Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR

Fuchs, Hendrik; Albrecht, Sascha; Acir, Ismail–Hakki; Bohn, Birger; Breitenlechner, Martin; Dorn, Hans-Peter; Gkatzelis, Georgios I.; Hofzumahaus, Andreas; Holland, Frank; Kaminski, Martin; Keutsch, Frank N.; Novelli, Anna; Reimer, David; Rohrer, Franz; Tillmann, Ralf; Vereecken, Luc; Wegener, Robert; Zaytsev, Alexander; Kiendler-Scharr, Astrid; Wahner, Andreas

The photooxidation of methyl vinyl ketone (inline-formulaMVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (inline-formulaRO2) mainly reacted with inline-formulaNO (“high inline-formulaNO” case) and for conditions at which other reaction channels could compete (“low inline-formulaNO” case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high inline-formulaNO case, the methylglyoxal yield was (19 inline-formula± 3) % and the glycolaldehyde yield was (65 inline-formula± 14) %, consistent with recent literature studies. For the low inline-formulaNO case, the methylglyoxal yield reduced to (5 inline-formula± 2) % because other inline-formulaRO2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 inline-formula± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of inline-formulaOH radicals in the experiments shows the need for an enhanced inline-formulaOH radical production at low inline-formulaNO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For inline-formulaMVK the model–measurement discrepancy was up to a factor of 2. Product yields and inline-formulaOH observations were consistent with assumptions of additional inline-formulaRO2 plus inline-formulaHO2 reaction channels as proposed in literature for the major inline-formulaRO2 species formed from the reaction of inline-formulaMVK with inline-formulaOH. However, this study shows that also inline-formulaHO2 radical concentrations are underestimated by the model, suggesting that additional inline-formulaOH is not directly produced from inline-formulaRO2 radical reactions, but indirectly via increased inline-formulaHO2. Quantum chemical calculations show that inline-formulaHO2 could be produced from a fast 1,4-inline-formulaH shift of the second most important inline-formulaMVK derived inline-formulaRO2 species (reaction rate constant inline-formula0.003inline-formulas−1). However, additional inline-formulaHO2 from this reaction was not sufficiently large to bring modelled inline-formulaHO2 radical concentrations into agreement with measurements due to the small yield of this inline-formulaRO2 species. An additional reaction channel of the major inline-formulaRO2 species with a reaction rate constant of (0.006 inline-formula± 0.004) inline-formulas−1 would be required that produces concurrently inline-formulaHO2 radicals and glycolaldehyde to achieve model–measurement agreement. A unimolecular reaction similar to the 1,5-inline-formulaH shift reaction that was proposed in literature for inline-formulaRO2 radicals from inline-formulaMVK would not explain product yields for conditions of experiments in this study. A set of inline-formulaH-migration reactions for the main inline-formulaRO2 radicals were investigated by quantum chemical and theoretical kinetic methodologies, but did not reveal a contributing route to inline-formulaHO2 radicals or glycolaldehyde.

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Fuchs, Hendrik / Albrecht, Sascha / Acir, Ismail–Hakki / et al: Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR. 2018. Copernicus Publications.

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