the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Feb 2023
Atmospheric oxidation of new 'green' solvents part II: methyl pivalate and pinacolone
Abstract. Lab-based experimental and computational methods were used to study the atmospheric degradation of two promising “green” solvents: pinacolone, (CH3)3CC(O)CH3 and methyl pivalate, (CH3)3CC(O)OCH3. Pulsed laser photolysis coupled to pulsed laser induced fluorescence was used to determine absolute rate coefficients (in 10−12 cm3 molecule−1 s−1) of k1(297 K) = (1.2 ± 0.2) for OH + (CH3)3CC(O)CH3 (R1) and k2(297 K) = (1.3 ± 0.3) for OH + (CH3)3CC(O)OCH3 (R2), in good agreement with one previous experimental study. Rate coefficients for both reactions were found to increase at elevated temperature, with k1(T) adequately described by k1(297 – 485 K) = 2.1 × 10−12 exp(−200/T) cm3 molecule−1 s−1. k2(T) exhibited more complex behaviour, with a local minimum at around 300 K. In the course of this work, k3(295 – 450 K) for the well-characterised reaction OH + C2H5OH (ethanol, R3) were obtained, in satisfactory agreement with the evaluated literature. UV-vis. spectroscopy experiments and computational calculations were used to explore (CH3)3CC(O)CH3 photolysis (R4). Absorption cross sections for (CH3)3CC(O)CH3, σ4(λ) in the actinic region were larger and the maximum was red-shifted compared to estimates used in current state-of-science models. As a consequence, we note that photolysis (R4) is likely the dominant pathway for removal of (CH3)3CC(O)CH3 from the troposphere. Nonetheless, large uncertainties remain as quantum yields ϕ4(λ) remain unmeasured. Lifetime estimates based upon (R1) and (R4) span the range 2–9 days and are consequently associated with a poorly constrained Photochemical Ozone Creation Potential estimate (POCPE). In accord with previous studies, (CH3)3CC(O)CH3 did not absorb in the actinic region, allowing for straightforward calculation of an atmospheric lifetime of ≈ 9 days and a small POCPE ≈ 11.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1271 KB) - Metadata XML
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Supplement
(571 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
greensafer solvents which present favourable advantages when compared to traditional solvents. Since the assessment of these green solvents often lacks air quality considerations, this study aims to understand the behaviour of these compounds, investigating their reactivity in the troposphere.
Interactive discussion
Status: closed
- RC1: 'Comment on egusphere-2023-282', Anonymous Referee #1, 22 Mar 2023
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RC2: 'Comment on egusphere-2023-282', Anonymous Referee #2, 23 Mar 2023
This paper presents an experimental and numerical study of the atmospheric oxidation of methyl pivalate (MPA) and pinacolone (PCO), both considered as “green” solvents. First, the reactions rate constants of MPA and PCO with OH radicals are measured using the PLP-LIF (Pulsed Laser Photolysis – Laser Induced Fluorescence) technique in the temperature range (295-485 K), showing results in line with the scarce data from the literature. UV-Vis absorption cross sections of PCO were also obtained experimentally (in liquid phase) and numerically, and compared to data for MEK (Methyl Ethyl Ketone). The authors also propose an estimation of the photolysis rate coefficients for PCO. Finally, lifetimes for removal of PCO and MPA from the troposphere are calculated, suggesting relatively low reactivity of MPA and more reactivity for PCO due to photolysis.
In general, this paper is of good quality, describing a very comprehensive work combining experiments and modelling, even if it is not perfect and leaves open questions, notably because of the lack of comparable gas phase absorption cross sections and quantum yields data for PCO and MPA, the authors must have made approximations.
Minor considerations:
- As mentioned by the authors (line 107): “rate coefficient determinations in this work relied critically on accurate knowledge of [OVOC], here estimated to a precision of ±15%”
Indeed, it is often difficult to accurately determine the concentrations of OVOCs in this type of experiment. It is not clear how the mixtures of different concentrations of MPA and PCO diluted in nitrogen are prepared. It is therefore difficult to understand how the ± 15% uncertainty is estimated. Could the authors give more details on this aspect?
- Concerning LIF measurements (line 116): “This tuneable laser light was used to pump the Q11 transition of A2S+(v = 1) - X2P(v = 0) at 281.997 nm for direct, off-resonant LIF detection of OH.”
What does this mean? At which wavelengths are resonance and non-resonance measurements made?
The Q1(1) line of OH is not an isolated line (the R2(3) line is very close)
Does this pose a problem for the interpretation of the LIF results? What is the wavelength resolution?
- line 304: “Considering the systemic errors, we quote more realistic values of k1 (296 K) = (1.2 ± 0.2) × 10-12 cm3 molecule-1 s-1 and k2(296 K) = (1.3 ± 0.3) × 10-12 cm3 molecule-1 s-1, that take into account the error over the estimation of [VOC]”
It is not clear how this concentration error is taken into account in the final uncertainty calculation
- Line 177: “Similar experiments were conducted at different temperatures, pressures and in the presence / absence of O2”
The authors should clarify the value of such measurements (with and without O2) and at least give an indication of the comparative results
Citation: https://doi.org/10.5194/egusphere-2023-282-RC2 - AC1: 'Comment on egusphere-2023-282', Caterina Mapelli, 18 May 2023
Interactive discussion
Status: closed
- RC1: 'Comment on egusphere-2023-282', Anonymous Referee #1, 22 Mar 2023
-
RC2: 'Comment on egusphere-2023-282', Anonymous Referee #2, 23 Mar 2023
This paper presents an experimental and numerical study of the atmospheric oxidation of methyl pivalate (MPA) and pinacolone (PCO), both considered as “green” solvents. First, the reactions rate constants of MPA and PCO with OH radicals are measured using the PLP-LIF (Pulsed Laser Photolysis – Laser Induced Fluorescence) technique in the temperature range (295-485 K), showing results in line with the scarce data from the literature. UV-Vis absorption cross sections of PCO were also obtained experimentally (in liquid phase) and numerically, and compared to data for MEK (Methyl Ethyl Ketone). The authors also propose an estimation of the photolysis rate coefficients for PCO. Finally, lifetimes for removal of PCO and MPA from the troposphere are calculated, suggesting relatively low reactivity of MPA and more reactivity for PCO due to photolysis.
In general, this paper is of good quality, describing a very comprehensive work combining experiments and modelling, even if it is not perfect and leaves open questions, notably because of the lack of comparable gas phase absorption cross sections and quantum yields data for PCO and MPA, the authors must have made approximations.
Minor considerations:
- As mentioned by the authors (line 107): “rate coefficient determinations in this work relied critically on accurate knowledge of [OVOC], here estimated to a precision of ±15%”
Indeed, it is often difficult to accurately determine the concentrations of OVOCs in this type of experiment. It is not clear how the mixtures of different concentrations of MPA and PCO diluted in nitrogen are prepared. It is therefore difficult to understand how the ± 15% uncertainty is estimated. Could the authors give more details on this aspect?
- Concerning LIF measurements (line 116): “This tuneable laser light was used to pump the Q11 transition of A2S+(v = 1) - X2P(v = 0) at 281.997 nm for direct, off-resonant LIF detection of OH.”
What does this mean? At which wavelengths are resonance and non-resonance measurements made?
The Q1(1) line of OH is not an isolated line (the R2(3) line is very close)
Does this pose a problem for the interpretation of the LIF results? What is the wavelength resolution?
- line 304: “Considering the systemic errors, we quote more realistic values of k1 (296 K) = (1.2 ± 0.2) × 10-12 cm3 molecule-1 s-1 and k2(296 K) = (1.3 ± 0.3) × 10-12 cm3 molecule-1 s-1, that take into account the error over the estimation of [VOC]”
It is not clear how this concentration error is taken into account in the final uncertainty calculation
- Line 177: “Similar experiments were conducted at different temperatures, pressures and in the presence / absence of O2”
The authors should clarify the value of such measurements (with and without O2) and at least give an indication of the comparative results
Citation: https://doi.org/10.5194/egusphere-2023-282-RC2 - AC1: 'Comment on egusphere-2023-282', Caterina Mapelli, 18 May 2023
Peer review completion
Journal article(s) based on this preprint
greensafer solvents which present favourable advantages when compared to traditional solvents. Since the assessment of these green solvents often lacks air quality considerations, this study aims to understand the behaviour of these compounds, investigating their reactivity in the troposphere.
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Caterina Mapelli
James K. Donnelly
Úna E. Hogan
Andrew R. Rickard
Abbie T. Robinson
Fergal Byrne
Con Rob McElroy
Basile F. E. Curchod
Daniel Hollas
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1271 KB) - Metadata XML
-
Supplement
(571 KB) - BibTeX
- EndNote
- Final revised paper