High-Accuracy Measurements of OH Reaction Rate Constants and IR Absorption Spectra: CH₂═CF−CF₃ and trans-CHF═CH−CF₃

Abstract

Rate constants for the gas phase reactions of OH radicals with two isomers of tetrafluoropropene, CH(2)=CF-CF(3) (k(1)) and trans-CHF=CH-CF(3) (k(2)); were measured using a flash photolysis resonance-fluorescence technique over the temperature range 220 to 370 K. The Arrhenius plots were found to exhibit a noticeable curvature. The temperature dependences of the rate constants are very weak and can be represented by the following expressions over the indicated temperature intervals: k(1)(220-298 K) = 1.145 x 10(-12) x exp{13/T} cm(3) molecule(-1) s(-1), k(1)(298-370 K) = 4.06 x 10(-13) x (T/298)(1.17) x exp{+296/T} cm(3) molecule(-1) s(-1), k(2)(220-370 K) = 1.115 x 10(-13) x (T/298)(2.03) x exp{+522/T} cm(3) molecule(-1) s(-1). The overall accuracy of the rate constant measurements is estimated to be ca. 2% to 2.5% at the 95% confidence level. The uncertainty of the measured reaction rate constants is discussed in detail. The atmospheric lifetimes due to reactions with tropospheric OH were estimated to be 12 and 19 days respectively under the assumption of a well mixed atmosphere. IR absorption cross-sections were measured for both compounds and their global warming potentials were estimated.

Hydroxyl radical reaction rate coefficients as a function of temperature and IR absorption cross sections for CF3CH=CH2 (HFO-1243zf), potential replacement of CF3CH2F (HFC-134a)

“…As it is also shown in Table 2, the reported independence of k OH for reaction 1 with total pressure was also observed, over a similar pressure range to that studied in this work, for other HFOs with one or two F atoms attached to the double bond, such as (E)-CF 3 CH=CHF, CF 3 CF=CH 2 , and (Z)-CF 3 CF=CHF (Orkin et al 2010;Papadimitriou et al 2008). The same conclusion was reported for lighter HFOs, such as CH 2 =CF 2 and CHF=CH 2 (Baasandorj et al 2010), and heavier HFOs, such as CF 3 (CF 2 ) 3 CH=CH 2 and CF 3 (CF 2 ) 5 CH=CH 2 (Vésine et al 2000).…”

“…A and E a /R parameters are listed in Table 3 for reaction 1 together with the Arrhenius parameters obtained by Orkin et al (1997) and those reported for other selected HFOs. As shown in Table 3, in general, E a /R values are slightly negative for the selected OH reactions, except for the OH+CF 3 CF=CH 2 and CF 3 (CF 2 ) 5 CH=CH 2 reactions (Orkin et al 2010;Papadimitriou et al 2008;Vésine et al 2000), where a small positive temperature dependence and no dependence were observed, respectively. Furthermore, the kinetic behavior is somewhat different for some of the HFOs and the non-Arrhenius behavior was observed for the OH reactions with (Z)-CF 3 CF=CHF (Papadimitriou et al 2008), (E)-CF 3 CH=CHF, and CF 3 CF=CH 2 (Orkin et al 2010).…”

“…As shown in Table 3, in general, E a /R values are slightly negative for the selected OH reactions, except for the OH+CF 3 CF=CH 2 and CF 3 (CF 2 ) 5 CH=CH 2 reactions (Orkin et al 2010;Papadimitriou et al 2008;Vésine et al 2000), where a small positive temperature dependence and no dependence were observed, respectively. Furthermore, the kinetic behavior is somewhat different for some of the HFOs and the non-Arrhenius behavior was observed for the OH reactions with (Z)-CF 3 CF=CHF (Papadimitriou et al 2008), (E)-CF 3 CH=CHF, and CF 3 CF=CH 2 (Orkin et al 2010). For these reactions, the Arrhenius plots exhibit a curvature and the modified Arrhenius expression, i.e., a T-dependent pre-exponential factor, was preferred (Papadimitriou et al 2008;Orkin et al 2010).…”

“…Furthermore, the kinetic behavior is somewhat different for some of the HFOs and the non-Arrhenius behavior was observed for the OH reactions with (Z)-CF 3 CF=CHF (Papadimitriou et al 2008), (E)-CF 3 CH=CHF, and CF 3 CF=CH 2 (Orkin et al 2010). For these reactions, the Arrhenius plots exhibit a curvature and the modified Arrhenius expression, i.e., a T-dependent pre-exponential factor, was preferred (Papadimitriou et al 2008;Orkin et al 2010). …”

Flammability of Trans-1, 3, 3, 3-tetrafluoroprop-1-ene and its binary blends

“…Orkin et al [8] and Søndergaard et al [9] concluded that the radiative efficiencies (RE) of R1234ze (E) was located in the range of 0.24e0.27 Wm À2 ppb À1 with a mean of 0.26 Wm À2 ppb À1 . While Hodnebrog et al [10] calculated the RE value of R1234ze (E) was 0.04 Wm À2 ppb À1 by using absorption cross sections method, and modified the GWP of R1234ze (E) to be even "lower than 1" for 100 years (relative to that of CO 2 ), which was different from the previous value of about "6" as the UNEP (United Nations Environment Programme) ozone secretariat reported [11].…”