| Autor: |
Mapelli, Caterina, Donnelly, James K., Hogan, Úna E., Rickard, Andrew R., Robinson, Abbie T., Byrne, Fergal, McElroy, Con Rob, Curchod, Basile F. E., Hollas, Daniel, Dillon, Terry J. |
| Předmět: |
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| Zdroj: |
EGUsphere; 2/23/2023, p1-23, 23p |
| Abstrakt: |
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 k 1(297 K) = (1.2 ± 0.2) for OH + (CH3)3CC(O)CH3 (R1) and k 2(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 k 1(T) adequately described by k1(297 – 485 K) = 2.1 × 10−12 exp(−200/ T) cm3 molecule−1 s−1. k 2(T) exhibited more complex behaviour, with a local minimum at around 300 K. In the course of this work, k 3(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 ϕ 4(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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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