23 Feb 2023
 | 23 Feb 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Atmospheric oxidation of new 'green' solvents part II: methyl pivalate and pinacolone

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, and Terry J. Dillon

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.

Caterina Mapelli et al.

Status: open (until 11 Apr 2023)

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  • RC1: 'Comment on egusphere-2023-282', Anonymous Referee #1, 22 Mar 2023 reply
  • RC2: 'Comment on egusphere-2023-282', Anonymous Referee #2, 23 Mar 2023 reply

Caterina Mapelli et al.

Caterina Mapelli et al.


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Short summary
Solvents are chemical compounds with countless uses in the chemical industry and they also represent one of the main sources of pollution in the chemical sector. Scientists are trying to develop new ‘green’ safer solvents which present favourable advantages when compared to traditional solvents. Since the assessment of these ‘green’ solvents often lack air quality considerations, this study aims to understand the behaviour of these compounds, investigating their reactivity in the troposphere.