Atmospheric Chemistry of E- and Z-CF3CHâCHF (HFO-1234ze): OH Reaction Kinetics as a Function of Temperature and UV and IR Absorption Cross Sections.
J Phys Chem A
; 121(43): 8322-8331, 2017 Nov 02.
Article
en En
| MEDLINE
| ID: mdl-28992690
ABSTRACT
We report here the rate coefficients for the OH reactions (kOH) with E-CF3CHâCHF and Z-CF3CHâCHF, 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 kOH needs to be elucidated. For the Z-isomer, this work constitutes the first absolute determination of kOH. No pressure dependence of kOH was observed, while kOH exhibits a non-Arrhenius behavior kOH(E) = [Formula see text] and kOH(Z) = [Formula see text] cm3 molecule-1 s-1, where uncertainties are 2σ. UV absorption cross sections, σλ, are reported for the first time. From σλ 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 × 10-8 s-1 and >1 year for the E-isomer and 2 × 10-7 s-1 and >2 months for Z-CF3CHâCHF, 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-1) and theoretically (0-2000 cm-1). From the theoretical IR measurements, it is concluded that the contribution of the 0-500 cm-1 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.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Idioma:
En
Revista:
J Phys Chem A
Asunto de la revista:
QUIMICA
Año:
2017
Tipo del documento:
Article
País de afiliación:
España