Kinetic and mechanistic study of the gas-phase reaction of CxF2x+1CH[dbnd]CH2 (x=1, 2, 3, 4 and 6) with O3 under atmospheric conditions
2018
Soto, A. | Ballesteros, B. | Jiménez, E. | Antiñolo, M. | Martínez, E. | Albaladejo, J.
The relative-rate technique has been used to determine the rate coefficient for the reaction of CₓF₂ₓ₊₁CHCH₂ (x = 1, 2, 3, 4 and 6) with ozone at (298 ± 2) K and (720 ± 5) Torr of air by FTIR (Fourier Transform Infrared Spectroscopy) and by GC-MS/SPME (Gas Chromatography-Mass Spectroscopy with Solid Phase Micro Extraction) in two different atmospheric simulation chambers. The following rate coefficients, in units of 10⁻¹⁹ cm³ molecule⁻¹ s⁻¹, were obtained: (3.01 ± 0.10) for CF₃CHCH₂, (2.11 ± 0.35) for C₂F₅CHCH₂, (2.34 ± 0.42) for C₃F₇CHCH₂, (2.05 ± 0.31) for C₄F₉CHCH₂ and (2.07 ± 0.39) for C₆F₁₃CHCH₂, where uncertainties represent ±2σ statistical error. The atmospheric lifetime of CₓF₂ₓ₊₁CHCH₂ due to reaction with ozone was estimated from the reported rate coefficients. Additionally, the gaseous products formed in these reactions were investigated in the presence of synthetic air simulating a clean atmosphere. Perfluoroaldehydes, CₓF₂ₓ₊₁C(O)H (PFALs), formaldehyde, formic acid and CF₂O were identified as reaction products in the investigated reactions. The identified products made possible to propose a reaction mechanism that justifies the observed products. The atmospheric implications of these results are discussed in terms of the potential contribution of the atmospheric degradation of these species to PFAL and PFCA burden.
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