescence (PLP–LIF). More than 80 determinations of k5 were carried out in nitrogen or air bath gas at various temperatures and pressures. The accuracy of the rate coefficients obtained was enhanced by in situ measurement of the concentrations of both HNO3 reactant and NO2 impurity. The rate coefficients show both temperature and pressure dependence with a rapid increase in k5 at low temperatures. The pressure dependence was weak at room temperature but increased significantly at low temperatures. The entire data set was combined with selected literature values of k5 and parameterised using a combination of pressure-dependent and -independent terms to give an expression that covers the relevant pressure and temperature range for the atmosphere. A global model, using the new parameterisation for k5 rather than those presently accepted, indicated small but significant latitude- and altitude-dependent changes in the HNO3 ∕ NOx ratio of between −6 and +6 %. Effective HNO3 absorption cross sections (184.95 and 213.86 nm, units of cm2 molecule−1) were obtained as part of this work: σ213.86  =  4.52−0.12+0.23  ×  10−19 and σ184.95  =  1.61−0.04+0.08  ×  10−17.

scholarly journals Temperature (208–318 K) and pressure (18–696 Torr) dependent rate coefficients for the reaction between OH and HNO<sub>3</sub>

2017 ◽  
Author(s):  
Katrin Dulitz ◽  
Damien Amedro ◽  
Terry J. Dillon ◽  
Andrea Pozzer ◽  
John N. Crowley
Keyword(s):  
Cross Sections ◽  
Pressure Dependence ◽  
Low Temperatures ◽  
Room Temperature ◽  
Rate Coefficients ◽  
Title Reaction ◽  
Dependent Rate ◽  
Temperature And Pressure ◽  
Entire Dataset

Abstract. Rate coefficients (k5) for the title reaction were obtained using pulsed laser photolytic generation of OH coupled to its detection by laser-induced fluorescence (PLP-LIF). More than eighty determinations of k5 were carried out in nitrogen or air bath gas at various temperatures and pressures. The accuracy of the rate coefficients obtained was enhanced by in-situ measurement of the concentrations of both HNO3 reactant and NO2 impurity. The rate coefficients show both temperature and pressure dependence with a rapid increase in k5 at low temperatures. The pressure dependence was weak at room temperature but increased significantly at low temperatures. The entire dataset was combined with selected literature values of k5 and parameterised using a combination of pressure dependent and independent terms to give an expression that covers the relevant pressure and temperature range for the atmosphere. A global model, using the new parameterisation for k5 rather than those presently accepted, indicated small but significant latitude and altitude dependent changes in the HNO3 / NOx ratio of between −6 % and +6 %. Effective HNO3 absorption cross sections (184.95 and 213.86 nm, units of cm2 molecule−1) were obtained as part of this work: σ213.86 = 4.52+0.23−0.12 × 10−19 and σ184.95 = 1.61+0.08−0.04 × 10−17.

Kinetics of the unimolecular reaction of CH2OO and the bimolecular reactions with the water monomer, acetaldehyde and acetone under atmospheric conditions

2015 ◽  
Vol 17 (30) ◽  
pp. 19862-19873 ◽  
Author(s):  
Torsten Berndt ◽  
Ralf Kaethner ◽  
Jens Voigtländer ◽  
Frank Stratmann ◽  
Mark Pfeifle ◽  
...  
Keyword(s):  
Rate Coefficients ◽  
Unimolecular Reaction ◽  
Atmospheric Conditions ◽  
Bimolecular Reactions ◽  
Kinetics Of

The rate coefficients of the unimolecular reaction of CH2OO and the bimolecular reactions with the water monomer and carbonyls were measured.

scholarly journals Evolution of OH reactivity in low-NO volatile organic compound photooxidation investigated by the fully explicit GECKO-A model

2021 ◽  
Author(s):  
Zhe Peng ◽  
Julia Lee-Taylor ◽  
Harald Stark ◽  
John J. Orlando ◽  
Bernard Aumont ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Oxidative Capacity ◽  
Rate Coefficients ◽  
Atmospheric Conditions ◽  
Alkene Oxidation ◽  
Volatile Organic ◽  
Wall Losses ◽  
Uv Lamp ◽  
Kinetics Of ◽  
Significant Underestimation

Abstract. OH reactivity (OHR) is an important control on the oxidative capacity in the atmosphere but remains poorly constrained. For an improved understanding of OHR, its evolution during oxidation of volatile organic compounds (VOCs) is a major aspect requiring better quantification. We use the fully explicit Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) model to study the OHR evolution in the low-NO photooxidation of several VOCs, including decane (an alkane), m-xylene (an aromatic), and isoprene (an alkene). Oxidation progressively produces more saturated and functionalized species. Total organic OHR (including precursor and products, OHRVOC) first increases for decane (as functionalization increases OH rate coefficients), and m-xylene (as much more reactive oxygenated alkenes are formed). For isoprene, C=C bond consumption leads to a rapid drop in OHRVOC before significant production of the first main saturated multifunctional product, i.e., isoprene epoxydiol. The saturated multifunctional species in the oxidation of different precursors have similar average OHRVOC per C atom. The latter oxidation follows a similar course for different precursors, involving fragmentation of multifunctional species to eventual oxidation of C1 and C2 fragments to CO2, leading to a similar evolution of OHRVOC per C atom. An upper limit of the total OH consumption during complete oxidation to CO2 is roughly 3 per C atom. We also explore the trends in radical recycling ratios. We show that differences in the evolution of OHRVOC between the atmosphere and an environmental chamber, and between the atmosphere and an oxidation flow reactor (OFR) can be substantial, with the former being even larger, but these differences are often smaller than between precursors. The Teflon wall losses of oxygenated VOCs in chambers result in substantial deviations of OHRVOC from atmospheric conditions, especially for the oxidation of larger precursors, where multifunctional species may suffer near-complete wall losses, resulting in significant underestimation of OHRVOC. For OFR, the deviations of OHRVOC evolution from the atmospheric case are mainly due to significant OHR contribution from RO2 and lack of efficient organic photolysis. The former can be avoided by lowering the UV lamp setting in OFR, while the latter is shown to be very difficult to avoid. However, the former may significantly offset the slowdown in fragmentation of multifunctional species due to lack of efficient organic photolysis.

scholarly journals KINETICS OF LOW PRESSURE AMMONIA OXIDATION OVER RH(111)

2018 ◽  
Vol 48 (1) ◽  
pp. 27-30
Author(s):  
U. N. FAGIOLI ◽  
B. V. BOEHN ◽  
M. RAFTI ◽  
R. IMBIHL
Keyword(s):  
Single Crystal ◽  
Mass Spectroscopy ◽  
Pressure Range ◽  
Ammonia Oxidation ◽  
Low Pressure ◽  
Quadrupole Mass ◽  
Catalytic Surface ◽  
Sticking Coefficients ◽  
Kinetics Of

The kinetics of the NH3 + O2 reaction over a Rh(111) single crystal catalytic surface was explored in the 10-6 mbar pressure range at temperatures between 300-900 K. Selectivity towards N2 and NO products, and reactive sticking coefficients were monitored in situ using differentially pumped quadrupole mass spectroscopy (QMS).

scholarly journals Evolution of OH reactivity in NO-free volatile organic compound photooxidation investigated by the fully explicit GECKO-A model

2021 ◽  
Vol 21 (19) ◽  
pp. 14649-14669
Author(s):  
Zhe Peng ◽  
Julia Lee-Taylor ◽  
Harald Stark ◽  
John J. Orlando ◽  
Bernard Aumont ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Oxidative Capacity ◽  
Rate Coefficients ◽  
Atmospheric Conditions ◽  
Alkene Oxidation ◽  
Rural And Urban ◽  
Volatile Organic ◽  
Wall Losses ◽  
Uv Lamp ◽  
Kinetics Of

Abstract. OH reactivity (OHR) is an important control on the oxidative capacity in the atmosphere but remains poorly constrained in many environments, such as remote, rural, and urban atmospheres, as well as laboratory experiment setups under low-NO conditions. For an improved understanding of OHR, its evolution during oxidation of volatile organic compounds (VOCs) is a major aspect requiring better quantification. We use the fully explicit Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) model to study the OHR evolution in the NO-free photooxidation of several VOCs, including decane (an alkane), m-xylene (an aromatic), and isoprene (an alkene). Oxidation progressively produces more saturated and functionalized species. Total organic OHR (including precursor and products, OHRVOC) first increases for decane (as functionalization increases OH rate coefficients) and m-xylene (as much more reactive oxygenated alkenes are formed). For isoprene, C=C bond consumption leads to a rapid drop in OHRVOC before significant production of the first main saturated multifunctional product, i.e., isoprene epoxydiol. The saturated multifunctional species in the oxidation of different precursors have similar average OHRVOC per C atom. The latter oxidation follows a similar course for different precursors, involving fragmentation of multifunctional species to eventual oxidation of C1 and C2 fragments to CO2, leading to a similar evolution of OHRVOC per C atom. An upper limit of the total OH consumption during complete oxidation to CO2 is roughly three per C atom. We also explore the trends in radical recycling ratios. We show that differences in the evolution of OHRVOC between the atmosphere and an environmental chamber, and between the atmosphere and an oxidation flow reactor (OFR), can be substantial, with the former being even larger, but these differences are often smaller than between precursors. The Teflon wall losses of oxygenated VOCs in chambers result in large deviations of OHRVOC from atmospheric conditions, especially for the oxidation of larger precursors, where multifunctional species may suffer substantial wall losses, resulting in significant underestimation of OHRVOC. For OFR, the deviations of OHRVOC evolution from the atmospheric case are mainly due to significant OHR contribution from RO2 and lack of efficient organic photolysis. The former can be avoided by lowering the UV lamp setting in OFR, while the latter is shown to be very difficult to avoid. However, the former may significantly offset the slowdown in fragmentation of multifunctional species due to lack of efficient organic photolysis.

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