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Issue 6, 2008
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CF3CF[double bond, length as m-dash]CH2 and (Z)-CF3CF[double bond, length as m-dash]CHF: temperature dependent OH rate coefficients and global warming potentials

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Abstract

Rate coefficients over the temperature range 206–380 K are reported for the gas-phase reaction of OH radicals with 2,3,3,3-tetrafluoropropene (CF3CF[double bond, length as m-dash]CH2), k1(T), and 1,2,3,3,3-pentafluoropropene ((Z)-CF3CF[double bond, length as m-dash]CHF), k2(T), which are major components in proposed substitutes for HFC-134a (CF3CFH2) in mobile air-conditioning units. Rate coefficients were measured under pseudo-first-order conditions in OH using pulsed-laser photolysis to produce OH and laser-induced fluorescence to detect it. Rate coefficients were found to be independent of pressure between 25 and 600 Torr (He, N2). For CF3CF[double bond, length as m-dash]CH2, the rate coefficients, within the measurement uncertainty, are given by the Arrhenius expression k1(T) = (1.26 ± 0.11) × 10−12 exp[(−35 ± 10)/T] cm3 molecule−1 s−1 where k1(296 K) = (1.12 ± 0.09) × 10−12 cm3 molecule−1 s−1. For (Z)-CF3CF[double bond, length as m-dash]CHF, the rate coefficients are given by the non-Arrhenius expression k2(T) = (1.6 ± 0.2) × 10−18T2 exp[(655 ± 50)/T] cm3 molecule−1 s−1 where k2(296 K) = (1.29 ± 0.06) × 10−12 cm3 molecule−1 s−1. Over the temperature range most relevant to the atmosphere, 200–300 K, the Arrhenius expression k2(T) = (7.30 ± 0.7) × 10−13 exp[(165 ± 20)/T] cm3 molecule−1 s−1 reproduces the measured rate coefficients very well and can be used in atmospheric model calculations. The quoted uncertainties in the rate coefficients are 2σ (95% confidence interval) and include estimated systematic errors. The global warming potentials for CF3CF[double bond, length as m-dash]CH2 and (Z)-CF3CF[double bond, length as m-dash]CHF were calculated to be <4.4 and <3.6, respectively, for the 100 year time horizon using infrared absorption cross sections measured in this work, and atmospheric lifetimes of 12 and 10 days that are based solely on OH reactive loss.

Graphical abstract: CF3CF [[double bond, length as m-dash]] CH2 and (Z)-CF3CF [[double bond, length as m-dash]] CHF: temperature dependent OH rate coefficients and global warming potentials

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Publication details

The article was received on 18 Sep 2007, accepted on 29 Oct 2007 and first published on 23 Nov 2007


Article type: Paper
DOI: 10.1039/B714382F
Citation: Phys. Chem. Chem. Phys., 2008,10, 808-820
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    CF3CF[double bond, length as m-dash]CH2 and (Z)-CF3CF[double bond, length as m-dash]CHF: temperature dependent OH rate coefficients and global warming potentials

    V. C. Papadimitriou, R. K. Talukdar, R. W. Portmann, A. R. Ravishankara and J. B. Burkholder, Phys. Chem. Chem. Phys., 2008, 10, 808
    DOI: 10.1039/B714382F

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