Rate Constants for the Reaction of OH Radicals with Hydrocarbons in a Smog Chamber at Low Atmospheric Temperatures

Abstract

Abstract:The photochemical reaction of OH radicals with the 17 hydrocarbons n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, cyclooctane, 2,2-dimethylbutane, 2,2-dimethylpentane, 2,2-dimethylhexane, 2,2,4-trimethylpentane, 2,2,3,3-tetramethylbutane, benzene, toluene, ethylbenzene, p-xylene, and o-xylene was investigated at 288 and 248 K in a temperature controlled smog chamber. The rate constants were determined from relative rate calculations with toluene and n-pentane as reference compounds, respectively. The results from this work at 288 K show good agreement with previous literature data for the straight-chain hydrocarbons, as well as for cyclooctane, 2,2-dimethylbutane, 2,2,4-trimethylpentane, 2,2,3,3-tetramethylbutane, benzene, and toluene, indicating a convenient method to study the reaction of OH radicals with many hydrocarbons simultaneously. The data at 248 K (k in units of 10 −12 cm 3 s −1 ) for 2,2-dimethylpentane (2.97 ± 0.08), 2,2-dimethylhexane (4.30 ± 0.12), 2,2,4-trimethylpentane (3.20 ± 0.11), and ethylbenzene (7.51 ± 0.53) extend the available data range of experiments. Results from this work are useful to evaluate the atmospheric lifetime of the hydrocarbons and are essential for modeling the photochemical reactions of hydrocarbons in the real troposphere.

Application of Chelating Agents to Enhance Fenton Process in Soil Remediation: A Review

“…A second dose of oxidant and Fe-citrate increases the target pollutant degradation [151], although this option would be only recommended when treating recalcitrant pollutants with low hydroxyl radical reaction rate constants. In this way, Liang et al reported that among four BTEX compounds, benzene was the most resistant to oxidation in the aqueous phase [152], the reaction rate constant of benzene with hydroxyl radicals (k benzene, OH • = 6.6 × 10 8 M −1 s −1 [145]) being one order of magnitude lower than those of toluene, ethylbenzene, and xylene, as summarized in Table 4. In this study, benzene conversion increased when using different CAs, following the descending order (at the same operating conditions): CitrA (100%) > EDTA (50%) [152], which is in line with the above mentioned.…”

“…• = 6.6 × 10 8 M −1 s −1 [145], Table 4), due to the high possibility for competition between EDDS and the pollutant for the hydroxyl radicals formed (Equations ( 23) and ( 24)).…”

Air Quality Assessment in the Central Mediterranean Sea (Tyrrhenian Sea): Anthropic Impact and Miscellaneous Natural Sources, including Volcanic Contribution, on the Budget of Volatile Organic Compounds (VOCs)

“…The predominance of heavier n-alkanes in the marine environment has already been reported [44] and the data obtained during the cruise generally agree with the previous studies. As well-known [45,46] the ability of these compounds to react with OH radicals increases with the chain length, therefore their predominance should likely be ascribed to the presence of local sources. On the other hand, comparing the different sampling periods, The C10 and C11 were abundant in all the samples, with only few exceptions, but the trends shown by remote areas and anthropogenically impacted sites (Sicilian coasts, Phlegraean Fields) are somehow different.…”

“…Analyzing CFC11 peaks exceeding 1.29 µg/m 3 , the average atmospheric level in the northern hemisphere [46,52], it was apparent that levels above the average were found in the area of Ischia and in some sporadic measurements around Stromboli and Vulcano (Figure S4). Trying to better characterize the general conditions affecting these measurements through backward trajectories analysis and wind records, no evidence could be found of a geogenic influence.…”

Pressure-dependent kinetics of the o-xylene reaction with OH radicals

“…For example, Hansen et al 16 (1975) and Anderson et al 17 (2003) studied the kinetics at room temperature at 101 torr by using a flash photolysis-resonance fluorescence technique and 760 torr with an isotope ratio mass spectrometer coupled on-line to the gas chromatograph, respectively. Han et al 18 (2018) performed reaction kinetics studies at 248 K and 288 K under atmospheric pressure by employing a gas chromatograph in a temperature-controlled smog chamber. What's more, the high-temperature kinetics study above 1000 K for o -xylene plus OH is rare.…”