scholarly journals Investigation of the reaction of ozone with isoprene, methacrolein and methyl vinyl ketone using the HELIOS chamber

2017 ◽  
Vol 200 ◽  
pp. 289-311 ◽  
Author(s):  
Yangang Ren ◽  
Benoit Grosselin ◽  
Véronique Daële ◽  
Abdelwahid Mellouki
Keyword(s):  
Gas Phase ◽  
Organic Aerosol ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Radical Scavenger ◽  
Oh Radical ◽  
Atmospheric Conditions ◽  
Experimental Conditions ◽  
Methyl Vinyl ◽  
Analytical Equipment

The rate constants for the ozonolysis of isoprene (ISO), methacrolein (MACR) and methyl vinyl ketone (MVK) have been measured using the newly built large volume atmospheric simulation chamber at CNRS-Orleans (France), HELIOS (Chambre de simulation atmosphérique à irradiation naturelle d’Orléans). The OH radical yields from the ozonolysis of isoprene, MACR and MVK have also been determined, as well as the gas phase stable products and their yields. The secondary organic aerosol yield for the ozonolysis of isoprene has been tentatively measured in the presence and absence of an OH radical scavenger. The measurements were performed under different experimental conditions with and without adding cyclohexane (cHX) as an OH radical scavenger. All experiments have been conducted at 760 torr of purified dry air (RH < 1%) and ambient temperature (T = 281–295 K). The data obtained are discussed and compared with those from the literature. The use of the HELIOS facility and its associated analytical equipment enables the derivation of kinetic parameters as well as mechanistic information under near realistic atmospheric conditions.

scholarly journals Secondary Organic Aerosol Formation from Nitrophenols Photolysis under Atmospheric Conditions

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1346
Author(s):  
Iustinian Gabriel Bejan ◽  
Romeo-Iulian Olariu ◽  
Peter Wiesen
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Degradation Mechanism ◽  
Organic Aerosol ◽  
Radical Scavenger ◽  
Oh Radical ◽  
Atmospheric Conditions ◽  
Aerosol Formation ◽  
Chemical Models ◽  
Secondary Organic Aerosol Formation

Nitrophenols are important products of the aromatic compounds photooxidation and play a considerable role in urban chemistry. Nitrophenols are important components of agricultural biomass burning that could influence the climate. The formation of secondary organic aerosol from the direct photolysis of nitrophenols was investigated for the first time in a quartz glass simulation chamber under simulated solar radiation. The results from these experiments indicate rapid SOA formation. The proposed mechanism for the gas-phase degradation of nitrophenols through photolysis shows the formation of biradicals that could react further in the presence of oxygen to form low volatile highly oxygenated compounds responsible for secondary organic aerosol formation. The inhibiting effect of NOx and the presence of an OH radical scavenger on the aerosol formation were also studied. For 2-nitrophenol, significant aerosol formation yields were observed in the absence of an OH radical scavenger and NOx, varying in the range of 18%–24%. A gas-phase/aerosol partitioning model was applied assuming the presence of only one compound in both phases. A degradation mechanism is proposed to explain the aerosol formation observed in the photolysis of nitrophenols. The atmospheric impact of nitrophenol photolysis is discussed and the importance for atmospheric chemical models is assessed.

scholarly journals Aqueous phase oligomerization of methyl vinyl ketone through photooxidation – Part 2: Development of the chemical mechanism and atmospheric implications

2014 ◽  
Vol 14 (15) ◽  
pp. 21565-21609 ◽  
Author(s):  
B. Ervens ◽  
P. Renard ◽  
S. Ravier ◽  
J.-L. Clément ◽  
A. Monod
Keyword(s):  
Gas Phase ◽  
Aqueous Phase ◽  
Formation Rate ◽  
Liquid Water Content ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Chemical Mechanism ◽  
Atmospheric Conditions ◽  
Methyl Vinyl ◽  
Oligomer Formation

Abstract. We developed a chemical mechanism based on laboratory experiments that have shown efficient oligomerization from methyl vinyl ketone (MVK) in the bulk aqueous phase. Kinetic data are applied (if known) or fitted to the observed MVK decay and oligomer mass increase. The mechanism is then implemented into a multiphase box model that simulates (i) oligomer formation upon uptake of MVK from the gas phase, and (ii) SOA formation from isoprene, as a precursor of MVK and methacrolein (MACR) in the aqueous and gas phases. Model results show that under atmospheric conditions, the oligomer formation rate strongly depends on the availability of dissolved oxygen. If oxygen is consumed too quickly or its solubility is kinetically or thermodynamically limited, oligomerization is accelerated, in agreement with the laboratory studies. The comparison of predicted oligomer formation shows that for most model assumptions (e.g. depending on the assumed partitioning of MVK and MACR), SOA formation from isoprene in the gas phase exceeds aqueous SOA formation by a factor 3–4. However, at high aerosol liquid water content and potentially high partitioning of oligomer precursors into the aqueous phase, SOA formation in both phases might be equally efficient.

scholarly journals Radical mechanisms of methyl vinyl ketone oligomerization through aqueous phase OH-oxidation: on the paradoxical role of dissolved molecular oxygen

2013 ◽  
Vol 13 (1) ◽  
pp. 2913-2954 ◽  
Author(s):  
P. Renard ◽  
F. Siekmann ◽  
A. Gandolfo ◽  
J. Socorro ◽  
G. Salque ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
High Resolution Mass Spectrometry ◽  
Organic Aerosol ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Chemical Mechanism ◽  
Methyl Vinyl ◽  
Phase Chemistry ◽  
Dissolved O2

Abstract. It is now accepted that one of the important pathways of Secondary Organic Aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the liquid phase chemical mechanisms leading to macromolecules are still not well understood. For α-dicarbonyl precursors, such as methylglyoxal and glyoxal, radical reactions through OH-oxidation produce oligomers, irreversibly and faster than accretion reactions. Methyl vinyl ketone (MVK) was chosen in the present study as it is an α, β-unsaturated carbonyl that can undergo such reaction pathways in the aqueous phase and forms even high molecular weight oligomers. We present here experiments on the aqueous phase OH-oxidation of MVK, performed under atmospheric relevant conditions. Using NMR and UV absorption spectroscopy, high and ultra-high resolution mass spectrometry, we show that the fast formation of oligomers up to 1800 Da is due to radical oligomerization of MVK, and 13 series of oligomers (out of a total of 26 series) are identified. The influence of atmospherically relevant parameters such as temperature, initial concentrations of MVK and dissolved oxygen are presented and discussed. In agreement with the experimental observations, we propose a chemical mechanism of OH-oxidation of MVK in the aqueous phase that proceeds via radical oligomerization of MVK on the olefin part of the molecule. This mechanism highlights the paradoxical role of dissolved O2: while it inhibits oligomerization reactions, it contributes to produce oligomerization initiator radicals, which rapidly consume O2, thus leading to the supremacy of oligomerization reactions after several minutes of reaction. These processes, together with the large ranges of initial concentrations investigated (60–656 μM of dissolved O2 and 0.2–20 mM of MVK) show the fundamental role that O2 likely plays in atmospheric organic aerosol.

scholarly journals Gas-phase selective conjugate addition of methanol to acetone for methyl vinyl ketone over SnO2 nanoparticle catalysts

2005 ◽  
Vol 16 (3b) ◽  
pp. 607-613 ◽  
Author(s):  
Humberto V. Fajardo ◽  
Luiz F. D. Probst ◽  
Antoninho Valentini ◽  
Neftalí L. V. Carreño ◽  
Adeilton P. Maciel ◽  
...  
Keyword(s):  
Gas Phase ◽  
Conjugate Addition ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Methyl Vinyl ◽  
Nanoparticle Catalysts ◽  
Sno2 Nanoparticle
Sign in / Sign up

Export Citation Format

Share Document