Mapelli, Caterina and Donnelly, James K. and Hogan, Úna E. and Rickard, Andrew R. and Robinson, Abbie T. and Byrne, Fergal P. and McElroy, Con Rob and Curchod, Basile F. E. and Hollas, Daniel and Dillon, Terry J. (2023) Atmospheric oxidation of new “green” solvents – Part 2: methyl pivalate and pinacolone. Atmospheric Chemistry and Physics, 23 (13). pp. 7767-7779. ISSN 1680-7316

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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 molec.−1 s −1 ) of k1(297 K) = (1.2 ± 0.2) for OH + (CH3)3CC(O)CH3 (Reaction R1) and k2(297 K) = (1.3 ± 0.2) for OH + (CH3)3CC(O)OCH3 (Reaction 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 molec.−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) was obtained for the well-characterised reaction OH + C2H5OH (ethanol; Reaction R3), in satisfactory agreement with the evaluated literature. UV–Vis spectroscopy experiments and computational calculations were used to explore cross-sections for (CH3)3CC(O)CH3 photolysis (Reaction R4), while (CH3)3CC(O)OCH3 showed no sign of absorption over the wavelengths of interest. 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 (methyl ethyl ketone (MEK) values) used in current state-of-science models. As a consequence, we note that photolysis (Reaction 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 Reactions (R1) and (R4) span the range 2–9 d and are consequently associated with a poorly constrained estimated photochemical ozone creation potential (POCPE). In accord with previous studies, (CH3)3CC(O)OCH3 did not absorb in the actinic r

Item Type:	Article
Keywords:	Atmospheric oxidation; new “green” solvents; methyl pivalate; pinacolone;
Academic Unit:	Faculty of Science and Engineering > Experimental Physics
Item ID:	18587
Identification Number:	https://doi.org/10.5194/acp-23-7767-2023
Depositing User:	Fergal Byrne
Date Deposited:	28 May 2024 11:42
Journal or Publication Title:	Atmospheric Chemistry and Physics
Publisher:	Copernicus Publications for European Geosciences Union (EGU)
Refereed:	Yes
URI:	Publisher
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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