title: 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).
abstract: CF3CH=CH2 (hydrofluoroolefin, HFO-1243zf) is a potential replacement of high global-warming potential (GWP) hydrofluorocarbon (HFC-134a, CF3CFH2). Both the atmospheric lifetime and the radiative efficiency of HFO-1243zf are parameters needed for estimating the GWP of this species. Therefore, the aim of this work is (i) to estimate the atmospheric lifetime of HFO-1243zf from the reported OH rate coefficients, k OH, determined under tropospheric conditions and (ii) to calculate its radiative efficiency from the reported IR absorption cross sections. The OH rate coefficient at 298 K also allows the estimation of the photochemical ozone creation potential (ε(POCP)). The pulsed laser photolysis coupled to a laser-induced fluorescence technique was used to determine k OH for the reaction of OH radicals with HFO-1243zf as a function of pressure (50-650 Torr of He) and temperature (263-358 K). Gas-phase IR spectra of HFO-1243zf were recorded at room temperature using a Fourier transform IR spectrometer between 500 and 4,000 cm(-1). At all temperatures, k OH did not depend on bath gas concentration (i.e., on the total pressure between 50 and 650 Torr of He). A slight but noticeable T dependence of k OH was observed in the temperature range investigated. The observed behavior is well described by the following Arrhenius expression: k OH(T) = (7.65 ± 0.26) × 10(-13) exp [(165 ± 10) / T] cm(3) molecule(-1) s(-1). Negligible IR absorption of HFO-1243zf was observed at wavenumbers greater than 1,700 cm(-1). Therefore, IR absorption cross sections, [Formula: see text], were determined in the 500-1,700 cm(-1) range. Integrated [Formula: see text] were determined between 650 and 1,800 cm(-1) for comparison purposes. The main diurnal removal pathway for HFO-1243zf is the reaction with OH radicals, which accounts for 64% of the overall loss by homogeneous reactions at 298 K. Globally, the lifetime due to OH reaction (τ OH) was estimated to be 8.7 days under the assumption of a well-mixed atmosphere. Assuming other removal pathways, the atmospheric lifetime (τ) was estimated to be ∼6 days. Considering the estimated τ OH and the measured IR absorption cross sections of HFO-1243zf in the atmospheric window (720-1,250 cm(-1)), its lifetime corrected radiative efficiency was calculated to be 0.019 W m(-2) ppbv(-1). GWP100 years for the HFO investigated, 0.29, is negligible compared to that of HFC-134a, the HFC to be potentially replaced (GWP100 years = 1,300, Hodnebrog et al. (Rev Geophys 51:300-378, 2013)). ε POCP for HFO-1243zf was estimated to be around 1 order of magnitude lower than that for ethylene. In conclusion, HFO-1243zf is fast degraded in the atmosphere, and it does not appreciably contribute to global warming and local/regional air pollution. Therefore, HFO-1243zf can be a suitable replacement for HFC-134a in air conditioning units.
authors.affiliation: Department of Physical Chemistry, Faculty of Chemical Sciences and Technologies, University of Castilla-La Mancha, Avda. Camilo José Cela s/n, 13071, Ciudad Real, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: González
authors.forename: Elena
authors.initials: E
authors.lastname: Jiménez
authors.forename: Bernabé
authors.initials: B
authors.lastname: Ballesteros
authors.forename: Ernesto
authors.initials: E
authors.lastname: Martínez
authors.forename: José
authors.initials: J
authors.lastname: Albaladejo
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D057232:Global Warming; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry*; D010782:Photolysis; D013055:Spectrophotometry, Infrared; D013696:Temperature; D004980:Ethane / Q000031:analogs & derivatives; D005466:Fluorocarbons
chemical_list: D000393:Air Pollutants; D006845:Hydrocarbons, Fluorinated; D017665:Hydroxyl Radical; D010126:Ozone; C063006:norflurane; D004980:Ethane; D005466:Fluorocarbons