Atmospheric fate of a series of saturated alcohols: kinetic and mechanistic study

摘要

The atmospheric fate of a series of saturated alcohols (SAs) wasevaluated through kinetic and reaction product studies with themain atmospheric oxidants. These SAs are alcohols that could be used as fueladditives. Rate coefficients (in cm3 molecule−1 s−1)measured at ∼298 K and atmospheric pressure (720±20 Torr) wereas follows: k1 ((E)-4-methylcyclohexanol + Cl) = (3.70±0.16)×10-10, k2 ((E)-4-methylcyclohexanol + OH) = (1.87±0.14) ×10-11, k3 ((E)-4-methylcyclohexanol +NO3) = (2.69±0.37) ×10-15, k4(3,3-dimethyl-1-butanol + Cl) = (2.69±0.16) ×10-10, k5 (3,3-dimethyl-1-butanol + OH) = (5.33±0.16)×10-12, k6 (3,3-dimethyl-2-butanol + Cl) = (1.21±0.07) ×10-10, and k7 (3,3-dimethyl-2-butanol +OH) = (10.50±0.25) ×10-12. The main productsdetected in the reaction of SAs with Cl atoms (in the absence/presence ofNOx), OH radicals, and NO3 radicals were (E)-4-methylcyclohexanone for thereactions of (E)-4-methylcyclohexanol, 3,3-dimethylbutanal for the reactionsof 3,3-dimethyl-1-butanol, and 3,3-dimethyl-2-butanone for the reactions of3,3-dimethyl-2-butanol. Other products such as formaldehyde,2,2-dimethylpropanal, and acetone have also been identified in the reactionsof Cl atoms and OH radicals with 3,3-dimethyl-1-butanol and3,3-dimethyl-2-butanol. In addition, the molar yields of the reactionproducts were estimated. The products detected indicate a hydrogen atomabstraction mechanism at different sites on the carbon chain of alcohol inthe case of Cl reactions and a predominant site in the case of OH andNO3 reactions, confirming the predictions of structure–activityrelationship (SAR) methods. Tropospheric lifetimes (τ) of these SAshave been calculated using the experimental rate coefficients. Lifetimes arein the range of 0.6–2 d for OH reactions, 7–13 d for NO3 radicalreactions, and 1–3 months for Cl atoms. In coastal areas, the lifetime due tothe reaction with Cl decreases to hours. The calculated global troposphericlifetimes, and the polyfunctional compounds detected as reaction products inthis work, imply that SAs could contribute to the formation of ozone andnitrated compounds at local, regional, and even global scales. Therefore,the use of saturated alcohols as additives in diesel blends should beconsidered with caution.