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

作者：Antinolo Maria; Bravo Ivan; Jimenez Elena; Ballesteros Bernabe; Albaladejo Jose^*

来源：Journal of Physical Chemistry A, 2017, 121(43): 8322-8331.

DOI：10.1021/acs.jpca.7b06174

We report here the rate coefficients for the OH reactions (k(OH)) with E-CF3CH=CHF and Z-CF3CH=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(OH) needs to be elucidated. For the Z-isomer, this work constitutes the first absolute determination of k(OH). No pressure dependence of k(OH) was observed, while k(OH) exhibits a non-Arrhenius behavior: k(OH) (E) = (7.6 +/- 0.2) X 10(-13) (T/298)(2.44) exp( T 666 +/- 10)/T and k(OH) (Z) = (1.4 +/- 0.1) X 10(-13) (T/298)(1.91) exp( 640 +/- 13)/T cm(3) molecule(-1) s(-1), where uncertainties are 2 sigma. UV absorption cross sections, sigma(lambda), are reported for the first time. From sigma(lambda), 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 X 10(-8) s(-1) and >1 year for the E-isomer and 2 X 10(-7) s(-1) and >2 months for Z-CF3CH=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(-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.

• 出版日期2017-11-2