Atmospheric breakdown kinetics and air quality impact of potential “green” solvents, the oxymethylene ethers OME3 and OME4
<p>Laboratory-based experiments were used to investigate the atmospheric degradation chemistry of two oxymethylene ethers, CH<span class="inline-formula"><sub>3</sub></span>O(CH<span class="inline-formula"><sub>2</sub></span>O...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/9169/2025/acp-25-9169-2025.pdf |
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| Summary: | <p>Laboratory-based experiments were used to investigate the atmospheric degradation chemistry of two oxymethylene ethers, CH<span class="inline-formula"><sub>3</sub></span>O(CH<span class="inline-formula"><sub>2</sub></span>O)<span class="inline-formula"><sub>3</sub></span>CH<span class="inline-formula"><sub>3</sub></span> (OME3) and CH<span class="inline-formula"><sub>3</sub></span>O(CH<span class="inline-formula"><sub>2</sub></span>O)<span class="inline-formula"><sub>4</sub></span>CH<span class="inline-formula"><sub>3</sub></span> (OME4). OME3 and OME4 have been proposed as promising “green” replacement compounds for problematic ethereal solvents such as 1,4-dioxane and tetrahydrofuran. Results from direct, absolute laser-based experiments and from a series of complementary relative rate studies demonstrated that OH <span class="inline-formula">+</span> OME3 proceeded with a rate coefficient <span class="inline-formula"><i>k</i><sub>3</sub></span>(296 <span class="inline-formula">±</span> 2 K) <span class="inline-formula">=</span> (1.0 <span class="inline-formula">±</span> 0.2) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>−11</sup></span> cm<span class="inline-formula"><sup>3</sup></span> molec.<span class="inline-formula"><sup>−1</sup></span> s<span class="inline-formula"><sup>−1</sup></span>, a factor of 2 smaller than predicted by structure activity relationships (SARs). Evidence for a complex mechanism was provided by <span class="inline-formula"><i>k</i><sub>3</sub></span>(294–464 K), characterised by deviations from Arrhenius-like behaviour close to room temperature. A further series of relative rate experiments were used to determine a rate coefficient of <span class="inline-formula"><i>k</i><sub>4</sub></span>(296 <span class="inline-formula">±</span> 2 K) <span class="inline-formula">=</span> (1.1 <span class="inline-formula">±</span> 0.4) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>−11</sup></span> cm<span class="inline-formula"><sup>3</sup></span> molec.<span class="inline-formula"><sup>−1</sup></span> s<span class="inline-formula"><sup>−1</sup></span> for OH <span class="inline-formula">+</span> OME4. These results allowed for lifetimes, <span class="inline-formula"><i>τ</i>≈1</span> d, to be estimated for the removal of each of OME3 and OME4 from the troposphere. The photochemical ozone creation potential estimate (POCP<span class="inline-formula"><sub>E</sub></span>) was calculated for northwest Europe conditions. These were considerably smaller than equivalent metrics for the problematic solvents they may replace, largely owing to their lack of C–C bonds. In the course of this work, rate coefficients (in 10<span class="inline-formula"><sup>−11</sup></span> cm<span class="inline-formula"><sup>3</sup></span> molec.<span class="inline-formula"><sup>−1</sup></span> s<span class="inline-formula"><sup>−1</sup>)</span> were determined for Cl <span class="inline-formula">+</span> OME3, <span class="inline-formula"><i>k</i><sub>6</sub></span>(296 <span class="inline-formula">±</span> 2 K) <span class="inline-formula">=</span> (17 <span class="inline-formula">±</span> 4), and for Cl <span class="inline-formula">+</span> OME4, <span class="inline-formula"><i>k</i><sub>7</sub></span>(296 <span class="inline-formula">±</span> 2 K) <span class="inline-formula">=</span> (19 <span class="inline-formula">±</span> 6).</p> |
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| ISSN: | 1680-7316 1680-7324 |