Atmospheric Chemistry of E- and Z-CF₃CH═CHF (HFO-1234ze): OH Reaction Kinetics as a Function of Temperature and UV and IR Absorption Cross Sections

Abstract

We report here the rate coefficients for the OH reactions (k) with E-CFCH═CHF and Z-CFCH═CHF, potential substitutes of HFC-134a, as a function of temperature (263-358 K) and pressure (45-300 Torr) by pulsed laser photolysis coupled to laser-induced fluorescence techniques. For the E-isomer, the existing discrepancy among previous results on the T dependence of k needs to be elucidated. For the Z-isomer, this work constitutes the first absolute determination of k. No pressure dependence of k was observed, while k exhibits a non-Arrhenius behavior: k(E) = [Formula: see text] and k(Z) = [Formula: see text] cm molecule s, where uncertainties are 2σ. UV absorption cross sections, σ, are reported for the first time. From σ and considering a photolysis quantum yield of 1, an upper limit for the photolysis rate coefficients and lifetimes due to this process in the troposphere are estimated: 3 × 10 s and >1 year for the E-isomer and 2 × 10 s and >2 months for Z-CFCH═CHF, respectively. Under these conditions, the overall estimated tropospheric lifetimes are 15 days (for the E-isomer) and 8 days (for the Z-isomer), the major degradation pathway being the OH reaction, with a contribution of the photolytic pathway of less than 3% (for E) and 13% (for Z). IR absorption cross sections were determined both experimentally (500-4000 cm) and theoretically (0-2000 cm). From the theoretical IR measurements, it is concluded that the contribution of the 0-500 cm region to the total integrated cross sections is appreciable for the E-isomer (9%) but almost negligible for the Z-isomer (0.5%). Nevertheless, the impact on their radiative efficiency and global warming potential is negligible.

Room‐Temperature, High‐SNR Upconversion Spectrometer in the 6–12 µm Region

“…The resolution is currently not limited by the linewidth of the 1064 nm pump (≈0.35 nm; see Figure S3 in the Supporting Information), which would account only for a 3 cm −1 broadening. In Figure 4c,d, the MIR transmission spectra of two gas species, nitrous oxide (N 2 O) and tetrafluoropropene (C 3 H 2 F 4 ), obtained by MIRUS are plotted and shown to agree well with corresponding reference data (HITRAN 2016 for N 2 O and FTIR measurement for C 3 H 2 F 4 found elsewhere [ 27 ] ). The two gases were individually introduced in the path of the collimated MIR beam in front of the upconversion module input aperture.…”

Degradation mechanism of 2-fluoropropene by Cl atoms: experimental and theoretical products distribution studies

“…These results are in excellent agreement with all previous determinations for the reactions of similar HFOs from the literature. 50,51…”

Distribution and dry deposition of alternative and legacy perfluoroalkyl and polyfluoroalkyl substances in the air above the Bohai and Yellow Seas, China

“…On the mainland, especially the cities, the precursor concentrations were higher than in remote areas (Chan et al, 2006), which could result in the high concentration of ODS products. While transporting to the coast and sea, TFAs were generated and deposited along the way (Antinolo et al, 2017;Jimenez et al, 2016). On the coast, the high concentrations of hydroxyl radicals possibly enhanced the photochemical transformation of precursors and then elevated the TFA levels (Mopper and Zhou, 1990).…”